EPHC10-EC Solar System Controller Rated Current：10A, 20A System Voltage：12/24V Auto Work Load work mode: ON/OFF. Ideal for off-grid solar system that loads are normally on or controlled by manual ★Solar home system ★Solar CCTV system ★Solar traffic system. Charge circuit voltage drop ≤0.26V. 30 AMP PWM CHARGE CONTROLLER MANUAL Charge Controller Specifications Technical Information (12/24V Auto Mode). This section provides a brief overview of how to begin using your solar charge controller. It is recommended that each user review the entire manual to ensure the best. Consider the temperature compensation of the charge. Just a quick video to get you started For cheap charge controllers and solar panels check here Get you started how to operate Pwm solar charge controller DIY TEK NUT.

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Photovoltaic System Charge Controllers and Linear Current Boosters

The charge controller is a necessary part of your power system that charge batteries, whether the power source is PV, wind, hydro, fuel, or utility grid. Its purpose is to keep your batteries properly fed and safe for the long term. (PDF 308Kb)

A charge controller is an electronic voltage regulator, used in off-grid systems and grid-tie systems with battery backup, that controls the flow of power from the charging source to the battery. The charge controller automatically tapers, stops, or diverts the charge when batteries become fully charged.

In off-grid facilities, PV systems are either stand-alone or centralized configurations that serve multiple units. The systems deliver either direct current (DC) or alternating current (AC). The main system components are the PV panel, battery, and charge controller; in addition, an inverter is used in systems that deliver AC electricity. (PDF 67Kb)

Solar panels charge the battery, and the charge controller insures proper charging of the battery. The battery provides DC voltage to the inverter, and the inverter converts the DC voltage to normal AC voltage.

A charge controller is needed in charging deep cycle lead acid batteries used in Solar PV System. Charge controller prevents the batteries from being overcharge by solar panel and may prevent against overvoltage, which can reduce battery performance or lifespan, and may pose a safety risk.

It may also prevent completely draining ('deep discharging') a battery, or perform controlled discharges, depending on the battery technology, reverse current flow at night, and to protect battery life.

For reverse polarity protection there are two commonly-used techniques; shunt and series diodes. In the shunt technique the fuse blows if the input is reverse-connected, as the diode is forward biased. This will prevent damage to the DC/DC converter but means that the fuse will need to be replaced. In this configuration the diode must be sized so that it will not fail before the fuse ruptures.

Diodes are semiconductor devices that allow current to flow in only one direction. The two uses of diodes in PV system electrical design are blocking diodes and bypass diodes. (PDF 201Kb)

Blocking diodes prevent power from going back into the panel from the battery at night. Blocking diodes are not necessary if a charge controller is being used, and are usually fitted as standard on smaller flexible modules.

No single component in a photovoltaic systems is more affected by the size and usage of the load than storage batteries. A charge controller ensures that the battery is not overcharged or deep-discharged, to provide as long a battery lifetime as possible.

Loads directly influence the performance of the entire photovoltaic system. Oversize or extra loads can cause a system to fail if the loads require more power than the modules can generate or than the battery can store.

A system for delivering power to a battery and to a load includes a power source that supplies energy to the battery and the load. The battery can be charged by the power source and used to supply energy or power to the load when the power source is unable to provide sufficient energy and power to the load. The system reduces injection of DC current into the load and, as a result, extends the operation life of the load, particularly if the load is an AC lighting or lamp system. Click this link to view more information about system and battery charge control for PV-powered AC lighting systems. (PDF 312Kb)

Load voltage limits need to be evaluated to determine whether the system will need some form of DC/DC converter or controller (regulator) between the load and battery to protect the load from over or under voltage due to the voltage range of battery. (PDF 157Kb)

A well designed PV system uses a charge controller. If a charge controller is not included in the system, oversized loads or excessive use can drain the batteries charge to the point where they are damaged and must be replaced. If a controller does not stop overcharging, the batteries can be damaged during times of low or no load usage or long periods of full sun. (PDF 260Kb)

The basic functions of a controller are quite simple. Charge Controllers block reverse current and prevent battery overcharge. Some controllers also prevent battery over-discharge, protect from electrical overload, and/or display battery status and the flow of power.

Sustainable/renewable energy sources such as wind turbines and hydro-generators produce uncontrolled electrical energy. Proper battery charging requires the charging source to be controlled.

Controller is for battery charging only. Controller for wind turbines can only directly connect to battery. You should never connect controller directly to any other devices such as inverters.

Power from the wind turbine is delivered through the product to the battery system. The controller monitors the battery/system voltage and supplies power for load consumption and battery charging. Click to view wind and solar hybrid charge controller 12v and 24v models. (PDF 213Kb)

A charge controller can maintain healthy battery voltage by either short circuiting the solar panel, disconnecting the solar panel from the battery or by diverting the excess electricity to a load such as an air heater, water heater or other electrical load. Click to view this 48Vdc 3kW charge controller controls battery charging such that batteries receive the correct charge and are not over or under charged. (PDF 562Kb)

One of the earliest tasks for the engineer who is designing a power system is to estimate the normal operating plant load. There are no ‘hard and fast’ rules for estimating loads, and various basic questions need to be answered at the beginning of a project. Estimation of Plant Electrical Load - Handbook of Electrical Engineering. (PDF 3.83MB)

PV modules and panels intended to be connected to electrical loads, controllers, or to static inverters that convert the dc power the modules or panels generate to other types of power compatible with the intended loads are investigated using UL 1703. Click to view alternative energy equipment code compliance requirement under UL 1703 and UL 1741 for Controllers use in Independent Power Systems. (PDF 1.39MB)

How to Size a Solar Charge Controllers

Your solar charge controller is an item well worth investing in and researching as you customize your solar panel electric system.

Make sure you choose an option that is scalable and appropriate for your power load and make sure that you have sufficient battery storage space for the solar panels you have chosen to install.

Solar charge controllers are rated and sized by the solar panel array current and system voltage. Most common are 12, 24, and 48-volt controllers. Amperage ratings normally run from 1 amp to 60 amps, voltages from 6-60 volts. (PDF 20Kb)

A PV array that does not perform as rated will not be compensated for by an extremely efficient charge controller or storage device. The charge controller efficiency can be estimated by the ratio of energy measured going out of the charge controller to the energy measured going in.

Energy losses are due to voltage drops in the charge controller and the energy consumption of the charge controller itself. Charge controller self-consumption is rated at less than 5mA.

How well the dc-energy available from the array is utilized by the system depends strongly on the remaining components in the system. Figure 3 shows a schematic for a typical stand-alone PV system indicating energy flow and energy losses.

The procedure measures battery capacity, determines appropriate set-points for charging, and based on daily intervals quantifies dc-energy available from the array, charge-controller efficiency, battery efficiency, inverter efficiency, overall system efficiency, days of autonomy, and ac-energy available by month.

Stand-alone systems have additional dc-energy losses and system design constraints associated with charge-controller efficiency (utilization of dc-energy available from the array), battery capacity, battery charge and discharge efficiency, and design (sizing) tradeoffs in selecting a suitable ratio between dc-energy available from the array and the anticipated ac-energy requirement. (PDF 449Kb)

The annual dc-energy produced by a photovoltaic module is influenced by a number of interactive factors. some related to the module itself and others related to the site environmental characteristics.

In poorly designed systems, combinations of these factors can quickly result in the inability of the system to power the intended load, constituting a 'system failure.'

Energy is lost during charging when reactions other than reversal of sulfation occur,

• At beginning of charge cycle, coulomb efficiency is near 100%
• Near end of charge cycle, electrolysis of water reduces coulomb efficiency. Can improve this efficiency by reducing charge rate (taper charging)
• Typical net coulomb efficiency: 90%
• Approximate voltage efficiency: (2V)/(2.3V) = 87%

Energy efficiency = (87%)(90%) = 78% - Click this link to download Battery-Powered Systems: Efficiency, Control, Economics. (PDF 710Kb)

Most modern charge controllers have an operating efficiency of at least 0.95 at their rated output. More energy, and thus higher efficiency, can be extracted from a photovoltaic system if the photovoltaic (solar) panel is operating at its maximum power point. Theory, Algorithms and Applications for Solar Panel MPP Tracking. (PDF 1.14MB)

For a particular operating condition shown in Figure. 5, the control of maximum power point tracking normally regulates either the voltage or current to a certain value that represents the local maximum power point. However, these conditions are time variant with the change of Insolation and temperature.

It is very important to follow the correct connection and disconnection sequences with system components. This is particularly true with batteries, charge controllers, and inverters.

Some charge controllers are sensitive to the connect and disconnect sequence and some wind machines need constant loads or they will be damaged. These requirements dictate that our switches must be placed very carefully. Failure to follow the manufacturer’s sequence can destroy components or create a personal hazard. (PDF 338Kb)

Make sure the voltage windows of the charge controller and the batteries are compatible. Confirm that the inverter, if used, is wired directly to the batteries, and not to the charge controller.

An array design with both lower voltage and a higher power rating would reduce energy loss in charging the batteries and also increase the inverter efficiency. Incorporation of a charge controller with an array maximum-power-point-tracking (MPPT) capability would further improve the system efficiency, and minimize the need for an array redesign. (PDF 2.99MB)

Battery Voltage - Charge controllers come in various sizes (amperages) and voltages. To choose the correct controller you would need to know your system's battery voltage (12, 24, and 48 etc).

A photovoltaic system should include a meter showing battery voltage. Readouts should be on only when a reading is being done. Battery voltage meter should be on every system using batteries, to display the voltage of the battery bank. (PDF 373Kb)

Amperage - The common unit of measure for a battery’s electrical storage capacity, obtained by integrating the discharge current in amperes over a specific time period. An ampere-hour is equal to the transfer of one-ampere over one-hour, equal to 3600 coulombs of charge. For example, a battery which delivers 5-amps for 20-hours is said to have delivered 100 ampere-hours.

Please note this is the amperage between the charge controller and the battery and not the input amperage of the solar panel. Generally charge controller should be size at least 25% larger than what is required. This allows the charge controller to operate cool and can also increase the lifetime of the unit.

Options - Many charge controllers contain different options. Be sure to check the specification sheet of your controller before making a purchase. It should give a good idea of the options available for the specific charge controller. (1.37MB)

Most PV systems require a charge controller. However, very tiny systems do not. As a general rule you need a charge controller if your solar modules are making more than 2 watts per 50 amp hours of battery (at the same voltage).

For example: if you have a 12 volt, 120 amp hour battery, any module 5 watts or less will not require a charge controller. (PDF 29Kb)

• The formula is (120 amp hours divided by 50 amp hours) X (2 watts) = 4.8 watts.
• If your solar module is larger than 5 watts - you need a charge controller.

Electrical Formulas - Ohms Law - Amperes = Volts/Ohms or Ohms = Volts/Amperes or Volts = Amperes x Ohms (PDF 90kb)

Click to download this 12 Volt 30 Amp Digital Solar Charge Controller that is design to work with all kinds of 12 Volt solar panels. (PDF 491Kb)

Although PV systems can be used without charge controllers, it needs to be stated that in planning the long-term operation of a stand-alone PV system, overcharge and deep discharge of the battery must be avoided.

The charge controller unit is the link between the PV array, the battery and the load. It prevents both overcharging and deep discharging of the battery. Fig. 6 is the detailed block schematic of an intelligent charge controller unit (ICCU) of the proposed PV supply systems.

Basic Electricity Terms - Electric Wiring and Electricity Basic (PDF 2.07MB)

• Ampere (Amp, A) – Basic unit of electric current, like the flow of water in a pipe. Link to online electric current conversion
• Volt (V) – Basic unit of electric voltage (potential), like the pressure of water in a pipe.
• Watt (W) – Basic unit of electric power.
  1 Volt X 1 Amp = 1 Watt
• Watt-Hour – Basic unit of electric energy.
  1 Watt for 1 hour = 1 Watt-hour (Wh)
  100 Watts for 10 hours = 1000 watt-hour = 1 kilowatt-hour (kWh)
• Power (Watts) = Voltage (Volts) x Current (Amps)
  Power = 14.2V x 7A = 99 Watts
• Wire size = Pipe size - Link to Wire Calculator
• Ohms = Friction losses due to length + diameter of pipe - Link to Ohm's Law Calculator

Do not connect a solar array in excess of 99 Watts to this charge controller, as it will damage the unit. The controllers should be chosen to meet the maximum power and current output of the source, and minimize energy losses. Click this link to view Sunforce 7 Amp Solar Charge Controller. (PDF 289Kb)

Photovoltaic Modules will be “live” upon exposure to light. There will be a voltage present on the output terminals. This voltage will vary according to the type of the photovoltaic module. The array will generate voltages substantially higher than the system nominal voltage, thereby resulting in a shock hazard.

Basically, electrical hazards can be categorized into three types. The first and most commonly recognized hazard is electrical shock. The second type of hazard is electrical burns and the third is the effects of blasts which include pressure impact, flying particles from vaporized conductors and first breath considerations. Click this link to view ELECTRICAL SAFETY HAZARDS AWARENESS GUIDE (PDF 2.96MB)

Carefully read the installation instructions before attempting to electrically connect any part of the power system. Most charge controllers are permanently damaged if the battery polarity is reversed when it is connected to the controller. The charge current monitoring circuit of the intelligent charge controller unit helps to avoid losses in the collection of PV energy. Click this link to view more information about Solar PV Power Array Charge Controller Wiring. (PDF 42.3Kb)

Energy and the Environment

Environmental requirements

All charge controllers are sensitive electronic devices that must be protected from corrosion. Charge controllers must be used in a clean, dry, reasonably cool environment. The cooler the battery is kept the longer its life. The solar charger should be lightning protected for severe lightning environments. This document present suggestions for maintenance programs that will help to keep corrosion control measures operating at maximum effectiveness. (PDF 8.91MB)

Charge controllers are sensitive to RFI and EMI, so they must be isolated from sources of electronic “noise.” Inexpensive inverters are a common source of noise in photovoltaic systems. Click to download Safety Guidelines for the Application, Installation, and Maintenance of Solid-State Control. (PDF 450Kb)

Although this is not under the heading of environmental conditions, the use of properly sized wire and appropriate terminal connectors will help total system performance, including that of the charge controller. (PDF 8.13MB)

Environmental condition

The charge controller should be clean. It should be securely mounted in a dry, protected area. It should not be subjected to unreasonable temperature extremes.

Most controllers are able to withstand a temperature range of 0-37.5°C. Beyond this range their calibration will drift and they may be damaged.

Several temperature sensing techniques are currently in widespread usage. The most common of these are RTDs, thermocouples, thermistors, and sensor ICs. Temperature sensors provide inputs to control systems. (PDF 796Kb)

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Make sure the charge controller is not installed in an unventilated space with the batteries. The hydrogen gas generated by charging can be ignited by sparks from the controller relay, even during normal operation.

To maintain a physical quantity, such as pressure, flow or temperature at a desired level during a technical process, this quantity can be controlled either by means of open loop control or closed loop control. Click this link to download Terminology and Symbols in Control Engineering. (PDF 326Kb)

Photovoltaic (PV) Solar Electrical System Power that exceeds what you can economically store must be either 'dumped', 'blocked', or 'diverted'. A charge controller usually blocks excess power input. But some models allow the use of a 'grid intertie', a 'dump load' or a 'divert load'. If you burn natural gas or propane (LP) to heat water, heat your home, or cook a meal, a charge controller can automatically switch on electrical versions of these loads for you. This allows you to have enough generating power to keep up with electrical demand even on cloudy or windless days. And it gives you the option to power loads that would normally burn fuels. (PDF 940Kb)

Mounting the Solar charger controller

The Solar charger controller is designed for indoor mounting. Care should be taken in selecting a location and when mounting the enclosure. Avoid mounting it in direct sunlight to prevent heating of the enclosure. The enclosure should be mounted vertically on a wall. In outdoor installations, the Solar charge controller must be installed in a rainproof enclosure to eliminate exposure to rain, mist or water-spray. Click this link to view 40 amp 12/24V Solar charger controller MPPT photovoltaic (PV) battery charge controller. (PDF 673Kb)

Charge Controller Operation

The charge controller protects the battery from overcharging by the solar module. The controller is connected in the circuit between the solar module and battery. Connect wires from the (-) and (+) terminals of the solar module to the corresponding terminals of the charge controller. Connect wires from the (-) and (+) terminals of the battery to the corresponding terminals of the charge controller. (PDF 359Kb)

Charge controllers, in particular, may need to be connected in the correct sequence to prevent damage. Always fuse the connections at the battery for safety.

The purpose of the Charge Controller for the 24-Volt PV array system installation in Figure 8 is to provide a proper charge current to the batteries and to prevent the batteries from becoming overcharged.

This overcharging situation would occur any time the batteries become fully charged and there is still PV energy available. The manual covers the wiring, installation, and use of the Charge Controllers.

Any stand-alone PV system that has unpredictable loads, user intervention, optimized or undersized battery storage, or any characteristics that would allow excessive battery overcharging or over discharging requires a charge controller and/or low-voltage load disconnect. Click this link to view evaluation of the batteries and charge controllers in small stand-alone photovoltaic system. (PDF 481Kb)

To decide on the charge controller connection for an application you need to decide how the controller is to be used from the following options (PDF 211Kb)

1. Battery Charging Only – No load connection
2. All system loads connected to the controller
3. Some system load connected to the controller

The following photovoltaic charge controller is a versatile, industrial quality charge controller for the efficient use of photovoltaic energy and the protection of expensive batteries. It is available for 12, 24, 36, and 48 volt negative ground systems with models for 30 amps of charge current (optional 50 amps available). This Photovoltaic Power Control (PPC) consists of a series-relay battery charge controller in a wall mount enclosure with low voltage load disconnect, a load circuit breaker, array fuse, metering and system status lights. Click this link to download Photovoltaic Power Control battery charge controller installation and operation manual. (PDF 114Kb)

The following 48V Charge Controller (Figure 9) is a sophisticated controller using advanced PWM charging technology. It is designed for use with all types of PV panel/system and Seal or Wet Type Lead Acid Batteries.

SAFETY PRECAUTIONS

1. DO NOT exceed the voltage or current ratings of the charge controller.
2. DO NOT SHORT CIRCUIT the solar array while connected to the charge controller. This will DAMAGE the charge controller.
3. DO NOT SHORT CIRCUIT the load terminal (or WHITE wire to any BLACK wire) when battery or PV panel is connected. This will DAMAGE the charge controller.
4. The negative terminal of the system conductor should be properly grounded for effective lightning protection.

Control Circuit: A circuit that carries the electric signals directing the performance of a controller, and which does not carry the main power circuit. (PDF 1.59MB)

A control circuit often is limited to 15 A. Click this link to view instructions for 10A Solar Charge Controller. (PDF 198Kb)

DC Circuit: The interconnection of various electric elements in a prescribed manner comprises as an electric circuit in order to perform a desired function. The electric elements include controlled and uncontrolled source of energy, resistors, capacitors, inductors, etc.

Analysis of electric circuits refers to computations required to determine the unknown quantities such as voltage, current and power associated with one or more elements in the circuit. To contribute to the solution of engineering problems one must acquire the basic knowledge of electric circuit analysis and laws. Introduction of Electric Circuit. (654Kb)

Circuit Breaker: A device designed to open and close a circuit by non-automatic means, and to open the circuit automatically on a pre-determined over current, without damage to itself when properly applied within its rating. Circuit breaker’s primary function is to protect wire. Click this link to download Guide to Power Protection. (PDF 1.08MB)

Circuit protection is an important part of any electrical installation. The wide variety of products and product ratings can make proper component selection a complex task. Compliance with the applicable local and national codes is necessary to ensure product safety.

Understanding the differences between branch circuit protection, supplementary protection, and self-protected products helps to ensure their proper use. Circuit protection includes protection from equipment overload conditions, under voltage and overvoltage conditions, ground faults, and short-circuits. (PDF 1.86MB)

Connecting Multiple Panels

1. Using the included bare wire connector adaptor, join positive wires to positive wires and negative wires to negative wires to ensure voltage. Make sure all connections are tight using wire nut connectors. Insulating materials may prove helpful.
2. For anything above 15W, use a Solar Controller Charger to prevent battery overcharge.
3. Solar Charge Controller should be placed within 5ft of the battery, and in a dry, well-ventilated area.

Solar Panel installation instruction - General Testing Protocol (For Solar Charge Controller) (PDF 925Kb)

Always test outdoors under optimal sunlight conditions.

1. Testing Solar Panels for Voltage. Connect Voltmeter to each individual panel separately and observe open voltage. Open Voltage can range from 16 Volts to 24 Volts. Once all panels are tested for voltage, proceed to step B.
2. Test Connection to Charge Controller for Voltage. Reconnect Solar Panels, can connect to Charge Controller as per Charge Controller instructions. Measure open circuit voltage at the battery side of the Charge Controller. Open circuit should read 5-10% lower than without Charge Controller, resulting in measurement between 15V and 23.5V.
3. Connect Charge Controller to Battery. First, disconnect solar panels and connect Charge Controller to battery. Always connect Charge Controller to battery first and remove last. Observe polarity – positive to positive and negative to negative.
4. Reconnect Solar Panels to Charge Controller. If battery voltage is 14.2 or higher, the GREEN light should be on. If battery voltage is between 13 and 14.2, the YELLOW light should be on. If battery voltage is 13 or lower, the Yellow light should be on. If all testing results with voltages within the above indicated ranges, solar system is in acceptable range. If voltage reading indicates lower ranges, repeat above connections and retest.

The charge controller must monitor the state-of-charge of the batteries and reduce current to the battery as necessary until the battery is fully charged. Charge controllers are designed to operate in various ways sometimes pulsing current to the battery or simply opening the circuit between the PV array and the batteries. (PDF 3.16MB)

Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding and significant PV array system performance gains could be obtained by the use of maximum power point tracking charge controllers. Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. Increased PV array performance leads to smaller arrays and reduced system cost. (PDF 159Kb)

In characterizing a charge controller, it is important to know the accuracy of its set points as well as its efficiency in delivering power between system components. The set points can normally be checked with a power supply and a voltmeter. Accurate set points in charge controllers are important to prevent damage to system components.

Circuit measurement is used to monitor the operation of an electrical or electronic device, or to determine the reason a device is not operating properly. Since electricity is invisible, you must use some sort of device to determine what is happening in an electrical circuit. (PDF 861Kb)

Various devices called test equipment are used to measure electrical quantities. The most common types of test equipment use some kind of metering device. Ultimately, your diagnosis of electrical system problems will come down to using a voltmeter, ammeter or ohmmeter to pinpoint the exact location of the problem. There are two types of each meter - analog and digital. (PDF 44.7Kb)

• Analog meters use a needle and calibrated scale to indicate values.
• Digital meters display those values on a digital display

The three types of meters - voltmeters, ammeters and ohmmeters - connect to the circuits or devices in different ways. A multimeter can measure all three depending on setting. (PDF 553kb)

The following document provide general information on theory, checks, tests, adjustments, and records which will serve as a simple and convenient ready-reference guide for testing and servicing meters in the field. Click this link to view watt-hour meter maintenance and testing. (PDF 1.59MB)

The charge controller regulates the voltage output of the panel to what the battery needs at the time. (PDF 587Kb)

• This voltage typically varies between about 11.5 to 14.5, depending on the state of charge of the battery, the type of battery, in what mode the controller is in, and temperature (Higher Temperatures mean Lower Voltage).
• Most 12 V batteries need around 14 to 14.5 volts to get fully charged.

A charge controller is an electronic circuit which monitors the charge in and out of the battery and, based on a set of voltage thresholds (termed set points), regulates current flow in order to limit overcharge and over-discharge.

Two basic methods, called 'interrupting' charging and 'constant voltage' (CV) charging, are used. Interrupting charging is also known as 'on/off' charging and constant voltage charging is also known as 'constant potential' charging.

The voltage regulation (VR) set point is one of the key specifications for charge controllers. The voltage regulation set point is defined as the maximum voltage that the charge controller allows the battery to reach, limiting the overcharge of the battery.

Once the controller senses that the battery reaches the voltage regulation set point, the controller will either discontinue battery charging or begin to regulate (limit) the amount of current delivered to the battery.

In some controller designs, dual regulation set points may be used. Figure 13 shows the basic controller set points on a simplified diagram plotting battery voltage versus time for a charge and discharge cycle.

Dual set point controllers have a more complex control action than ON/OFF controllers. The controllers are similar during bulk charging.

Both apply full solar panel output to the battery until an upper battery voltage is reached. But unlike ON/OFF controllers, this voltage is a set point and not a switching threshold (Figure 14).

When the set point is reached, dual set point controllers hold this voltage for a fixed period by cycling the solar panel on and off. This allows time for the battery to finish charging.

The voltage regulation (VR) and the array reconnect voltage (ARV) refer to the voltage set points at which the array is connected and disconnected from the battery.

The low voltage load disconnect (LVD) and load reconnect voltage (LRV) refer to the voltage set points at which the load is disconnected from the battery to prevent over discharge.

Charge Controller Configurations

Two basic methods exist for controlling or regulating the charging of a battery from a PV module or array - shunt and series regulation. While both of these methods are effectively used, each method may incorporate a number of variations that alter charge controllers basic performance and applicability. (PDF 120Kb)

Simple designs interrupt or disconnect the array from the battery at regulation, while more sophisticated designs limit the current to the battery in a linear manner that maintains a high battery voltage.

The algorithm or control strategy of a battery charge controller determines the effectiveness of battery charging and PV array utilization, and ultimately the ability of the system to meet the electrical load demands. Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems. (PDF 593Kb)

A PV generator can contain several arrays. Each array is composed of several modules, while each module is composed of several solar cells.

The battery bank stores energy when the power supplied by the PV modules exceeds load demand and releases it backs when the PV supply is insufficient. The load for a stand-alone PV system can be of many types, both DC (television, lighting) and AC (electric motors, heaters, etc.). The power conditioning system provides an interface between all the elements of the PV system, giving protection and control. The most frequently encountered elements of the power conditioning system are blocking diodes, charge controllers and DC-AC converters.

Most importantly, the charge controller algorithm defines the way in which PV array power is applied to the battery in the stand-alone system. The following document proposed a new maximum power point tracking algorithm for photovoltaic arrays system. The algorithm detects the maximum power point of the PV. The computed maximum power is used as a reference value (set point) of the control system. (PDF 399Kb)

In general, interrupting on-off type controllers require a higher regulation set point to bring batteries up to full state of charge than controllers that limit the array current in a gradual manner.

Charge controllers designed for hybrid PV systems must manage multiple current sources simultaneously. The following document presents a novel strategy, optimized by genetic algorithms, to control stand-alone hybrid renewable electrical systems with hydrogen storage. (PDF 299Kb)

The optimized hybrid system can be composed of renewable sources (wind, PV and hydro), batteries, fuel cell, AC generator, and electrolyzer.

If the renewable sources produce more energy than the one required by the loads, the spare energy can be used either to charge the batteries or to produce H₂ in the electrolyzer. The control strategy optimizes how the spare energy is used.

Charge controllers can have different algorithms for regulating the current and voltage from a PV array. Sample charge controller profiles have been compiled from tests on PV lighting systems at the Florida Solar Energy Center (FSEC). The measured parameters include solar irradiance, battery voltage (V_bat), battery current (I_bat), array voltage (V_array), and array current (I_array). (PDF 262Kb)

A new control algorithm with improved regulation is presented for a switching dc buck converter. The controller is realized with hardware description language (HDL) and can be implemented in any process. The controller uses four decision levels, combines pulse frequency modulation (PFM), pulse width modulation (PWM), and uses dithering for improved regulation. (PDF 2.23MB)

The controller is prototyped on a field programmable gate array (FPGA) and experimental results show good performance over input and load disturbances. This document present the development of a novel real-time PV simulator, based on Field Programmable Gate Arrays (FPGAs) (PDF 665Kb)

Importantly, the controller does not require high resolution analog-to-digital conversion for signal processing, and also does not require fast digital clocking. The controller has significant potential to be widely used in industrial applications where cost and design time are of great concern. Click this link to view A Low-Cost Digital Controller for a Switching DC Converter With Improved Voltage Regulation. (PDF 203Kb)

The following report presents a fundamentals and application overview of battery technology and charge control strategies commonly used in stand-alone photovoltaic (PV) systems. Requirements for battery charge control in stand-alone PV systems are covered, including details about the various switching designs, algorithms, and operational characteristics. Specific recommendations on voltage regulation set point for different charge control algorithms and battery types are listed to aid system designers. (PDF 226Kb)

At present, many of the cheaper charge controllers use a shunt type of switching principle: the module short-circuited after the HVD set point is reached, as shown in figure 19. The main reason for this is the general thought that less electronics is required than in the series type controllers. Furthermore, it is known that there is less voltage drop (=energy loss) while charging. The Schottkey is necessary, because it prevents the battery from discharging via the module during the night. Click this link to view sample 12 volt 14 amps shunt type PWM charge controller. (PDF 34.3kb)

Series & Shunt Linear Controllers (Regulators)

Linear controllers utilize a series voltage divider principle to obtain the required output voltage. The term 'linear' is used because the voltage drop across the control device is varied continuously to dissipate unused power. Linear and Switching Voltage Regulator Operation. (PDF 149Kb)

Current flowing through two resistors in series will create a voltage drop across each resistor that is proportional to the resistor’s value. The sum of the two resistor voltage drops equals the applied input voltage (V_in).

Series and the Shunt Controllers are two basic Linear Regulator configurations used in integrated circuits that utilize the voltage divider principle. For control purposes, one resistor element value is variable while the other is fixed.

The series controllers has the variable resistor element (R_series) in series with the load current (I_load) and thus the name series controller. As the load resistance changes, I_load changes, causing the output voltage (V_o) to change. By monitoring (sampling) V_O and modulating (varying) R_series, the output voltage can be maintained at a constant (regulated) value.

The shunt controllers has the variable resistor element (R_shunt) in parallel with I_load (shunting the I_load ) thus the name shunt controller. Again, as the load resistance changes, I_load changes, causing V_o to change. By monitoring (sampling) V_o and modulating (varying) R_shunt, the output voltage can be maintained at a constant (regulated) value.

Linear controllers are easier to design and generally less expensive but waste more power because the power elements (transistors) operate in their active or linear mode. Click this link to view block diagram of linear voltage controller introduction. (PDF 1.82MB)

Switching controllers are more complex and more difficult to design but are more power efficient because their power elements (transistors) are switched ON and OFF alternately and consume very little power.

Figure 18 show a standard linear regulator. The Zener diode and potentiometer set the reference voltage V_ref.

A Zener diode is a PN junction that has been specially made to have a reverse voltage breakdown at a specific voltage. Its characteristics are otherwise very similar to common diodes. In breakdown the voltage across the Zener diode is close to constant over a wide range of currents thus making it useful as a shunt voltage regulator. (PDF 51.3Kb)

This Linear & Switching Voltage Controller Handbook describes ON Semiconductor’s voltage regulator products and provides information on applying these products. Basic Linear controller theory and switching controller topologies have been included along with practical design examples. Other relevant topics include trade–offs of Linear versus switching controllers, series pass elements for Linear controllers, switching controller component design considerations, heat sinking, construction and layout, power supply supervision and protection, and reliability. (PDF 1.09MB)

Shunt-Interrupting Controllers (On/Off)

A shunt controller is needed to protect components in the system from over voltage and regulates the charging of a battery by interrupting the PV current by short-circuiting the array. A blocking diode is required in series between the battery and the switching element to keep the battery from being shortened when the array is shunted. This controller typically requires a large heat sink to dissipate power. (PDF 182Kb)

Shunt type controllers are usually designed for applications with PV currents less than 20 amps due to high current switching limitations.

A shunt-interrupting charge controller suspends charging current to a battery system by short-circuiting the array through a shunt element inside the charge controller.

This moves the array’s operating point on the I-V curve to very near the short-circuit condition, limiting the power output. When the battery voltage falls, the controller reconnects the array to resume charging.

This ON/OFF cycling may occur over a period of several minutes or a few seconds, depending on the charge rate and battery state-of-charge.

Charge controllers must be installed in a dry location which is out of direct sunlight. During normal phases of operation, shunt-type controllers build up a significant amount of heat, which must be removed by adequate ventilation.

Shunt-Linear Controllers

Shunt-Linear algorithm maintains the battery at a fixed voltage by using a control element in parallel with the battery. The simplest shunt controller is a resistor to limit input current and a Zener diode to regulate the voltage across the load. (PDF 581Kb)

This control element turns on when the VR set point is reached, shunting power away from the battery in a linear method (not on/off), maintaining a constant voltage at the battery.

Once a battery becomes nearly fully charged, a shunt-linear controller maintains the battery at near a fixed voltage by gradually shunting the array through a semiconductor regulation element.

There is generally more heat dissipation in a shunt-linear controllers than in shunt-interrupting types. Shunt-linear controllers are popular for use with sealed VRLA batteries.

This algorithm applies power to the battery in a preferential method for these types of batteries, by limiting the current while holding the battery at the regulation voltage.

Series-Interrupting Controllers

A series-interrupting charge controller algorithm terminates battery charging at the VR set point by open-circuiting the PV array. As the battery reaches full state-of-charge, a switching element inside the controller opens, moving the array’s operating point on the I-V curve to the open-circuit condition and limiting the power output. (PDF 0.97MB)

When the battery voltage falls, the controller closes the series switching element to reconnect the array and resume charging the battery.

Similar to shunt-interrupting charge controllers, the rate of the ON/OFF cycling is dependent on charge rate and battery state-of-charge.

A blocking diode may or may not be required, depending on the switching element design. Some series controllers may divert the array power to a secondary load.

Series-interrupting, 2-step, constant current: Similar to the series interrupting however, when the VR set point is reached, instead of totally interrupting the array current, a limited constant current remains applied to the battery. It is expected that this will allow for an increased charging effectiveness of the basic series interrupting algorithm.

Pwm Solar Charge Controller Pdf

Series-interrupting, 2-step, dual set point: Similar to the series interrupting, however there are two VR set points. A higher set point is only used during the initial charge each morning. The controller then regulates at a lower VR set point for subsequent cycles for the rest of the day. This allows a daily gassing period or equalization of the battery.

Series-Linear Controllers

In a series-linear, constant-voltage controller design, the controller maintains the battery voltage at the voltage regulation set point. The series regulation element acts like a variable resistor, controlled by the controller battery voltage sensing circuit of the controller.

The series element dissipates the balance of the power that is not used to charge the battery, and generally requires heat sinking. The current is inherently controlled by the series element and the voltage drop across it. Designing With Low-Dropout Voltage Linear Regulators. (PDF 1.43MB)

Regardless of the type of feedback control, almost all DC-DC converters and linear regulators sense the inductor current for over-current (over-load) protection. Current-Sensing Techniques for DC-DC Converters. (PDF 65.8Kb)

In terms of performance, a linear regulated supply has very precise regulating properties and responds quickly to variations of the line and load. Hence, its line and load regulation and transient recovery time are superior to supplies using other regulation techniques. Click this link to view Linear Power Supply Operation. (PDF 91.8Kb)

Series-linear, constant-voltage controllers can be used on all types of batteries. Because they apply power to the battery in a controlled manner, they are generally more effective at fully charging batteries than on-off type controllers. These designs, along with PWM types are recommended over on-off type controllers for sealed VRLA type batteries.

Series-interrupting, Pulse-Width Modulated (PWM)

Series-interrupting, Pulse-Width Modulated algorithm uses a series element which is switched on/off at a variable frequency with a variable duty cycle to maintain the battery at the voltage regulation set point. (PDF 340Kb)

Mppt Solar Charge Controller

Similar to the series-linear, constant-voltage algorithm in function, power dissipation within the controller is considerably lower in the series-interrupting PWM algorithm.

Photovoltaic cell converts solar energy directly into electricity. A PWM Charge controller circuit is designed and developed to sense the voltage of the solar panel. Figure 20 shows the Flow Chart of the PWM Charge Control program.

According to the flow chart a program is written in assembly language and loaded the program in to the microcontroller. The PWM design allows greater control over exactly how a battery approaches full charge and generates less heat.

PWM type controllers can be used with all battery type, however the controlled manner in which power is applied to the battery makes them preferential for use with sealed VRLA types batteries over on-off type controls. Click to download Evaluation of VRLA Batteries and PWM Controls. (PDF 777Kb)

Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage battery charging by switching the solar system controller’s power devices. When in PWM regulation, the current from the solar array tapers according to the battery’s condition and recharging needs. (PDF 313Kb)

When a battery voltage reaches the regulation set point, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

The design of charging control system requires a good understanding of the system dynamic behavior of the lead acid battery. To regulate the charging current and fix the battery voltage after the overcharge point V_o, a metal-oxide-semiconductor-field-effect transistor (MOSFET) is used to switch the charging current (on/off) from solar PV via a PWM signal. The mean charging current after the overcharge point can be controlled by regulating the duty-cycle D_uty in order to fix the battery voltage at the overcharge point. (PDF 886Kb)

Series-interrupting, Sub-Array Switching

Series-interrupting is typically used in systems with more than 6 PV modules or current greater than 20 Amperes. The array is sub-divided into sections, switched individually (3-5 sub-arrays).

As the battery becomes charged the sub-arrays are switched off in a sequence of voltage steps to reduce current and maintain battery voltage and not overcharge the system. This minimizes the need for high current switching gear and reduces problems associated with high current and voltage drops in the system. Click this link for more information about maintenance and operation of stand-alone photovoltaic charge controllers systems. (PDF 13.6MB)

For larger arrays, the commonly available charge controllers used for small stand-alone PV applications may alone not be rated to handle the higher array currents.

Charge regulation for arrays larger than 500 to 1000 peak watts is generally accomplished by grouping the array into parallel sub-groups or sub-arrays, and by regulating each of the sub-arrays independently.

The common operational mode for sub-array switching controllers is that each sub-array regulator is set to a slightly different cut-off voltage. As the battery voltage rises, first one sub-array disconnects at the lowest regulation voltage, and then the next is disconnected, gradually reducing the charge current into the battery as the voltage increases to the highest regulation voltage setpoint.

No Controller: Self-Regulating PV Module

In small photovoltaic powered systems, such as house-number illumination or power supplies for measurement systems, a charge controller can be avoided in special cases. Some PV modules have a special circuitry which keeps the battery from overcharging. This means that no controller is needed when the self-regulating PV module is properly matched to battery storage capacity. (PDF 510Kb)

• Usually these are modules with only 32 solar cells or less for 12V systems, to match the required charging voltage to the battery;
• With self-regulation the battery capacity may need to be increased to prevent frequent overcharging;
• With VRLA batteries, the charge rate should not exceed about 10 ampere per 100 amp-hours capacity (C/10 charge rate);
• In hot climates the use of VRLA batteries with self-regulated modules should be avoided.
• The major advantage of using self-regulated PV modules is maximum simplicity. In practice the battery is generally not working in the best conditions and its life will be shortened, so that more frequent battery replacement will be needed.

To make this kind of system operate reliably, the load profile as well as the Insolation and temperature at the place of operation must be known accurately. Because cheap and reliable charge controllers are available today in the market, such “self-regulating” systems should be avoided.

Over discharging protection

Solar Charge Controller is a component of a photovoltaic system that controls the flow of current to and from the battery to protect it from overcharge and over discharge.

The charge controller may also indicate the system operational status. Click this link to view various outline and functions of the PV charge controller overcharge and over discharge protection. (PDF 2.47MB)

Applying a charging current to an already full battery produces gases in the battery that build up pressure and can damage the battery.

Also, a mismatch in the voltage output from the solar array and the charging requirements of the battery can reduce the charging efficiency - requiring more time to reach full charge.

To ensure optimum charging of lead acid batteries, the charge voltages should be adjusted to compensate for battery temperature. Battery temperature is affected by ambient temperature and by the battery's own internal resistance in conjunction with the amount of current passing through it. (PDF 186Kb)

Generally, lower temperatures require higher charge voltages to ensure complete charging, while higher temperatures require lower charge voltages to prevent overcharging.

Charging methods are dependent on battery applications, and the applications are roughly classified into main power application and stand-by/back-up power applications. (PDF 71Kb)

The charge controller regulates the voltage and current to charge from the panel to the battery, stops the charging when the battery is fully charged, and cuts off the power from the battery to the loads when the battery is depleted below a safe level.

It also detects when the battery is full and switches to a trickle charge mode to maintain float voltage for a total of 15% losses (factor of 0.85), which maintains the battery's full state without causing damage.

In trickle charge, the battery is continuously charged at a very low rate. Because the terminal voltage of batteries is dependent upon the state-of-charge, the type of battery and the temperature, charge controllers often incorporate temperature compensation using sensors located at battery. Methods of charging the valve regulated lead acid battery. (PDF 48.7Kb)

The temperature sensor should be attached to the batteries according to the manufacturer’s instructions. It may be necessary to adjust the temperature compensation rate in the charge controller for the type of battery so the controller will employ the proper temperature compensated voltage. Click this link to view Blue Solar charge controller 10A at 12V or 24V - Low cost PWM controller with internal temperature sensor and stage battery charging (bulk, absorption, float). (PDF 1.44MB)

Every controller has a maximum input voltage rating. The array must have a temperature compensated V_oc less than the controller’s maximum input voltage rating. During PWM or MPPT switching cycles, the controller input is exposed to the array open circuit voltage. Using an array with a temperature compensated V_oc greater than the controller input rating will damage the regulator. (PDF 213Kb)

Self-discharge of NiMH and NiCd batteries is estimated based on an internal timer and temperature sensor. Compensations for battery temperature and rate of charge or discharge are applied to the charge, discharge, and self-discharge calculations to provide available charge information across a wide range of operating conditions. Click to view Gas Gauge IC with External Charge Control. (PDF 488Kb)

Renewable Energy applications that depend on battery power as part of the system operation must be at maximum performance at all times.

To ensure this high rate of performance, the charging system must be set properly. A battery that is undercharged or overcharged will affect the performance of the entire system.

Commonly, lead-acid batteries are used because of their wide availability in many sizes, low cost and well understood performance characteristics. Click to view the renewable energy charging parameter for setting charge controllers to properly charge lead acid battery. (PDF 104Kb)

Generally, battery manufacture refers to four distinct charging stages within a battery charging cycle, namely, bulk, absorption, equalization and float as shown in Figure 23.

A typical good charge profile:

1. Bulk charging at maximum power - Terminate when battery is 80% charged (when a voltage set point is reached)
2. Charging at constant voltage - The current will decrease. This reduces gassing and improves charge efficiency “Absorption” or “taper charging”
3. Trickle charging / float mode - Equalizes the charge on series-connected cells without significant gassing. Prevents discharging of battery by leakage currents. Occasional pulsing helps reverse sulfation of electrodes

However, not all battery chargers have the four stages. The following proposed charger controller uses the PWM charging technique in order to deal with the gassing voltage problem at the equalization stage presented by Tamer T.N. Khatib, Azah Mohamed, Nowshad Amin of National University of Malaysia. (PDF 246Kb)

The first charging stage is the bulk stage, where the charger delivers all available PV array current to the batteries. During the bulk charging stage, the battery terminal voltage increases as the battery charges.

Once the voltage of the battery reaches the BULK voltage setting, the controller goes to the next stage. Current is sent to batteries at the maximum safe rate they will accept until voltage rises to near (80-90%) full charge level.

Voltages at this stage typically range from 10.5 volts to 15 volts. There is no 'correct' voltage for bulk charging, but there may be limits on the maximum current that the battery and/or wiring can take.

Many battery chargers are designed to be used as ‘bulk’ charge sources and are constant voltage output. This means you don’t really gain anything by connecting it through the regulator, as opposed to direct connection to the battery. Please read the following notes if considering connecting a battery charger to the SOLAR terminal. (PDF 51.1Kb)

During the absorption stage, the charge controller continues to deliver its maximum available current output until the battery voltage reaches the absorption voltage setting.

The charge controller then operates in constant voltage mode, holding the battery voltage at the absorption voltage setting for a pre-set time limit. During this time, current falls gradually as the battery capacity is reached.

At the end of the absorption period, the battery terminal voltage is reduced to the float voltage setting, which is lower than the bulk voltage setting. Voltages at this stage are typically around 14.2 to 15.5 volts.

During the floating stage, the batteries continue to charge at a reduced current level. If the load requires current, excess PV array current will flow to the load while the batteries provide any additional current requirements.

After batteries reach full charge, charging voltage is reduced to a lower level (typically 13.6V) to reduce gassing and prolong battery life.

This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. Different types of PV systems batteries require different bulk and float voltage settings. (PDF 1.49MB)

If a PV powered system will have loads that are switched off or not operating for long periods of time, then thecharge controller should include float voltage operation to prevent excessive overcharging of the batteries. The following paper reports on some results to date from a program of study to better understand the influence of factors which influence the long-term float behavior of lead-acid batteries. (PDF 87Kb)

An additional charging stage provided in many charge controllers is the equalization stage. During the equalization stage, the charging voltage is raised above the bulk-voltage level for a period of time after the battery is fully charged.

When this is done, all cells are brought up to the highest state-of-charge that they can accept (the battery is equalized), the cell voltages continue to rise, and more of the electrolyte electrolyzes into gases. This is typically called gassing.

The gassing process produces a boiling-type action in the electrolyte, which helps to scrub the battery plates and destratifies the electrolyte. Some charge controllers automatically incorporate an equalization charge at intervals of approximately 30 days.

In order to protect the battery from gasification, the switch opens the charging circuit when the voltage in the battery reaches its high voltage disconnect (HVD) or cut off set point.

The leading cause of premature battery failure is improper charging and poor battery maintenance. To avoid battery sulfation, a lead acid battery must be equalized or given a controlled overcharge on a regular preventive basis. (PDF 72.5Kb)

The following PV battery testing using vented (flooded) thin plate deep-cycle lead/antimony batteries and PV charge controllers purchased using the charge controller manufacturer’s recommended regulation voltage resulted in significant battery capacity losses, in most cases due to under charging.

Figure 24 summarizes the results from this work and plots the charge controller array reconnect voltage (Vrr) vs. percent of initial battery capacity. When a constant voltage or pulse width modulated (PWM) charge controller is used, the Vrr and Vr are the same or nearly the same value.

With some controllers, it is also possible to manually control the equalization stage. Note that equalization is not recommended for many sealed, or valve-regulated lead-acid (VRLA), battery types or for nickel-based batteries. Always consult the battery manufacturer before attempting to equalize batteries. Click this link to download charge control options for valve regulated lead acid batteries. (PDF 358Kb)

For some types of batteries, equalization at voltages higher than the bulk voltage setting is prohibited and can damage the battery. With these batteries, special precautions should be taken to ensure that the equalization functions of the controller are disabled.

In some systems, the PV output current may exceed the input current rating of a single charge controller. The PV output circuit must then be split into two or more circuits, each of which has an output current that is within the input current limits of a charge controller.

Simply connecting a solar panel to a battery or a load can further decrease the available efficiency. Solar power systems benefit from an MPPT device in order to extract the maximum available power from the solar panels in the system.

The MPPT is a charge controller that compensates for the changing Voltage vs. Current characteristic of a solar cell. By monitoring the voltage and current output of the solar panel, the MPPT tracks the always-changing operating point in order to draw the maximum amount of power available during all periods of the day. (PDF 7.9MB)

Normally, the output current of the charge controller will be less than or equal to (≤) the input current. The exception to this rule is a maximum power point tracking (MPPT) charge controller, for which the output current may exceed the input current.

If a MPPT charge controller is used, it is important to consult the manufacturer’s specifications for the device to determine the maximum charge controller output current. (PDF 115Kb)

Two or more charge controllers can then be connected with their outputs in parallel to the batteries. If multiple charge controllers are used, then multiple combiners will be needed and it is advisable to use a separate surge suppressor at the output of each combiner box.

Also, each charge controller will need to have separate disconnects at its input and output. Look at a recent PV system schematic, and you’ll see a component between the PV array and the charge controller—it’s called a combiner box. (PDF 1.8MB)

A combiner box is similar to a junction box (J-box). The #12 or #10 (3 or 5 mm2) conductors used to wire the PV array come into this box.

This combiner box are connected via a power distribution block to the larger conductors that run to the charge controller and batteries. The conduit between the junction box (JB) and the source-circuit combiner box contains four current-carrying conductors.

A combiner box also permits the combining of multiple photovoltaic source circuits (sub arrays, panels, or series strings), and provides a method of removing a module or sub array/panel from the array without interrupting the rest of the array.

Larger PV systems often use independent charge controllers for each array source circuit. Separate charge controllers are usually recommended for charging independent battery banks.

Sections 690-4(c), 690-14(b), and 690-18 of the NEC address this situation and make the combiner box an essential component of a code-compliant system. Click this link to download Solar PV Building and Inspecting Code and Standard. (PDF 642Kb)

A solar array may be one panel or many in series, and may range from a single 12 volt panel up to multi-panel high voltage array for grid-tied systems.

Grid-tied systems can go as high as 1000 VDC, while battery systems are typically 12, 24, or 48 V. Higher voltage systems (over 48 V) have different NEC code requirements than those for low voltage battery systems. Click this link to view solar combiner box designed solution for higher voltage circuits used in grid-tied applications. (PDF 1.27MB)

Charge controllers have maximum input voltage and current ratings specified by the manufacturer and the listing agency. It is required that the PV array is not capable of generating voltage or current that will exceed the charge controller input voltage and current limits. All combiners, controllers, and Inverters listed to UL1741. Inspecting Photovoltaic systems for code-compliance. (PDF 9.46MB)

The charge controller rated continuous current (sometimes specified as input current, sometimes as output current) must be at least 125% of the PV array short-circuit output current, and the charge controller maximum input voltage must be higher than the maximum system voltage, as determined by NEC 690.7. (PDF 8.51MB)

Solar electricity can be either disconnected or diverted. Wind turbines and water turbines must remain connected to the batteries at all times so their electricity must be diverted or dumped in order to protect the batteries and helps to prevent over-spin damage.

Where batteries are located in a separate room or at some distance (typically, five feet or more) from the inverter and charge controllers, a disconnect is required at the battery location, and this disconnect is usually merged with an over current protective device.

NEC 690.15 - Charge controller input and output disconnects are required for maintenance on PV electrical systems with batteries disconnects. (PDF 701Kb)

Diversion charge controllers are often used in stand-alone systems to take advantage of excess generation that would normally be wasted once the batteries are fully charged. Diversion charge controllers typically use a resistive load, such as a water heating coil in a water heater, to consume the excess power from the array.

The attractive feature of the diversion charge controller is that it uses an alternate load for the array output rather than wasting the array output by shorting or opening the array. Using a shunt controller to dump load when the batteries are full is the only realistic way to regulate DC hydro and wind generators. (PDF 46.2Kb)

Article 690.72 of the NEC includes a requirement that the power rating of the diversion load be 150% of the power rating of the array. This provision ensures that the load is sufficiently oversized to handle the entire output of the PV array. Diversionary charge controllers regulate charging current by diverting excess power to an auxiliary load when batteries are fully charged.

2002 NEC & Beyond - 690.72 (B) Diversion Charge Controller. (PDF 88.7Kb)

Subparagraph (1) requires that any system using a diversion charge controller have a second independent method of charge control. With diversion controllers, if the diversion circuit fails, the batteries may be overcharged, and can pose hazards (explosions, smoke, and fire). This requirement would apply to both AC and DC diversion controllers.

1) Sole Means of Regulating Charging. A photovoltaic power system employing a diversion charge controller as the sole means of regulating the charging of a battery shall be equipped with a second independent means to prevent overcharging of the battery.

2) Circuits with Direct Current Diversion Charge Controller and Diversion Load. Circuits containing a dc diversion charge controller and a dc diversion load shall comply with the following:

• The current rating of the diversion load shall be rated at least 150% of the current rating of the diversion charge controller.
• The conductor ampacity and the rating of the over current device for this circuit shall be at least 150% of the maximum current rating of the diversion charge controller.

The basic operating philosophy of a diversion controller is quite simple. Monitor the battery voltage, and if it should rise to a predetermined level, connect a “Dummy Load” of sufficient size, to the battery or energy source to prevent the battery voltage from increasing any further. This is a very simple, yet very effective way of preventing battery overcharging. Click this link to view Coleman Air Diversion Controller Model C40. (PDF 465Kb)

The following Wind Turbines Charge Controller Type 0801 uses dynamic electronic shunt control. All the available energy is shared between the consumer load, battery charging and dumping. The load consumption is always supplied, followed by the battery requirement. When the battery is fully charged, the regulator “Floats” the battery while continuing to supply the load. Any excess energy is converted to heat and dumped. (PDF 935Kb)

Charge controllers intended for solar panels work by monitoring the battery voltage, and once it reaches full charge, the controller simply shorts the solar panel leads together. This doesn't harm the solar panels, but it does waste whatever power they're generating. The energy ends up heating the transistors in the controller.

This type of controller is not ideal for a wind generator, since shorting the output of the genny while it's spinning at high speed will generate a huge current spike, possibly destroying the controller and perhaps even the generator in the process. Click this link to download experiments with a small wind generators and charge controllers. (PDF 1.53MB)

This 16-bit microprocessor powered Solar/Wind Hybrid Charge Controller delivers electricity generated by both a wind turbine and solar modules into batteries. The controller has over-charge protection, low-voltage protection, pole-confusion protection and automatic dump-load function. The controller adopts the constant voltage charging mode - PWM, and it is reliable and safe with a highly efficient, long service life. (PDF 104Kb)

Many charge controller problems result from either oversized loads or loads which required high surge of current. Load related problems range from blown fuses to low battery voltages and improperly operating loads.

If the temperature of the system battery varies more than 5°C (9°F) during the year, temperature compensated charging should be considered. Variations in battery temperature can affect charging, battery capacity, and battery life. The greater the range of battery temperatures, the greater the impact on the battery. The following manual describes solar battery charging, and specific load control or diversion charge control instructions. (PDF 353Kb)

Many controllers will also sense when loads have taken too much electricity from batteries and will stop the flow until sufficient charge is restored to the batteries. This last feature [commonly referred to as the Low Voltage Disconnect (LVD), ed.] can greatly extend the battery’s lifetime. Charge controller - Primary Balance of PV System Equipment. (PDF 305Kb)

Low Voltage Disconnect Controls

Charge controllers play a key role in properly managing battery state-of-charge in small PV systems. In addition to providing overcharge protection for the battery, most charge controllers provide load control functions to prevent battery over-discharge. Recommendation for maximizing battery life in photovoltaic system - A review of lessons learned. (PDF 76.9Kb)

Although a wide variation exists in the types, set points and features of commonly available battery charge controllers, there are generally optimal (or preferred) control characteristics for specific types of batteries and system configurations. The purpose of the low voltage disconnect (LVD) in the system in Figure 29 is to prevent the batteries from becoming over discharged. This might occur if the array does not provide sufficient daily charge to meet the daily load requirements. (PDF 544Kb)

If more than 80% of full charge is removed from deep-discharge lead-acid batteries and the batteries are left in that state for several weeks or months, the batteries may sustain permanent damage.

If voltage from the batteries gets too low, some inverters will shut off until the voltage rises back up. Like a charge controller’s low voltage disconnect, this protects the batteries from discharging too deeply. It also protects the loads from operating at too low a voltage.

The LVD monitors the battery state-of-charge (SOC) and disconnects the loads from the batteries if the battery SOC decreases below a certain, sometimes programmed level. It will reconnect the loads only when the battery voltage has substantially recovered due to the accumulation of some charge. A typical LVD reset point is 13 volts (26 V on a 24 V system). (PDF 1.82MB)

Some smaller charge controllers incorporate the overcharge and over discharge functions within a single controller. Generally, for larger dc load currents, separate charge controllers must be used for each function. If two charge controllers are used, it is possible that they may be the same model but simply installed with different settings for different purposes.

On larger inverter-based systems, there are programmable set-points for the Low Voltage Disconnect and reconnect points. Generally, the factory defaults are fairly low, allowing the batteries to be discharged significantly below 50%. As an example, the default LVD values on some of the more popular inverters is 44V on a 48V system. The installer should consider raising the voltage level of these default LVD settings to protect the battery.

An alarm system that notifies the operator when the batteries are getting close to the LVD cut-off value is a good addition to the battery system. This lets the operator know when the battery bank needs attention before the LVD takes over. These alarm systems can be set up fairly easily, utilizing the auxiliary contacts that are programmable on most inverters and controllers.

Low voltage disconnects must be capable of handling the maximum load current as well as the maximum system voltage. Under normal operation, these charge controllers will have the battery voltage as their input voltage; but, if the batteries are disconnected, then the charge controller input voltage may rise to the maximum PV system voltage defined in NEC 690.7(A). (PDF 1.83MB)

It is also possible to employ multiple LVD controllers on the load side of the batteries. In fact, it is possible to group loads in order of importance and then have different disconnect settings on the charge controllers, depending upon the priority of the loads connected to the output of the charge controller.

In most larger systems with ac loads, inverter/chargers are used as power management devices. The low voltage disconnect function is often programmable and is a function of the inverter/charger. In these cases, the solar charge controllers are utilized to manage the incoming power from the solar array and provide the optimum charging current to the batteries.

In systems with batteries, great care has to be given to the programmable settings of the low voltage disconnect. These factory defaults are generally set at a fairly low level, and it is often desirable to raise the settings to provide greater protection for the batteries. Click this link to download Solar Charge Controller with Programmable Night-Light Function User Manual. (PDF 981Kb)

If you purchase a charge controller with built-in LVD, make sure that it has enough capacity to handle your DC loads. For example, let's say you need a charge controller to handle less than 10 amps of charge current, but you have a DC water pressurizing pump that draws 20 amps (for short periods) plus a 6 amp DC lighting load.

A charge controller with a 30 amp LVD would be appropriate. Don't buy a 10 amp charge controller that has only a 10 or 15 amp load capacity! http://www.wholesalesolar.com/Information-SolarFolder/chargecontroller-article.html

Linear Current Boosters and Maximum Power Tracking Charge Controllers

The pump controller is an electronic linear current booster that acts as an interface between the PV array and the water pump. It operates very much like an automatic transmission, providing optimum power to the pump despite wide variations in energy production from the sun.

Pwm Solar Charge Controller Design

It is particularly helpful in starting the pump in low light conditions. A charge controller is installed when batteries are used in the solar powered pumping system to keep the batteries from overcharging or becoming completely discharged.

Pwm Solar Controllers

A PV array produces nearly full operating voltage at very low irradiance levels (75 W/m2). In a water pumping system without batteries, it may be several hours after sunrise before the PV array produces sufficient current to start the pump. GUIDE TO SOLAR POWERED WATER PUMPING SYSTEMS. (PDF 1.46MB)

A linear current booster (LCB) is a device that converts the high input voltage and low input current into a lower voltage and a higher current so the pump can start at a sunlight intensity level of 75 W/m2 rather than 375 W/m2 (for examples) and can continue operating until the intensity level drops again to 75 W/m2.

Furthermore, at intermediate intensity levels, some LCBs may continue to track array maximum power. So, for example, at 375 W/m2, rather than operate at point B′ in Figure 30, as it would without the LCB, it will operate at point D′, which corresponds to the maximum available power at this intensity level.

As the sunlight intensity increases toward maximum, the point on the pump operating curve moves closer to the array maximum power point; thus, when sunlight is near maximum intensity, the LCB improvement in pump performance is minimal. The greatest improvement in pump performance occurs at low and intermediate sunlight intensity levels.

Manufacturers of LCBs claim that a pump with a LCB controller will pump at least 20% more water in a day than a pump without the LCB controller. What this means is that a LCB will deliver at least 20% more energy to the load as opposed to a system without the LCB controller. The exact savings depends on the efficiency of the LCB and on the operational I-V curve of the pump motor. Linear Current Booster Operation (PDF 35.2Kb)

The principle of operation of the LCB is also the principle of operation of the electronic MPPT. Maximum power tracking is sometimes used in charge controllers to ensure that a maximum amount of available array power is used to charge batteries. Both types of systems can allow the PV array to operate at maximum power while supplying that power to the pump, inverter, or batteries at a lower voltage and higher current. CURRENT BOOSTING - MAXIMUM POWER POINT SOLAR CHARGE CONTROL. (PDF 212Kb)

A linear current booster (LCB) efficiently couples a photovoltaic solar array to a DC motor. Under low sun, it promotes early start and reduces stalling. In full sun, it provides over speed and overload protection. It also provides remote on/off switching by float switch or thermostat. Dankoff LCB™ is a variable voltage converter with maximum power point tracking (MPPT) to draw the most available power from a photovoltaic (PV) array. Most positive displacement solar pumps require a current boosting controller for a non-battery system. It also helps centrifugal pumps and fans under low-light conditions. Dankoff LCB™ Solar Pump and Fan Controllers. (PDF 206Kb)

Additional Charge Controllers Resources.

OutBack PV MX60 Maximum Power Point Tracking (MPPT) charge controller enables your PV system to achieve its highest possible performance. Rated for up to 60 amps of DC output current, MX60 can be used with battery systems from 12 to 60 vdc with PV open circuit voltages as high as 140 Vdc. The MX60’s setpoints are fully adjustable to allow use with virtually any battery type, chemistry and charging profile. (PDF 1.19MB)

Tycon Power Systems unique POE/Solar charge controllers have dual inputs to charge batteries from a POE source and also a secondary source like solar panels in order to provide redundancy and insure 100% uptime for critical applications. TP-SCPOE : POE /Solar Charge Controllers. (PDF 276Kb)

Through the use of MPPT technology, the BlueSolar MPPT series can increase charge current by up to 30% compared to conventional PWM controllers. BlueSolar’s sophisticated three stage charge control system can be configured to optimize charge parameters to precise battery requirements. The unit is fully protected against voltage transients, over temperature, over current, reverse battery and reverse PV connections. (PDF 402Kb)

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This publication is an annex to PV GAP Recommended Specification PVRS 6, Charge controllers for photovoltaic (PV) stand-alone systems, with a nominal system voltage below 50V. This document describes the test items, technical requirements, testing methods, sampling plan, test equipment and quality assurance for certification of PV charge controllers used in solar home systems. It covers the charge controllers for stand-alone PV systems with maximum PV array size of 500 peak Watts (Wp). (PDF 339Kb)