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Charge Controllers

Updated: Jan 10, 2020

What Is A Charge Controller?

A solar charge controller or charge regulator, as implied in the name, is a voltage and/or current regulator which serves to keep the batteries in a solar panel-deep cycle inverter system from overcharging. A charge controller may be a stand-alone device which has to be bought and installed separately or it may be a control circuitry integrated within a battery pack, battery-powered device or charger.

Stand-alone charge controllers or solar regulators.

Stand-alone charge controllers are bought and installed as separate devices, often in conjunction with the solar panels, for uses such as RV, boat, and off-the-grid home battery storage systems.

Integrated charge controller circuitry

A charge regulator may be encapsulated in a single microchip, an integrated circuit, an integrated circuit (IC) usually called a charge controller IC or charge control IC. It may also consist of several components integrated within the circuit. Charge controller IC are used for rechargeable electronic devices such as cell phones, laptop computers, portable audio players, and UPS.

Solar charge controllers are available in different specifications according to features, costs and sizes. The range of charge controllers are from 4.5A and up to 60 to 80A.

A solar charge controller is needed in virtually all solar power systems that utilize batteries.


  • It regulates the voltage and current coming from the solar panels going to the battery. Most 12V solar panels put out about 16 to 20 volts. Most batteries need about 14V to 14.5V to get fully charged. Therefore if there is no regulation, the batteries will be damaged from overcharging.

  • Since solar panels can only work during the day, a solar charge controller will ensure that the deep cycle batteries are not overcharged during the day, and that the power doesn’t run backwards to the solar panels overnight and drain the batteries. This is called ‘reverse current protection’ or ‘electronic blocking’.

  • Some charge controllers are available with additional capabilities, like lighting and load control, but managing the charge that flows from the solar panels to the batteries is its primary job.

  • Many controllers are configurable, allowing settings for a few hours or all night, or somewhere in between.

  • Some charge controllers have additional features, such as a low voltage disconnect (LVD), a separate circuit which powers down the load when the batteries become overly discharged. Overcharging can ruin some batteries.

  • A series charge controller or series regulator will disable further current from flowing into the batteries when they are fully charged. A shunt or parallel charge controller or shunt regulator will divert excess electricity to an auxiliary or "shunt" load, such as an electric water heater, when the batteries are fully charged.

  • Simple charge controllers stop charging a battery when they exceed a set high voltage level. They re-initiate charging when battery voltage drops back below that level following use.

  • Charge controllers may also monitor battery temperature to prevent overheating.

  • Some charge controller systems have displays that may show voltage of battery bank, state of charge, amps coming in from solar panel, etc.

What are the Types of Solar Charge Controllers?

There are three types of solar controllers.

  • Simple 1 or 2 stage controls

  • PWM (pulse width modulated)

  • Maximum power point tracking (MPPT)

Simple 1 or 2 Controls

This is the most basic solar controller. It has transistors connected in parallel to control the voltage in one or two steps. This controller shorts the solar panel when at a certain voltage.

A PMW solar charge controller.

(PWM) Pulse Width Modulated

This is the traditional industry-standard type charge controller.

A PWM solar charge controller operates by making a direct connection from the solar array to the battery bank. During bulk charging, that is, when there is a continuous connection from the array to the battery bank, the solar panel array output voltage is reduced to the battery voltage. As the battery charges, the voltage of the battery rises, so the voltage output of the solar panel rises as well, using more of the solar power as it charges.

PWM solar controllers can create interference in radios and TV's due to the sharp pulses that they generate.

MPPT (Maximum power point tracking)

The MPPT solar charge controller is the ultimate in solar controllers. Though relatively very expensive and larger in size, they can help users save considerable money on larger systems since they provide 10 to 30% more power to the battery than the PWM and have efficiencies reaching up to 98%.

It operates by measuring the Vmp voltage of the panel, and reducing the PV voltage to the battery voltage.

Most MPPT controllers come with some kind of indicator, either a simple LED, a series of LED's, or digital meters. Many newer and recent ones now have built in computer interfaces for monitoring and control. The simplest usually have only a couple of small LED lamps, which show that you have power and that you are getting some kind of charge. Most of those with meters will show both voltage and the current coming from the panels and the battery voltage. Some also show how much current is being pulled from the LOAD terminals.

Our engineers at SolarKobo will help you choose a charge controller that suits your needs and fits your budget.

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