Solar Charge Controller for Charging Batteries with Solar Power

solar charge controllerSolar charge controller regulate and controls the current from solar panels to the battery. Life of a deep cycle battery depends on how it charged and discharged. It works as solar battery charger, protect the battery from overcharging and deep discharging . A charge controller works like kidney in our body, as kidney eliminate impurities from blood, similarly charge controller rectify the input voltage/current from solar panels.

With a spacial realy switch arrangement you can convert existing inverter to a solar inverter.

Importance of solar charge controller

Solar panel voltage depends on the intensity of solar radiation so, It increases as sun goes up and reaches to maximum at noon and decreases towards evening.
Suppose you have a 12-volt solar panel, A 12 voltage solar can produce maximum 17-18.5 volts in peak hours. 18 volts, is enough to damage a 12 volt battery if supplied constantly.

1. Ideal voltage to charge a 12 volt lead acid battery is 14.5 volts. If battery charged above that voltage, It may increase the battery internal temperature and damage the battery.
Charge controller provide a stable voltage to battery and stops the charging if a battery is the fully charge and starts the charging when required.

2. Now let’s talk about direct load appliances which operate on 12 volt DC. Most DC appliance needs a constant voltage to operate, but solar panel never generate a constant voltage, as a result it can damage the connected appliance. Charge controller provides the constant voltage and current to the appliance and keep direct load safe.

3. At night solar panel voltage decreases to zero and becomes less than the battery voltage. Keep in mind that voltage always flows from higher potential to the lower potential. Here, battery voltage drains to solar panels and discharge the battery even not in use. Charge controller prevents the reverse current flow from batteries to solar panels and ensures voltage must flow from solar panel to battery only.

4. Beside the basic functions charge controller with LCD display and networking interface, used for monitoring the output of solar panels. LCD display stores data and can be used to compare the performance of solar panels in each month.

It ensures to charge a battery with constant voltage and current to increase the battery life and keeping the DC appliance safe.

Type of charge controllers

1. PWM charge controller
2. MPPT charge controller

PWM Charge controller does the basic job such as prevent overcharging, prevent deep discharge. Charge controller with PWM technology relatively inexpensive than the MPPT. PWM controllers relatively inexpensive than the MPPT charge controller.

MPPT Charge controller does the basic tasks and designed to receive maximum power from solar panels. It can generate up to 30% more power with the same setup.

Let’s understand the difference by an example:
Suppose you have 100W solar panel connected to a 12-volt battery having Vmax=18.2 V and Imax=5.5amps.

Case 1 -PWM charge controller output
Usually, a 12-volt battery charged at 14.5 volts.
Maximum output : 14.5×5.5 = 79.5W
Wastage of power: 100-79.5 =20.5W

Case 2 – MPPT charge controller output
MPPT charge controller transforms the extra voltage to the current, which makes it more efficient than the PWM charge controller.
Charging voltage: 14.5 volts
Charging current: 6.5 amps
Maximum output : 14.5×6.8 = 98.6 W
Wastage of power: 100-98.6 = 1.4W

Size of charge controller

The capacity of charge controller measured in watts and it must be higher than the sum of solar panels. We recommend to choose a charge controller with multiple voltage option. Depending on battery bank it can be 12 volt, 24 volt and 48 volt. Choose a controller which can operate on 12 volt as well as 24 volt.


MPPT controller 30% more efficient than the PWM charge controllers. We recommend having a MPPT charge controller if your budget allows. We suggest buying it from an MNRE approved manufacturer.

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