What is a Solar Charge Controller?

Solar charge controller required in nearly all renewable energy systems that employ batteries, it regulates the power going from the solar panels to the batteries. Overcharging the batteries will considerably reduce the battery life and at the worst damage the batteries to the point that they’re unusable.

The most basic charge controller merely monitors the battery voltage and opens the circuit, stopping the charging, once the battery voltage rises to a precise level. Older charge controllers used a mechanical relay to open or shut the circuit, stopping or beginning power going to the batteries.

The main function of solar charge controllers is to prevent reverse-current flow. At night, when solar panels are not generating any electricity, electricity can actually flow backward from the batteries through the solar panels, draining the batteries. You don’t want to waste all that power stored in the battery during the full day.The charge controller can sense the energy coming from the solar panels, in case of no energy from the solar panels it opens the circuit, disconnecting the solar panels from the batteries and stopping the reverse current flow.

Types of Solar Charge controller

The two sorts of charge controllers most commonly utilized in today’s alternative energy systems are pulse width modulation (PWM) and maximum power point tracking (MPPT).


 More trendy charge controllers use Pulse Width Modulation (PWM) to slowly lower the amount of power applied to the batteries because of the batteries nearer and closer to completely charged. this kind of controller permits the batteries to be charged with less stress on the battery, extending battery life. It also can keep batteries in an exceedingly absolutely charged state (called “float”) indefinitely. PWM is a lot complicated, however, doesn’t have any mechanical connections to interrupt.


The most recent and best sort of solar charge controller is termed maximum power point tracking or MPPT. MPPT controllers are primarily ready to convert excess voltage into an electrical phenomenon. This has benefits in completely different areas.Solar panels deliver more voltage than is required to charge the batteries. By, in essence, converting the excess voltage into amps, the charge voltage can be kept at an optimal level while the time required to fully charge the batteries is reduced. This allows the solar power system to operate optimally at all times.

Another area that is enhanced by an MPPT charge controller is power loss. Lower voltage in the wires running from the solar panels to the charge controller results in higher energy loss in the wires than higher voltage.

PLoss=I2V (higher current leads to higher losses).

With a PWM charge controller used with 12v batteries, the voltage from the solar panel to the charge controller typically has to be 18V. Using an MPPT controller allows much higher voltages in the cables from the panels to the solar charge controller.

The MPPT controller then converts the excess voltage into additional amps. By running higher voltage in the cables from the solar panels to the charge controller, power loss in the cable is reduced significantly. 

The difference in Output :


PV array sized in Watts (based on the Controller Max. Charging Current x Battery Voltage)

PWM Charge Controller MPPT Charge Controller
Array Voltage PV array & battery voltages should match PV array voltage can be higher than battery voltage
Battery Voltage Operates at battery voltage so it performs well in warm temperatures and when the battery is almost full Operates above battery voltage so it is can provide “boost” in cold temperatures and when the battery is low.
System Size Typically recommended for use in smaller systems where MPPT benefits are minimal ≈ 150W – 200W or higher to take advantage of MPPT benefits
Off-Grid or Grid-Tie Must use off-grid PV modules typically with Vmp ≈ 17 to 18 Volts for every 12V nominal battery voltage Enables the use of lower cost/grid-tie PV Modules helping bring down the overall PV system cost
Array Sizing Method PV array sized in Amps (based on currently produced when PV array is operating at battery voltage) PV array sized in Watts (based on the Controller Max. Charging Current x Battery Voltage)

Factors affecting the performance of solar power plant.

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