What is difference between PWM and MPPT Solar Charge Controllers?
A simple comparison between the two most used types of solar charge controllers.
Solar charge controllers are devices that regulate the rate of electric current that has to be added to a solar panel batter, in order to prevent overchanging or overvoltage. Since panels in solar street lights need to be charged, these solar charge controllers are essential for a long-lasting, best-quality installation. But there is no universal solar charge controller and it is important to choose the adequate device for each application.
The two main types of solar charge controllers are the PWM and the MPPT. While PWM is essentially a switch that connects a solar array to the battery, the MPPT is more sophisticated, since it will adjust its input voltage to harvest the maximum power from the solar array and then transform this power to supply the varying voltage requirement of the battery plus load.
To compare them on the technical level, below you find a comparison table, that takes into account six different aspects: the array voltage, the battery voltage, the system size, the off-grid or grid-tie and the array sizing method.
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 current produced when PV array is operating at battery voltage) PV array sized in Watts (based on the Controller Max. Charging Current x Battery Voltage)
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