PWM or MPPT: choosing a controller for a small solar system
Check panel input, battery compatibility and regulated output before selecting a controller.
Input limits come first
Compare the panel open-circuit voltage, including expected cold-weather variation, with the controller maximum PV input. Also confirm short-circuit current limits and maximum power for the selected battery voltage.
Battery compatibility
The controller must have a charge profile suitable for the battery chemistry. A 12V label does not determine chemistry or charging limits. Confirm the battery management system and the permitted charge voltage and current.
PWM and MPPT roles
PWM controllers directly switch the panel connection to the battery. MPPT controllers track the panel’s power operating point and convert voltage and current. Actual gains vary by panel, temperature, battery voltage and controller performance; do not assume a catalogue efficiency claim applies to the whole system.
Device output and monitoring
Check whether the load requires regulated 12V, 24V or another supply. Confirm output current, low-voltage cutoff and any remote monitoring interface. Request a wiring diagram for the complete kit before purchase.
