Maximum Power Point Tracking (MPPT) solar charge controllers are significantly more efficient than the cheaper Pulse Wave Modulation (PWM) solar charge controllers. Please be very careful when buying this type of MPPT charge controller as there are charge controllers on the market which have model numbers such as MPPT T40 which are only PWM charge controllers. See YouTube review videos below. A true MPPT solar charge controller needs a large transformer coil and capacitors inside, it is a bigger heavier unit and will usually takes at least 100V-150V input.

An MPPT solar charge controller in cool conditions can produce 25-30% more battery charging power than a simple PWM controller and you can connect high voltage panels to lower voltage battery banks. By using higher voltage on the panel side will also benefit by less volt drop and can use thinner cables. On large arrays we run everything at 100V – 150V.

Cheaper PWM charge controllers are a good low-cost solution for small systems only. To fully exploit the potential of MPPT charge controllers, the solar panel array voltage should be substantially higher than the battery voltage and is generally recommended for systems of 100-150W and upwards. The MPPT controller enables higher PV system voltages which can then reduce cabelling costs by allowing for smaller cable cross sectional areas. The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45 C), or very high (above 75 C).

To calculate which size controller you need, take the peak solar panel watts and divide by the / battery voltage to give the MPPT rated charge current in Amps, for example 150W/12V = 12.5A, therefore a 20A rated charge controller is recommended.