>>>MPPT controllers

To charge batteries from the larger 60-cell and 72-cell solar panels an MPPT type charge controller is needed. MPPT charge controllers run the solar panel at the best Voltage to get the most power out of them (generally around 30 Volt for a 60-cell panel) and convert that down to the battery Voltage to best charge the batteries. PWM controllers do not change the Voltage between panel and battery, where MPPT controllers do. MPPT controllers also actively control their output current, meaning that you generally can oversize the amount of solar PV on the input for the size of the controller (something PWM controllers cannot handle!).