PWM charge controller
With a PWM charge controller, it is important that you try to match the nominal voltage of a solar panel with the battery voltage of the system. Please use the reference table below:
| # cells in series | Nominal Voltage | Open Circuit Voltage | Maximum power point voltage | Typical applications |
|---|---|---|---|---|
| 36 | 12 V | 22 V | 18 V | 12 V battery systems |
| 60 | 20 V | 38V | 31 V | Rooftop modules |
| 72 | 24 V | 44 V | 36 V | 24 V battery systems |
Reference: https://learn.libre.solar/system/solar_panel.html#panels-and-arrays
The maximum current of the charge controller refers to the load output and charging current. Therefore the maximum power output of the panels you can use with our 20A variants are:
18V x 20A = 360W
36V x 20A = 720W
In theory, there is no lower limit to the size of panels you use but it would not be recommended to use anything smaller than 20W.
MPPT charge controller
With an MPPT controller, you are able to use higher voltage solar panels compared to the battery bank you are using. For example, you could use a 20V panel with a 12V battery and you will be able to use all of the available power.
To learn more about this, here is a good resource: https://www.altestore.com/store/info/solar-charge-controller/