Choosing the appropriate size/capacity of solar charge controller will go a long way to ensure the efficiency of your solar power system.
Most customers complain about the poor performance of their solar power system. On close observation we usually find out that while they made the right investment in solar panels and also went for good batteries and very reliable inverter, they did not go for the appropriate size/capacity solar charge controller for their solar power system installation.
Choosing the right size/capacity of solar charge controller is very important. There are so many sizes/capacity of charge controller in the market and so you need to know a few things before selecting one for your use.
Let us consider another method.
Take the number of panels x watts to get the total watts of the solar array. You then divide it by the voltage of your battery bank to get amps, add 25% to allow for cold temperatures and as always, round up.
Example: 2 units of 140 watt solar panels in series = 280 watts / 12 VDC battery bank + 25% = 29.18 amps. You would choose a 30 amp, 12 VDC charger in this example.
Another example: 4 units of 250 watt solar panels = 1,000 watts / 24V battery bank = 41.7 amps + 25% = 52.09 rounded up = 60 amp controller.
Please do not forget that solar charge controllers are rated and sized by the solar panel array current and system voltage.
These examples are simple calculations for small systems. If you have a larger system with muliple strings you are considering, you should consult a good solar technician for help.