Frequently Asked Question
When do I need a charge controller and why?
The safest way to figure out if you need a charge
controller is to take
Battery Amp Hour Capacity and divide this by the Solar Panel max. power
amp rating. If the quotient is above 200, you don't need a controller.
If the number is less than 200 than you need a controller.
For example if you have a 100 amp hour battery and a 10
you take 100 and divide it by .6 (600mA) and you get 166.6. Since this
is less than 200 you need a charge controller. If you have a five-watt
panel in the above example you take 100 divided by .3 (300mA) and you
up with 333.3. Since this is larger than 200 you do not need a charge
However you still need a blocking diode, to prevent the battery from
to the panel at night. So as a general rule of thumb you don't need a
controller unless you have more than five watts of solar for every
hours of battery capacity.