I have a solar water heater which uses a 12v march 809br dc brush motor powered by a pv panel. My problem is that sometimes even with full sun the motor won't start pumping. If I tap the pump housing with a hammer it will start and continue running until a cloud goes buy sometimes it will restart on its own sometimes not. I am guessing that it is a friction problem with the impeller. Is there something Capacitor? simple circuit that I can add to give the motor a boost?

 

Most such problems can be solved by using a battery for power and the solar panels for recharging.

 

Most such problems can be solved by using a battery for power and the solar panels for recharging.

 

Don't want it to run full time only when sun is shining otherwise no solar gain. Problem is restarting after it stops when sun returns.

 

You can run it whenever you want. The battery is simply the proper power source that can supply the amperage needed to get the motor started. If you only want to run it when the sun is bright use a photodetector circuit to activate a relay.

 

Google Solar maximiser, this is what solar pump systems use to assist pumps to keep going with int clouds. This is a picture of one I repaired for a farmer. With out it in the system the out put of the pump was a lot lower.