Charging a battery with solar, while using it

Thread Starter


Joined Jun 28, 2019
Hi all, I'm a bit new to electronics but I want to make a project and need your help.

I want to power a pump using a battery.
The battery need to get recharged every time the solar panel can supply the needed current but in the same time still supply the needed power to the pump.

I suppose I need some kind of a charging regulator board for this?
Also, do I connect the Solar panel in series to the battery and the pump or there are parallel connections needed?

The specifications of all parts are:
Solar panel:
20W, 5V, 1.2A (All rated for max output, after the regulator)
3.5-9V, 1-3W

how would you make this? and what battery would you use?


Joined Sep 7, 2010
So the solar panel outputs 5V when delivering max power , that's about 7 V open circuit (No load) ...

You would not need a very big battery , and no regulator is needed if you have a battery protection circuit ...

The voltages for the panel and the pump don't match very well ... lithium is the best choice for battery and you may get away with 1 cell .... that's a voltage between about 4.2 and 3.6 ... the pump will be a bit under powered , but will work ...

You just need two components ... the battery ...

just one of these is enough ... get a recognised brand panasonic ..6 pounds UK it will hold 10WHrs enough to run the pump 10 hrs (at 4V)

and a protection circuit ..... many different types .... very cheap

this will connect panel with battery and prevent overcharging , and the pump is connected to the battery