Building a Solar Powered circuit to charge a battery and run a small air pump

Thread Starter


Joined Mar 6, 2020
Hello, I am new here and hoping I can get some direction regarding a prototype design I have been working on for my Biology & Ecology classes. It is a small, single plant, hydroponic system in which I hope to have run off of a NiMH AAA rechargeable battery while being trickle charged by the solar cell.

Here is my setup
- (1) 6v Solar Cell - Runs at 4.5v - 7.6mA (under the full spectrum LEDs)
- (1) AAA 1.2v * 850mAh rechargable battery and battery holder
- (1) Koge air pump runs at 1.2v - 323mA (start up current 690mA)
- (1) 1N4148 Blocking Diode

Here is the schematic I am running off of:

My issue is I don't know if this is going to trickle charge the battery. I also am not sure if this circuit is balanced appropriately so as to not cause a fire or burn out. Any help would be appreciated! This has been a boondoggle to me for the last 2 weeks!

Also, if your suggestions are to purchase better equipment, please let me know what, where or SKU numbers so I can go that direction. Thanks a TON!


Joined Jan 23, 2018
At 7.6 mA all that you can accomplish is a trickle charge, about 45 minutes of charging for every minute of pump running. That may be a challenge and a problem. Keep in mind that amp-minutes in must be a bit more that amp-minutes out.