I have a solar panel, a battery and a charge controller. I didn't pay for any of it so I thought I would just wire them up and see how it goes.

The battery won't charge. The charge controller has a battery level indicator and it has stayed at middle for over a week. The solar panel doesn't have a high wattage so I wasn't expecting it to charge quickly but I think It would have charged by now. Could somebody tell me if there is anything wrong with the setup?

I believe I need 2x 12V solar panels to give 24V to actually start charging the battery. Is this correct?

All of the parts are definitely working. I also would like to know how long it would take to charge the battery fully with no load. I have worn Google out searching for how to do that but I need it to be put simply and into context. If someone could briefly demonstrate, that would be great. Anyway, the info on the different parts:

Solar Panel

  • 12V
  • 5W


  • 12V
  • 4.5AH

Charge Controller

  • 12/24V (auto)
  • 5A


  • \$\begingroup\$ Related: electronics.stackexchange.com/questions/36273/… \$\endgroup\$
    – jippie
    Commented Aug 17, 2013 at 11:20
  • \$\begingroup\$ Questions: Is your solar panel fully illuminated? Even a small strip of shadow can hurt your power generation. Also, is there anything on the charge controller indicating that it thinks it is delivering power to a load or a battery? I've seen several issues with the cheap blue charge controllers you can buy via online shops: The solar panel wiring was backwards, the order you connect the panel versus battery is important, etc. Can you share the charge controller part number and maybe post a connection diagram? I have charged 12V batteries with a 12V solar system. Depends on controller \$\endgroup\$ Commented Sep 1, 2021 at 22:09

2 Answers 2


You do need more than 12 volts to charge a 12 battery. Also how do you know that your solar panel is producing even 12 volts? Just because that is it's rating doesn't mean it always produces that value. Do you have enough sunlight? Have you measured the output of the panel? Can you provide more information on the charge controller? If you did provide 24 volts to the charge controller, how much voltage will it apply to the battery which is important because 24 volts is probably too much. Your panel is rated at 12 volts and 5 watts. Thus, assuming it is getting sufficient sunlight, its maximum current is 0.42 amperes. At that level, charging a 4.5 AH battery, would take a minimum of almost 11 hours.

  • \$\begingroup\$ Thank you sir for your answer. I know for sure now that the solar panel definitely won't charge the battery since it's only 12V and probably isn't actually producing that much anyway. Could you tell me then if adding another 12v 5w solar panel in series would charge the battery (how ever slow it would be)? \$\endgroup\$ Commented Aug 17, 2013 at 15:41
  • \$\begingroup\$ Adding anther 12v solar panel in series would probably allow for charging the battery assuming the charge controller is designed for this application. \$\endgroup\$
    – Barry
    Commented Aug 18, 2013 at 1:23

Buy a DC-DC step up converter then u can change output voltage from 12V solar panel to lets say 14,5V then it will charge your battery.

  • \$\begingroup\$ I have a "12V solar panel" that is sold for trickle-charging a car battery. It measures 18VDC with no load and measures 114.5V with a 1A load. See, it is rated at "12V". You MUST measure the voltage of your solar panel, with and without a load. \$\endgroup\$
    – Audioguru
    Commented Sep 1, 2021 at 15:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.