0
\$\begingroup\$

I'm pretty new to solar panels and basically, I'm trying to charge a 40V 4Ahr lithium ion lawn mower battery using solar panels. 40V solar panels aren't nearly as common of a size as 12V so I'm thinking maybe I could just wire up a few solar panels in series to stack up the voltage but I'm now unsure of how I should go about that.

Say I did four 12V solar panels in series to get 48V, could I safely charge the 40V battery with that? Is it dangerous to supply more voltage than a battery is rated for? I would have a solar charge controller of course but I'm not sure if that would help with supplying too high of a voltage.

Or maybe I should just do three 12V solar panels to get 36V? Would that harm the battery at all supplying too little voltage?

\$\endgroup\$
2
  • 1
    \$\begingroup\$ Bad idea. You cannot charge your batteries straight from solar panels. You need a charge controller or you will quickly damage your batteries. Larger 60-72 cell solar panels output the higher voltages you seem to need (30-36V) and are really not that hard to find. \$\endgroup\$
    – StarCat
    Commented Apr 27, 2021 at 7:10
  • \$\begingroup\$ @StarCat Yes, I said in the question that I would use a charge controller. Thank you for the input though! \$\endgroup\$
    – LukeyP
    Commented Apr 28, 2021 at 7:38

1 Answer 1

Reset to default
1
\$\begingroup\$

Lithium Ion batteries require precise current and voltage control during charging. You cannot (should not) connect solar panels directly to a Lithium Ion battery for charging. If you do, you are almost certain to seriously damage the battery and possibly start a fire.

Since 40V is not a standard battery voltage for solar charge controllers, you are going to have some difficulty finding a solar charge controller for that battery.

\$\endgroup\$
3
  • \$\begingroup\$ Hmmm, so if I were to find a 40V solar charge controller this should work fine? \$\endgroup\$
    – LukeyP
    Commented Apr 28, 2021 at 7:43
  • 1
    \$\begingroup\$ Assuming the maximum charge current was appropriate and the exact pack voltage was correct, yes. It is still probably not a good solution to whatever problem you are actually trying to solve. If you are just trying to reuse the lawn mower battery because you have it, I would reconsider and just get a 12V or 48V battery pack with matching charge controller/BMS. \$\endgroup\$
    – Dean Franks
    Commented Apr 28, 2021 at 18:27
  • \$\begingroup\$ Yeah, I did a little more research and it seems like I would need a charge controller specifically designed for lithium ion batteries too. 40V charge controllers are already hard to find and a 40V designed for lithium ion brings my options close to 0. I ended up biting the bullet and got a 48V battery pack instead. But I appreciate all the input you've given! It probably saved me from some massive headaches down the road. \$\endgroup\$
    – LukeyP
    Commented Apr 29, 2021 at 21:44

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.