Is it possible to have at least one battery connected to our trailer circuits while both batteries in series (ie. 24v) are being charged by our two 33v solar panels?

Will solution require a "charge controller"?

Presently, trailer has two 12v batteries in parallel connected to the 12v. trailer circuit.

The two 33v solar panels were originally for charging a single 24v battery load for my driveway gate opener (actually two 12v batteries in series).

  • \$\begingroup\$ You should include the solar panel and battery models, include pictures of them and your setup or area of your setup. The more details you provide, the better we can answer your questions. \$\endgroup\$ Commented Apr 23, 2023 at 23:27

1 Answer 1


If you connect the batteries in series while using only one of them, you will definitely need a voltage balancer between them.
I would recommend keeping them in parallel and getting a good MPP PWM charger for them to get the maximum power out of the panels.
You do need a charge controller, because without if your batteries would keep overcharging and die quickly. Don't fall for the cheap, false garbage out there (typically less than $100 or even less than $50; the cheaper, the worse) - they rarely have MPPT and their "PWM" does NOT include an inductor which enables much higher efficiency.
You should see with someone who has a good knowledge of such chargers/charge controllers and an experience with specific models.
If you're OK with an over 60% efficiency loss, you could go with the cheap solar charge controllers. I just don't rely on their charging logic which keeps neither very accurate voltage, nor is its regime very helpful for a long battery life.


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