Can Two Batteries be Connected to Single Device on Trailer
Updated 02/17/2026 | Published 06/21/2024
Question:
Hello, Have a trailer with two 12Vdc batteries that will be powering the same device, but I also would like to be able to turn either one or both batteries on/off switch. It would be nice to charge both batteries from the tow vehicle, but also from an onboard AC charger. I believe that an isolator would be needed but am unclear on the wiring to perform what was described. Can someone help me out with this? Thank you, Greg
asked by: Greg H
Expert Reply:
Hey Greg, as far as wiring the two batteries to the single device that would be just a matter of running switches from the batteries to the device as there's no reason you can't power a single device with two 12 volt batteries as long as they are wired in parallel.
Now to charge them yeah you'd need a isolator and the Redarc part # 331-SBI24D would work for that.
Product Page this Question was Asked From
Redarc Smart Start Battery Isolator - Dual Sensing - 24 Volt - 100 Amp
- Battery Charger
- Battery Isolators
- 24V
- Maintains Only
- Vehicle Battery to Auxiliary Battery
- Redarc
more information >
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Jameson C.
2/17/2026
Hey Greg, how did things go with wiring your two 12V batteries in parallel and using the Redarc isolator? It’d be great to hear if the setup worked the way you wanted for charging from both the tow vehicle and the onboard charger. Your update could make it easier for others planning a similar setup.