Does 12 Volt Output Circuit of Trailer Wiring Charge Hydrastar Breakaway Battery

Updated 02/11/2025 | Published 02/10/2025

Question:

Doesnt the 12v tow vehicle wire also charge the RV house battery? When wiring the breakaway battery to the 12v power, wont this also be connecting it to the rv battery through the 12v wire? Will the breakaway battery not just charge and drain with the house battery? Does it matter if the house batteries are lithium and the charge controller has a higher shut off voltage for the lithium batteries? Could this damage the breakaway battery?

asked by: Mike

Expert Reply:

Hey Mike, yes the 12 volt aux circuit of the trailer wiring does charge house batteries typically. If you have Lithium batteries as your house batteries and they are connected to your tow vehicle wiring through the trailer wiring they aren't getting charged though since they require a higher voltage than what will have made it through the 7-way connectors.

It sounds like you maybe have a BCDC style of charge controller to charge the lithium batteries though. I would recommend bypassing that to run to the breakaway battery of the Hydrastar kit part # HBA16-252-82 to eliminate any leeching from one battery to the other. Is the charge controller installed on the trailer or the vehicle?

expert reply by: Jameson C

Mike

2/11/2025

The converter/charger on the trailer for when you're plugged into shore power. What's the easiest way to isolate the breakaway battery from the rest of the system?

Jameson C.

2/11/2025

@Mike You could use a diode like the part # RM-690. This only allows current to flow one direction through it and is rated for 85 amps. Or depending on how things are wired you could use a diode like the part # RM-790 which has two inputs and one output.