What Can I Use to Charge Auxiliary Trailer Batteries?

Updated 07/01/2026 | Published 06/27/2026

Products Featured in This Question

Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 50 Amp

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$690.00

Question:

Hiya. We have a gooseneck trailer with hydraulic jacks on there. and what is best way to charge the battery for it? I have a GRP 27 deep cycle marine battery. And got a Battery Isolator 140 amp, part 303303. I just want to charger of the aux wire on the 7 way cord. im thinking the isolator is not the correct way to go.

asked by: Lloyd H

Expert Reply:

Hi Lloyd,

Trying to charge the battery from the 7-way probably won't be able to supply enough power to charge the battery because it's coming from the alternator and would only have a trickle charge running to your batteries. Instead, I recommend going with something like the Redarc In-Vehicle BCDC Battery Charger part # 331-BCDC1250D. It's a DC-to-DC battery charger that will pull energy directly from the vehicle's battery rather than pulling from the 7-way. A normal 7-way trailer connector is limited to 10-15amps of current, which isn't able to fully restore a battery for use. The # 331-BCDC1250D however can transfer up to 50 amps of current to the battery to both charge and maintain it. It can install inside the cabin of the vehicle, along the frame rail, in the engine compartment, or on the trailer so you can keep it tucked out of the way.

Where is your battery located that you use to power your hydraulic jacks?

expert reply by: Claire H