Alternative to dual battery isolator?

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Thread Starter


Joined Nov 5, 2011
I am working on a trailer with a 12V battery and an electric-hydraulic brake actuator (pump).

The charge wire from the truck powers up the brake actuator only and does not connect to the trailer battery for charging. The manufacturer wired the trailer this way to prevent the actuator from draining the battery when parked (.3A draw when actuator is energized)

I wired two SPST relays on the trailer to split this hot wire (from the truck) and power up the actuator and also charge the trailer battery. This would keep the actuator from draining the trailer battery.

However, I did not foresee that because I used the incoming wire for both the relay coil(87) and feed through(86) that once the relays were closed, my trailer battery would backfeed and prevent the relay from opening.

I haven't figured out a way to resolve this problem without buying a dual battery isolator.

Any ideas would be much appreciated


Joined Mar 24, 2008

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