Power Trailer Winch from 7-pin?
 

Tried searches in the E53 forum didn't turn up any answers (but a few similar old questions). So here goes (again). :stickpoke

Got a Trailex with a winch that is wired to use the 12V Battery (pin 4) and Ground (pin 1) from a 7-pin receptacle / plug. From trial & "error" I have found pin 4 is run thru a 20AMP fuse (in the curb side side panel fuse box #78) on the OEM hitch package on the X5. 20AMP is enough for some 12V trailer accessories (interior lights, etc), but not a winch motor.

The trailer has electric brakes and a small 12V "breakaway" brake controller battery that I believe is also "charged" off the 12V Power pin.

So any solutions suggested? Is a second 12V battery mounted in the trailer the best alternative (maybe charged like the breakaway battery)?

Has anyone found a way to get more AMPS on pin 4? Maybe a direct(heavy duty fused) line from the X5 battery positive terminal that bypasses OEM 20AMP connection on the receptacle?

If it were me I would wire in my own large gauge through an ignition controlled relay. I don't think a second battery is going to offer you much more then run time, your saying that the trailer already has a battery on board, and the wench is on the trailer, or not part of it?

Thanks for the reply. The existing "on rail" battery is a small (hobby size) 12 volt that is only used for the electric brakes (break away controller) to engage the brakes (once). Not enough to power a winch for more than a few nanoseconds.

Leaning toward second battery for "disconnected" reasons, to run trailer interior lights and such when not on the hitch. May go with a solar panel to trickle charge it when at track and off hitch.