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Is a Diode Needed to Prevent Backfeeding from Trailer to Tow Vehicle


What size diode is needed in the charging line from the tow vehicle to protect the tow vehicle electrical system? Is it possible for a back feed from the winch and brake away battery to damage the tow vehicle electrical system, in the event the emergency break away power is activated by the break away switch while towing?. A local brake control installer mentioned this could happen but I have not thought to much about it until lately. I do not think by tow vehicle is charging my trailer battery while towing. Sounds like a good idea to keep the battery up on the road.


Expert Reply:

There is a possibility of back feeding but this should not really be of a concern as the odds of it happening are slim to none. If you did choose to use a diode then you would need one rated for the components it would be powering. The highest rated diode we carry is the Roadmaster Single Park Light Diode part # RM-690 which is rated at 85 amps.

There are a few things you will need to take into consideration for your winch and breakaway system. For starters, it is not advised to run both a breakaway switch and winch off of the same battery. A breakaway switch like part # 50-85-313 should always be connected to a 5-amp hour battery. This battery should not be used to power or charge any other circuits.

The winch can then be either hooked up to a separate auxiliary battery on the trailer or ran directly to the tow vehicle with a wiring kit like the Bulldog Winch Rear Wiring Kit part # BDW20206. If you will be using an auxiliary battery on the trailer to power the winch then you will need to use a battery charger like the Redarc BCDC Dual Battery Charger part # 331-BCDC1240D.

The 12 volt power coming from the vehicle's 7-way trailer connector can then be ran to the breakaway battery and auxiliary battery to maintain their charge. This charge line should not be used to charge a winch battery as it would be far too underrated. I have attached our " How to Wire an Electric Winch" help article for you as well.

expert reply by:
Conner L

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