Can I Wire Directly to Trailer Battery from 12V Pin on e99011?
Updated 06/18/2026 | Published 06/12/2026
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Question:
Question about 7-pin trailer cord: Can the aux 12V power terminal in the 7-pin trailer cord be connected directly to a 12V battery on my car hauler that powers a winch? Does that aux 12V line come from the tow vehicle alternator? Thanks.
asked by: David B
Expert Reply:
Hi David!
The 12V auxiliary pin on a 7-pin trailer cord such as etrailer Trailer Wiring 7-Way Upgrade Kit w/ Junction Box and RV Style Connector # e99011 can be connected directly to the battery on your trailer, such as Replacement Battery for Superwinch Hand Hauler Portable Winch # SW92SR. The power supply when connected to your tow vehicle will come from your alternator, but it is not directly wired into the alternator. When you're wiring to your battery, I recommend using 10 gauge wiring to ensure you get the proper charge voltage, and you'll be good to go!
Are you planning on towing with this setup consistently or is it a vacation setup?
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Product Page this Question was Asked From
etrailer Trailer Wiring 7-Way Upgrade Kit w/ Junction Box and RV Style Connector
- Trailer Wiring
- Trailer Connectors
- Trailer End Connector
- 7 Blade
- Plug and Lead
- etrailer
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Marshall N.
6/17/2026
Depends on your car’s wiring, but it should keep your battery charged if you drive it enough. Mine is a work trailer, so it is run weekly at a minimum.