I'm concerned about the battery on my trailer which powers both my breakaway brake switch and an electric winch on my car hauler.

The trailer battery is a full size deep cycle battery. I've read numerous posts that indicate that the 7 pin can be used to charge the trailer battery. Is, there any chance that the battery will over charge?

 

No, it won't overcharge.

 

yep what he said

 

I watched a video yesterday where a fellow/company was installing an onboard air system to fill air bags. He claimed that the 2017 differs from previous years in that the battery charge wire running to the 7 prong is only powered when a battery is attached and the truck senses that voltage is low/needing to be charged. This change on the 2017 necessitated that they power the air compressor from an upfitter switch, and not the 7 prong rv plug as they had done in the past. I stumbled across this as I was looking for upfitter wiring info.

 

I installed a brand new, out of the box, breakaway switch and battery box kit on my car hauler trailer. The battery box has a test button on it, and the small battery inside is a 12 volt sealed battery like the ones used as home alarm back up power or emergency lighting in commercial buildings.

Everything looked good hooked up. I pulled the trailer one time and smelled electrical burning. It was the trailer brake breakaway battery box. The circuit board had burned up and melted a hole in the plastic box containing the battery. I double checked all of the wiring. Everything was wired correctly. Maybe it was a defective circuit board? I read on another F250 forum post that the 7 wire positive lead was a 40amp output. That's why I was questioning overcharging the trailer battery without using some type of voltage regulator. Additionally, I was / am concerned about amp draw on the 7 wire while using the winch. That won't be a problem as long as I turn the ignition key off. I just hope I don't forget.

So plan B is to use my large winch deep cycle battery to power the breakaway brake circuit. I just don't want to burn that new battery up too.

I'll have to read up on it and report back.

 

You've mentioned that you checked the wiring, but it can't hurt to check it out again. This link will show you a wiring diagram:

https://www.etrailer.com/faq-trailer...tallation.aspx

A quality breakaway system should have an internal charging system that shuts off the feed to the battery when it has a full charge.

As an aside, that 12-volt circuit (although it's a 40 amp circuit) is limited by the small gauge of the wire feeding the pin on the trailer connector (16 or 18 gauge) and by the distance away from the tow vehicle battery. It can't charge a dead or nearly dead battery. Best bet is to use a quality charger whenever you have shore power available.

For more information, click the link below:

https://www.etrailer.com/expert-122.html