Cargo trailer battery

I think OP is talking about the little battery system that comes on cargo trailers to work the break away brake system. It has a small 12V AGM battery in it.

The box should have a little device wired in it so the running lights can be used to charge the battery (that way it will work on a 4 wire system)

I replace mine with a standard 12V battery so I could run the inside lights while trailer was disconnected.

Get anOptima Battery from Auto Zone

I've bought similar batteries at HomeDepot pretty cheap. It has been a while so don't know if they still stock them.

Just replace the whole setup on my trailer as it wasn't just the battery that was stone cold dead. Friend borrowed the trailer and pulled the cord out when he didn't unhook it and it broke the tab instead of pulling the release. I know.... you should check that they work every now and then:(

It only needs a charge while the trailer is being towed ,it may be that the charge from the truck will charge it .

I have several, 5 I think, dome lights in my cargo trailer. I have a couple of 6 volt batteries wired in series for 12 volts. This Torklift solar battery box works wonders for keeping them charged up. The batteries power the electric jack as well as my breakaway switch.

Thanks guys. I guess Im buying a battery.

Those small batteries are short-lived so if it is several years old - get new one and don't waste time on recharging.
Checking brake-away operation if one of the thing where DOT cops make easy money and on west coast when you have to drive via scales, you have 50-50 chances to get pulled over.
I keep lot of equipment with batteries in it. Even when there nothing turn on, the wires leak the current and will drain battery in longer storage.
Disconnecting battery clamp will keep the charge for a year.
Solar panel without controller can kill the battery.

If it's one of tiny panels I suggested, it will not catch up. You need something bigger to actually put some energy back into the battery. My new camper will have sufficient solar to not worry about running the LPG heater or leaving phantom draws on while not in use. We're out and about at least twice a month, so this may never be a true test compared to others.

Bedlam wrote:
If the trailer sits where there is available light, consider adding a 5w or 10w solar panel to keep the battery charged. A little panel like this will not charge a battery, but it will maintain the charge that is on the battery.

When I bought my class C I wanted to put solar on it and the sales guys says "It has solar" so I checked the roof and it has a tiny panel up there. I thought what good is that little thing, but I have been shocked how well it does to keep the batteries topped up (not charged but maintained). I would say any thing with a battery that sits should have a small solar set-up to compensate for any phantom draw. For the few dollars that it costs it sure is worth it in always having a good/full battery when you need it and not having to always plug in.

This past winter I only had to plug the RV in once as I noticed during a dark and snowy time that the level was starting to drop and I probably was being too cautious as it cleared up a few days later and the solar probably could have caught up.

If the trailer sits where there is available light, consider adding a 5w or 10w solar panel to keep the battery charged. A little panel like this will not charge a battery, but it will maintain the charge that is on the battery.