Utility trailer battery.

Went to haul a tractor and checked ever thing, brakes not working. Checked the little battery on trailer, one post corrode off. Bought new battery brakes now working.But lost a day till got new battery. Is there a way to bypass the battery and brakes still work.

Check your wiring, my breaks work and I haven't had a battery on the trailer in years (it only powers the winch). The battery should only power the emergency breakaway switch witch my trailer never had.

There is but if you get pulled over they might test your brake away switch on the trailer. This is the little box switch on the trailer that the cable also hooks up to the hitch of the truck. Fine the wire at this switch that go's back to the brake of the trailer and tie in to it with the truck wire that puts power from the brake control box.

You have a wiring issue. The brakes should be energized from the truck during normal use, even if the small battery is missing. The small battery should only energize the brakes if the break away switch (which is normally open) is tripped closed.

If you can find the name of the breakaway switch on your trailer most companies have the wiring/installation instructions on line so you can check your wiring. I have Curt breakaway switches and battery holders on my trailers and their wiring diagrams are on line.

Your question" Is there a way to bypass the battery and brakes still work.
YES sort of, see below HOWEVER it depends on your braking system wiring and grounds, and if its working !!!!!!!!!!!!

I have no idea how YOUR trailer brakes and control/actuator is wired or works, however:

"Many" electric brake trailers are actuated by the TRUCK (NOT battery on trailer) battery via an electronic brake controller via a pin on the truck to trailer wiring.

On many trailers an onboard battery is ONLY (unless also a winch perhaps) used to set the trailer brakes in case it comes detached from the truck IE Breakaway switch if pulled applies trailer brakes using the TRAILER battery.

Sounds like you have a wiring problem or a wire/terminal is disconnected or broke or corroded

The OTHER major electrical problem with trailers is lack of a GOOD GROUND

CHECK WIRING (lose or broke or corroded connection/terminal),,,,,,,,,,,,,,CHECK FOR A GOOD GROUND,,,,,,,,,,,CHECK THE TRUCK TO TRAILER PLUG CONNECTOR and insure the trucks brake controller is actually working to send voltage back to the trailer brakes

Basically YES often on many trailers the onboard trailer battery IS ALREADY BY PASSED AND DOES NOT operate the brakes normally but ONLY if the breakaway switch closes

DISCLAIMER if your system uses the trailer battery all the time to operate the brakes post back the answer changes

DID I MENTION A BAD GROUND AS THE PROBLEM lol Did I mention the brake controller may be bad or not wired right or a wire is broke/open ??

See if other gents agree or disagree????????????

John T

Get a tester and check your connectors. When facing the female 7 pin connector on your truck with the notch up, the lower right pin should have 12 volts to the trailer brakes when the brake pedal is depressed. The upper right pin provides a constant auxiliary 12 volts that will charge your trailer battery. When facing the plug, notch up, the brake activation pin hole is the lower left side and the constant 12 volts is the upper left hole.

Sometimes you get corrosion around a pin or pin hole and sometimes a wire breaks/corrodes off inside the connectors. I replaced my connectors a few years ago after getting pulled over for no lights. Got out and wiggled the connector and they came on so he let me go.

It could be that the broken terminal wire on the battery just broke the circuit so no current would flow to the brakes from the truck. They should work even with a dead trailer battery. Maybe you could disconnect that wire on your new battery to see if you have the same problem.

I guess i should have had more imfo. This is a 7 pin hookup I have a tester and every thing tested out ok. All lights on trailer work.
This is a 2015 GMC Siera with factory brake controller. The trailer is a16 ft..The little battery positive terminal was coroded beyond repair.

(quoted from post at 13:08:20 10/10/20) I guess i should have had more imfo. This is a 7 pin hookup I have a tester and every thing tested out ok. All lights on trailer work.
This is a 2015 GMC Siera with factory brake controller. The trailer is a16 ft..The little battery positive terminal was coroded beyond repair.

Click to expand...

The location of the different circuits running through trailer plugs and connectors is pretty standard in manufacturing of the systems. When people install controllers and wire trailers the standard diagrams often don't get used and that can lead to trouble when swapping the trailer between vehicles. I find it hard to believe GM would stop all brake action if your vehicle didn't see the small battery. I know of similar GM vehicles pulling trailers with no breakaway set up and their brakes work. If the brakes don't work with out the trailer battery I still think you have a wiring issue. If the tow vehicle doesn't see feedback from the trailer brakes (wiring issue) or the controller's gain is set too low, the brakes may not work.

The 7 pin connector should have one pin that supplies power to the battery to keep it charged. There is a separate pin in the connector that powers the brakes when the brake pedal, or hand controller if you have one, is pushed. The ground terminal of the trailer battery should connect to the same point on the trailer the ground from the tow vehicle connects to. The positive lead of the trailer battery goes to one side of the breakaway switch. The other side of the breakaway switch is connected into the wire going to the trailer brakes. This is the same wire the tow vehicle sends power to the brakes through. Basically the two power sources (tow vehicle brake controller and small battery) are parallel so either can apply the brakes without the other. The small battery only supplies power to the brakes when the normally open breakaway switch is tripped so it is closed to complete that circuit.

There is a AMODULE of some kind also in this battery box. What is its purpose? About 2in x 1in. 1/4 in thick wired from the battery..

(quoted from post at 15:35:57 10/10/20) There is a AMODULE of some kind also in this battery box. What is its purpose? About 2in x 1in. 1/4 in thick wired from the battery..

Click to expand...

If you can find the brand of yours, you could google it and tell for certain but that is the size of the battery charger that fits in the battery box of the CURT breakaway systems I am using. This link will take you to their wiring diagram for the kit with a charger that I am using, to give you an idea the system wiring. Yours should be similar.
https://assets.curtmfg.com/masterlibrary/52028/installsheet/52028_INS.pdf

Thanks for all the information..