Breakaway Battery Charging

[FlaDon]

I just walked next door with my test light and my 7 round tester and check my neighbors 2007 3500 Dmax SRW 4x4 in Classic trim, same truck as Builders. His pin #1 is 12 volt and #4 is ground as is standard now days. No power with key off, as soon as he turned the key to simulate the truck is running my light lit up. I also check it with my trailer plug tester for 7 Round and the same result was seen. There must not be any consistency in GM products if you guys are seeing different and I think it would be crazy to want it hot all the time, it will lead to problems of drained batteries. I can tell you for sure all Fords 1997 and newer are wired the correct way with a relay included to kill power when the truck is not running. 75% of the customers I have drive Fords so I deal with dozens of them each year.

Just to confirm I check my 2004 and 2006 SuperDuties and my new Titan and no power with the key off on any of the 3. As soon as the key was moved to the start position power was observed on all 3 via the 7 pin tester and confirmed with the lest light.

Chris

My 2001 Chevy 3500 dually had a live feed until the controller and fuse under the hood were installed. Then it went to keyed power on only. Truck has the factory towing package, It was nice before the controller as an electric cooler could be plugged in the lighter outlet and the travel trailer plugged in the 7 pin and keep the battery charged off the trailer charger.

 

[Diamondpilot]

My 2001 Chevy 3500 dually had a live feed until the controller and fuse under the hood were installed. Then it went to keyed power on only. Truck has the factory towing package, It was nice before the controller as an electric cooler could be plugged in the lighter outlet and the travel trailer plugged in the 7 pin and keep the battery charged off the trailer charger.

That's how you end up with a truck that will not start if the truck sits too long without running.

Chris

 

[GaryBDavis]

If the truck battery is being drained down to nothing within a few days, something is wrong.

With the brake-a-way battery in good condition and fully charged, it won't drain the truck battery down to nothing. Even with the high end brake-a-way systems that have the charging LED on, they aren't really charging when the truck is not running (assuming the trailer battery is charged up). The LED on the TAP brand is just an indicator that there is power on the truck side. That LED and isolation circuitry draws so little current (~20mA or less), that it would take weeks and weeks to drain a truck battery in decent condition.

If you have access to a multi-meter, check the current draw from the truck to the trailer while the truck is off. The draw should be only a few miliamps. If it is more, start disconnecting things in the trailer to find whatever it is drawing it down.

 

[Iplayfarmer]

I still think something is not right with your guys trucks that have 12V at the plug with the truck off. I can tell you that if that were the case on all trucks I would be jump starting about 200 vehicles every weekend at the marina and campground with trailers left hooked up to them.

Chris

Why would that be? If the campers have good batteries and the break-away controllers have good batteries, there shouldn't be any draw on the truck's battery.

If if the charge circuit were always on, it wouldn't kill the truck's battery unless there's some draw... bad break-away battery, a short somewhere in the trailer, etc.

I think the OP has a bad break-away battery.

 

[Diamondpilot]

Why would that be? If the campers have good batteries and the break-away controllers have good batteries, there shouldn't be any draw on the truck's battery.

If if the charge circuit were always on, it wouldn't kill the truck's battery unless there's some draw... bad break-away battery, a short somewhere in the trailer, etc.

I think the OP has a bad break-away battery.

What I am getting at is if say you were hooked up to a trailer with a bad battery, now you will end up with a dead truck battery. The bad battery will drain the good one. These batteries never get checked and no one pays attention to them. Also dump trailers and travel trailers use the trailers main battery for brake-away. No separate battery. So every time you dump or use something in a travel trailer with the truck off you are also drawing from the trucks battery, do this enough you will end up with a truck that will not start.

Chris

 

[Scrounger]

Ok here's the end of this one on a 2000 Yukon XL. Both trailer and truck battery are both in fine working order. Brake controller with GMC harness is installed along with fuse in stud1.

The power charge lead is hot with the key ON and when its OFF.

Called dealer and he stated that some of the 2000 to 2005 trucks are this way. Mostly the Yukon/Tahoe and the XL/Suburban SUVs.

Only why to change it is to put in an aftermarket relay to make it key ON function only.

 

[Diamondpilot]

Ok here's the end of this one on a 2000 Yukon XL. Both trailer and truck battery are both in fine working order. Brake controller with GMC harness is installed along with fuse in stud1.

The power charge lead is hot with the key ON and when its OFF.

Called dealer and he stated that some of the 2000 to 2005 trucks are this way. Mostly the Yukon/Tahoe and the XL/Suburban SUVs.

Only why to change it is to put in an aftermarket relay to make it key ON function only.

Good to know. I have only one customer with a GM SUV and its a 2500 Suburban with a 6.5 diesel, actually my uncle. I know his is not hot but maybe they are different on diesels or 2500 series. Still, not a smart way to do the wiring for GM. They should not be hot with the key off, period. That is why guys like you are ending up with dead batteries.

Chris

 

[FlaDon]

That's how you end up with a truck that will not start if the truck sits too long without running.

Chris

Note the part about the travel trailer having a charger that kept both the trailer and truck battery charged.

 

[Reg]

Charging a breakaway battery won't drain your truck battery, unless it is BAD BAD BAD.
My '03 Chevv batteries get drained if I leave it hooked to the big horse trailer for a week without running, but that is because day/night temperature changes cause the air ride to cycle.
If I leave it with the small equipment trailer or 2 horse trailer hooked up the truck batteries stay up.
This is 7 pin, nothing had to be changed on any of these trailers to match the truck.
I bought it as chassis/cab and had a flat bed put on, so MAYBE the upfitter made the choice of power to the trailer with key on or off.

I have read elsewhere that the Fords don't but the GMs do, but I don't know how that varies by model year.
I have the whole wiring schematic for the GM trucks, so i could look it up if it mattered to me, but right now I know how mine works and I'm fine with it.

 

[Reg]

What I am getting at is if say you were hooked up to a trailer with a bad battery, now you will end up with a dead truck battery. The bad battery will drain the good one. These batteries never get checked and no one pays attention to them. Also dump trailers and travel trailers use the trailers main battery for brake-away. No separate battery. So every time you dump or use something in a travel trailer with the truck off you are also drawing from the trucks battery, do this enough you will end up with a truck that will not start.

Chris

That is just "living with the problem" and encouraging folk to leave the problem not fixed.
I doubt that it is "ticketable", but there is a requirement that breakaway batteries hold the brakes on for some minimum amount of time.
Come to think of it, that must be the ONLY equipment check that the good officers at the Union, CT weigh station have never done for me (-:

I am ONE of the NO ONES that DOES check breakaway batteries regularly and replace them as needed.
It isn't hard; just hook up the trailer, don't plug it into the truck, pull the pin and hear the brakes hum (or not), then try to drag it with the truck, just a foot or so.
This will tell you if it has retained charge for the time it has been parked.
By the time you get out of the truck again to put the pin back in there will be a change in the tone of the hum if the battery is weak.
This isn't a rigorous check and the results take some judgment; if the trailer has been laid up all winter with the battery left in vs only parked for a week after a 6 hour trip.

The standard 7 pin offers more than one source of +12 volts, so it is at least POSSIBLE that some trailers pick up their breakaway battery charge from the AUX line and others pick it up from the (usually black) +12