Breakaway Battery Charging

[Scrounger]

I wanted to start a new thread to get some details on this one. I have a 2000 Yukon XL with a brake controller installed. When I leave my trailer plugged in for a few days, it will drain my trucks battery to nothing. I've read in several posts that the battery is not supposed to charge unless the truck is keyed on.

That is not the way my truck is working.

How can I test to see that it is charging while the key is off.

 

[kennyd]

Does your brake controller indicate that is has continuity with the trailer? If so that could cause the draw down of your battery.

To check the charging ability while the key is off, you will need a voltmeter to check the 12v pin of your trailer plug.

 

[RobertN]

All the factory charge lines I have seen have power to the trailer plug all the time. You have to add an isolator; that will only allow power to the charge line, when the vehicle is on.

 

[kennyd]

All the factory charge lines I have seen have power to the trailer plug all the time. You have to add an isolator; that will only allow power to the charge line, when the vehicle is on.

My '92 F250 does not, there is a relay that only allows 12v to the plug when the key is is the RUN position...pretty sure all the newer vehicles are setup that way-especially if they have the "trailer towing" option.

 

[BOBBYROGERS]

all the systems i have seen that charge the break away battery off of your truck have a led light on them to let you know that they are charging you may want to look at yours and see it .would let you know pretty quick if yours is constently drawing power when the key is off

 

[George2615]

Attached is trailer plug info for 7, 6, and 4 pin wiring.

On the 7 pin plug Pin 4 is 12 V hot from the vehicle. On GM trucks this lead comes from the fuse box under the hood and is the charge lead that feeds the trailer battery. It has battery voltage at all times and does not go through the brake controller.

Pin 2 is the blue lead from the brake controller. It should only have voltage on it when the vehicle brakes are applied.

Turn signals and running light pins (5,6,&3) also do not have power unless they are operated with the ignition key on.

Pin 7 backup light pin should not have voltage unless the ignition key is on and truck is in reverse.

Of course the ground (pin 1) should not have voltage.

If your trailer is plugged into the truck plug the ONLY PIN that should have voltage is pin 4 (the 12v charge lead). If there is voltage on the other leads there is a problem with the controller. Your trailer battery may be draining the truck when left plugged in.

When leaving your trailer hooked up for several days and you are not going to use the truck it would be best to unplug the trailer and put a note or tag on the steering wheel reminding you to plug it back in before use.

I have an 07 GM 2500HD and this wiring explanation has been correct for GM's as far back as I can recall.

 

[Diamondpilot]

All the factory charge lines I have seen have power to the trailer plug all the time. You have to add an isolator; that will only allow power to the charge line, when the vehicle is on.

I have to disagree with you on that one. I sell boats and trailers on the side and have wired over 25 vehicles since the first of the year and have seen none that were hot with the key off. I deal with 75% Fords and the rest are GM with a few Nissans, Toyota's, and Jeeps but very few Dodges.

Chris

 

[Diamondpilot]

My '92 F250 does not, there is a relay that only allows 12v to the plug when the key is is the RUN position...pretty sure all the newer vehicles are setup that way-especially if they have the "trailer towing" option.

You are correct Kenny. That is the way it should be.

Chris

 

[Scrounger]

all the systems i have seen that charge the break away battery off of your truck have a led light on them to let you know that they are charging you may want to look at yours and see it .would let you know pretty quick if yours is constently drawing power when the key is off

No idea where the LED would be. On the truck or the trailer. Nothing on the trailer that I can see. This is a mystery to me. Maybe I should call a GM service line if I can find one.

 

[RobertN]

I have to disagree with you on that one. I sell boats and trailers on the side and have wired over 25 vehicles since the first of the year and have seen none that were hot with the key off. I deal with 75% Fords and the rest are GM with a few Nissans, Toyota's, and Jeeps but very few Dodges.

Chris

My exposure has been, very limited in that arena. For my Dodge, I got an isolator when I went to put the camper on.

 

[Scrounger]

Update, spoke to a GM engineer, nice to have media connections, and the hot lead to the charge/aux circuit is hot with the key on or off if the fuse is installed under the hood for it in slot 1. Its labeled in my truck pretty well.

Looks like I have to install and isolator myself.

 

[Egon]

On my system the when ever the trailer plug is plugged in the green light on the controller is on. If this light is on I just assume the break away battery is on a live line.

 

[medicshawn]

My 2004 Dodge is hot all the time as indicated by a charging led on my trailer battery.

 

[Diamondpilot]

No idea where the LED would be. On the truck or the trailer. Nothing on the trailer that I can see. This is a mystery to me. Maybe I should call a GM service line if I can find one.

High end brake-away battery boxes have a LED on them to show you the charger is working. Most we see in my neck of the woods do not have the LED. Only way you can tell its working is once a year put a volt meter on it and look at the brake-away voltage, something around 12V. Now start the truck and if things are working right you will see something around 14V.

Chris

 

[Diamondpilot]

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

 

[Egon]

I still think something is not right with your guys trucks that have 12V at the plug with the truck off

I'm pretty sure that with my 96 Dodge the breakaway battery has power to it even with the key turned off as the controller always shows a green light. Never had any problems with low batteries as the breakaway battery is just the third battery in the system. There is no draw on the breakaway battery as the trailer brakes are not activated.

The camper plug is on a solenoid the is activated by the key being turned on.

 

[Diamondpilot]

I'm pretty sure that with my 96 Dodge the breakaway battery has power to it even with the key turned off as the controller always shows a green light. Never had any problems with low batteries as the breakaway battery is just the third battery in the system. There is no draw on the breakaway battery as the trailer brakes are not activated.

The camper plug is on a solenoid the is activated by the key being turned on.

I think you guys are talking about 2 separate things here. Your controller is wired hot all the time. Its that way so that if for some reason you lose everything you have the ability to activate the trailer brakes manually.

There is a wire that also runs to the trailers on board battery to keep it charged. It is totally separate from the the brake's circuit and its only job is to charge. It is a CHARGE CIRCUIT so it SHOULD only be hot when the vehicle is charging, ie running. Now the circuit is not smart enough to tell if the truck is running or not, all it knows is the keys position.

Chris

 

[Egon]

There is a wire that also runs to the trailers on board battery to keep it charged. It is totally separate from the the brake's circuit and its only job is to charge. It is a CHARGE CIRCUIT so it SHOULD only be hot when the vehicle is charging, ie running. Now the circuit is not smart enough to tell if the truck is running or not, all it knows is the keys position.

Darned if I know??

I should check it out some day.

 

[George2615]

As I stated before and Matthew backed me up that on GM products the trailer plug charge lead is a separate circuit connected to the under hood fuse box. If the fuse is installed the charge lead on the trailer plug is hot whether the key is on or off. There are no relays or anything else in line to turn it off. If someone who owns a GM wants the charge lead not to be hot when the key is on then a relay can be installed in the engine compartment between the charge lead and the fuse box post it connects to.

 

[Diamondpilot]

As I stated before and Matthew backed me up that on GM products the trailer plug charge lead is a separate circuit connected to the under hood fuse box. If the fuse is installed the charge lead on the trailer plug is hot whether the key is on or off. There are no relays or anything else in line to turn it off. If someone who owns a GM wants the charge lead not to be hot when the key is on then a relay can be installed in the engine compartment between the charge lead and the fuse box post it connects to.

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