factory isolator in tow package - I recently wanted to add a 2nd battery just so I may not be stranded when I dry camp. I took it to a ...

I recently wanted to add a 2nd battery just so I may not be stranded when I dry camp. I took it to a place where they would install an isolator and battery tray. After he checked with someone when ordering the part, they said that there is already an isolator in the tow package. My question is where is it? How can I hook up a second battery? The place I took it to said there is current to the trailer battery and if the trailer is on shore power that charges the battery so there is no need to do the job. This is very ironic since my truck battery died in my driveway this weekend and had to be replaced. What if I was in the middle of nowhere? I would feel better if I could jump start from a second battery. Does anyone have any information about this?

This is what we use on a lot of boats that want to sit at the beach with the stereo on. When the key is off it isolates the batteries from each other that way you will always have one charged battery. Once you start the engine both are connected and start getting charged.

http://www.stingerelectronics.com/produ ... tegoryID=2

Thanks Chasmanian. I understand the operation but I'm not quite sure if and where the isolator is located. I suppose I could try to trace the hot wire from the harness back to the cab.

If you have a volt meter you can check the voltage at each battery and see if they are the same. Then get a battery charger and put it on one of the batteries and the voltage should raise. While the battery charger is on one battery the voltage should be different on the other if there is an isolator. Just make sure the key is off while testing.

I think I'll give that a try, thanks.

Must admit that I kind of randomly picked this post to pose this question, so break out the torches and pitchforks if I'm way out in left field (again). Also get that this may have been definitively answered in a different post, but I sure haven't come up with the right search phrases to find it. So if anyone has pointers to that thread (if it exists), please let me know.

In any case, here's what I"m after. I get that the NNBS trucks have a lot of "common" elements, some of which may or may not be used depending on the model options. With that, I also get that the 2nd battery tray is basically there in the engine compartment, although it seems that it's generally only used on the diesels.

What I take away from that is there's likely an "official" GM setup to run dual batteries in any NNBS truck although it may only be commonly used on the diesel setup. Also figure that it may be difficult and/or expensive to set up on a non-diesel truck.

Regardless, what I haven't been able to find so far is a parts list/schematic on how a dual battery setup is done from GM's point of view. Anyone have any concrete info on how "they" do it from the factory?

I don't know how they do it but when I bought my truck I asked about a second battery. The salesman told me about 800$ for them to do it. I've had good luck with this guy so I'm thinking it's somewhat accurate.

Makes sense that something exists, especially if it's somewhat regularly done with diesels. Anyone out there have a part number/parts list?

Also, ran some errands at lunch and got a 40 AMP fuse. Popped it in and my small inverter powered right up off the trailer plug.

Which also reminds me, what's the "other" red wire tucked between the power center and the driver's fender?

The factory dual battery set up is option TP-2.There are several factory variations of TP-2,to really complicate things.The Diesels batterys are hooked together,in parallel,to provide 1000+ cranking amps for cold starts.
The gas versions,now this is important,are not hooked together,they are isolated.The main battery is for starting,and running the truck,and its system.The second battery feeds the hot pin on the trailer plug,all the time.Usually there is a camper harness at the front of the bed,that is fed also.That is all it feeds.That is so you can feed your trailer plug,or camper plug,and run lights in the trailer,the fridge,whatever.And run them till the battery is dead.The truck will still start,of the main battery.They are isolated.If you hook the batterys together,they will both be dead.
That being understood,it is a simple system,but hard,and expensive to add.You probably would be just as well to use an aftermarket isolator,and wire the second battery to it.Then hook the hot pin of the trailer plug to the second battery.
You cannot hook the second battery into the truck system,then they are not isolated.
I have dual batteries in my truck,factory TP-2 option.I use a yellowtop Optima battery on the second battery,deep cycle RV type.Use a redtop Optima on the main,starting battery.I also have a yellowtop Optima in my enclosed trailer.Have spent many weekends at the track,or airport,camping and working in the trailer.Lites on,stereo on,computer on,invertor on,etc.Only once killed both batterys,and that was an all nighter rebuilding an engine.The truck started right up,and the 400 mile ride home,the batterys were charged again when we got home.135 amp alternator.

Thanks for the information. I'll likely do this when I get my system hooked up. I'm leaning towards the isolator that Chasmanian offered up.