I was told it provides only 2 amp an hour, which is way to low amp to recharge a low battery. I was thinking of connecting a bigger wire to the truck isolator, but like you say it is probably too small ampacity. I do not even know where is that isolator.
What do you mean by using the trailer charge circuit to turn the isolator on off, do you mean instead of using the ignition relay?

 

Yes. Find the wire that goes to pin 4 on your bumper plug. That is the +12V wire, which is the battery charge wire. Use that wire to control the isolator relay, like the one Scott linked to.

The advantage this has, is that the truck does not energize that wire to pin 4 until the truck is running. That is different than energizing it when the ignition is simply turned on.

Then all you need is a HEAVY wire between your truck battery and the camper battery. I would say about an #0 sized wire. You should also put a fusible link in the line to protect that wire.

 

This way, don't you recharge all the times from the truck batteries instead of the truck alternator switching from truck to camper batteries.

 

There is no switching back and forth. That is not how it works. When your truck is running, the truck battery and the camper battery are connected together, and they equalize. When the truck is shut off, they are separated.

 

Converter only connected when loading the camper using the electric jacks. This way I can connect the truck while still using the house power to raise or lower.

 

Since the isolator doesn't connect until the truck batteries reach 13.2v, it usually takes a few minutes after starting.

The reverse is also true, that the battery voltage will not instantly drop to 12.7v to open the solenoid, so there will be a delay there depending on your load.

 

This might come in handy for wire size selection (for this or other projects):

Amps column= Copper conductor,Polyethylene/Neoprene/Polyurethane/Polyvinylchloride insulation.
Single Conductor in Free Air 30°C Ambient Temp.noncontinuous load.

Continuous Amps Column= Copper conductor TW-60C insulation. updated to 2011 NEC on 04/03/2011.

Gauge........AMPS..........Continuous
30...............2.................AMPS
28...............3
26...............4
24...............6
22...............8
20..............10
18..............15
16..............19
14..............27..............<1-12
12..............36...............13-16
10..............47...............17-24
8................65...............25-32
6................95...............33-44
4...............125..............45-56
3..................................57-68
2...............170..............69-76
1..................................77-84
1/0...............................85-100
2/0..............................101-116
3/0..............................117-132
4/0..............................133-157
250kcmil.......................158-172
300kcmil.......................173-


Dang, My "dot typing finger" just got a cramp!

 

Thank you all, I see the wire gauge is of big concern, the bigger the better. I will start shopping for an isolator, does look like the trailer isolator is big ennough of a system to properly recharge a dropped deep cycle battery.

 

Another idea that might work for you is installing a roof mounted solar system to keep your batteries charged. I would think you could use it in conjunction with the truck's charging system, while in transit, to assist with bringing batteries back up quicker after the night draw. They would also charge and keep the batts up during daytime camping so batts are good before each night on multiple day camping stays. There are many systems to choose from. The bigger the system, the more efficient and better the results.

 

When we were shopping for our last camper I saw several used units with solar panels. A couple had 3 maybe 2x4 ft. Panels installed in a sort of arch lay out ( / - \ ) . Any idea of how much power you can get out of something like that?

 

I do a lot of dry camping and have 6 large batteries on board. Main bank is 4 - 6 volts and a couple 12's as backup. It can get awful cold on a hunting trip and the furnace is the biggest killer of batts. What I've done in the past when I'm way down on power is hookup my truck with jumper cables to my main bank and let it run. I know this isn't the proper way but there are times when I'm deep in the woods and have to improvise.

On my 96 I had an isolator and a large wire(I think 00) run to the back bumper. I used to plug my dump trailer into it and I could also plug my camper batteries into it and run the truck to charge. Didn't do that with the 04 though.

Since then I've added solar which helps but if it's cold the batts can still get run down low and 100 watts of solar won't bring them up fast enough.