Charging AGM battery from truck (never really charges)

[kmcintyre]

Ok, I've got a nice AGM battery in the Eagle but it never really gets charged above 12v. I have an isolator but am worried that the battery isn't really reaching it's potential.

I have thick (don't remember the guage) wire running from my truck battery to the camper via a blue sea's isolator. Fuses installed, etc. and everything works, it's just not great.

I've read that you need more amps to the aux battery to get it fully charged but not sure what I should use. I have driven for 12hrs and the agm is only at 12v.

I've searched around the forum, web, etc. and while it's an easy question, there are a variety of opinions and suggestions out there so I thought I'd check with this group.

Thanks,

Kevin

 

[ntsqd]

The devil is in the details. What was the exact battery voltage after charging? What model isolator do you have? Anything larger than 10ga. is probably big enough, but it wouldn't hurt to know what it is.

 

[Wandering Sagebrush]

Kevin, how accurate is your meter? Is there a chance that it's off?

 

[LAWNMOWERMAN]

What is the voltage at the house battery with the truck running?Also check truck battery voltage when running.This is basic info needed to start diagnosing the problem.

 

[kmcintyre]

Ok, in doing the diagnosis and looking for answers to the questions above I found out why my camper battery wasn't getting charged. I had a blown fuse at the truck battery where I placed a fuse before the wiring to the camper. It was a 20amp fuse so now I'm wondering if I should use a 30A? I'm sure the alternator is putting out quite a bit of amps but I don't want to risk burnt wiring. I'm using 8ga wire from my truck battery to the camper battery.

 

[Wandering Sagebrush]

Depending on which alternator you have, you could be seeing as much as 200 amperes possible. My gut feeling is that with 8 AWG wire, and a 30 ampere fuse, you should be fine. That said, I'd do a bit of research first.

 

[DrJ]

In my experience monitoring camper charging from the truck, I have never seen it above 18 amps. I have a duramax and the standard FWC wiring. I don't see a issue with going to 30 amp fuse. Maybe your alternator puts out more amps than mine does.

I do not believe FWC uses a fuse in between the truck and camper - only the isolator. I've had to replace my isolator before too.

 

[PaulT]

FWC uses a automatically resetting circuit breaker like these Mine is a Pollak 12v 30a breaker
Found it available at etrailer

Yellow wire nuts are there courtesy of a previous thread. Can't remember who posted it but what a great idea to prevent accidental shorts under my hood.

One of the wire studs is connected directly to the battery. The other is attached to the power cable to the camper.

These circuit breakers cycle on and off in an over current situation and are not as safe as an actual fuse. It is on my list to install a fuse at the truck battery as that is superior protection to the resetting circuit breaker.

Paul

 

[ntsqd]

I used a non re-setting breaker at both ends of the charge wire. Like these: http://www.westmarine.com/buy/blue-sea-systems--285-series-thermal-circuit-breakers-surface-mount--P011975596
Both ends because there's a battery at both ends of the charge wire. I have seen a version of the Pollack breaker linked above that was a manual re-set. There we go: http://products.pollakaftermarket.com/viewitems/circuit-breakers--1035/mal-type-breakers-plastic-push-button-manual-reset

In my case the charge wire and the ground wire both run from battery to battery and are 6ga. so I set the breakers at 80 amps. There are other systems tapped into the charge wires so 80A is more to accommodate those circuits than purely just for charging the camper batteries while underway.

 

[kmcintyre]

I think I'll try a 30amp fuse first and see how it goes and monitor the output from the alternator. I have a 40amp fuse too. I'll post results on the next trip and see how it goes.