The alternator is 130 amp and I after some investigation, planned to to get a battery combiner or battery isolator. Then I found out the alt has a 130 amp output potential, I figured it was enuff to keep 3 batteries charged.



I have installed a 6 gang fuse/switch box in the cab roof and added two exterior and one interior camera and have everything tucked up in the headliner. The third battery will mainly be for running a 19" LCD TV and lap-top or DVD player off an inverter for passengers.


Whadaya think?

 

Should work fine,my last motor home had 4 30H batteries one was isolated for the main engine and generator starter

 

If you wanna isolate the 3rd battery, put a heavy duty solenoid in the power wire between it and wherever you connect to the factory ones. This way you can set it up to isolate that battery to run your toys and not worry about draining the main ones, yet charge up when you flip the switch on. That way also lets you give yourself a jump if the batteries are a little low. The isolators all have some voltage drop, so the 3rd will never be as charged as the others.

 

I used an oil pressure make switch to activate the solenoid with a dash switch in case I needed a jump

 

So its kinda like a time delayed relay then?

 

I've been wanting to do this for a while. Where were you planning on putting the third batt.? I'd think mounting somewhere under the truck would work, but I haven't really looked that hard at a good place for it.

 

To an extent,on a warm start it's almost instant with a 5lb switch as soon as the engine spins a couple times.With a 30lb switch it would take a little longer.
With these trucks you could hook it to fuel pressure or if you like just hook it to a wire that's hot with ignition on

I done it that way so I didn't have to remember to turn it off and on

 

Right now i have the 3rd batt in a plastic batt box behind the driver seat but it's not hooked up yet. Ideally, it should be next to the frame like the 2nd batt but I haven't figured out exactly where to put it because of cables and whether to try to balance by putting opposite of the #2 batt but that would put it next to the fuel lines. In all cases, there's the routing of the batt cables. Also the 6 ga wires to the inverter.

 

I also read somewhere once (I think it was on this site somewhere) that put his in the bed of his truck and made a special lockbox for it so no one could just walk away with a nice battery.

Be sure when you're routing cables you cover them with something. You don't want them rubbing through and touching the body.

I had a work truck that had that happen..........

 

I like the idea and I plan to do the same by adding a 3rd battery. But I look at it a little different since I work on boats for a living. They make a marine alt/battery isolator to charge batteries. It takes a single output alt and makes it 2 output with digital reg. So when one battery is charged it only charges the one that is low on voltage. And can't back feed to other battery. No over charging bank 2. and less work the alt has to do.
Now our trucks having 2 batteries is actually only one bank since they wired together. The 3rd battery would be bank 2. Also as far as you using 6awg wire is not going to be big enough. You need toknow what wattage you will be drawing and then remember that your voltage will drop on a long run. 10% voltage drop every 10ft/. Make sure you use rubber hose to wrap wire or grommet and fuse it at the battery and at the inverter. This way if it does rub to body you don't have a melt down. You only blow a fuse.
I like the idea of mounting it under the body or bed. But where... I am going to look into that. Custom box plumbed into rear of cab.
Good luck and please let us know how it turns out. I'll do the same but I don't think I'll get to that until spring.

 

Baddog,
I work on boats, too, but not professionally. I have an extra 70 amp isolator but with a 130 amp alt, I figured it would be more of a problem than a solution.

The idea of using 6 ga was the intended short run from batt to inverter...maybe 2'.(the 19" LCD tv only draws 35 amps) I have a bunch or 6/0 welding cable I used hooking up a second batt in a previous van and ran the cables along the frame with the batt in the rear. It was mainly because of the winch I had back there and the elec trailer winch. I wanted as short a run as possible from batt to winches.

I have a couple extra 3 pole manual batt switches but I always considered them a PITA.

I might have to beak down and buy a gel batt for the house batt just to be on the safe side if I keep it behind the driver seat.

 

Yea you are right about the 130 alt. and 70 amp isolator. And the digital reg. are about $300 for a 130amp. And like you said about keeping the wire down to a short run you shouldn't have a voltage drop. So how big an inverter are you going to use.I would think that 400 watt would do it. Or at least that is what I am going to use it rated 600watt peak but 400 load. I like the idea of the switch but it is alot to remember or forget. You and both know this from the boats. But simple and easy and could always combine if needed.
The gel battery is a good idea and check this out Car Audio wholesale distributor Alpine Pioneer HID Lights Clarion Hifonics Kenwood Boss - Ikesound.com - SPL SBT-800 it has a Digital Capacitor built into the gel battery. I am thinking about installing one in my boat in the cabin due to the amps are too much draw and a digital capacitor 2.0 can't keep up.
Keep after it it sound like you have some great ideas.

 

WOW! That batt is $100 less than the sears platinum AGM or Optima. Gotta do some investigating on that one.

Reading more, it only has 8 amp/hr and one year warranty. Not too sure about those specs.

I got a harbor freight 750 watt on sale with online coupon(Xmas special) for $29. Just too good a deal to pass up. I was thinking 450 watt before that.

One of the auto mechanics on one of the boat forums also recommended a solenoid connected to the starter solenoid so It is only charging or connected to the system when running. I think I got it figured out.


Oh yeah, a couple of the guys on the boat forum have small Ford diesel fleet and both say the dual battery set-up that ford has gives them plenty of power, even to run a 2000 lb lift on the back.

I guess the main difference being boat people think in terms of deep cycle for long periods of use and hundreds if not thousands of recharge cycles.