Should be easy to charge the back battery. If you just want to periodically top it off, just rig up a wire from the front battery or alternator back to the battery. Connect it when you want to charge (hook back battery in parallel with the front battery), then disconnect it manually. Only time you need/want to isolate the batteries is when they are not being charged.

I'm running a pseudo 3-battery setup in my 1st gen using a small portable 12V battery pack in the cargo area. I plug in the lighter plug for charging then plug my cooler into the battery pack. This was the cooler runs off that battery (and can for about 24 hours) and is charged automatically whenever the engine is running.

 

well this all sounds awesome. im not sure what im going to do yet. i really will just need some way of charging that battery back up, so i think i might just run a wire back from the alternator. i took a few pics today of the stock battery location. with some type of very very solid plate (tray), 2 red tops can be mounted in the stock battery location IF you find a place to put the coolant reservoir. im not sure of the size of the yellow top, which i know is the popular 2nd battery, but i had a red top laying around. so if anyone wants to run a serious dual battery setup in a 3rd gen in the stock battery location area, it can be done, without much work.

 

nice. thanks for the pics

 

I will warn you, if your stock battery location is like my '04 Taco (and it looks like it is) you will wind up with your inboard battery resting against your radiator. A little work with a BFH could probably help that.

 

i dont plan on putting a 2nd battery there. i will put mine in the trunk. simply put, im just too lazy.

those pics just show basically, it can be done.

 

have you tried this, put two batteries there? how'd it work? did you keep it this way?

 

I'm in-process right now. I stuffed two group 34 yellow tops there and they were up against the headlight wire harness and the radiator. Some work with a BFH against the fender may help that. It's extremely close, maybe an 1/8 inch or so, and extremely tight. Other than tight, my other objection is that it is a bunch of weight to throw out on that fender.

Right now, I'm looking at ways to move the air cleaner to the back of the engine bay and pipe it out to a snorkle to free up space on the passenger fender - that ABS controller at the back of the passenger fender really should have gone over on the driver's side.

With a bit of will and skill I'm sure you could get two group 34 Optimas to fit where the single stock battery is. If I remember correctly, for the Maya Hunter (pictured earlier) the fabricators cut into the wheel well to make a bit of additional room and move the battery out away from the headlight wire harness. I don't think they had the same problem with the inboard battery touching the radiator since the '05 is a bit wider.

 

When I was doing the car audio competition thing, I had six batteries (2 under hood, 4 in a custom box under the bed) all wired in parallel off one alternator lead. I never had a battery problem, so I don't think an isolator is REALLY necessary. What IS really necessary is ventilation. As the battery charges, it releases toxic/explosive gasses that need to be dispersed. DO NOT INSTALL A BATTERY IN THE PASSENGER CABIN WITHOUT VENTILATION.

They sell metal battery boxes - why not get one and weld it to the inside of the frame? Run a large wire back there (I used 1/0) from the underhood battery, and good to go!

 

Oh - one other thing. Any way to find out what the underhood of a diesel looks like? They sometimes have two batteries to run the starter against the high compression ratio...

 

Almost every diesel will have dual batteries, you are correct.... almost positive our across the pond friends with diesels will chime in and say yes...