would'nt it be difficult to do this with the angles in the space where the air box is?

 

I need to run duel battery's my self, you could put one where the air box is but all the snorkel kits ha e found use the oe air box and I wanna run a snorkel :/

 

I am doing the same thing - adding a second battery. My original alternator is 117A but the OEM cables are so thin, it's like plugging a garden hose to a fire hydrant.

I ordered a new set of high gauge cables from Jeepers and Creepers. This will provide much better connections to the starter, alternator and ground. That's going in next week. http://www.jeepersandcreepers.com/10701.html

I have one Optima in the original battery location and will be installing a second one, with an opto-isolator from Painless, in the air box location, once I install the Spectre cold air intake and free that space.

I found a company that makes a tray for my XJ - Wrangler Power NW - http://www.wranglerpower.com/
Wrangler also sells alternators for all Jeeps in the 150A to 175A range that should fit the XJ. Might do that next...

 

I'm wounded...

As far as the "opto-isolator" bit - I'm used to an opto-isolator being a small solid-state component used to electrically isolate to circuits that need to interact - it uses a shrouded/shielded photon emitter and (usually) a photosensitive PN junction as a sort of transistor - allowing one circuit to influence or control the other without requiring that anything be shared between them electrically (you can therefore even run separate power supply lines and ground planes - even in the same chassis.)

However, this is usually a low-current device, how are they making this work for the high currents used in battery isolation setups? Or am I missing something?

 

That is exactly what it is.
The "solid state" battery isolators typically use MOSFET switching, with the MOSFET gate driver optically isolated from the low level logic circuits. The marketing folks saw "opto" somewhere in the engineering specs, and well... you know how marketing folks are, lol. Ends up on the box in huge letters.

FWIW, these units will survive misconnected jumper cables exactly zero times. The relay/solenoid-based units, low-tech as they are, are more durable. And unlike the epoxy-encapsulated solid states- they are field repairable.

 

This is the set up I'm going to run when ever I get around to doing it..

http://www.sleeoffroad.com/technical..._batteries.PDF

 

I started a thread on this check my profile for it!

 

I didn't see what year your jeep is but for mine, a 99 you can use a 160 amp alternator out of a 2001 - 2003 rango with the 5.9 and it's plug and play, be careful if you get one from the wreckers because they also come with a 136 amp alternator. And car audio supplies! That's where your gonna get large fuses and heavy Gage wire! Also solenoids are way better then Isolators! Do some research! The ford ones don't work so well but if you know a car audio / video guy go speak to him/her about it