cornfed85

new guy here looking for some info.i seen a write up on here about the dual battery setup in the engine bay,that kit is too expensive for my budget.im wondering if someone can give me some info on my project on what im wanting to do.i recently purchased 2 ever start 58-3N batteries and a battery box.

im wanting to replace my engine bay battery with one and place my secondary battery in the cargo area.i currently have just my 1 battery in the engine bay with my winch ran directly to it,and the power cable for my lights.my lights are ran off of a 70's ford starter solonoid as seen in this picture..


im having a big issue with my alternator ******* down when i turn on my 4 lights on the front of my roof rack and when i run my winch.i taked to a local alternator/starter shop and he told me he would build me a 200 amp alternator for $100.im wanting to safely run a battery in the back for my accessories with this 200 amp alternator build so im looking for some good advice to do this safely.i have so far only been told to get the alternator built and run this battery isolator and 4 guage wire to the cargo area to my battery.

http://www.powerstream.com/battery-isolator.htm

i also plan on running this on board air compressor in the back next to my battery so i can have air when i need it and to run my horns.this air compressor is 12 volt.

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if anyone can give me some info about this project i will greatly apreciate it,its slowin me down on other work on the jeep and no one likes a bump in the buildin road...thank you for looking and if anyone wants to see my lights winch etc to help me out i posted an introduction about myself and my jeep on here in the introduction section.

5-90

A lot of the issue with your alternator "******* down" could be that you're just pulling too much current at idle. Does this happen only when you're idling, and it picks back up when you give it some throttle?

Alternators typically only give you some 40-45% of max rated output at idle, and you need to get up around 3000-3500rpm at the spindle (~1200-1500rpm at the crankshaft) to get full output. This isn't a sign that your alternator is "getting old" - it's working just like it's supposed to.

Fix for that? Upgrade. 40-45% of 90A is still a good deal less than, say, 40-45% of 160A - and you can get 160A with a COTS unit (you can go higher if you want to special-order from a place like Mean Green, High Output Alternators, Nations Auto Electric, or similar.) NB: An alternator upgrade requires a wiring upgrade as well - since the wiring is sized "just enough" for the OEM unit running full output at about 30-40% duty cycle (it's sized for 100% duty cycle at 75% or so of max rated.) You'll also have to upgrade the fuse protection in that circuit anyhow.

First, make sure your battery will fit in the underhood battery tray (or you won't be able to secure it properly in the first place.) I think a BCI #58 will, but I'm not sure.

Second, plan on where you're going to put your second battery.

Third, decide whether you are going to want to uprate your alternator or not (now or in the future.)

Fourth, decide what accessories you're adding that you'd like to be able to run with the engine OFF (because those are what you're going to want to wire directly to your second battery.

Fifth, decide where you're going to put that secondary battery (bearing in mind you want to try to keep high-current leads as short as practicable.)

You are going to want a battery isolator. Why? Because you're not going to be running these batteries "in bank," they may not be the same age anyhow (batteries "in bank" must be the same age/rating/type - as close to perfectly identical as possible. Else, they'll drain each other "handing a charge back and forth.") You can use a 100% duty cycle solenoid (not a Ford starter motor solenoid - this is different) or a solid-state isolator (essentially a diode pack.)

Once you have that settled, hit me backchannel (link in sig,) and I'll roll up my sleeves and help you design a system that will be reliable and safe for you. Sound good?

4.3L XJ

I would be real interested in knowing who will build a 200 amp alternator for $100. I would ship him one to do in a heart beat.

firstime00XJ

is this a dd or a trail rig? I don't know if I would feel comfortable running a battery in the cargo area, being that it is a common space with passengers. (I know people do it, but still) I would try to mount it in the engine compartment first. Sounds like a good idea though, running dual batteries.

Troth

I have a 170 amp powermaster alternator for $200 and a new 540 battery. I have 2 12 inch subs, 6 bajas, and 4 overhead lights. even at idle with everything on full blast I dont drain my battery. are you sure you need to do that stuff?

blkcherokee

if you remove your air box you will have plenty of room for a secondary battery just a thought

cornfed85

ya i looked at the setup to run on the drivers side in place of the air box and thats pretty high for my budget,anyone know of a cheaper way to do this?

cornfed85

its a mixture of both due to not having a way to haul it being a strict trail rig i just want to do something to where my volt guage dont bottom out when i kick on my front rack lights,or my winch.i know a guy with a cj that has the same winch i have and his jeep dont dog out a bit running his winch.

svt cobra

if you are mounting a battery in the cargo area only use a jell battery like optima . A regular car battery has toxic fumes that u dont want to be breathing.

5-90

All batteries will outgas when charged - so vent your battery box to outside the passenger cabin.

However, the idea of using an AGM (Optima) or Gel Cell (Odyssey) in the cabin still stands - you don't want to spill your battery if you tip too far...

4.3L XJ

I have dual optimas in my rear cargo area and have had no problems at all with them.

posjeepxj

try 136amp alt of of a 96-98 grand cherokee ($35 at my local jk)
try car-part.com

5-90

True - the Optima is an AGM (Absorbed Glass Mat) battery, and therefore has no liquid to spill. You still have outgassing issues, so you may want to run a ventline outside the passenger cabin before too long...

cornfed85

i may just save up the money and get this setup i seen that replaces the air box...but do i need to buy a special air setup and spend more money or can i get a filter to fasten onto the end of the hose that runs to the oem air box?

keith two tone cherokee

just get a flat peice of steel some threaded rod nuts washers move your air filter and go to town. thats what the kits going to be you just pay 3 times more than what you can do it yourself