Where is the aux battery?

[wanderer]

My auto stop start light has been on for a while! Guessing the aux battery is low maybe getting ready to be dead.
If it dies will I be stranded ?

Is this some place I can get too reasonably easy ? What is involved in changing it out and is there a more robust battery available ?

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[Beemer533]

If you have the 3.6 it's basically under the main battery.

You can get to through the fender or from the top. Through the top requires pulling the Fuse box, which isn't too bad.

Supposedly going through the fender is easier, but I haven't done it personally.

If it is really dead, you won't be stranded but ESS won't work (if you care).

Eventually though it will kill the main battery, so you will want to get them tested.

 

[Lunentucker]

Not under the main battery. Under the fuse box.
Disconnect it by removing the ground cable for the AUX battery from the main ground group.
If it's made before mid 21 it's the smaller ground. If it's after mid 21 it's typically the larger ground cable.
Tape the end with electrical tape and zip tie it in place so that there will be no incidental contact.
Remove fuse F42 to disable the ESS system.

Now it won't drain your main battery by repeatedly trying to recharge.

From that point you can either leave it as is or replace the AUX battery at your leisure.

I'll post a video on removal and or replacement.

 

[Lunentucker]

Method 1 - From the top
Genesis Dual Battery System for the Jeep Wrangler JL / Gladiator JT - YouTube

 

[Lunentucker]

Method 2 - Via the fender liner

 

[Beemer533]

Not under the main battery. Under the fuse box.
Disconnect it by removing the ground cable for the AUX battery from the main ground group.
If it's made before mid 21 it's the smaller ground. If it's after mid 21 it's typically the larger ground cable.
Tape the end with electrical tape and zip tie it in place so that there will be no incidental contact.
Remove fuse F42 to disable the ESS system.

Now it won't drain your main battery by repeatedly trying to recharge.

From that point you can either leave it as is or replace the AUX battery at your leisure.

I'll post a video on removal and or replacement.

Semantics I guess, yes it's directly under the Fuse box but you aren't getting it out without pulling the main battery which is why I said "basically" under the battery and that you need to pull the Fuse box....

 

[Beemer533]

Method 2 - Via the fender liner

I went through the top because I was doing the Genesis system, but if all I was after was the aux battery, this definitely seems like the way to go.

 

[ecidiego]

Go the fender liner way. You don't have to remove anything up top, including the main battery....just disconnect cables and isolate them.

 

[Dougstdig]

If you have the 3.6 it's basically under the main battery.

You can get to through the fender or from the top. Through the top requires pulling the Fuse box, which isn't too bad.

Supposedly going through the fender is easier, but I haven't done it personally.

If it is really dead, you won't be stranded but ESS won't work (if you care).

Eventually though it will kill the main battery, so you will want to get them tested.

3.6 its under the fuse box.
3.0 us under the battery

 

[ecidiego]

Lot of people argue about the "correct, Jeep endorsed way" to change the Aux battery for the 3.6 gasser. This is straight from the factory service manual:

 

[Lost1wing]

My auto stop start light has been on for a while! Guessing the aux battery is low maybe getting ready to be dead.
If it dies will I be stranded ?

Is this some place I can get too reasonably easy ? What is involved in changing it out and is there a more robust battery available ?

Guesses get expensive and are a waste time in some cases. Get a volt ohm meter and remove the ground cable at the fender, the negative aux cable from the main battery. Now you can check both batteries separately. If you have have access to an agm battery charger you can charge both batteries independently. After charging each battery, let sit disconnected for a few hours and check with the meter again. This doesn't give you the complete story on battery condition, but if you have a bad cell in one of the batteries it will show itself.

Or delete the aux as mentioned above. However, if the main battery is your problem, a potential no start may be in your future.

You can do the aux delete and install a new main battery. You won't know what the issue was but you may not care, just a possible premature battery replacement is all.

 

[sharpsicle]

I would test it out before going at replacing it. If the Auto Start/Stop warning light is on, chances are good it could be something completely different from the battery. Usually a failing battery has different warnings on the dash.

I would recommend diagnosing the problem before throwing parts at it. I'd hate for you to go through the battery replacement process just to find it wasn't the cause.

 

[AnthonyC]

Today, I'm going to try and reseat the aux battery tray so I can get the third bolt back in haha!.

 

[1550jrit]

I just spent the past two hours replacing my Auxiliary battery with an Odyssey Extreme. I decided to go through the top after watching Wyalife’s video on YouTube. The dude was sweating when he was finished, and now I know why. It was actually pretty easy getting everything apart and the new battery installed. It was getting the fuse box back together that was the ass kicker. It took me 30 minutes of gently fighting with it to get it lined up and snapped back together. I was honestly worried for a bit, but then my wife came home and glared at me knowing I bought more Jeep stuff, and a few seconds later it snapped together perfectly. She either cast a spell on me or is my good luck charm. Either way I don’t care because it all went together and the truck fired up with zero issues.

If I was to do it all over again, I’d go from the fender. Though, going through the top allowed me to see that the Odyssey had slightly wider post bases and the factory connectors had tabs that needed to be bent out of the way to properly mount them. I don’t believe I would have been as easily visualized from the bottom. Both my batteries are brand new now just before I leave for the Black Hills Jeep jamboree.

 

[ShadowsPapa]

I just spent the past two hours replacing my Auxiliary battery with an Odyssey Extreme. I decided to go through the top after watching Wyalife’s video on YouTube. The dude was sweating when he was finished, and now I know why. It was actually pretty easy getting everything apart and the new battery installed. It was getting the fuse box back together that was the ass kicker. It took me 30 minutes of gently fighting with it to get it lined up and snapped back together. I was honestly worried for a bit, but then my wife came home and glared at me knowing I bought more Jeep stuff, and a few seconds later it snapped together perfectly. She either cast a spell on me or is my good luck charm. Either way I don’t care because it all went together and the truck fired up with zero issues.

If I was to do it all over again, I’d go from the fender. Though, going through the top allowed me to see that the Odyssey had slightly wider post bases and the factory connectors had tabs that needed to be bent out of the way to properly mount them. I don’t believe I would have been as easily visualized from the bottom. Both my batteries are brand new now just before I leave for the Black Hills Jeep jamboree.

There's a far better video out there of a guy doing it through the fender and proving you don't need to pull the liner out like most do. I think he removed only some of the fasteners and cut the time from what others have shown. Wish I had saved the link. He made it look simple and fast.

I do hope you charged it first...........

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