IMPORTANT BATTERY INFO FOR ALL JT OWNERS

[SoK66]

"So the second battery is purely for Auto stop/start? Or more so for driving all the electronics? I would have guessed it would bring a lot more problems removing the battery entirely. Thanks for the help guys "


Many of us have simply removed it and Most likely someone has already said so. I removed the aux battery long ago and found the JT has aux battery leads long enough for me to simply run them up the the main battery. I do not allow stop-start to function so I don't need it or the aux battery headaches it causes. Some people say pull some fuse to do the delete, I never have bothered nor found it necessary. Cheers, mate!

Pull fuse #42. It eliminates the switching relay for the small battery.

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[IamPro2A]

If your mechanic didn't know Jeeps and many other modern vehicles now have auxiliary batteries, it might be time for a new mechanic. Maybe someone more experienced with cars built in the 21st century?

 

[ShadowsPapa]

Just like with a flashlight, where you wouldn't just replace one of two batteries because the weaker one will shorten the life of the new one, same goes for this bloody system. When the little POS in the fender needs replacing (it will always die first) you should dig deep, pony up the cash and replace the main battery as well.

FWIW, we run five '21 JT Sport Max Tows in our Jeep Tour business. We've been doing the aux battery delete (removing the aux battery negative cable and pulling fuse 42) on them one at a time as the "A!" warnings come up on the dash. We've run several of them that way for two years now and haven't had a single issue.

That's for series
These parallel systems have different rules.
Can't compare to a flashlight in any way.
You can indeed mis batteries of different capacities and ages in parallel. Major battery bank systems do it all the time, including our network ups systems.

 

[ShadowsPapa]

Or, make no mods like most of so and do just fine for years. Have had these for a decade, no problems. Find a smarter mechanic

 

[Flyboy2109]

"Pull fuse #42. It eliminates the switching relay for the small battery."

Necessary? With both aux batt leads on the main batt and the auxiliary gone I just let the JT think it has the aux in there and let the relays function as normal. All electrical needs are met. That's my theory of not pulling any fuses with my delete.

I can't speak for disconnecting the aux negative lead and pulling the fuse and leaving the aux in in place, I didn't do it that way. I wanted that aux batt gone. When the OEM main batt dies I will get a larger battery for my main.

 

[ShadowsPapa]

"Pull fuse #42. It eliminates the switching relay for the small battery."

Necessary? With both aux batt leads on the main batt and the auxiliary gone I just let the JT think it has the aux in there and let the relays function as normal. All electrical needs are met. That's my theory of not pulling any fuses with my delete.

I can't speak for disconnecting the aux negative lead and pulling the fuse and leaving the aux in in place, I didn't do it that way. I wanted that aux batt gone. When the OEM main batt dies I will get a larger battery for my main.

It's looking for the aux battery to check it.

There's hundreds of posts in dozens of threads explaining how this works.
Disconnecting is disconnecting - leads there or gone. Doesn't matter if you take off only the negative lead or pull both cables - it's the exact same thing electrically.
It's checking the battery level of the auxiliary battery.
If it's not there, it can generate errors when that relay opens.
If you pull the fuse, that relay can't open so the main battery voltage is still there and it sees that.

Pulling the aux battery NEG cable off the top of the IBS does the exact same thing as completely removing the cables and/or battery - electrically speaking. So "your method" is no different electrically than pulling the whole thing out like @Hootbro does.
Same thing as far as the electric system is concerned - the battery "disappears" once that negative cable is disconnected from the top of the IBS. Removing the other cables doesn't change that.

 

[Flyboy2109]

"It's looking for the aux battery to check it.

There's hundreds of posts in dozens of threads explaining how this works.
Disconnecting is disconnecting - leads there or gone. Doesn't matter if you take off only the negative lead or pull both cables - it's the exact same thing electrically.
It's checking the battery level of the auxiliary battery.
If it's not there, it can generate errors when that relay opens.
If you pull the fuse, that relay can't open so the main battery voltage is still there and it sees that.

Pulling the aux battery NEG cable off the top of the IBS does the exact same thing as completely removing the cables and/or battery - electrically speaking. So "your method" is no different electrically than pulling the whole thing out like @Hootbro does.
Same thing as far as the electric system is concerned - the battery "disappears" once that negative cable is disconnected from the top of the IBS. Removing the other cables doesn't change that.
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As Peewee Herman says, "There's always a big but..."

But, I didn't just disconnect the negative lead, I simply placed aux batt cables on the main, removed the aux.. Therefore, the JT doesn't see anything as missing, functions normally. No need to muck up the fuses. The relays and aux test circuits simply see the main batt as the aux...no big deal; everything powered, simple mod. Now no aux batt death can kill the JT in the outback.

Two years running, no issues, no warnings.

 

[ShadowsPapa]

It's looking for the aux battery to check it.

There's hundreds of posts in dozens of threads explaining how this works.
Disconnecting is disconnecting - leads there or gone. Doesn't matter if you take off only the negative lead or pull both cables - it's the exact same thing electrically.
It's checking the battery level of the auxiliary battery.
If it's not there, it can generate errors when that relay opens.
If you pull the fuse, that relay can't open so the main battery voltage is still there and it sees that.

Pulling the aux battery NEG cable off the top of the IBS does the exact same thing as completely removing the cables and/or battery - electrically speaking. So "your method" is no different electrically than pulling the whole thing out like @Hootbro does.
Same thing as far as the electric system is concerned - the battery "disappears" once that negative cable is disconnected from the top of the IBS. Removing the other cables doesn't change that.
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As Peewee Herman says, "There's always a big but..."

I didn't just disconnect the negative lead, I simply placed aux batt cables on the main, removed the aux.. Therefore, the JT doesn't see anything as missing, functions normally. No need to muck up the fuses. The relays and aux test circuits simply see the main batt as the aux...no big deal; everything powered, simple mod. Now no aux batt death can kill the JT in the outback.

Two years running, no issues, no warnings.

Ah, and now we know the REST of the story, as Paul might have said - you didn't remove cables at all, you routed them back.
And you muck up zilch by pulling a simple fuse - what's to muck up. Pulling a fuse for some, I suppose, can be "gee, what am I breaking", but muck up?

Even my wife's JLU has issues where it now and then says "aux switches temporarily unavailable".
I know for a fact it's not the aux battery. I just put a charger on it and the messages go away until a few weeks later.

Yeah, that aux battery fear is almost funny - the main dies just as often, and leaves you stuck.
It's not the system that's problematic, it's the Jeep OEM batteries and how these don't get driven.

 

[Flyboy2109]

"Yeah, that aux battery fear is almost funny - the main dies just as often, and leaves you stuck.
It's not the system that's problematic, it's the Jeep OEM batteries and how these don't get driven."

To continue to beat the dead horse...No aux battery fears, I just do not have that inaccessible battery to change...ever. Or to strand my wife anywhere. Or to disable my JT for no good reason but an aux batt failure. I'd much rather have the single main and make it heavier duty on down the road. Simple is better, especially for an Aussie in the outback!.

 

[ShadowsPapa]

"Yeah, that aux battery fear is almost funny - the main dies just as often, and leaves you stuck.
It's not the system that's problematic, it's the Jeep OEM batteries and how these don't get driven."

To continue to beat the dead horse...No aux battery fears, I just do not have that inaccessible battery to change...ever. Or to strand my wife anywhere. Or to disable my JT for no good reason but an aux batt failure. I'd much rather have the single main and make it heavier duty on down the road. Simple is better, especially for an Aussie in the outback!.

Location, location, location, as they say here.

 

[Gvsukids]

@Flyboy2109 save yourself time by using the "reply" button. Also, the person you are quoting will receive a notification.

 

[Swegian]

Speaking of....location....location.....location, they have that really cool new battery holder do-hicky that holds the battery and I think moves the little battery right up on top... Genisis jl/jt real cool. If you dont want to delete and dont want to dig for it ever again.

I

 

[AustinKalb]

True enough lol. But it’s hard to look for something when you don’t know there is a thing to look for haha. Without going to page 169 of the owners manual to look for a possible second battery. Also wouldn’t have thought to search for aux battery on this forum when I was trying to solve the service shift debacle.

I think the biggest take away that everyone can agree on is that across the board the messages that come up on the dash aren’t best suited to what the actual problem is a lot of the time!

Thanks everyone!

I read the manual cover to cover at least twice when I get a new vehicle. That’s just me. YMMV

 

[gonemad]

I called a friend, who also happens to own a Gladiator, about two hours after I got home with my first Glad. He asked, “Did they tell you about the two batteries?"

Me: “Why no, no they didn’t"

Nevertheless, that was in 2024, and I now own a 2025. Still ticks me off, but we take the good with the bad, right?

 

[Mr Miami]

Recently I had been having issues with my electronics starting to fail in my gladiator.

The Auto stop/start symbol come up on my dash months ago (which I actually wasn’t upset about) then more recently remote start stopped working, which was more annoying as I live close to work and would start it from inside 10 minutes before I left. Then I was having messages like “aux function unavailable” and “parking sensors disabled” etc. etc.

The battery had been testing fine but finally decided to replace it. Once I replaced it, it came up with an unclearable code and a message “service shifter”.

I know from searching the forum and all over the net that the message seems fairly common, with a number of ways people have fixed it.

Short story long, I had to have it towed less than a kilometre to my mechanic, because I found that pulling the park release cord only works while you’re pulling on it and won’t allow the engine to run once you’ve released the brake, making it impossible to flat tow.

Side note; the nearest dealership is 3 hours away in Melbourne, as they all seem to slowly but surely be abandoning Jeep/Dodge/Chrysler, presumably to make way for all the Chinese crap coming into the country.

After 3 days of scratching their heads, they managed to find a SECOND SMALLER BATTERY underneath the main battery. Changed that out and everything is fine again (including auto stop/start)

I could be wrong but I haven’t found a single sources of information to say that they have a second battery. In fact the tray under the main battery showed no indication that there was anything hidden under it!

Anyways, hopefully this is some helpful info for you guys. Sorry for the long rant.

Cheers legends!

Yes, I just came back from a 2 week drive all through Australia and as you mention, Jeep dealers are few and far between; and I mean really far between.

The Outback region is ALL Toyota Hi-Lux but cities do have a much wider range of vehicles and a ton of Chinese things whose name I can't even pronounce. China definitely has a strong presence in Australia. Some of the stuff looks really good. Just doubt how they would hold up in the real world.

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