AUX Battery Replacement Experience and FYI

[Verne]

I had my Aux battery replaced today at my local dealer. For the record, I like my dealer and would buy again from them. For context my 21 Mojave did not go into limp mode or throw an error code, etc. Instead, my stop/start feature just wouldn't ever work. It stopped working about 3 months ago (I enjoyed it not working haha, but didn't want to risk getting stranded). I read somewhere that if stop start isn't ever ready, it is the aux battery. Before replacing, the tech did test the battery and it did show that the battery did not need replaced. In fact, they tried to talk me out of it. Instead I just had them swap it out for a new one because at some point the battery is going to go, and eventually this jeep is going to my son to drive. It was worth the investment and peace of mind to me. About 10 mins into my drive home, and at the first stop light, the stop/start worked again. So, either the battery did need replaced or swapping it caused a system reset.

Anyway, post is just for your reference and my experience in case you are experiencing the same. NOW my only concern is that my clock, set to GPS time, is completely off. I assume that will come back eventually.

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[ShadowsPapa]

I read somewhere that if stop start isn't ever ready, it is the aux battery.

BE CAREFUL reading that sort of thing.
It MIGHT be the main battery, or - could be you don't drive it enough.
Those who have posted that are repeating things from people who don't understand electrical systems, batteries, and so on.

It could be you didn't drive it often enough or far enough to keep the batteries above about 12.4 volts, and now they are fully charged - if it happens again, invest in a battery tender and use it.

 

[Verne]

BE CAREFUL reading that sort of thing.
It MIGHT be the main battery, or - could be you don't drive it enough.
Those who have posted that are repeating things from people who don't understand electrical systems, batteries, and so on.

It could be you didn't drive it often enough or far enough to keep the batteries above about 12.4 volts, and now they are fully charged - if it happens again, invest in a battery tender and use it.

I drive 40+ miles daily. No matter what conditions the start stop didn't work. The display would say cabin cooling, not ready or cabin, heating not ready. Then after cooled or heated it would just say not ready. Spring weather, no heat or cool, windows down, would never be ready. Again, as I stated, both batteries were showing fully charged at dealer. And as I stated, this was my experience. Rig is almost 5 years old so investing in a new AUX battery is fine. I don't have any empirical data that suggests a connection but it is a strong correlation, no? Again, just my experience being shared for those that want to consider.

Also, as stated, could just simply be a system reset from the main battery disconnect. Nonetheless it wasn't working before the swap...now it is. That is worth something given my driving patterns and experience. At least I have peace of mind...

 

[In3briatedPanda]

I had my Aux battery replaced today at my local dealer. For the record, I like my dealer and would buy again from them. For context my 21 Mojave did not go into limp mode or throw an error code, etc. Instead, my stop/start feature just wouldn't ever work. It stopped working about 3 months ago (I enjoyed it not working haha, but didn't want to risk getting stranded). I read somewhere that if stop start isn't ever ready, it is the aux battery. Before replacing, the tech did test the battery and it did show that the battery did not need replaced. In fact, they tried to talk me out of it. Instead I just had them swap it out for a new one because at some point the battery is going to go, and eventually this jeep is going to my son to drive. It was worth the investment and peace of mind to me. About 10 mins into my drive home, and at the first stop light, the stop/start worked again. So, either the battery did need replaced or swapping it caused a system reset.

Anyway, post is just for your reference and my experience in case you are experiencing the same. NOW my only concern is that my clock, set to GPS time, is completely off. I assume that will come back eventually.

did you or have you considered the genesis dual battery setup? Im interested in this 'upgrade' but it is an expensive upgrade vs changing out batteries.

I have a 2021 as well, still on both original batteries, my start/stop still works too.

 

[Verne]

did you or have you considered the genesis dual battery setup? Im interested in this 'upgrade' but it is an expensive upgrade vs changing out batteries.

I have a 2021 as well, still on both original batteries, my start/stop still works too.

I have. I just never wanted to spend the money on it.

 

[ShadowsPapa]

4 years is a long time on original Jeep batteries - watch for the main battery to go.
Also watch that it might start doing the same thing in the near future.

It's all about battery SoC and battery health.
It doesn't matter if it's the main or the aux - if it senses/knows that either or both batteries might not support a restart, it won't let ESS function.
In other words - if it senses battery CAPACITY is low, regardless of the voltage, it won't allow a shut down.

I resolved my 2020 by disconnecting the batteries, recharging each properly with a good AGM charger (with the IBS fully disconnected so it would reset to defaults). After that, ESS worked fine for months, and was still working when I traded it in for my 2022.

I had similar happen with my 2022 - batteries were fine, but it was never getting charged fully enough even with 45-60 minute drive times (Alternators are topper-offers, not battery chargers!!!!!).
So once I started using a BatteryMinder on it now and then ESS worked every time.

40+ miles would count if it was at a time, all at once, but it's only 20 miles two times, it's likely barely keeping up.

DO check your battery voltage now and then, engine off, open the hood, and use a meter on the main battery posts and see how the voltage is looking. Anything under about 12.5 or so - it's not keeping up.
And if it sits between drives, it's going to be worse.

 

[ShastaJT6]

did you or have you considered the genesis dual battery setup? Im interested in this 'upgrade' but it is an expensive upgrade vs changing out batteries.

I have a 2021 as well, still on both original batteries, my start/stop still works too.

Not OP, but have a 2021 and installed the genesis kit last summer.

Do it. Now. Its amazing. My aux went out and I didnt want to waste time and money replacing something that was just going to go out again later. The Genesis kit is a major upgrade, the busbar system is great, and the peace of mind I have from know I can run accessories and not worry about having enough juice to start the truck, awesome.

 

[In3briatedPanda]

Not OP, but have a 2021 and installed the genesis kit last summer.

Do it. Now. Its amazing. My aux went out and I didnt want to waste time and money replacing something that was just going to go out again later. The Genesis kit is a major upgrade, the busbar system is great, and the peace of mind I have from know I can run accessories and not worry about having enough juice to start the truck, awesome.

thats my thinking as well, just hate spending closer to 800-1k vs $350 for two batteries and two hours of my life. lol.

I run lights and accessories so i want the can bus, i just feel i can build one cheaper but the pull of a complete kit appeals to me, the price point hurts my feelings tbh.

Thanks for sharing, you confirmed what im thinking. appreciate it!

 

[ShadowsPapa]

Not OP, but have a 2021 and installed the genesis kit last summer.

Do it. Now. Its amazing. My aux went out and I didnt want to waste time and money replacing something that was just going to go out again later. The Genesis kit is a major upgrade, the busbar system is great, and the peace of mind I have from know I can run accessories and not worry about having enough juice to start the truck, awesome.

There's a lot easier and a lot cheaper ways.
Many of us don't need the double-capacity battery setup, the space it takes and the massive crazy money they get for the mounting and brackets.
OVERKILL for most people.
A lot easier to put in a massive, high quality main battery that equals the capacity of the two combined and just leave out the aux and pull a fuse.

Explain why 3/4 of us would ever benefit from a thousands dollar dual battery setup when most Jeeps do great on one.
You can drop in a nice lithium battery with management built in and never worry about running out of power to start the engine.
Fraction of the cost, no complexity at all.

 

[ShadowsPapa]

I run lights and accessories so i want the can bus, i just feel i can build one cheaper but the pull of a complete kit appeals to me, the price point hurts my feelings tbh.

You can have a great system at half the cost, and taking a lot less space. I refuse to give up that much space, and that much money for no benefit in my case.

You can get the parts from Redarc and others to manage dual batteries, and get creative in other ways.
I feel that "kit" is at least 30% more expensive than it should cost.

 

[In3briatedPanda]

You can have a great system at half the cost, and taking a lot less space. I refuse to give up that much space, and that much money for no benefit in my case.

You can get the parts from Redarc and others to manage dual batteries, and get creative in other ways.
I feel that "kit" is at least 30% more expensive than it should cost.

100% agree. im positive i can build a bus bar system cheaper. i always think of markup as a 'convenience fee'. what do i make an hour? can i build one in my time cheaper taking that into account?

its not even a need, it would only be a QoL upgrade at this point. You are spot on, it is overkill for my needs.....but i want it all the same. lol

 

[Deleted member 57233]

I had my Aux battery replaced today at my local dealer. For the record, I like my dealer and would buy again from them. For context my 21 Mojave did not go into limp mode or throw an error code, etc. Instead, my stop/start feature just wouldn't ever work. It stopped working about 3 months ago (I enjoyed it not working haha, but didn't want to risk getting stranded). I read somewhere that if stop start isn't ever ready, it is the aux battery. Before replacing, the tech did test the battery and it did show that the battery did not need replaced. In fact, they tried to talk me out of it. Instead I just had them swap it out for a new one because at some point the battery is going to go, and eventually this jeep is going to my son to drive. It was worth the investment and peace of mind to me. About 10 mins into my drive home, and at the first stop light, the stop/start worked again. So, either the battery did need replaced or swapping it caused a system reset.

Anyway, post is just for your reference and my experience in case you are experiencing the same. NOW my only concern is that my clock, set to GPS time, is completely off. I assume that will come back eventually.

I had the same situation, and the aux tested fine because the main battery was the one that went bad.

 

[ShadowsPapa]

I had the same situation, and the aux tested fine because the main battery was the one that went bad.

Yeah, also interesting how there's always "spend more money! You need this!" all when a simple fix or some other mod will handle it for $600 less.
There's some heavy-duty overlanding and crawling going on without the massive expenditures often advised.

100% agree. im positive i can build a bus bar system cheaper. i always think of markup as a 'convenience fee'. what do i make an hour? can i build one in my time cheaper taking that into account?

There are a lot of great fabrication examples here in the forums by multiple members. You can take your time, modify as you go or need, etc.
It's really simple to rig up terminal strips, or buy ready to go, to attach lighting to.
I made a simplistic "buss" system for my aux switches - with places for multiple grounds without going to the fender ground points. It was covered so I couldn't drop anything on it and short things out, but I could connect in a light or other accessory in seconds with just a screwdriver.
You can use much heavier setups from electronics sources and build what you want - and take less space.
That's another thing - I don't want my engine bay so full of stuff I have to keep moving things to get to anything. I like a clean engine bay, easy to work on.

 

[ShastaJT6]

All valid points. Definitely could have built my own and saved a few bucks, but it was within the budget and sometimes my time is more important. Others may want to put their own together and theres nothing wrong with that, but if you can afford it the Genesis kit is a great option.

 

[GCHunter]

I had my Aux battery replaced today at my local dealer. For the record, I like my dealer and would buy again from them. For context my 21 Mojave did not go into limp mode or throw an error code, etc. Instead, my stop/start feature just wouldn't ever work. It stopped working about 3 months ago (I enjoyed it not working haha, but didn't want to risk getting stranded). I read somewhere that if stop start isn't ever ready, it is the aux battery. Before replacing, the tech did test the battery and it did show that the battery did not need replaced. In fact, they tried to talk me out of it. Instead I just had them swap it out for a new one because at some point the battery is going to go, and eventually this jeep is going to my son to drive. It was worth the investment and peace of mind to me. About 10 mins into my drive home, and at the first stop light, the stop/start worked again. So, either the battery did need replaced or swapping it caused a system reset.

Anyway, post is just for your reference and my experience in case you are experiencing the same. NOW my only concern is that my clock, set to GPS time, is completely off. I assume that will come back eventually.

My experience was similar with the start/stop system ceasing to shut down the engine. I started by having my batteries checked at the dealer. They told me no problem. I am guessing they hit the batteries once with a check. I then went to a third party for a battery check, they showed 98% the first two hits and then the batteries dropped to %27 on the third hit. So I installed new batteries.

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