I'm joining the "aux battery won't charge" club. Should I just delete it?

[Blue Ridge]

Well, for this time, I'm replacing both. But if the issue appears again sooner than I think it should, I feel safe removing the aux. I appreciate everyone's feedback.

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[JeepOfTheseus]

The aux battery is there (in my understanding) to stabilize the computer electronics during a stop/start event, (although many other vehicles do it with only one battery).
If you don't use, and/or have disabled the stop/start "feature" not having the aux battery is fine, although I can't speak for having aux switches.
I disconnected my aux battery months ago (and pulled the fuse, I think #42) and everything works just fine. In fact, according to my Banks gauge the voltage went from around 12.9 to 13.7 after I did that because I believe (and I may be wrong) that before, the voltage reading was both batteries in parallel and the aux battery was getting weak.

Interesting about the fuse…what component is it for? My aux battery is gone, but I don’t believe I removed a fuse.

 

[Bananaman]

Interesting about the fuse…what component is it for? My aux battery is gone, but I don’t believe I removed a fuse.

Pulling the F42 fuse just forces the startup test to look at the Main Battery instead of the Aux Battery.
I just followed what I read here, (dangerous I know), but it's working.

 

[Andy29847]

Pulling the F42 fuse just forces the startup test to look at the Main Battery instead of the Aux Battery.
I just followed what I read here, (dangerous I know), but it's working.

Pulling F42 disables the power control relay and silences the alarm for the missing aux battery.

 

[ShadowsPapa]

Pulling the F42 fuse just forces the startup test to look at the Main Battery instead of the Aux Battery.
I just followed what I read here, (dangerous I know), but it's working.

What Andy here says -

Pulling F42 disables the power control relay and silences the alarm for the missing aux battery.

Yes, PCR can't open so it won't know there's 0 volts there.
If the PCR can't open as the starter engages for the PCM to do its check, it will see the voltage of the main battery.

It prevents an error - fools the PCM for a while.

 

[Blue Ridge]

Well sh*t, I would have deleted it and certainly will when it inevitably fails again. I was worried about having my first vehicle with even power windows, let alone a car computer (as I call it) altered in a way that could leave me stranded.

 

[ShadowsPapa]

I would have deleted it and certainly will when it inevitably fails again.

It's not really inevitable. Heck, we've had several Jeeps with the 2 battery system.
Only had a failure with one - the main battery failed.

 

[Blue Ridge]

I suspect half the problem is my driving pattern. I drive to and from work every day with about 1.5 mile trip each way. The grocery store is about a mile. Downtown is .5 from my house. And then I have the occasional road trip where I might drive several hundred 2-3 times a year. But my usual driving habits just don't give the aux time to charge. At least that's my theory.

 

[NC_Overland]

I suspect half the problem is my driving pattern. I drive to and from work every day with about 1.5 mile trip each way. The grocery store is about a mile. Downtown is .5 from my house. And then I have the occasional road trip where I might drive several hundred 2-3 times a year. But my usual driving habits just don't give the aux time to charge. At least that's my theory.

That’s definitely a factor. When my batteries got weak, after five years, the auto start stop only worked after long drives.

 

[ShadowsPapa]

I suspect half the problem is my driving pattern. I drive to and from work every day with about 1.5 mile trip each way. The grocery store is about a mile. Downtown is .5 from my house. And then I have the occasional road trip where I might drive several hundred 2-3 times a year. But my usual driving habits just don't give the aux time to charge. At least that's my theory.

They both charge at the same time - in parallel. You really aren't getting either battery properly fully charged at that rate.
That's terribly hard on batteries.

 

[Lunentucker]

Well sh*t, I would have deleted it and certainly will when it inevitably fails again. I was worried about having my first vehicle with even power windows, let alone a car computer (as I call it) altered in a way that could leave me stranded.

Get a portable jump box, and at least learn how to bypass the AUX battery if need be on the road.
There have been a few cases where the owners couldn't even get the vehicle jump started until the AUX battery was taken out of the picture.

 

[Lunentucker]

I suspect half the problem is my driving pattern. I drive to and from work every day with about 1.5 mile trip each way. The grocery store is about a mile. Downtown is .5 from my house. And then I have the occasional road trip where I might drive several hundred 2-3 times a year. But my usual driving habits just don't give the aux time to charge. At least that's my theory.

That's really bad for everything, including your engine.
You need an EV.

 

[ShadowsPapa]

That's really bad for everything, including your engine.
You need an EV.

That is indeed an engine killer - and not great on the other parts, either. I've seen engines ruined over short drives, never getting hot enough.

 

[Blue Ridge]

I drove my last truck (1996 Chevy Silverado) for over 20 years primarily to work and back and never had battery problems (out of the ordinary), let alone other engine issues. I guess modern cars are a different beast. There are days I wish I'd just kept it. I love my JT, but in 4 years I've just got 21K on the engine. And that's with taking a couple of 1000 mile round trips to the Outer Banks twice a year. Never thought I'd own an EV but it makes sense.

 

[Splenda]

That is indeed an engine killer - and not great on the other parts, either. I've seen engines ruined over short drives, never getting hot enough.

What would you consider "long enough"? My commute is about 8 miles each way, half through town and the other half down a 55mph two lane country road. I've always worried about it being too short.

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