The famous aux battery failure with a twist 3.6

[Jrat831]

So after reading and reading I decided to make my own post to see if anyone is expierencing the same problem as I am.

The events:
- 1 month ago my car failed to restart from start stop feature at a red light. Was able to jump and go about my day, continued volt watching on dash
- 2 nights ago my car failed to cold start (dead battery) was able to jump it only to loose power steering, displaying all kinds of warnings and messages. Pulled it into a parking spot and eventually sputtered down and lost COMPLETE electric power. Windshield wipers going, all the normal posted issues with aux batteries. Eventually had the car towed to home, and without knowledge at this point of the aux battery I went to replace just the main battery, no luck, no power after researching I learned about the aux battery and dug into the engine the very next day to swap that out.
-the next day I got the aux battery out, swapped and put back together start the engine to a rough idle, no start stop available and eventually the wonderful “pull over the vehicle will Shut off shortly” which eventually happened.
My question now is first, has anyone had any similar experience or would like to add any input? Because I’m completely stumped.
tonight I have both battery’s separately on a trickle charge. due to the fact that I had batteries changed separately, my thoughts are that maybe by chance one drained the other. But in the morning I will put back together and see what we’re working with.
Could it be the alternator? My jump box test the alternator and said it was good but I wouldn’t understand why the car would START but then loose the power...

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[Carolina Jeeper]

It's hard to tell without hands on your Jeep. Check the easy stuff like loose wiring connections/plugs, unseated fuses.

First thing to verify is voltages at a standstill and engine running. Standstill should be close to 12.2V to 12.5 after sitting overnight. Anything under 12V is a warning sign that your batteries are not doing well. Engine running battery voltage should be closer to 14V or even higher.

If all battery and alternator connections are in order but you have a lower voltage around or just above 12V while engine running = failing batteries or alternator. Even lower voltages will be seen when aforementioned problems exist and you are running the climate control, headlights radio, wipers, etc...

 

[PocketsEmptied]

Most things I've read say you should change both batteries when you need to change 1, it could be your main going bad that drove the AUX to fail.

 

[MyDaughters20JL]

If you re-read his post, he replaced the main battery and then learned about the presence of the auxiliary so changed it as well. Both batteries have been changed from what I read

 

[MtCamper]

I'd also check the buss bar in the fuse box. Jumping could have blown one of the high amp fuses. Before you remove any of the cables attached, use a sharpie to label them. It really sounds like you still have a low voltage battery in the mix.

 

[Rhinebeck01]

@Jrat831

There is a wealth of information here on the forum in regard to the JL's, dual battery system.. With that said .... there is no one explanation so to speak that fits all in regard to what you are seeing with your JL..

After those 2 batteries of your JL's have been fully charged, reinstall them...

After reinstall use/drive your JL, but do disregard any ESS related messages that are displayed on the EVIC.

You did a reset of the IBS Sensor, so for the next few days, the IBS Sensor will not have it's head screwed on straight so to speak... it will thus be incorrectly reporting what's going on with your JL for awhile.

Read here:
https://www.jlwranglerforums.com/forum/threads/ibs-clear-reset.67955/

Just know though, that if you inadvertently blew high amp fuse N3 in the high amp fuse array found in the PDC, your alternator will not/cannot charge the Aux battery.

So, after a few days the Aux will be depleted (it's hooked up in parallel with the Main so the main is negatively impacted) as it is not being charged by the alternator... Of course, with that depleted Aux battery and the main impacted negatively, too....you will see all the EVIC messages continue.

So, for now..... reinstall the 2 fully charged batteries and keep an eye on things for a few days... Hopefully, in a few days your JL will be without the ESS messages, etc..

---
Forgot to mention.. forgot to tell you how you may have inadvertently blown fuse N3 in the high amp fuse array..

-When the positive cable is removed from the main battery, the Aux battery positive is still connected to it. You incorrectly thought that, all 12v battery power was cut.....

Anyway if you now got a tad careless, and allowed that disconnected main battery positive cable to contact ground, well you created a short circuit from ground to the Aux battery positive terminal and that blew the N3 fuse in the PDC.

As I mentioned in the last post, thanks to that blown N3 fuse, the alternator can no longer charge the Aux battery. The Aux will deplete and not be recharged... the Aux and Main are connected in parallel so the complete dual battery system is very negatively impacted...

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[jaymz]

It's hard to tell without hands on your Jeep. Check the easy stuff like loose wiring connections/plugs, unseated fuses.

First thing to verify is voltages at a standstill and engine running. Standstill should be close to 12.2V to 12.5 after sitting overnight. Anything under 12V is a warning sign that your batteries are not doing well. Engine running battery voltage should be closer to 14V or even higher.

If all battery and alternator connections are in order but you have a lower voltage around or just above 12V while engine running = failing batteries or alternator. Even lower voltages will be seen when aforementioned problems exist and you are running the climate control, headlights radio, wipers, etc...

A fully charged 12v battery should be at least 12.6-12.8 volts.

 

[Carolina Jeeper]

A fully charged 12v battery should be at least 12.6-12.8 volts.

Yes this is true. I was giving bare minimums for after sitting over night.

 

[Jrat831]

Just wanted to update sorry for the little to no response. Upon further research and after hooking up my battery and still dealing with the same issue I realized that we probably do have this high amp fuse array blown. Looking through more forums Today I learned that if I blew fuse n3 I could simply put it on to connection n4 because they are both 150 amp fuses after doing so my car started right up and ran perfectly fine all in all the issue was I had blown my N3 fuse.

 

[Rhinebeck01]

Just wanted to update sorry for the little to no response. Upon further research and after hooking up my battery and still dealing with the same issue I realized that we probably do have this high amp fuse array blown. Looking through more forums Today I learned that if I blew fuse n3 I could simply put it on to connection n4 because they are both 150 amp fuses after doing so my car started right up and ran perfectly fine all in all the issue was I had blown my N3 fuse.

@Jrat831

You should replace the high amp fuse array.

IF/when you go to replace the high amp fuse, do know there are two different ones.. One for JL's that do not have the tow package and another for those with the tow package...

Read here for part numbers,.... more info on this:
https://www.jlwranglerforums.com/forum/threads/alert-high-amp-fuse-array-related.65085/

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