Battery issue

[Jxzi]

Few days back I noticed that the Jeep told me that the start/stop function was disabled because the battery was in protection mode. I was on the way to AutoZone and when I came to a red light, the Jeep shut off, like the normal ESS - but it did not start up again. I tried a few times and then called roadside assistance. They towed me home (I was only about 2 miles away) and I tried to jump the Jeep. I tried by using just the battery terminals and then trying first post in the fuse box - nothing worked. I used a multimeter, and the main battery test good - 12.51. That is with the auxiliary battery that is still hooked up. The main battery is the one that came in the Jeep from 2019 - and the auxiliary battery is about 1 year old. Do I need to remove them both and test them separately? I would prefer to test them myself and not have AutoZone do it.

Sponsored

 

[kah.mun.rah]

5 years on the battery? I'd say,

 

[andy29847]

Some of the early JLs were wired so if the aux battery was dead, the Jeep would not start. Your test with both batteries hooked together is worthless.

Don't waste your time testing batteries. Change them both. You old main battery has likely sucked the life out of your new aux battery. Even better would be to remove the aux battery and put in a Group94/H7 battery in for the main. You will have nearly the same battery power and the simplicity of just one battery to worry about. There are tons of guys and gals here who have changed to one battery and shared how they did it. Look in the forum in the battery section.

https://www.jlwranglerforums.com/forum/forums/battery-talk.195/

 

[AndySpill]

Some of the early JLs were wired so if the aux battery was dead, the Jeep would not start. Your test with both batteries hooked together is worthless.

Don't waste your time testing batteries. Change them both. You old main battery has likely sucked the life out of your new aux battery. Even better would be to remove the aux battery and put in a Group94/H7 battery in for the main. You will have nearly the same battery power and the simplicity of just one battery to worry about. There are tons of guys and gals here who have changed to one battery and shared how they did it. Look in the forum in the battery section.

https://www.jlwranglerforums.com/forum/forums/battery-talk.195/

Dual AGM battery JLs from early 2018 only, void of being flashed by the dealer with TSB 18-092-19, are the ones that won't crank, ever, as factory wired, if the Aux battery lacks adequate power as tested in the pre-crank test.

The OP has a 2019 which will crank on the second try if the main battery has ample cranking power.

 

[AndySpill]

Few days back I noticed that the Jeep told me that the start/stop function was disabled because the battery was in protection mode. I was on the way to AutoZone and when I came to a red light, the Jeep shut off, like the normal ESS - but it did not start up again. I tried a few times and then called roadside assistance. They towed me home (I was only about 2 miles away) and I tried to jump the Jeep. I tried by using just the battery terminals and then trying first post in the fuse box - nothing worked. I used a multimeter, and the main battery test good - 12.51. That is with the auxiliary battery that is still hooked up. The main battery is the one that came in the Jeep from 2019 - and the auxiliary battery is about 1 year old. Do I need to remove them both and test them separately? I would prefer to test them myself and not have AutoZone do it.

* I'd like to see more than 12.51 volts.
* When you tested the main battery did you disconnect the Aux? If not your voltage reading was a composite of both batteries and of very limited value.
* If you had used your multimeter on each battery isolated that too would have been a limited metric as well. It might identify by instantaneous voltage a battery on its way out, but the gold standard in battery testing is a load, not a multimeter test, as done on each battery individually. Load tests check a battery's ability to deliver and accept charge: a true test of that a battery needs to do.
* You can pick up a load tester at places like Harbor Freight if you don't feel like taking it to the dealer.
* If you take it to the dealer make sure they load test each battery independently.
* To separate the batteries, with the engine off, locate to black cables that connect to the main battery's negative post. One of those cables has as its other end the body ground connector over the passenger's front tire. Leave that alone. That other cable has as its distal end the Aux battery negative, and if you disconnect that cable at the main battery's negative post, insulating its loose end from metal, any testing where the tester is placed on the main battery's posts will be solely of that battery. Moving your tester's negative side to the temporarily uninsulated end of the dangling cable, even as you keep the positive side of a tester on the main battery's positive post, will solely test the Aux battery.
* If you want to run with just one battery keep that cable disconnected and insulated, turn ESS off at the dash, and pull Fuse 42 in the Power Distribution Center (PDC): the black box near the passenger's front seat, just right under the hood. Keep the fuse someplace safe. This cable and fuse disconnected reroutes all calls for current from just the Aux or both the Aux and main battery to just the main battery. We turn ESS off to not rob the main battery of cranking power in an ESS event designed at the factory to run off the ESS battery only to otherwise spare the main battery to bear the bulk of the cranking power after an ESS event.

Sponsored