Battery, aux battery or alternator. No idea whats going on.

[Osctwn]

I have a 2018 sport s. Went to start it the other morning, and nothing. Got it jumped drove around, voltage read 14.5 is and the ess start stop light came on. Went home and turned vehicle off, immediately tried to start again, and nothing. So it sat for a few days was reading forums and watching videos. Last night I disconnected the aux battery sensor and the jeep fired right up. Awesome. Figured something is up with the aux battery. Sat overnight, woke up this morning and again, fired right up. Drove home and it sat for an hour, went outside, and nothing. Won't start again. All the dash lights and screens turn on, Headlights all of it. Jumped it again and drove to oreillys to have them check the battery and alternator. They say battery is good, but not the alternator. I've had alternators go out and it has killed everything in the vehicle while driving it. I'm at a Loss. Any ideas, advice?

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[Jebiruph]

If you're running voltage is 14.5v, your alternator is working. Make sure your battery cables are tight and your fuses are pushed in all the way.

 

[Osctwn]

If you're running voltage is 14.5v, your alternator is working. Make sure your battery cables are tight and your fuses are pushed in all the way.

What do you make of the ess light on after the first jump and still plugged in?

 

[Jebiruph]

What do you make of the ess light on after the first jump and still plugged in?

The aux battery is tested before a cold start and yours failed the test. Not a surprise since both batteries combined were not able to power a cold start.

 

[Osctwn]

Still no luck. Checked all the connections and fuses. The battery reads 12.0 when I try to start it.

 

[GreySportySpice]

In my experience killing car batteries can impact them significantly. Voltage might be fine on the main battery but it can't handle the load needed to start.

 

[BDinTX]

If their test is pointing to the alternator… could it possibly be the battery sensor? If it is reporting voltage incorrectly, the alternator may not be given the signal to charge. No idea how to diagnose it though.

https://www.jlwranglerforums.com/forum/threads/3-6l-ess-ibs-information.22585/

 

[Jebiruph]

Still no luck. Checked all the connections and fuses. The battery reads 12.0 when I try to start it.

Is it 12 before you try to start or does it drop to 12 while starting. What happens when you try to start, no crank or slow crank?

 

[mwilk012]

Have you disconnected the aux battery and tested individually?
Replace both batteries.

 

[GSLSE21B]

Still no luck. Checked all the connections and fuses. The battery reads 12.0 when I try to start it.

12.0 is dead . AGM should be 12.7-12.9

 

[WranglerMan]

As stated 12.0 is way to low for an AGM, you need to be in the 12.7-12.9 range when the batteries are at rest and this would be read directly at the batteries, 14+ while running should be good as it shows the alternator is doing what it needs to do.

If your Jeep is not a daily driver and does not sit on a quality battery tender this is a big no- no and the fact that it’s a 2018 the batteries likely are done and I would replace both , the main is easy to get to and the aux you have to remove a fender flare, also check for any corrosion on the IBS connection off the main negative.

If one battery is bad and the other is good the bad one will pull down the other and eventually both will be bad, for healthy AGM battery life it’s best to keep them fully charged as they only can be cycled so many times and the factory ones are not prone to do well being deep discharged over and over.

 

[Trainman]

If that's the original batteries on the 2018 replace them both, it's time, they have lasted there life expectancy. If my batteries in my vehicles last four years I replace them, they will leave you stranded one day if you don't life being stranded for the price of a battery.

 

[Osctwn]

As stated 12.0 is way to low for an AGM, you need to be in the 12.7-12.9 range when the batteries are at rest and this would be read directly at the batteries, 14+ while running should be good as it shows the alternator is doing what it needs to do.

If your Jeep is not a daily driver and does not sit on a quality battery tender this is a big no- no and the fact that it’s a 2018 the batteries likely are done and I would replace both , the main is easy to get to and the aux you have to remove a fender flare, also check for any corrosion on the IBS connection off the main negative.

If one battery is bad and the other is good the bad one will pull down the other and eventually both will be bad, for healthy AGM battery life it’s best to keep them fully charged as they only can be cycled so many times and the factory ones are not prone to do well being deep discharged over and over.

This is my daily driver. After doing nothing and sitting all last night, fired right up this morning. Going to replace both batteries today and see if that resolves the issue.

 

[Osctwn]

Found a loose connection, lmao. Seems to be fine now. Thank you for all the input.

 

[mwilk012]

Found a loose connection, lmao. Seems to be fine now. Thank you for all the input.

where at?

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