2022 JLURD Aux Battery Question

[Terpsmandan]

I have a Quart Stage 6 system installed three years ago. Recently started getting an alternator whine. I reached out to Quart support and they said that when they encountered this issue that it was an indication that the aux battery was failing. So the whine was intermittant and I installed a noise suppressor from the LCI to the amp and that seemed to work bit it just started again last week. I also have a Tazer to disable the ESS which has been there since day 5. So this morning in my ride in after about 45 minutes-35 miles I went through the on screen to the start stop status, turned the ESS back on and the display said start stop not ready. Is a good indicator that the aux battery is on the way out? First time I have even checked the ESS status since I biought it. Thanks.

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[AndySpill]

I have a Quart Stage 6 system installed three years ago. Recently started getting an alternator whine. I reached out to Quart support and they said that when they encountered this issue that it was an indication that the aux battery was failing. So the whine was intermittant and I installed a noise suppressor from the LCI to the amp and that seemed to work bit it just started again last week. I also have a Tazer to disable the ESS which has been there since day 5. So this morning in my ride in after about 45 minutes-35 miles I went through the on screen to the start stop status, turned the ESS back on and the display said start stop not ready. Is a good indicator that the aux battery is on the way out? First time I have even checked the ESS status since I biought it. Thanks.

Hey Dan:

This may be unrelated, but on reliable sourcing the talk around the ESS/Aux battery's initial implementation in the JL was not so much about the need for the extra power it provided, as many vehicles run ESS systems with one battery, (and besides voltage during ESS events is monitored to early terminate them if said voltage drops too low--so as to make sure the battery/ies have enough power to crank the engine and get the alternator back online to charging the battery/ies back up), but rather issues with ESS event voltage drops causing noise in the entertainment system.

But this noise, I'm to understand, was detected during ESS events, not when the engine was on.

That said, the fact that you have disabled the ESS system from engaging via a JL Tazer, (or for that matter via any of the available methods,) in no way divorces you from issues related to this ESS battery. The latter can only be achieved by replacing an aged out ESS battery or bypassing it.

Because it seems to me that you have no desire to run ESS events, I would urge you to disconnect that Aux battery. To do so, locate the two factory black cables on the main battery's negative post. One of those cables will have at its distal end the body ground connection on the front passenger's fender. Leave that cable connected and intact.

It is the other cable that should be disconnected from the main battery's negative post, whereafter you should electric tape up its exposed end. This cable has as its distal end, sight unseen, the negative post of the ESS/Aux battery. Your actions have removed this ESS/Aux battery from ever energizing vehicle appliances or receiving alternator charge going forward

The second thing you should do is locate the black box just under the hood near the front passenger seat. That's the Power Distribution Center or PDC: your intelligent fuse box.

Remove its cover, locate Fuse 42 and pull it. Save that fuse.

Doing so will prevent the Power Control Relay (PCR--I know, lots of acronyms!) from every being energized: something that when it happens separates the batteries, as happens for an instant at cold crank and during ESS events.

With these two steps completed all requests for battery power now go to all connected batteries, all of the time, of which you will only have one: your main battery.

Please continue to not run ESS events.

With the Aux battery out of the equation, its status as a working battery or not becomes moot.

Its possible your (smart) alternator is working hard to compensate for an ESS/Aux battery that won't charge. It's also possible the steps I advise above may not solve your problem. But what they will do is prevent that Aux battery from cannibalizing your main battery, and rule out one variable (the Aux battery) in diagnosing your noise issues.

It's even possible that your main battery's aging out. After disconnecting the Aux battery you may want to have it load tested (e.g. https://www.harborfreight.com/100-amp-612v-battery-load-tester-61747.html ) . Please don't effect this test with both batteries connected. Batteries connected in parallel (as in the dual AGM battery JL) can be helped out by the stronger ones of the connection and lead to wrong or misleading load testing results.

And if, for some reason you desire to load test the Aux battery, that's done by moving the negative load of the load tester on to the exposed end of the cable that's removed above. Even as the load tester's positive lead remains on the main battery's positive terminal, the connection I describe will still, solely, test the Aux battery.

 

[Terpsmandan]

So I went out and looked at the neg terminals and both of the cables run into the harness that runs next to the battery. One is closer to the post and one is farther back at about the middle of the battery. Anyone chime in as to which one goes to the aux battery and which one runs to the chassis ground?

 

[AndySpill]

So I went out and looked at the neg terminals and both of the cables run into the harness that runs next to the battery. One is closer to the post and one is farther back at about the middle of the battery. Anyone chime in as to which one goes to the aux battery and which one runs to the chassis ground?

At some time in 2020, it's been reported, Stellantis swaped the two cables on the negative post of the main battery of dual AGM battery JLs.

https://www.jlwranglerforums.com/forum/threads/ess-battery-cable-change.86624/

It's for this reason that I wrote instructions as a did, which work for all model year dual AGM battery JLs. But let me qualify that guidance.

Start at the body ground https://www.jlwranglerforums.com/forum/threads/missing-bolt-on-underhood-ground.59406/

Follow the cable that originates there and ends up at the negative terminal of the main battery. That's the cable you leave connected. The other factory cable at your main battery's negative terminal is the one you disconnect and whose end you wrap with electric tape, and whose distal end, sight unseen, is at the negative terminal of your Aux battery.

It is this guidance that is appropriate for all model years of dual AGM battery JLs.

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