Aux battery test?

[teddyballgame]

Is there a test for the JL aux battery that can easily be performed? Like a load test for amperage?

How long do they typically last before it’s recommended to change them and the main battery out?
Thanks and Happy Holiday everyone!

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[Heimkehr]

@teddyballgame
Speaking just about battery life, my personal standard for any 12V battery is 5 years. With just 1 or 2 exceptions through the years, every such battery that I've had in service has provided no less than 6 years of practical service. E.g., as I type this post, the original battery in my 2015 Suzuki continues to reliably crank the engine, 8 years running. The Jeep's [original] main battery does the same, 3+ years on.

I replace such batteries at the first hint of compromised operation, no matter how modest...but not before that point. Just my way of doing things.

Hope this helps. ?

 

[Packnbeer]

the Aux batteries usually only last about 3 years. aftermarket replacements will only have a 1 to maybe 3 year warranty on them. OEM's are no different. Mine went bad after about 2 1/2 years. Trying to get the dealer to acknowledge one going bad under warranty is a complete joke. I had mine in several times and they just kept saying it was a little low on charge and should be good. It wasn't. I gave up and just replaced it myself and haven't had another issue since. I got tired of the BS and removing the tazer each time. Was worth just replacing it and saying the hell with the warranty. My jeep service experiences have been less than stellar. I didn't use my free oil changes because I don't want them touching it. I have had excellent service from my GM dealer, Jeep... forget it

 

[AndySpill]

Is there a test for the JL aux battery that can easily be performed? Like a load test for amperage?

Yes. And it is a load test with the vehicle shut down, not a simple test of voltage.

And it is not taking said load tester to the main battery's terminals. That would be a load test of both batteries and potentially reveal nothing.

Rather, it involves first, and temporarily removing the negative cable from the Aux battery on the main battery's negative post and attaching only this loose cable's end to the negative lead of the load tester.

The positive lead of the load tester can attach to the main battery's positive terminal. In this setup the only battery the load tester will test is the Aux, despite the load tester's connection to the main battery's positive terminal. This is because the positive terminals of both batteries are connected with the engine off, so you've effectively put your positive side of the load tester on the Aux battery, and the previously loose cable on the negative side of the load tester directly and solely connects to the Aux battery's negative terminal. The Aux battery is the only one here completing a circuit as seen by the load tester.

Reconnect the cable when you're done. It's the factory cable on the negative terminal of the main battery whose other end doesn't connect to the body ground on the passenger's side under the hood. I'm not going to say which cable on the main battery's negative terminal that is: left/right, up/down as I think Stellantis has switched the cables since the 2018 JL first rolled out.

 

[jeepoch]

@teddyballgame,

Ted, my track record with both these batts have been terrible. Really horrendously miserable. I've gone through four sets in three years. Thankfully my last set has lasted for more than a year now. But I replaced both batteries with non-Mopar, much more top-of-the-line AGM units from a more reputable manufacturer.

I went through the dealership hell. Yes hell! I was being somewhat cooperative with their diagnostic info, figuring that they would be the most knowledgeable. Boy did they prove me wrong. And I kept going along for the proverbial ride.

Let me start out saying that I really love my JL. It's been the most fun and enjoyable daily driver I've ever owned. I'm having a fribben blast with this thing driving it all around every inch of my home state of Colorado. I'm living and sharing John Denver's Rocky Mountain dream.

I also rather enjoy using, playing and toying with the ESS system. It really makes traffic lights way more enjoyable. Instead of wasted time sitting there mind numb waiting for the green, I'm now more lazer focused at watching the overall intersectional dynamics. I'm now much more focused at the 'Seven Second' Rule. I try and determine and deduce whether I'd I let the ESS stop the engine while stopped, will it actually save fuel? The most accepted time (so far) is 7 seconds. If you remain stopped with the engine off longer than this time, then yes you're saving fuel and naturally extending your tanks overall range. If not, you're no worse off or even wasting fuel due to the restart.

Also truthfully, I like the additional silence when idling. There's something soothing about it.

So you can see I really despise it when, rather than playing this game at traffic stops I'm presented with "Battery Charging" or "Battery Protection Mode" complaints instead. So yes I take the charging health of these batteries to be more important than the average ESS disabled Joe Schmoe who just waste's away his Red Light Life time.

Granted I'm draining my batts, rather than continuously charging them while engaged in playing this silly SSR game. So obviously, I'm way more demanding on my charging system than the people who push the button or disable their ESS altogether.

But the dealership just gave me the constant run around. Like Jamie's (@Packnbeer) experience, they gave me every excuse they could come up with that it's just low charge. Of course there could be some truth to that but only IF the charging system in this jalopy is not providing enough charging energy to support the ESS system in general. Which is likely the true underlying culprit. DESIGN FLAW!

However, the next biggest contributing factor is poor (cheap) Mopar batteries. The worst of the worst batteries on the planet. As I said, three sets were eventually replaced only after the dealership load testing had indicated low output. Three sets, all exchanged at the dealership under warranty in three years. The final set, naturally out of warranty they quoted me $960. Pound Sand!

The fourth set I did myself (I did let a trusted repair shop do the AUX). I used the more expensive AGM technology as replacements and it's been more than a year now since having any ESS issue whatsoever.

Noting that I do periodically connect a battery maintainer overnight to overcome the pithy alternator's low output current. But I was also doing that on the Mopar batts. And yes I disconnect the negative terminals and charge them independently.

Rule of thumb:
Get rid of the crappy Mopar garbage as soon as possible, and never (NEVER) let the dealership raise your blood pressure. Go elsewhere and really enjoy life.

Especially at stop lights.

Best regards,
Jay

 

[bcupton]

Wow. I’m not sure if I should feel lucky or worry. I’m going on 5 years (I bought my 18 JLUS used in 20). I’ve never messed with the garden tractor battery stashed in the passenger fender. I’ve replaced the main battery last year. Now, I run a Tazer JL Mini and have the stop / start turned off. Maybe that has something to do with it. I’ve thought about having it replaced. Does that count? LOL

 

[DKAwildcat]

I’ve had my JLU just over five years. My first auxiliary battery lasted three years and I replaced both batteries at the same time. I did the auxiliary battery delete mod the other day so I’m now only using the main battery. The ESS works the same as before and there have been no warnings on the dash.

 

[hexeis]

I’ve had my JLU just over five years. My first auxiliary battery lasted three years and I replaced both batteries at the same time. I did the auxiliary battery delete mod the other day so I’m now only using the main battery. The ESS works the same as before and there have been no warnings on the dash.

Can you share the auxiliary battery delete mod ? I want to try it on my Jeep.

 

[jromanmd]

the Aux batteries usually only last about 3 years. aftermarket replacements will only have a 1 to maybe 3 year warranty on them. OEM's are no different. Mine went bad after about 2 1/2 years. Trying to get the dealer to acknowledge one going bad under warranty is a complete joke. I had mine in several times and they just kept saying it was a little low on charge and should be good. It wasn't. I gave up and just replaced it myself and haven't had another issue since. I got tired of the BS and removing the tazer each time. Was worth just replacing it and saying the hell with the warranty. My jeep service experiences have been less than stellar. I didn't use my free oil changes because I don't want them touching it. I have had excellent service from my GM dealer, Jeep... forget it

Brother...so true. Thank goodness its not just me. The dealers in the MD DE VA Area are just as bad. the horror stories about missing bolts, overfilling oil, holding onto the jeep for weeks when the repair took a day..on and on.

I will use anything over the dealer.

 

[DKAwildcat]

Can you share the auxiliary battery delete mod ? I want to try it on my Jeep.

Remove fuse F42 (10 Amp) and the auxiliary battery‘s negative cable from the main battery (be sure to wrap it with electrical tape and zip-tie it to an adjoining cable so it doesn’t come it contact with any metal). You can leave the auxiliary battery in place with the positive and negative cables attached it. With the negative cable disconnected at the main battery, it is isolated. It’s that simple. The “Jumperless Aux Battery Bypass“ thread explains it all and has pictures. The ESS system still works when you stop at a light, but the engine cranks back up using the main battery. I believe they suggest you upgrade to the large H7 battery if you don’t have one, but my Jeep came with one so that didn’t affect me.

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