Is this the original battery?

[Anachronism]

The aux battery just died in my 21 jlu. If the main battery is still the original than I figure I should change it too but I don’t know if it is. It’s a mopar battery but I can’t find a date on it anywhere.

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[Vanburi]

Replace both at the same time regardless.

 

[rk911]

Mopar says that battery serial number was mfg between 2014-2024. Assuming that battery is original to your '21 then it is at least 3-yrs old.

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[Reinen]

It probably is original and if so, it's around the end of it's expected lifecycle. This is just standard expected maintenance.

Always replace both Main & Aux at the same time or your batteries will die much sooner than they should. You want both to be the same age and have the same level of use.

 

[zouch]

i see there's a 2019 Copyright logo on the sticker, so we know it's not older than that.
but it's probably time for both of them to be replaced anyway.
mine didn't make it 3 years.

do yourself a favor and get a pair of decent AGM batts and forget about the junk Mopar put in there stock.

 

[Anachronism]

I was leaning towards replacing both anyway, I’d rather be out a couple hundred bucks than be stuck somewhere.

I wasn't going to go with mopar. Just whatever I can find at a local auto parts store, with the h7 upgrade.

any recommendations on brands to look for or avoid?

 

[Terrymo]

I was leaning towards replacing both anyway, I’d rather be out a couple hundred bucks than be stuck somewhere.

I wasn't going to go with mopar. Just whatever I can find at a local auto parts store, with the h7 upgrade.

any recommendations on brands to look for or avoid?

https://www.jlwranglerforums.com/forum/threads/main-battery-replacement-talk-jl-jt.100534/

 

[munkeymike]

I was leaning towards replacing both anyway, I’d rather be out a couple hundred bucks than be stuck somewhere.

I wasn't going to go with mopar. Just whatever I can find at a local auto parts store, with the h7 upgrade.

any recommendations on brands to look for or avoid?

I hate Walmart but I went with Everstart Platinum. One of the higher rated ones (850CCA), one of the longest warranties (4 years) and one of the cheapest.

Also, I highly recommend aux delete if you can live without ESS. The aux battery will always die first and kill your main with it. In addition to killing your main battery early, you also have to pay for its replacement as well so it's extra expensive for just ESS for most of us. Aux batteries are low capacity and not made by good manufacturers. The procedure is very easy 100% reversible.

 

[ParadigmDawg]

I was leaning towards replacing both anyway, I’d rather be out a couple hundred bucks than be stuck somewhere.

I wasn't going to go with mopar. Just whatever I can find at a local auto parts store, with the h7 upgrade.

any recommendations on brands to look for or avoid?

100% Odyssey. That is the only battery I will run.

Just find a NAPA Auto and they can usually have one there the same day.

This is the one I use and it fits right in the stock tray.

AGM BATTERY Part #: ODP AGM95R H7L4

 

[AndySpill]

I hate Walmart but I went with Everstart Platinum. One of the higher rated ones (850CCA), one of the longest warranties (4 years) and one of the cheapest.

Also, I highly recommend aux delete if you can live without ESS. The aux battery will always die first and kill your main with it. In addition to killing your main battery early, you also have to pay for its replacement as well so it's extra expensive for just ESS for most of us. Aux batteries are low capacity and not made by good manufacturers. The procedure is very easy 100% reversible.

Jim @Anachronism

If you wish to be able to run ESS events then replacing both batteries is indicated. But if you are not one to run ESS events, either because you turn ESS off, or your driving habits (which I'm not judging, just saying) are such that the shortness of your trips and/or infrequency of the vehicle's use finds inadequate engine time to charge the ESS battery, such that ESS events are rare for your vehicle to engage, then I think Mike @munkeymike has a really good point.

You can not only save on the cost of the new Aux battery but its removal from the electrical schematic of the vehicle, even if it remains under the hood, eliminates the possibility of it becoming a parasitic drain on your new main battery: something reported all to commonly on this forum given the, by design, parallel connection of the batteries but for an instant at cold crank and during ESS events.

If you wish ESS events were happening despite short/infrequent trip driving then applying a trickle charger to the batteries while the vehicle is parked is an option, but one that's a bit of a fool's paradise for most as the gasoline savings is offset by the electrical cost (and potential carbon footprint) of energizing the trickle charger. Such a device connected to the main battery's terminals while the vehicle is parked will charge both batteries.

Disclaimer: I run a short trips/infrequent use JL with dual batteries and ESS events, but trickle charge off of a solar panel already on my vehicle's roof rack that was purchased to charge batteries that run aftermarket appliances that tend to operate when parked and the engine/alternator produces no battery recharging power, that I piggyback for factory battery trickle charging as well.

Buying the solar panel to keep the dual batteries trickle charged is simply another fool's paradise where solar part cost not only offsets ESS event gasoline savings, but likely doesn't improve carbon footprint given the costs of ESS battery disposal and the green footprint of manufacturing the solar parts.

Since you may be new to this, Mike's idea is effected with the least work by opening the Power Distribution Center (PDC), your vehicle's intelligent fuse box: it's a black box just below the hood just in front of the passenger's seat (at least on your model JL) and removing (and keeping) Fuse 42, while parked

Also, during this parked session, remove and insulate the cable end of the factory cable on the negative post of the Main battery that does not have as its other end the body ground point on the front passenger's quarter panel. Leave this latter cable connected. You won't see the other end of the cable you yank, which is connected BTW to the negative post of the ESS battery.

The fuse pull prevents the vehicle from separating the batteries, as it does during ESS events, and the cable pull takes the Aux battery out of the vehicle's electrical schematic. Now, without complaining, your vehicle's attempt to isolate the Aux battery (such as during ESS events) causes all available batteries to be tapped, which by virtue of the cable pull will only be your main battery.

It's recommended, if taking this route to turn ESS off at the button, either by pushing it each time your start up, or buying aftermarket tech to do this for you such as the device from https://www.smartstopstart.com/, a forum sponsor. It's not a tragedy if you occasionally forget. But you risk running down he battery designed to crank the vehicle when an ESS event ends, on appliances powered by this battery during the ESS event.

Sure, nearly all other vehicles run ESS events on one battery. But not only might the JL have been designed to early terminate ESS events less aggressively than other vehicles because of its two batteries, its also true that Wrangler owners tend to run more aftermarket power hungry appliances.

 

[zw470]

Better than the Napa battery that mysteriously appeared in my Jeep while it was at the body shop

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