Main vs Aux battery replacement question on 2021 JT

[Mojave2021]

Thanks. Yes I imagine I just reset the IBS - and it will re-learn again that my batteries are weak. Will load test them tomorrow. Need to figure out how to load test the aux battery without pulling it out first.

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[LouisvEarlleJT]

Yeah I’m in the same boat, though I did try the ibs reset just for kicks. Was trying to put off buying batteries for as long as possible

It’s frustrating that they put the aux battery under the main, like, “hey, here’s this thing that’s probably going to fail 1st…let’s put it under the giant thing that is going to fail second…”

 

[Mojave2021]

Well good news at least is I’ve confirmed my ESS isn’t totally broken. I don’t recall it working since I added the Banks Pedal Monster to it and thought maybe that disabled its functionality. I was wrong.

No warnings again today.

My JT only has 16K miles on it so was hoping I could squeeze a bit more life out of them but I know batteries are more sensitive to years than mileage.

 

[Mojave2021]

Over the past 2 days the start/stop is no longer showing as ready. Haven’t gotten the aux switches unavailable warnings but the voltage gauge has been holding firm at 14.4. Thinking it’s probably time to replace the 2 batteries (main again is 4 years old and aux is 3 years old). Initial aux battery failed after 1 year.

 

[LouisvEarlleJT]

Over the past 2 days the start/stop is no longer showing as ready. Haven’t gotten the aux switches unavailable warnings but the voltage gauge has been holding firm at 14.4. Thinking it’s probably time to replace the 2 batteries (main again is 4 years old and aux is 3 years old). Initial aux battery failed after 1 year.

Same here, thankfully still in the 3/36 warranty so the dealer is going to take care of it.

 

[ecidiego]

After you replace the batteries, charge them every so often with a correct AGM charger such as a C-Tek. The alternator will *never* fully charge the batteries as it cuts off too early.

 

[LouisvEarlleJT]

After you replace the batteries, charge them every so often with a correct AGM charger such as a C-Tek. The alternator will *never* fully charge the batteries as it cuts off too early.

That's curious.

 

[ecidiego]

I use this in "Snowflake" ( for Odyssey, X2 Power etc ) mode:

and this adapter for the CTEK:

and this adapter to plug the Cig plug into the 7-pin:

 

[Mojave2021]

Thanks. I do have a Black & Decker charger that I've used to charge up the battery from time to time. How do you charge up the aux battery directly though?

Wondering if I should charge it up again and see if that helps anything at all.

 

[ShadowsPapa]

Over the past 2 days the start/stop is no longer showing as ready. Haven’t gotten the aux switches unavailable warnings but the voltage gauge has been holding firm at 14.4. Thinking it’s probably time to replace the 2 batteries (main again is 4 years old and aux is 3 years old). Initial aux battery failed after 1 year.

Nobody checks battery voltage or has batteries load tested and so on before replacing them these days?

How much has it been driven? Are you sure it's just not in need of charging?

Maybe they are going south - but you really have n information one way or another other than - ESS not working and the voltage staying high while driving. That can mean it needs to sit on a quality charger.

Or, you can just go and replace batteries - and wonder.

 

[Gatorized]

@ShadowsPapa keeps hinting at it but hasn’t come right out and said it - you need to put it on a good AGM charger for a couple days. Just do it! 16k miles on a 2021 is not driven enough.to properly maintain the battery.

 

[ShadowsPapa]

@ShadowsPapa keeps hinting at it but hasn’t come right out and said it - you need to put it on a good AGM charger for a couple days. Just do it! 16k miles on a 2021 is not driven enough.to properly maintain the battery.

Sort of beating around the shrub?

Yes, just do it. Charge it with a proper AGM charger. (one that will revitalize would be better, which most decent ones do these days)

 

[Lost1wing]

Thanks. I do have a Black & Decker charger that I've used to charge up the battery from time to time. How do you charge up the aux battery directly though?

Wondering if I should charge it up again and see if that helps anything at all.

You will need to separate the two cables at the main negative. One goes to the fender ground the other goes to the aux negative post. Your positive charging cable can just stay on the main positive post. Your aux positive is connected there via the PCR. Connect your negative charging cable to one of those cables that you disconnected and isolated. If you charger shows that it is charging, you chose the correct cable. When it is finished, simply move the negative charging cable to the main negative post. When it is finished, you can wait 20-30 minutes and test the voltage with a meter. If 12.6 or higher you can reconnect your cables to your main negative, starting with the aux negative cable. Leave the fender ground for last.

 

[Mojave2021]

When verifying the voltage at the negative cable I got readings for both cables. Do I have to completely detach the thinner one to verify the aux voltage? The nuts do not budge at all.

 

[Mojave2021]

Main battery load tested at about 11.3-11.4V which i believe is decent. That was tested after I had charged it up fully (resting voltage was 12.9).

If I understand correctly I can charge the aux by connecting to the terminal on top of the negative post circled here? How do I load test just to verify the aux battery health without removing it?

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