Dead 12V Battery 2025

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Mar 10, 2026 | 12:31 PM

triplenet66

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Dead 12V Battery 2025

Thought maybe my FOB was dead so changed the battery but nope - the 12V died after a year... Somewhat odd...

Going to jump it and drive 3 miles to dealer ... fingers crossed she makes it ...

Assume just a fluke but figure I would check here to see if it could be another issue - Alternator ?

Thanks guys

Mar 11, 2026 | 09:17 AM

Mikes62

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Do you keep the car on a Battery Tender if it’s not driven daily?

Mar 11, 2026 | 09:29 AM

triplenet66

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Quote:

Originally Posted by Mikes62

Do you keep the car on a Battery Tender if it’s not driven daily?

I drive it probably 4 days a week... got it started with the jumper and into dealer ... probably just defective battery but who knows..

Mar 11, 2026 | 09:50 AM

Mikes62

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4 days a week should be enough, but you may need to get a Tender. It solves a lot of problems. I’ve got 11 Tenders going all the time on various cars and toys.

Mar 11, 2026 | 12:46 PM

mikapen

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From: Colorado

'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan

Quote:

Originally Posted by Mikes62

4 days a week should be enough, but you may need to get a Tender. It solves a lot of problems. I’ve got 11 Tenders going all the time on various cars and toys.

I agree about maintaining a good charge to prolong battery life. A depleted battery loses more capacity (dies) than one that's fully charged. In general, at 12.2v your AGM battery is 50% depleted. It wants to be at 13.8v for longevity and health.
I found that a daily drive for less than an hour would gradually deplete the battery (in our newer cars), because the car is always on alert, "looking for" a key , a download, or a query from your app. It seems that it takes an hour of highway driving to charge the battery, and this is confirmed by warnings that pop up.

I had seven Battery Tenders (brand name) on several cars/mowers/RV's for decade or so. Then, one by one, they failed, and the failure mode was MAX CHARGE, and each one ate a battery; boiled it to death.
Earlier I was proud to make my Lead Acid batteries last a minimum of seven years, but the accomplishment faded as, one by one, they ate a battery. I gave away my "fleet" of Battery Tenders after the fourth battery.

Now I use a couple of CTEK maintainers, and I attach them twice a month and let them run for a day or more. If I'm going to be away for an extended period of time (2 weeks+) the CTEK is on duty full time.
Lots of folks are using NOCO maintainers, but the important thing is NOT to use a "trickle charger," which will also overcharge a battery.

Mar 11, 2026 | 03:30 PM

nc211

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2020 GLS450 (wife) / 2024 Ford Bronco (mine) / 2014 VW Tiquan (son)

2020, same battery, many many many short trips to the store, schools, errands, etc nearly every day over the last several years. Often too short for transmission temperature to rise into the normal range. Rarely long drives anymore. Battery still strong and happy. Mine is constantly garaged when not in use. I think you've either got a bad battery (likely) or a parasitic drain on it from something. But my bet is just a bad battery. It happens sometimes to the best of 'em.