AGM battery compatibility with e53 alternator

[Blowout]

Replaced the acid flooded battery with an Champion AGM H7 in 2018 with 120k on the X5. According to records, dead battery occurred 3/2021. The car isn't drive much and thought that might have been the cause.

Radio stopped working sometime in 2022.

6/2022 battery dead but took a charge using a CTEK charger that has an AGM charging mode. Radio working again.

9/2023 battery dead, replaced with a Walmart Everstart Premium H7 AGM. Around 137k on odometer. I didn't record if radio worked.

3/2026 battery dead and CTEK charger died when trying to charge it. Over charged battery with an old 10 amp charger to a point where acid was discharged through the overflow. Replaced battery with a new Everstart H7 AGM. Radio worked again.

6/2026 battery dead but recharged fully with a new 5A AGM compatible charger. Radio works again.
.............................................

Radio has only worked occasionally over the past several years and could figure out whats wrong with it. Now I'm thinking it could be caused by the voltage being below a threshold. The car gets battery tendered every so often over the years because it becomes sluggish to start and tailgate unlock, dimmer interior lights and such have been noticed over the past several years.

After fully charging with a AGM charger the battery with the engine off all doors closed has been steady at 12.8V for 48 hours. The car wasn't run during that time. I don't think it has a parasitic drain anymore because the voltage has been steady.

Battery voltage with engine off - 12.8V
Voltage with engine started idling (headlights always on) - 13.8V
Engine 2000rpm- 14.0V

I'm thinking OEM alternator might not be compatible with charging an AGM battery. Anyone have thoughts or experienced something similar to this?

Not sure if I should change back to a flooded battery or change the alternator to a higher output model that would be AGM compatible.

[andrewwynn]

I used AGM with my e53 lasted until i replaced the car. I also use on my E70 with IBS and it killed my battery in just under two years so which ever get one with warranty. Took me weeks to get mine replaced under warranty


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[Blowout]

Originally Posted by andrewwynn

I used AGM with my e53 lasted until i replaced the car. I also use on my E70 with IBS and it killed my battery in just under two years so which ever get one with warranty. Took me weeks to get mine replaced under warranty


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New battery was only $200, so I skipped the hassle of the warranty process at the time, plus I killed it from over charging.

[80stech]

No problem with using AGM battery on the E53. There are some pretty good threads on here about some of that, it might be interesting to check those out. I have had both my E53 and my wife's E83 switched over for a long time and they have been great. I go out of my way to use Delco batteries though and have been for more than 40 years!

I'm not a big fan of maintainers and they are known to be hard on batteries, maybe some more or less than others, but if you can avoid them and take the draw off the battery it will for sure last longer.

[Blowout]

Originally Posted by 80stech

No problem with using AGM battery on the E53. There are some pretty good threads on here about some of that, it might be interesting to check those out. I have had both my E53 and my wife's E83 switched over for a long time and they have been great. I go out of my way to use Delco batteries though and have been for more than 40 years!

I'm not a big fan of maintainers and they are known to be hard on batteries, maybe some more or less than others, but if you can avoid them and take the draw off the battery it will for sure last longer.

Good to know your e53 didn't have issues with an AGM battery.

I might put the charger/maintainer on the battery 2-3 times a year for a day or two. The X gets driven maybe once a week to the store, so disconnecting the battery really isn't an option with it being buried in the back of the vehicle.

Been using what's called a smart charger. The CTEK goes through an 8 level charge cycle and the NOCO Genius I just picked up does a 4 level charge cycle.

I've had a different experience with a battery maintainer. I've used the CTEK on a jetski AGM battery for 6 years now. Usually your lucky to get a couple years before needing to replace them. That battery is taken out and stored on a bench each year with the smart charger left on it. I agree, disconnecting the battery from any draw extends the life quite a bit.

I also use a smart charger on my 2 truck batteries (primary/secondary) and get about 10 years of life. Again they only get charged 2-3 times a year.

[EODguy]

My AGMs have each lasted 3 years or more and it's a rough atea (heat wise) today was 55c, so who knows how bad it gets inside the White Witch.

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[80stech]

yep, charging a battery 2 or 3 times a year for a day or two if needed is the way to go, much better than having it on a maintainer.

[haigha]

I normally have a Battery Tender Jr hooked up to the garage queen, which usually sees one or two trips per week. My batteries last six or seven years (on my fourth since Oct 03). I use the Duracell 49/H8 flooded batteries from Sam's Club, 900CCA (04 4.4i).

I recently got the Autel BT506 because Gemini Pro said it would work on the engine bay battery terminals. AI lied. So, I'm thinking about checking the hard way because the current battery is about six years old.

https://www.aliexpress.us/item/3256809815963828.html

[sroth004]

Old school 1.25 amp Battery Tender brand on all the cars when they sit for more than a couple of weeks. Works fine through the under hood charge/jump lugs on the e53, e46, e39 and e90; all are AGM and 6-8 years on a battery typical using Interstate from Costco when possible, Diehard, Duracell, Deka as alternates. Recently replaced a 15 year old Interstate in an infrequently used ‘82 MB when I realized how old it was though still working and testing fine. You all probably know this but 3 or 4 companies make nearly all the batteries is the US so comparing current specs and price versus buying by brand matters. Also, be careful about buying chargers on eBay and other sites, bootlegs are out there and look real including packaging but are not, I learned the hard way. Check with the charger manufacturer regarding which sites sell legit product.

[workingonit]

I've used charger/maintainers (hereafter referred to as C/Ms) for well over a decade, actually since 2006 (in the case of my drag race car, with two batteries and no alternator, stored between races), now.

For the other cars & trucks, it began when my wife had to drive mainly to school and work, while I would be 50 miles away (or more) at work or at more distant drag strips, racing. Didn't have time to waste if one failed to start, so we'd just grab a backup! So, we had two vehicles for her to use (commuter car and pickup), and three for me (commuter vehicle, dedicated tow vehicle/backup truck), starting around 2007. All had/have flooded standard batteries, except for the Optima Yellowtop AGM, which I installed in my home-built squareback trailer in 2012 (still works). The vehicle lineup has changed over the years, but my reliance on C/Ms hasn't.

I'm currently using five C/Ms:

• 1) two Amazon Basics 2amp on the two trucks, '98 GMC and '04 Chevy 2500HD,
• 2) a Battery Tender 1.25amp on the '01 X5,
• 3) an Autozone 1.25amp on the '09 HHR Panel,
• 4) a really old BatteryMinder 1.5amp on the trailer's AGM, and
• 5) 'just added yesterday', a Nexpeak 1.75amp for the new battery on the '98 Dixon ZTR3304 riding mower.

At first, all the batteries were lasting between 7 and 11 years (the AGM is now over 14, though), but a couple as few as 3 (X5 and mower). I' don't think the batteries are as good as before, but I am only buying AC Delco and Duracell batteries (made by East Penn Mfg., for Sam's Club) in the last eeight years.