I have a AGM from 2017 that even after leaving it charging for 3+ days, as soon as its disconnected and I turn the lights on for 3 minutes to remove that "phantom" charge and the battery drops down to about 12.38v-12.4v.

Is that a typical sign the battery is beginning to degrade, or nothing to worry about?

Reason I ask is that after a few weeks I'm dropping down to 12.2v and then starting begins to be a little sluggish.

thoughts? thanks

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Yep, battery getting tired. 5 years is a good life on batteries anymore.

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Jim

i got ripped buying a used AGM once so i sprung for a hand held tester and it has really come up huge for me. i went to see a 'new' old stock' red top optima that was showing 12.4 v but the CA and CCA were both at about 20% of what they should be (1000 CA was 225 and 850 CCA was 171)

also invested in a C-tek charger that has a reconditioning function and that has rejuventated a few that seemed to be going away on me

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0o==o0

James 4:8

"...let us put aside the blindness of mind of those who can conceive of nothing higher than what is known through the senses"
-Saint Gregory Palamas, ---Discourse on the Holy Transfiguration of Our Lord God and Savior Jesus Christ


Centrally located in North East Central Pa.

I could try and use the reconditioning on my Nocco 5amp charger and see. I know the CCA are still pretty good at 750.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

does the battery have above 12.5V after being parked overnight? If you are getting low volts after a few weeks, then probably your battery is toast.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I would test the cold cranking amps on the battery to see what percentage it holds compared to what it is rated for.

Also, after putting that load on the battery you might have to wait a while for the voltage reading to rise and to be accurate.

Good advice! I always do that if a battery is suspect. But you do have to get the battery fully charged first (or at least full as it will take in say 12 hours with a decent charger.

I used to only have those basic Sears and other chargers. I then bought a marine smart charger and haven't looked back. It is marine version of this one that they now sell here in Canada I am sure there are equivalent units available in USA.

Basically what I am trying to say - Get a decent charger! Get the battery as fully charged as you can, then do a load test with a cheap unit like this.
https://www.schumacherelectric.com/products/battery-load-tester/
Or maybe one of the more sophisticated electronic units! They were out of my price range, but looked neat
https://canadianbestseller.com/pd/ancel-bst500-12v-24v-100-2000-cca-automotive-battery-load-tester-car-cranking-and-charging-system-analyzer-scan-tool-with-printer-for-heavy-duty-trucks-cars-motorcycles-and-more/?v=3e8d115eb4b3#gsc.tab=0

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I had a problem charging an AGM battery with a C-Tek charger.

With the battery connected it charged only to 12.4 Volt.
With the battery disconnected it charged to 12.85 Volt
The battery is a 5 year old Varta AGM.

A warning, the reconditioning program of the C-Tek can destroy the voltage regulator of the alternator. Always disconnect the battery when using this program!

Rob