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Recovering AGM auto and truck batteries

3500GMC

3500GMC

What T F, over
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Nashport, Ohio
I have a 1800 amp Kinetik brand AGM battery that I run in the '74 C10. It sits most the time but gets toyed with every now and then. Never had any discharge issues until a few months ago. Battery went totally FLAT like .1 V. It's not a cheap mistake BY FAR. So now I'm trying to resuscitate the thing. It's maybe 4 years old.

Won't draw any current from a charger no matter how big or small. Have it on a 600ma trickle and have it to 6.45v +/- resting but no real amperage output.. Will read 14v when on the 600ma charge. Stop charge, voltage will drop immediately to 6 and a half thereabouts.



Could it be a gonner? Any methods? Drastic or simple?
 
I've heard you can put a lead acid battery next to it and hook them together and then put the trickle charger on the lead acid battery. Supposedly the AGM battery won't take any charge until the voltage in it get up to a certain level.
 
Hmmm. Seems I'm at the point of diminishing returns. Somewhat pricey charger to 'maybe' save an aging $200 battery.. Or new batt and a cutoff switch..

Then there's the barley used DC arc welder in the corner..
 
Ok final chapter. Was able to nurse this battery back to a functioning energy storage device. Had it holding a steady 13.x volts. Amperage was 'there' although never verified how much.

Means to an end: Said cell was designated to light duty with a hopeful temporary stay in the '65 C10. All that was required was maybe 100 amps or whatever to whirl over the six in a row that resides beneath the patina'd hood.

Only a week passes and the battey was flat once again. There is zero draw on my old '65s electrical system so... Yeah this is the death knell for an exotic agm cell.
 
Not often talked about but all GM CS generators (called generators in GM's regulator patient) and newer designs use pulse width modulation (PWM) which are by design to maintain charge on the battery (s) and best for AGM batteries.

These PWM regulators need a minimum voltage and to maintain battery charge and have thermal protection that shuts them down when the going gets hot.

All information I've come across is that a good HD MIL GRADE AGM battery can be pulled down 50% about 3 to 4 hundred times, down 80% 2 to 3 hundred times and down to zero much less. Only chargers I've seen recommended for charging AGM's are PWM types.

I suspect older non pwm generators/alternators will kill the AGM's longevity.
 
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For whatever it's worth (and I didn't read the battery university stuff, although I will at a later date) I recall some instructions on my Odyssey AGM battery for my ATV telling me, specifically, to use the battery at least once/month. I fire it up and drive it monthly, just due to that, no matter the need to use it.
 
SnowDrift said:
For whatever it's worth (and I didn't read the battery university stuff, although I will at a later date) I recall some instructions on my Odyssey AGM battery for my ATV telling me, specifically, to use the battery at least once/month. I fire it up and drive it monthly, just due to that, no matter the need to use it.
Click to expand...

"Sorry honey, I have to go riding, for the battery!" :thumbsup:
 
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