Success at Repairing Military AGM Batteries?

[G3isMe]

I had a pair of these Absorbent Glass Mat (AGM) batteries lying about for a while as I could not get them to take a charge. In fact the battery charger would stop and not even attempt to charge the battery. I bought a new battery charger a while ago and didn't really pay much attention to all of the extras as I really had purchased it to charge the in-law's lawn mower battery. The other day I noticed it had a battery repair setting. I hsd read about this battery repair/recovery from a military memo (I don't think it was a tech memo. I will dig around and see if I can find it) and I think one of those comic book type memos last year so I thought ahaaa, hoping the repair mode of my $50 battery charger will actually work.

So I hooked up the charger to one of the batteries, pushed the repair button, and it went all night working in the repair mode. In the morning I charged it with the 10 amp setting. I then hooked the other battery up, set it to the repair mode, let it do its thing overnight, and then charged it to 100%. The batteries are now both showing about 13.4 volts. This is a huge improvement from not even being able to accept a charge.

I guess one way to check on how well this worked is to have a shop do a load test on them. I am pretty excited about this if I can recover these batteries. Has anyone else had any luck with this.

 

[Coug]

With a smart charger the recommended method (in PS magazine) is to hook a second, good battery in parallel with the completely discharged one and place the pair on the charger for a while (I forget exactly how long). The good battery has enough voltage to keep the charger working, and the amperage goes to the depleted battery.

Found the page, someone had it on a facebook group I follow.

 

[Gear Report]

How I resurrected a few old HMMWV batteries that wouldn't take a charge from my "smart charger" is listed in here. https://gear-report.com/humvee-upgrade-best-hmmwv-batteries

 

[G3isMe]

How I resurrected a few old HMMWV batteries that wouldn't take a charge from my "smart charger" is listed in here. https://gear-report.com/humvee-upgrade-best-hmmwv-batteries

Thank you as there is a wealth of information contained in your linked site. Required reading right there.

Coug thanks for the comic book post.

 

[TOBASH]

Please do a battery load test and report back the results.

 

[G3isMe]

Please do a battery load test and report back the results.

I brought the battery's over to NAPA and the parts guy retrieved a handheld load tester and came out to the truck. He did it right at the back of the truck. Thank God as I didn't look forward to humping those batterys to the back of the shop.

So he load tested them with the initial setting of 1200 cold cranking amps, which I think is about their original capacity. It drew one them down to 937 CCAs, and the other battery had a similar result. Accordingly they failed. That being said I don't know what the criteria are for it to be a failure. He didn't seem to know the answer. I am guessing it is in part the drop in CCAs. So would you guys use these?

 

[TOBASH]

I would discharge and recharge, and then keep them on trickle charge as good emergency backup batteries, IMHO. Others might disagree.

 

[G3isMe]

I would discharge and recharge, and then keep them on trickle charge as good emergency backup batteries, IMHO. Others might disagree.

That is s good idea as you know what they say, great minds and all that...plus my hoarding, ah, err, I mean collecting tendencies arose when I considered tossing them out. I drew them down yesterday and I am recharging them at a trickle charger rate (a 2 amp slow charge).

 

[Bulldogger]

I second the recommendation to give them a few charge and discharge cycles before writing them off completely, but it's looking unlikely for sure. Even so, they do have some capacity and could be good spares for unforeseen issues where some portable 12V power might come in handy (if we first consider those heavy suckers "portable"). If all else fails, Interstate All Battery Centers (that's the local warehouse, not the small distribution closets) pay a lead bounty on used batteries of any kind. It's usually between $0.20 and $0.25 per pound. While that seems low, it adds up when 6T batteries are involved!
Let us know how it goes and don't forget to check the electrolyte concentration and water levels.
Bulldogger

 

[4x4Junkie13]

How have these batteries held up after this process?

 

[T9000]

I brought the battery's over to NAPA and the parts guy retrieved a handheld load tester and came out to the truck. He did it right at the back of the truck. Thank God as I didn't look forward to humping those batterys to the back of the shop.

So he load tested them with the initial setting of 1200 cold cranking amps, which I think is about their original capacity. It drew one them down to 937 CCAs, and the other battery had a similar result. Accordingly they failed. That being said I don't know what the criteria are for it to be a failure. He didn't seem to know the answer. I am guessing it is in part the drop in CCAs. So would you guys use these?View attachment 791546

If the battery delivered 937A at 12.45V that’s still a great battery as the SAE standard considers the pass criteria based on the battery staying at 7.2V or above for 30 seconds at 0F, and based on the ambient temperature between 60F and 70F (just guessing the temperature at that shop) the voltage should be around 95% of the fully charged battery voltage (about 12.75V-13V for AGM). If that test is a simple GO/ NO-GO I would try to find what was the voltage during the discharge, maybe it failed by a small amount like 0.1V or 0.2V in which case re-run the test in decrements of 50A-100A and see where it passes. Just because it lost some capacity it doesn’t necessarily mean it’s a bad battery if it still can deliver 800-1000A (ideally at low temp).

EDIT: I just now noticed that this is a 2 years old thread

 

[Mogman]

Those testers are wiz-bang gizmos, they do not actually load the batteries (as evidence they have small multi meter like test leads)
So it did not load the battery to 900+amps, (it would need 2-0 cables and massive clamps) I do not trust them. I would have them load tested on a real tester.

 

[98G]

I've got a couple of 12 year old Hawkers in my HMMWV. I thought I'd be replacing them this spring because they were acting weak last fall and they were flat dead when I went to start the HMMWV a couple weeks ago, despite the solargizer.

A ran them through a resurrection cycle on my battery charger through the slave port. Now they're taking and holding a charge, and easily starting the HMMWV after cycling the glow plugs.

While I'm not completely convinced this is a complete success, I'm having hope of getting through another season on them.

 

[98G]

Those testers are wiz-bang gizmos, they do not actually load the batteries (as evidence they have small multi meter like test leads)
So it did not load the battery to 900+amps, (it would need 2-0 cables and massive clamps) I do not trust them. I would have them load tested on a real tester.

Do you have a suggestion for a real tester?

 

[Mogman]

Do you have a suggestion for a real tester?

Snap On YA275 500 Amp Carbon Load Tester | eBay

Snap On YA275 500 Amp Carbon Load Tester.

www.ebay.com

Or check with the local starter/alternator repair shop.

 

[T9000]

Those testers are wiz-bang gizmos, they do not actually load the batteries (as evidence they have small multi meter like test leads)
So it did not load the battery to 900+amps, (it would need 2-0 cables and massive clamps) I do not trust them. I would have them load tested on a real tester.

I didn’t see the cables and presumed that a car shop would have a real load tester, which you are right, would require a heavy gauge cable to load the battery at 1,200A.

 

[T9000]

Most inexpensive battery load testers are just a high power resistor that can be set at different values (i.e. 1,000A @ 12V = 0.012 ohms, or 12 milliohms, which would in theory have to be 12kW (the voltage drops when the battery is loaded, so the actual dissipated power is lower) but in order to control cost and size, the resistor is underpowered, maybe by 50-75% and provides only a reduced test time like 15 seconds, which in most cases it’s sufficient to get an idea if a battery can deliver high current.
In engineering labs they use constant current loads, which maintain the current at the programmed value regardless of the voltage, until it hits a certain voltage threshold (low voltage cutoff) and those are in the multiple thousand$,

 

[spankybear]

Those testers are wiz-bang gizmos, they do not actually load the batteries (as evidence they have small multi meter like test leads)
So it did not load the battery to 900+amps, (it would need 2-0 cables and massive clamps) I do not trust them. I would have them load tested on a real tester.

They are real testers just testing the battery differently. They measure the internal resistance and calculate the CCA. For the most part they work... only have an issue when the battery heats up internally and the internal resistance goes up. Both a resistance load tester and the ones that measure internal resistance have there place. Any battery that has been "repaired" by a smart charger should be tested with a resistance load tester and not a internal resistance tester.

 

[loosegravel]

I guess it's what you're used to that gives the best results. I'm kind of old school when it comes to testing batteries. I've always used a carbon pile load tester with an inductive amperage clamp. The rule of thumb is to load the battery to 1/2 of the cold cranking amps (CCA) for 15 seconds. The voltage should not be below 10.5 at 60 degrees F. There is a temperature table which shows that the lower the ambient temperature is, the lower the battery voltage will be at the end of 15 seconds. I remember when the internal resistance testers first came out. I was admittingly skeptical of them. But those in the field that I have come to know all say that they're pretty accurate. The nice thing about the carbon pile load testers is that they can also be used to put a healthy load on a charging system in order to check the output of an alternator. If the alternator is rated at 100 amps for example, you can clamp the carbon pile load tester to the battery posts and pull a 100-amp load. With the engine running at a fast idle you can move the inductive amp clamp over to the positive battery terminal and point the arrow towards the battery. It will accurately measure the output of the alternator. I don't think that you can do this test with the internal resistance type of battery tester!

 

[chucky]

harbour freight 21.99 100 amp