Topic: Is there any hope of reviving a weirdly failed but not dead AGM battery?

[fizzlebottom]

Long story short, I am 99% certain that my old battery tender failed and took the AGM battery with it.

I had it on trickle during the off season and rarely had a peak at it for a long while. In that time, I realized the battery tender wasn't tending batteries when I tried to charge a different one. Threw it out, got a new one, hooked things back up and off we went.

I just went to fire up the bike with the AGM and it cranked about as slow as a dead battery would. Except it had a very healthy 12.4+ volts. I read voltage as it cranked and it dropped down to 5-6v. Battery takes a charge, but does absolutely nothing when asked. Momentarily got the bike started via other means and the charging system is working perfectly.

So is my nice pricey AGM battery dead dead dead or is there hope to revive it in any way? I've got a shiny new normal flooded lead acid charging up right now so the AGM isn't required. Just wondering if it's destined to be a core or can be a backup when needed.

[Alan F.]

If a battery, AGM or lead-acid is under a certain voltage, battery tenders won't sense them as chargeable. You can hook up a 'not so smart' charger for 30 minutes or so and switch to a Tender, or:

If your battery tender shows a solid red Led = not charging, connect another battery in parallel and connect your battery tender. This fools the tender into thinking the battery can be charged.

After 30 minutes disconnect the second battery to check if your AGM will charge alone, red led flashing will indicate battery is charging.

[newday777]

So, how old is this battery??

[fizzlebottom]

If a battery, AGM or lead-acid is under a certain voltage, battery tenders won't sense them as chargeable. You can hook of a 'not so smart' charger for 30 minutes or so and switch to a Tender, or:

If your battery tender shows a solid red Led = not charging, connect another battery in parallel and connect your battery tender. This fools the tender into thinking the battery can be charged.

After 30 minutes disconnect the second battery to check if your AGM will charge alone, red led flashing will indicate battery is charging.

The new tender is charging the AGM battery just fine. Shows a pretty green light and all. Voltage confirms a charge, but as soon as the bike cranks, it behaves like a nearly dead battery.

So, how old is this battery??

Little over a year. Used it for a season, put the bike in the garage and plugged in the tender. Like I said, I'm fairly certain the old tender failed and took this battery with it.

I just hooked the new freshly charged flooded battery up and the bike came to life right away. Really confused about what exactly failed in the AGM, but I've confirmed it is toast.

[HondaMan]

If the AGM battery was dragged down to 'dead' by [certain kinds of smart] battery charger, it may need a pre-charge to reset the chemistry before the plates will be able to charge again. For the home version, this requires a low-tech 'trickle charger' capable of less than 1.5 amps charge rate. The best would be an old 'tender charger' of about 0.5 amp capacity. The pre-charge supplies a low-current repolarization of the acid at the surface layer of the plates to 'open' them again to accept a charge. The AGM is a sort of flattened-out version of the spiral-wound closed-chemistry batteries, but with immersed lead instead of captured electrolyte.

I used to make these: I don't know if I still have any parts of them left, though? Will have to go dig around...

[fizzlebottom]

I've only ever had the Battery Tender Jr that charges at a whopping 750mA. Bought the new model once that old one kicked the curb. The manual does describe it as what I might call a little "smart" in that it has a few modes it switches between depending on charge state of the battery it is connected to. But there isn't anything saying that it goes through charge / discharge cycles at all. Only 0-80%, 80-100%, and 100-103%.

[Rayzerman]

A Battery Tender JR. will not revive a battery that is dead dead, it hasn't got enough oomph.  Recommend charging it with a 1.2-2 amp charger, then have the battery load tested.... my guess is it's on the way out and you'll likely need a new battery.

[Alan F.]

I've only ever had the Battery Tender Jr that charges at a whopping 750mA. Bought the new model once that old one kicked the curb. The manual does describe it as what I might call a little "smart" in that it has a few modes it switches between depending on charge state of the battery it is connected to. But there isn't anything saying that it goes through charge / discharge cycles at all. Only 0-80%, 80-100%, and 100-103%.

That's the model I talked about below, I've had mine for 14 years and it's very reliable.

I actually picked it up at a Toyota dealer, they sent me a 15% off coupon for their parts department, I'd seen these on the shelf while having a recall performed. I think I payed $26.

[scottly]

I've revived AGM batteries before by putting a load on them, like a headlight, and monitoring the voltage as it drops, then when it drops down to 8 volts or so, disconnect the load and connect a 2 amp charger. If the battery is drawing current, the voltage will go up slowly, but if the voltage very quickly goes up to 14.5V or more, which any proper charger should be capable of, the battery isn't drawing current, and some "smart" chargers or tenders will take that as a sign that the battery is fully charged and will switch into a float mode, holding the battery at a lower voltage.
If the battery does seem to take a charge, note the time it takes for the voltage to get to 14.5V, then put the load back on and note the time it takes for the voltage to drop to 8 volts again. If the discharge and recharge times increase with each cycle, it might be salvageable.     

[Deltarider]

[...] then have the battery load tested.... [...]

What do you think starting a cold engine is? I do this - battery charged(!) - while monitoring the voltage drop at the beginning of every season. An analogue voltmeter is best for this. When voltage drops towards 9V, your battery won't live much longer. More info is here: http://forums.sohc4.net/index.php/topic,205097.msg2316714.html#msg2316714

[BallAquatics]

For the home version, this requires a low-tech 'trickle charger' capable of less than 1.5 amps charge rate. The best would be an old 'tender charger' of about 0.5 amp capacity. The pre-charge supplies a low-current repolarization of the acid at the surface layer of the plates to 'open' them again to accept a charge. The AGM is a sort of flattened-out version of the spiral-wound closed-chemistry batteries, but with immersed lead instead of captured electrolyte.

I used a small solar panel to bring one back to life.  Very small charge rate, but the battery has been going strong for several years now...   

[MauiK3]

I have a small solar panel charger I decided to not use because I was unsure if it was so unsophisticated it may hurt the battery. I still have it, I should try it on a small spare battery I have.

[OPKP]

I've saved marine AGM batteries by hooking up another good battery in parallel to the dead one with jumpers, then charging the good one.  Yours may be salvageable.

[HondaMan]

I've revived AGM batteries before by putting a load on them, like a headlight, and monitoring the voltage as it drops, then when it drops down to 8 volts or so, disconnect the load and connect a 2 amp charger. If the battery is drawing current, the voltage will go up slowly, but if the voltage very quickly goes up to 14.5V or more, which any proper charger should be capable of, the battery isn't drawing current, and some "smart" chargers or tenders will take that as a sign that the battery is fully charged and will switch into a float mode, holding the battery at a lower voltage.
If the battery does seem to take a charge, note the time it takes for the voltage to get to 14.5V, then put the load back on and note the time it takes for the voltage to drop to 8 volts again. If the discharge and recharge times increase with each cycle, it might be salvageable.     

Gates energy invented the tech that is now the AGM plate cells, though originally they were all spiral-wound style.
Scottly's approach is the best one here, given non-'smart' chargers. What is happening is: the discharge sloughs off the lead oxide molecule(s) that grew on a low-charged ion of lead: there is that 'magic' point (8.0 volts on most plate-like lead, 6.8 volts on spiral-wound matte cells) where the oxide molecule loses its grip on the lead molecule and lets go. Gates Energy then shook (vibrated) the battery (pretty violently!) at that point, then immediately charged it with 1-1.5 amps (depending on capacity) until fully charged. The modern AGM battery is very similar in construction and chemistry. When the oxide falls off, the lead plate molecule(s) at that point are virgin again and will accept the most charge they can possibly hold. While some of those molecules 'died' to create that oxide molecule, it's less than 2% typically, so the battery comes back strong.

I don't have any of my old transformers left for the tricklers I use to make. Dang...

[BenelliSEI]

I've saved marine AGM batteries by hooking up another good battery in parallel to the dead one with jumpers, then charging the good one.  Yours may be salvageable.

I did this, on the AGM (1 year old) that I thought was finished. Been using it in the cb750K1 for a few weeks, and it seems back to life. Give it a try! Used an old fashion charger on the 2 amp setting for 12-24 hours.

[fizzlebottom]

I don't have any of my old transformers left for the tricklers I use to make. Dang...

Time to start winding up your own I guess.

[HondaMan]

I used a small solar panel to bring one back to life.  Very small charge rate, but the battery has been going strong for several years now...   

That's almost a perfect version of a 'smart' charger! It can't overcome a low-charge situation, but can 'tender' a low battery up to [even] a fuller charge very slowly.