Rejuvenate AGMs

[shonky]

Hi, all.

Found this in a Hotrod magazine, and apparently it's specific to AGMs

"However, the trouble isn't really with the battery or even, necessarily, the charger. Here's the real problem: Once the battery's voltage falls below a certain level, the charger can no longer sense the
battery's presence and will refuse to deliver the current. In some cases this can occur at any point below 10.5 volts. Older and more basic chargers are more prone to this hang-up than newer, fancier models, which are equipped with control circuitry to deal with these issues. So there are two solutions available: Buy a new, expensive charger equipped with the extra brainpower, or employ a simple trick the Optima engineers laid on us.

Here's all you need to do: Grab another car battery with a decent charge on it (12.4 volts or better) and connect it in parallel to the problem battery using a set of jumper cables. Then activate the charger and charge the battery normally, being careful to follow the manufacturer's instructions for current and voltage limits. It's as simple as that. The second battery supplies the voltage that tricks the charger into supplying the necessary current. After an hour or so, you can remove the second battery and continue charging. We tried it and it works. No matter how deep the discharge we applied, we were able to bring the battery back to a full state of charge using our cheap but trusty bulk charger."

[T1 Terry]

With the PL40 you have the solar will charge the battery as long as the voltage does not drop below 9v, the internal transistor needs at least that voltage to turn on. The "dumb" charger you have will most likely charge the battery no matter how low the voltage gets as it doesn't have a relay inside that needs battery voltage to turn it on.
I have seen the same trick with the jumper leads done using 2 x 9v batteries is series (- to + between the 2 batteries) a quick touch on the battery terminals will kick the charger in and the charger will keep itself powered, 2 x 6v lantern batteries works well too.

T1 Terry

[supersparky]

I have a couple of little 20ah AGM's at work that are being replaced next week as they won't accept charge. I will try that trick and see how it goes.

[shonky]

Hi, all

http://www.walleyecentral.com/forums/ar ... 33228.html
Seems the method has approval in some quarters.

[supersparky]

Shonky, The method certainly works, but it didn't help the little batteries I was trying to resuscitate. They wouldn't hold a charge and were beyond help.