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Old 14-06-2021, 17:53   #1
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Reviving AGM Battery

An oldie, a divisive one at that, but here is my experience.

My first 2 cheap at $US200 for 130AH each Chinese batteries lasted 2 1/2 years. Stupid me then bought 2 more offered at a discount because the first two didn't go the distance. Now, after 4 years, they do died.

I tested them with an Ancel B101 analyser, and they showed about 30% capacity, with a "replace battery" readout. I went through several charge/discharge cycles with a 16 amp load, but always got a "replace battery".

With nothing to lose, I thought I'd add distilled water.

The cells are covered with a thin plastic plate glued into the battery. The plates stop the rubber fill caps directly under it from popping out during charging.

I put in 20 millilitres (2/3 of an ounce) of distilled water into each cell, and recharged the batteries.

This time I got a "good battery" reading, with a consistent percentage good in the mid 60's %.

Even after a few more charge/discharge cycles.
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Old 14-06-2021, 18:02   #2
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Re: Reviving AGM Battery

Quote:
Originally Posted by starcruiser View Post
.

This time I got a "good battery" reading, with a consistent percentage good in the mid 60's %.
.

Just one comment: most batteries are considered functionally “dead” when they drop below 80% of their initial capacity.

Sounds like you have brought yours from fully dead to just comatose.
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Old 15-06-2021, 08:19   #3
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Re: Reviving AGM Battery

Were it me, I would try equalizing the batteries. While not normally recommended for AGMs, Lifeline does for their AGMs. Google "lifeline battery equalization charge" for instructions.

Since you have essentially dead batteries, you have nothing to lose.
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Old 16-06-2021, 00:18   #4
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Re: Reviving AGM Battery

Haha, I like the description. Hope to find out soon if the patients have at least a reflexive kick.
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Old 16-06-2021, 00:20   #5
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Re: Reviving AGM Battery

James's, Yeah, I've considered that but unfortunately my chargers are too smart to go over 14.7 volts.
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Old 16-06-2021, 08:19   #6
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Re: Reviving AGM Battery

Quote:
Originally Posted by jamhass View Post
Were it me, I would try equalizing the batteries. While not normally recommended for AGMs, Lifeline does for their AGMs. Google "lifeline battery equalization charge" for instructions.

Since you have essentially dead batteries, you have nothing to lose.
I recently equalized our set of Lifeline batteries and I think our start battery is healthier. Before equalizing, the start battery voltage would drop to about 9 volts and would barely start the boat. I haven't checked the voltage drop, but the boat starts much easier.

In my case, I put the house and start in parallel and equalized all the batteries. I didn't have a way to equalize just the start battery.
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Old 16-06-2021, 08:28   #7
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Re: Reviving AGM Battery

http://https://www.bing.com/videos/s...%252FntudJ7PaQ
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Old 16-06-2021, 09:11   #8
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Re: Reviving AGM Battery

Quote:
Originally Posted by starcruiser View Post
I put in 20 millilitres (2/3 of an ounce) of distilled water into each cell, and recharged the batteries.

This time I got a "good battery" reading, with a consistent percentage good in the mid 60's %.

Even after a few more charge/discharge cycles.
yeah, but what is their real capacity in 20C Ah????
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