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Old 01-12-2009, 16:31   #1
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Equalizing AGM Batteries

I have 160AH of batteries hooked to 260 watts of solar panels. Obviously it is easy to overcharge the batteries, so I got a 20 amp charge controller. I then realized the batteries voltage still reached 14.6. I read in the manual that the controller holds at 14.6 for 10 minutes, then reduces to 14.4 for a while, and finally lower (like 13.6 or something)

I think this is probably fine for most batteries, but I have AGM batteries, and when you go above 14.4 they make crackling sounds. Is this bad for the batteries? Should I seek a controller (or modify this one) so that I never exceed 14.4 volts?
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Old 01-12-2009, 16:37   #2
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14.6 in not enough to equalize and that voltage should not be enough to cause any imediate damage, but a crackling sound? that does not sound good I am curious what the experts have to say
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Old 01-12-2009, 17:07   #3
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I'm no expert either, but AFAIK you don't equalise AGM batteries.

As I understand it, equalising is where, for a short time, batteries are overcharged, which "boils" them, causing the dissolved lead in the acid to mix more evenly throughout the cells, rather than tending to sink to the bottom. ie- it "equalises" the distribution of the lead.

In AGM's and gel cells, the lead is physically held in place, so no equalisation is needed, and overcharging, even briefly, is more likely to do harm than good.
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Old 02-12-2009, 05:30   #4
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Geckosenator,

I suspect you may be miss-using the term "equalizing". Your posts asks about normal charging of the batteries by your solar panels. Equalizing (conditioning) is something else entirely; generally done when the batteries are partially sulfated and have lost some of their charge-holding capacity.

For normal charging, your charge controller needs to be programmed to match the charging voltage profile specified by your batteries' manufacturer. Three stage "smart" charging is the best way to prolong battery life. You can probably find the specs for the recommended Bulk, Absorption and Float voltage limits on the manufacturer's website. Lifeline, for example, has everything you need to know in their manual--LINK.

BTW, Lifeline does recommend equalizing (they call it conditioning) for their AGMs: 15.5 volts for 8 hours, at 77* F.
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Old 02-12-2009, 12:07   #5
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Thanks for letting me know the AGM "condition" at 15.5v. When they are doing this, do they make any sounds (like hissing or cracking)?

My batteries are 2 month old werker 80ah. I cannot find the specs. I assume they are very similar to any 12v AGM battery, but it is hard to tell because maybe the venting is different.
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Old 05-12-2009, 12:09   #6
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gs,

15.5 V is what Lifeline recommends for their AGM batteries. Other manufacturers may have different specs. I think that the Werker batteries are an in-house brand sold by BatteriesPlus. You should find out what they say before doing something that might fry your batteries. "Hissing and cracking" isn't something I'd classify as a good thing.
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Old 05-12-2009, 14:13   #7
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14.4 - 14.6 are typical absorption voltages for AGM / SLA batteries...

does your charger have a temperature sensor ?
Charge voltages are temperature dependent...without a temp sensor and a decent 3 stage charger you could be under or overcharging your batteries.

Agree with everyone else...hissing / cracking sounds are not good under any circumstances...maybe your batteries have cracked cases...there is some H2 gas formed when batteries are charging...maybe that's whats hissing out of the cracks ?....if that's what's happening...then this is a potentially explosive situation.

I would replace the batteries and set up a "proper" charging system.

Cheers

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