Charging AGM Batteries

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Old 02-05-16, 11:06 AM
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Charging AGM Batteries

I just bought a Noco Genuis G1100 battery charger/maintainer and it has a setting for "normal" charging and "cold/AGM" charging. I am currently using it to charge my dirt bike battery, which is an AGM battery, so I will of course be using the cold/AGM setting. My question is what does the charger do differently for an AGM battery? And does "cold" refer to charging a physically cold battery (sub-freezing)? Do AGM batteries need to be charged more gradually or more rapidly? Perhaps it's the floating voltage applied after charging. I read that AGM batteries are more sensitive to over-charging.
 
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Old 02-05-16, 01:28 PM
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AGM and and regular wet cells charge similar with a slight voltage difference.

Typical chargers will not charge a low S.O.C agm batts below like 10 v... They will kick off and not chargel. And many times you have to trick the charger by hooking another semi charged battery in parallel to start the charging process..

[ATTACH=CONFIG]62502[/ATTACH]
 
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Old 02-05-16, 01:29 PM
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AGM batteries ARE more sensitive to overcharging so an AGM charger has a lower terminal (ending) voltage than will a standard (wet) lead-acid battery
I believe thats a myth and it was the gel batterys that were sensitive...

From my knowledge anyway...
 
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Old 02-05-16, 05:45 PM
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Well the battery is 100% charged and now in float mode. However, the voltage is only 12.8V. According to the graph you posted, it should be 13.8V.
 
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Old 02-05-16, 05:52 PM
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However, the voltage is only 12.8V. According to the graph you posted,
What are you checking the voltage with?
Ill read specs on your charger.,,, give me some time
 
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Old 02-05-16, 05:58 PM
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Its only a 1.1 amp maintainer charger so ignore my graph I posted...

Sorry I did not look up actual specs.....


NOCO Genius® G1100 - Wicked Smart™ Battery Charger (1100mA, 6V/12V)
 
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Old 02-05-16, 06:16 PM
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I'm measuring the battery in situ with my digital multimeter. Based on what I've read, an AGM battery should be floated between 2.2V and 2.3V per cell. My battery is 12V, so that's 13.2V to 13.8V.

I just monitored the voltage while it went through a cycle and it fluctuates between 13.5V up to 15.2V, back down to 13.5V, up to 15.2V again then settles to 13V at 100% charge, then gradually drops to 12.8V. Weird.
 
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Old 02-05-16, 07:15 PM
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AGM batteries are more sensitive to over-charging
They are in one way in particular...... if you overheat them just once they're basically shot.

That charger you're using uses pulse technology for charging and it may also introduce AC pulses for desulfating batteries.
 
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Old 02-05-16, 07:32 PM
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I didn't think AGM batteries needed desulfating. Regardless, I don't think the float voltage should be so low.
 
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Old 02-06-16, 05:59 AM
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I'm beginning to think that maybe I have a bad battery. It's been connected to the charger overnight and it's sitting at 12.8V. That's only 2.13V per cell. Based on what I've read, the lowest recommended float voltage is 2.2V. The battery is only a year old, but I don't ride my dirt bike for extended periods so the battery probably doesn't have a chance to charge fully everytime I ride. I suppose I should be connecting the charger when I get home from riding and leaving it connected until next time I ride? By the way, the battery is a Yuasa YTZ7S, and it wasn't cheap.
 
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Old 02-06-16, 06:38 AM
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A fully charged battery is 12.7 volts.. If its fully charged then your charger may be in standby..

Drain the battery some and put it back on the charger..

You did say this so I see nothing wrong ...


I just monitored the voltage while it went through a cycle and it fluctuates between 13.5V up to 15.2V, back down to 13.5V, up to 15.2V again then settles to 13V at 100% charge, then gradually drops to 12.8V. Weird.
It states its a 7 stage charger in the docs...
 
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Old 02-06-16, 06:40 AM
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Whats the charger mode say? Stand by ? LED's?
 
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Old 02-06-16, 07:56 AM
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It's only in standby when you first plug the AC cord in. After it charges the battery, the 100% LED remains lit and the mode LED remains lit. I'm wondering why the charger is not floating the battery at 2.2V to 2.3V per cell as stated in everything I've been reading about charging and maintaining AGM batteries.
 

Last edited by mossman; 02-06-16 at 10:04 AM.
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