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AGM charging advice

Old 08-04-2013, 07:44 AM
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Default AGM charging advice

Got 2 new dual-purpose AGM batteries from Cabelas, but because of an injury I won't be able to install them for a month or so.

Is it better to just let them sit and charge them before I install them, or charge them fully now and leave them on trickle charge?

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Old 08-04-2013, 09:17 AM
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Charge them fully now. Sitting a month is not an issue for agm's but if you want to charge them every week is so that is fine. Continuous trickle charge is not needed for a 30 day period. New batteries sit for 6 months or more prior to sale a lot of times with no charge.
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Old 08-04-2013, 09:18 AM
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no diff but I'd charge them now..why wait?
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Old 08-04-2013, 06:55 PM
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Originally Posted by Flatout71 View Post
...Sitting a month is not an issue for agm's...
This is misleading. There is nothing about the construction method of absorbent glass mat that makes the self-discharge rate lower. Only lead-acid batteries made with high purity lead have low self-discharge rates. There is no guarantee that a particular AGM battery will be made with high-purity lead.

AGM batteries are sealed and valve regulated (VRLA). They should not be over-charged or they will lose electrolyte. If you leave them on a trickle charger, make sure the float voltage is proper. Some VRLA AGM batteries want to float at only 13.8-Volts.
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Old 08-04-2013, 09:18 PM
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Originally Posted by jhebert View Post
This is misleading. There is nothing about the construction method of absorbent glass mat that makes the self-discharge rate lower. Only lead-acid batteries made with high purity lead have low self-discharge rates. There is no guarantee that a particular AGM battery will be made with high-purity lead.

AGM batteries are sealed and valve regulated (VRLA). They should not be over-charged or they will lose electrolyte. If you leave them on a trickle charger, make sure the float voltage is proper. Some VRLA AGM batteries want to float at only 13.8-Volts.
What charger do you recomend?
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Old 08-04-2013, 10:06 PM
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Originally Posted by Ironworker View Post
What charger do you recomend?
I used a Xantrex True Charge 20 for my AGM's. This is an older unit but is still a true 3 stage charger with great voltage sensing capabilities. The latest version is probably a better unit. The key is getting a charger that has the ability to charge AGM batteries.
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Old 08-04-2013, 11:48 PM
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Originally Posted by saltwaters View Post
I used a Xantrex True Charge 20 for my AGM's. This is an older unit but is still a true 3 stage charger with great voltage sensing capabilities. The latest version is probably a better unit. The key is getting a charger that has the ability to charge AGM batteries.
?? Most AGM batteries are quite similar in charge profile to LA batteries (Optima Bluetops as example) - and they will not like "AGM" charge profiles at all. Other like Lifeline prefer quite different charge setups - very different from what I have seen as AGM profiles in most chargers.

Bottom line - read the AGM spec sheet for charging - and find a charger that is compatible with it. No two AGM profiles are alike. Or get a charger with a programmable charge setup like Pronautic 12xx series (not the C3 model) and create your own profile as pr. the spec sheet.

EDIT: And an extra little hint - you do not change alternators when changing batteries do you? .... The Alternator is your biggest charger on your boat and it works fine with both LA batteries and AGM batteries. But you can buy "programmable" alternators that might treat your batteries better. But that is rare.
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Old 08-05-2013, 10:46 AM
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Originally Posted by kaz911 View Post

EDIT: And an extra little hint - you do not change alternators when changing batteries do you? .... The Alternator is your biggest charger on your boat and it works fine with both LA batteries and AGM batteries. But you can buy "programmable" alternators that might treat your batteries better. But that is rare.
Exactly, in 10 years I have used regular chargers on agms with no problems...read all you want, but I think the sears, odysseys and cabellas batts lasted fine for me....
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