I switched last weekend from flooded to AGM batteries. With the flooded, I would always leave the battery charger on to keep the batteries charged. My understanding is that the self-discharge for AGM's is about 3% month so if the batteries are left charged it should not be necessary to keep the charger on unless absent for more than several months. Is that the correct protocol, or is it fine to keep the battery charger on for AGM's whenever at dock. If so, does that shoerten/extend battery life? Thanks in advance for advice.
AGM batteries and charging
- Thread starter davidkahn53
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AGMs don't sulfate as wet cells so keeping them fully charged isn't as important. The more important issue for your to consider is the need to ensure they do reach a full re-charge, which isn't always apparent, before letting them sit. Prolonged under-charge can effect lifetime
This should be okay unless you have refirgeration or some other source to drain your batteries. I have Gel's and we leave our charger on 24/7.
You don't say what brand of AGM you have but Lifeline is probably the one company that has done the most research on this type of battery. It is a myth that AGM batteries don't suffer from sulfation. This is why it is wise to charge them to 100% as often as possible as most brands, other than Lifeline do not allow equalization charging cycles.. Here's some points on storage of Lifeline batteries.
"Storage:
The following recommendations may be helpful if the battery is to be stored: When storing the battery, it is not necessary to leave it on charge. Disconnect the negative battery cable. This will prevent inadvertent discharging of the battery that may lead to a complete discharge.
Fully charge the battery before putting it in storage and store in a cool place.
Boost charge the battery every 3 months to ensure maximum battery life."
"Storage:
The following recommendations may be helpful if the battery is to be stored: When storing the battery, it is not necessary to leave it on charge. Disconnect the negative battery cable. This will prevent inadvertent discharging of the battery that may lead to a complete discharge.
Fully charge the battery before putting it in storage and store in a cool place.
Boost charge the battery every 3 months to ensure maximum battery life."
related question. Doesn't AGM battery require a higher output voltage form the regulator or charger (higher than for wet Cell Battery)?
No, most require a voltage in the 14.2 - 14.6 range and the voltages in absorption are very similar to wet cells. Some wet cells, like Trojans, can be charged at up to 14.8V..
If you haven't yet, you should really read this: http://forums.sbo.sailboatowners.com/showthread.php?t=124973
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