Charging Battery

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Is there any benefit to periodically {once per month/quarterly etc} using a battery charger to "top off" a car battery that sees daily use in a car that has a correctly operating electrical system? Will it extend the life of a newer battery? Someone told me that alternators rarely charge the battery to 100%, and by periodically using a charger, you force a 100-105% charge on the battery, which helps it? The battery in question is a AGM model, if that makes a difference.
 
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Overcharging isn't any better than to undercharge, just different but still problems. If daily use is short trips in cold temps, this makes some sense, as battery may not get full charge. SLI batteries don't like deep cycling and 90% full charge is the safe lower limit. Modern versions may be more tolerant of the lower charged state than past ones. IMHO.
 

qship1996

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I read you must periodically force charge to 100-105% capacity otherwise battery will only accept a partial charge{90%} from just the alternator?
 
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Modern voltage regulators "overcharge" when cold as a means to overcome additional chemical resistance within the battery. I think the "charge it" crowd is from an old school where that may have desulfated at some point in the past when alternators weren't as good as they are today. There are lots of chargers out there that claim to "float charge" as if it's a good idea... also on emergency power failure hall lights etc. Car alts are "float chargers" at a constant voltage (at temperature) that gradually taper off putting the starter motor's deficit back in the battery. If a battery is $60 and last 6 years... how much more does one expect with aggressive maintenance? This is not a sarcastic question, but rather one of "what's your time worth" (as well as your electric bill)
 
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