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Old 05-09-2021, 09:59 AM   #28
eccerr0r
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Default Re: Harbor Freight car battery chargers any good?

absorption phase = on a multiphase charger, the battery has reached terminal charging voltage, but still taking in charge slowly. Usually higher than 80% charged.
CA = Cranking amps. A fairly useless metric, but it's related to battery specific power, but nothing directly about capacity.
CCA = Cold crank amps, a metric also related to specific power, but when the battery is cold. Useful metric, but still doesn't tell anything directly about capacity.
RC = Reserve Capacity, which indeed is a metric of capacity.

If you take RC and divide by 2, it's very, very roughly the ampere*hour rating of the battery which then you can calculate how long a battery will take to charge from empty.

Due to the exact chemistry of the specific batteries, voltage can be slightly higher and lower. Flooded batteries tend to have a slightly lower voltage than AGM. In any case you do need to wait for an hour or after disconnecting to take a voltage reading to know exactly what's going on, it's OK to be at 13V, and AGM packs are frequently significantly above 13V when fully charged.
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