How Long Does It Take to Charge a 12-Volt Car Battery From Flat?

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Charging a 12-volt battery with 450 cold cranking amperes and a 5-ampere charge rate takes about nine hours. The length of time required to charge a battery varies with the voltage, the charge rate and the CCA capacity of the battery.

Care must be taken that positive terminals are never crossed with negative and that accessories are turned off when batteries are removed or replaced from a vehicle. The grounded terminal should always be removed first. Some battery cells need to be topped up with distilled water. Baking soda and water can be used to neutralize and clean up acid that builds up on the battery and terminals. Proper eye and skin protection should always be used when working with batteries.