12.2 volts or less means the battery is good but totally discharged. Charge it at a slow rate for at least an hour, then remeasure the voltage. It must be near 12.6 volts to be considered fully-charged. If that's what you find, measure the battery voltage again with the engine running. It must be between 13.75 and 14.75 volts.
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Friday, December 28th, 2012 AT 5:40 AM