ok ***........Once the battery is fully charged to 12.6 volts, it requires less power from the alternator. This system of discharging and charging is called a cycle. If a battery is drained until it is nearly dead, the charging process completes what is called a deep cycle. Most automotive batteries are not capable of deep cycling and typically cannot handle this type of use more than once or twice. Having 2 batterys will keep it in a charge cycle cuz they wont get low as easily, and it wont have to go through deep cycles. Make sense, dumbo?
