7 At this time you should hear the charger come on and see the gauge move. To increase the battery life, you should choose 5 amps or a slow charge, as this will increase you battery life! If you need a quick charge, use 10 amps. The further the gauge moves to the right, the more your batteries need charged. This process could take several hours, so be sure to check on the charge periodically. Once the needle on the gauge is all the way to the left, your batteries are finished charging.