Many advanced boat electric battery chargers and on-board battery pack chargers nowadays has a two voltage system capability both for 12 and 24-volt batteries with multiple-current charging system like 30, 15 and 6 amps. They are also loaded with a 3 stage charging system that allows it to charge different types of batteries to its optimum potential. It operates by firstly releasing a high current followed by a low current and a much lower current when it is nearly full. The voltage and current induced by the charger and the time between changing from each and every phase is completely different depending on the type of battery you choose. For example if you have a Gel Cell battery pack you can use the configurations for this kind of battery through display console.