The BT-BC 12 D-SE is an automatic battery charger controlled by a microprocessor. This means it’s especially to charge maintenance-free batteries as well as for long-time charging and for charge maintenance from batteries that are not permanently in use, such as boats, lawn mowers, and whatnot. Due to the integrated micro-processor, the charging curve has 3 steps. Step one charges the battery with nearly constant current up to approx. 85%, step two with constant voltage up to approx. 95%. Step three keeps the battery voltage constant (IUoU-charging characteristic) and so is the battery always fully loaded. Therefore is a tool also for lead-acid batteries and gel batteries optimally proper. An integrated fault diagnosis system advises the LED display onto battery fault and connection problem. The charging will be controlled electronically and accordant indicated. The charging current can attune to 2 / 6 / 12 ampere. This battery charger has also a 12 V d.c. output socket which provides working power up to 140 Watts for 12 V d.c. operated appliance.