In contrast to chargers with I/U characteristic, this device charges with constant current. This makes charging much faster, because batteries are charged with the max. current until the end of charging. Another advantage is that the batteries are charged to 100% of their capacity. Controlled gassing is desirable, as it significantly influences the formation of sulfate layers and thus prolongs battery life. Charging principle: Up to a voltage of 14.7 V the battery is charged with the max. current. Then the device switches to timer mode and the battery is charged for 1 h with steadily decreasing current. After approx. 1 h, the device automatically switches to standby mode and trickle charging with 13.8 V is initiated. Of course, the devices are short-circuit proof and reverse polarity protected.