Application The BL20 is a widely applicable DC - supply unit which is used as battery charger or also as stabilized power supply. As charging unit it is used for charging, as well as for maintaining the fully charged condition of of 12 V or 24 V Pb- or NiCd-batteries. Simultaneous supply of DC-consumers (parallel operation) is possible. Operated in parallel with a battery or other consumer, the BL20 guarantees the supply of the consumers up to the rated output of the charging unit even after disconnection of the battery, for example during maintenance or for exchange. The BL20 is short-circuit proof so that it is not necessary to shut down the charging unit during operations which could cause nearly a short-circuit (for instance start of a diesel engine). As stabilized power supply unit, the BL20 supplies connected consumers with a stabilized d.c. voltage which is adjustable in the range of 11.5 ~ 15.5 V DC (Pos. 12 V) or 23 V DC to 31 V DC (Pos. 24 V)