If we consider only the name-battery chargers (BCs)—we can make the erroneous assumption that BCs are only intended to charge the accumulator batteries and maintain them charged. But this is not true. BCs represent a main power source of auxiliary circuits under the normal mode of operation of a direct current auxiliary power system (DCAPS) at a substation or power plant. While the battery is activated, the BC cannot supply enough energy to DCAPS consumers. This happens in the absence of power in the AC auxiliary power, when the BC is inoperable or when the BC is not powerful enough to cover rare peak loads of the DCAPS.