When a battery is connected to a load with capacitive input, there is an inrush current surge as the capacitance is charging to the battery voltage. The input current depends on the input capacitance; the larger the batteries and the more powerful the load, the larger the input capacitance. A large inrush current (in the pre-charge circuit, without protection) can cause the following : damage to input filter capacitors, blowing of the main fuse if it is carrying the inrush current without protection, contact failure (and reduction in current carrying capacity) due to arcing and pitting from high inrush current and damage to the battery cell, which is not rated for inrush current.