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2007


Analysis of Battery Cable Faults Using a Dynamic Battery Model

Nosh Medora

Alexander Kusko



Fault current calculations for the selection of circuit breakers or fuses for battery cables is normally conducted for the voltage of fully charged batteries and cables at operating temperatures (Ref. 1). However, batteries at a low state of charge not only have a lower terminal voltage, but also have an internal resistance up to three times the nominal value (Ref. 2). Heating of the cables during a fault also increases the circuit resistance. The consequence can be a low fault current, with a time delay, or a failure of the fuses or circuit breakers to trip, possibly resulting in an ignition and fire. The problem is more acute when the voltage drop per unit length is high resulting in a power density per unit length that is high. Such a condition may occur in a nearly discharged battery in an electrically powered vehicle.


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