Neil Johnson, in Alternative Fuels and Advanced Vehicle Technologies for Improved Environmental Performance (Second Edition), 2022 The battery pack high-voltage system includes the cells and other components designed to maintain power flow to and from the cells within the design envelope.
Actual system designs of this configuration do not allow any charging of the battery from the grid. Therefore it is possible that batteries can stay for longer periods of time in disadvantageous state of charge ranges, which affects the lifetime of certain battery technologies like lead-acid batteries.
For example, the contactors can be opened by the battery management system if a charger failure allows the charger to begin overcharging the battery pack. The secondary safety function qualifies the contactors as a critical safety device in a modern high voltage battery pack.
Iftikhar A. Khan, in Power Electronics Handbook (Fourth Edition), 2018 A secondary motivating factor for the introduction of a higher system voltage is the challenge of achieving higher fuel economy. The average fuel economy of present-day automobiles in the United States is in the vicinity of 30 mpg.
You can use a system neutral that is derived from a grounding transformer to ground high voltage systems. A single point grounded or multi-grounded neutral can be used for solidly grounded neutral systems and the neutral conductor needs to have a minimum insulation level of 600 V.
However, contactors are also a safety item that can be opened to disconnect the battery pack when a malfunction pushes the battery pack voltage or current outside its design envelope. For example, the contactors can be opened by the BMS if a charger failure allows the charger to begin overcharging the battery pack.