Answer:
Unlike a low voltage battery such as 12V, high voltage from a High Voltage battery should not be grounded to the chassis for several numbers of reason which are;
- HV up to 350V have a corresponding high current which generate unwanted magnetic field and causes magnetic interference. This can be reduced by using a twisted conductor so that the interference can be cancelled.
-HV can result to surges which result to spark over and flash over between phase and ground.