EV -high voltage battery -- is Vibration Isolation needed?

A high voltage (HV) battery is integrated rigidly on the chassis or body in almost all EVs. This makes the floor of the Body massive and stiffer, too. This advantage will be lost if rubber isolators are introduced between this HV Battery and the body.

A question comes if the vibration isolation to such heavy Batteries is really needed similar to when we decouple an IC Engine or an electric Motor from the car-body with the fine tuned sets of rubber-mounts.

It should be noted that the I C Engine has a lot of low & mid frequency firing excitations [till 400 Hz] which would cause tactile vibrations &/or a structure-borne noise. Whereas the Electric motor has mid & high frequency electromagnetic excitations which would cause tonal sound (whine) inside the cabin at all speeds of the EV-running. Here the vibration isolation for them is vital for good In-cab NVH of the vehicles.

The same is not true for the high voltage Battery of EVs where there will be very negligible vibrations due to chemical reactions inside it and even if some high frequency vibrations from power electronics, electric drives or cooling systems get transferred to it to such a HV heavy battery, it will not have any influence on the EV-NVH.

Still some EVs, such as Tesla Model S, Chevrolet Bolt, Nissan Leaf or Ford Mustang Mach-E are reported to have given the isolation to their HV Batteries on the car-body.

A major reason for these specific cars could be to minimize road-impacts received by the Battery-base. The low frequency forces [0.1 to 20 Hz] are generated by the tyres on rough or bumpy roads, transferring them to the monocoque car-body thru' its front and rear suspensions. Thus, the rubber-pads between the body & the HV Battery should increase its long cycle fatigue life by minimizing transfer of the vibrations from the road thanks to damping of the rubber.

But most of all passenger and commercial EVs in India are observed to have no such isolators below their HV Batteries. If at all they need be introduced, it will be a challenge before the NVH Engineers to decouple rigid body modes of the Battery-mounting from those of the Vehicle-sprung & un-sprung mass modes as well as the motor-train mounting system.

Since the HV Battery of passenger cars & Buses is so heavy, its natural frequency of bounce will be < 10 Hz even for stiffer rubber pads and then care should be taken for it not to be close to the wheel-tramp or bounce frequencies of the EV in the range of 8 to 15 Hz.

While taking care of durability of the HV Battery against the road-impacts, the vibration isolators should not cause any resonances, right ?