Occasional Knocking Sound and feel from underneath the car

[zpaul]

Yesterday took a 600 mile trip.
Outside temperature was around 18-36 degrees. BTW milage was horrible and MY advised me to drive below 70mph to get to Supercharger.
Occasionally through out the trip I felt knocking like almost some rock hit the bottom of the car.
However, the highway was very nice and clean from debris and snow.
Then I would feel the same knock while Supercharging the car from 15% to 75% at Supercharger couple times.
Today took another 80 mile drive (20 degree weather) and felt the same knock couple times.

My guess that is something switching in the battery and makes this sound and feel.

Anyone know what it is?
People who drive in temperatures below 30, do you experience the same?

The only recent change I did to MY was adding Acceleration Boost. But I still feel like this is more to do with cold weather.

 

[iamnid]

This has been documented before. It has to do with the expansion in the battery caused by changes in temperature. It's most commonly noted during supercharging.

 

[todd2fst4u]

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163736-9999.pdf

 

[zpaul]

https://static.nhtsa.gov/odi/tsbs/2019/MC-10163736-9999.pdf

Thank you very much! That helps.

 

[Cavity]

Gremlins under the floor....trying to get in to stay warm.

 

[zpaul]

Gremlins under the floor....trying to get in to stay warm.

Considering moving to FL
Hope you do not have Gremlins there

 

[WattsappMTL]

This has been documented before. It has to do with the expansion in the battery caused by changes in temperature. It's most commonly noted during supercharging.

I've also heard it during battery conditioning on the way to Supercharger. That can cause significant termperature increase in winter conditions, hence the expansion "thunk" that might not happen in summer. I also noticed that conditioning added a battery drain of about 7.5kW in those conditions!