[AYBABTME]

The loud "pops" at superchargers and when driving after supercharging surprised me for a while. I would stop to look under the car if I had hit something. The pops while charging are sort of self-explanatory, but those while driving took me a while to associate back to the prior supercharging.

Basically, changes in temperatures are causing the pops. It's kind of weird and slightly annoying. Sometimes it happens for quite a bit after charging, particularly when driving through changing climate (i.e. climbing mountains). Having done Reno/SF round trips a good few times now, I've gotten used to it.

[masto]

I appreciate those pops and bangs, as a reminder of what it means to pump 250kW into a battery I'm sitting on top of. Especially in comparison to the 48kW that supplies my entire house.

[jacquesm]

What is the cause? Thermal expansion?

I have a room in my attic that can make really loud bangs on hot summer nights (enough to scare the crap out of me when I am concentrating on something and do not expect them) when it contracts again after a day in the heat. The root cause there is stick slip: the thing doesn't move for a long time due to its weight so tension builds up and then suddenly it will shift a little and the whole structure amplifies the sound from the shockwave passing through it.

Your 'pops' remind me of that (and supercharging must have some thermal effects).

[Kirby64]

Similar mechanism as your attic noises. There's a giant metal plate on the bottom of the thing, so all the heat generated while it's supercharging (in a very cold environment) causes that 'snap' which makes a loud noise. Same thing happens if you've ever heated up a thin metal baking sheet. It'll 'snap' from one position to another and make a horrible racket.

Same thing apparently happens if you are heavy on regenerative braking when descending a mountain pass. Cold air, plus 50kW+ of regen braking is similar to just supercharging the car.

[flutas]

Something else interesting when supercharging in the cold...LOTS of steam(?) at times.

Shocked me the first time it happened. Cold (~5F outside), low and hot battery (just went from 80 to ~5%). Legit thought the car was on fire at first.

[Kirby64]

Never experienced the steam myself, although I can't say I've ever tried supercharging the car at 5F. Coldest I've ever done it was probably in the 40s, which is plenty cold enough to cause that popping sound when it's pulling 250kW.

[flutas]

Oh yeah, the popping was crazy loud as well.

Thinking back to it, the battery must have been extremely warm at the time too, since that 5F was after two hours through a 2 lane mountain road (crossing the range).

[alliao]

thanks! I've heard the pops during my winter trips but never associated with thermal expansion! Always thought I'd hit some animals or debris on the road.

[jacquesm]

Oh, that last one is an interesting one.

[pests]

They also had a recall on the pressure release valves. The car was allowing the pressure to get too high inside thr battery and would make a pop on release.

[93po]

I've never heard these pops but I've also never supercharged in the cold