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Thunk while supercharging

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The description of an acorn hitting the car is perfect too, the first time it happened I was in the Rockies supercharging and thought someone whipped something at my car. After the second one I started googling which led me to this thread!
 
Car now has loud thunks while super charging or charging at home when it is cold. Have not experienced until just recently. Was sitting in car reading news and sound went off. Felt it in the car frame. It seems disconcerting, since the car actually does tremor.
 
I had experienced the loud thunk sounds on my model 3. I have only supercharged the car around 5 times over 8000 miles. Yesterday while supercharging I heard the thunk sounds and car was unable to drive after charging and put up 3 error messages and required a tow. Don't think the sounds are normal. I never heard them on my X and that one is supercharged more frequently.
 
I drove 23k miles on superchargers the first two months of ownership. I had hundreds of thunks and never any issues with the car working properly. Inferring cause and effect is a weak argument, IMO. Models S and X are built completely differently and do not share this build characteristic. The Model 3 has no inherent structural integrity with the battery removed. Service is not allowed to move a Model 3 with the battery out. There is a very hollow sounding floor pan you can confirm by lightly striking the floor in front of the rear seats. This is the likely source of the sound and clearly it’s extensive as the sound can emanate from many disparate locations. Much of this was gleaned while camping out at a service center for two days while my Model S was being repaired on a cross country trip.
 
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New owner of a LR AWD M3 ~1400 miles, stopped at SC today to have the sounds investigated. I, like others, hear the ‘thunk’ sound both within minutes of starting supercharging, and ~40 minutes into a drive. The SC tech asked if there are any errors/alerts on the screen when the sounds happen. I have not had any errors/alerts on the screen. The SC tech said the A/C compressor (located in front of the front passenger footwell and likely under the frunk, rear leftish area, as you look at the car from the front) turning on will cause this sound ~40 minutes into a drive as the car starts cooling down the battery. While Supercharging the same loud sound is caused by the high voltage contacts (located under the rear seat) connecting, per the SC tech. Here’s an example of the sound I found online that another M3 owner recorded Clunk On M3 P3D-
 
New owner of a LR AWD M3 ~1400 miles, stopped at SC today to have the sounds investigated. I, like others, hear the ‘thunk’ sound both within minutes of starting supercharging, and ~40 minutes into a drive. The SC tech asked if there are any errors/alerts on the screen when the sounds happen. I have not had any errors/alerts on the screen. The SC tech said the A/C compressor (located in front of the front passenger footwell and likely under the frunk, rear leftish area, as you look at the car from the front) turning on will cause this sound ~40 minutes into a drive as the car starts cooling down the battery. While Supercharging the same loud sound is caused by the high voltage contacts (located under the rear seat) connecting, per the SC tech. Here’s an example of the sound I found online that another M3 owner recorded Clunk On M3 P3D-

It's a flexing metal plate, so all of those thoughts from Tesla reveal that they are still in the dark.
 
From Model 3 Owners forum (Colorado Electric) response from Denver service:
“I've also done some research on the banging sound under the floorboards, and I've found that the issue is considered normal operation related to thermal expansion of the battery pack. Due to the battery pack using a thinner steel on the top of the battery pack, temperature changes of the pack can result in an "oil canning" type noise that will be most noticeable when driving or charging.”
 
From Model 3 Owners forum (Colorado Electric) response from Denver service:
“I've also done some research on the banging sound under the floorboards, and I've found that the issue is considered normal operation related to thermal expansion of the battery pack. Due to the battery pack using a thinner steel on the top of the battery pack, temperature changes of the pack can result in an "oil canning" type noise that will be most noticeable when driving or charging.”

Like thin steel trays in the oven when it flexes and makes a loud clunk after heating up? I’ve never heard it while driving but always when supercharging.
 
Like thin steel trays in the oven when it flexes and makes a loud clunk after heating up? I’ve never heard it while driving but always when supercharging.
Exactly—another good analogy. Temperature needs to be on the chilly side. Happens frequently on mountain passes and it may also be a sealed container phenomenon because it seems to happen even with small power draws.
 
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New owner of a LR AWD M3 ~1400 miles, stopped at SC today to have the sounds investigated. I, like others, hear the ‘thunk’ sound both within minutes of starting supercharging, and ~40 minutes into a drive. The SC tech asked if there are any errors/alerts on the screen when the sounds happen. I have not had any errors/alerts on the screen. The SC tech said the A/C compressor (located in front of the front passenger footwell and likely under the frunk, rear leftish area, as you look at the car from the front) turning on will cause this sound ~40 minutes into a drive as the car starts cooling down the battery. While Supercharging the same loud sound is caused by the high voltage contacts (located under the rear seat) connecting, per the SC tech. Here’s an example of the sound I found online that another M3 owner recorded Clunk On M3 P3D-
I heard the same noise multiple times while supercharging yesterday - it was 30 degrees out - I owned a MX 3 years and never heard these noises while charging even in 0 degree weather, they must be using cheaper metal around the batteries - Not acceptable for Tesla to say it is normal. It sounds dangerous to me.
 
I heard the same noise multiple times while supercharging yesterday - it was 30 degrees out - I owned a MX 3 years and never heard these noises while charging even in 0 degree weather, they must be using cheaper metal around the batteries - Not acceptable for Tesla to say it is normal. It sounds dangerous to me.
It's frequently referred to as "oil canning", and it has nothing to do with "cheap metal". The oil canning phenomenon is this: Have you been around some kind of metal container that is sealed airtight? And there is some kind of changing of temperature going on, so the air inside the container is getting hotter or colder. The trapped air is changing in pressure, and can be starting to push or pull on the metal bottom of the can. If the surface has a bit of a curve against that air pressure direction, it's just building up force against it. At some point, the air pressure will make a "thunk" sound as the metal gives way to be curved in the other direction. You can hear this kind of thing with sealed gas cans or oil cans or things like that that sit in the sun or maybe were sealed when it was warm and then they sit overnight and get cold.

So the "breather valves" people are talking about must be some kind of thing to let some air pass through, so there is not a trapped air space on one side of this metal shield building up pressure that would make it pop past that curved tension point. It's not something dangerous or bad for the car, but is probably pretty disturbing for people hearing it if they don't know what's going on or don't like movie jump scares.
 
Today we started our first roadtrip since we purchased the 3. Got to the first Super (also the first time we've done that). Within 5 minutes of plugging in we heard a loud bang. I looked it up and found that it's a known issue and "normal". What I didn't find anywhere was the car stopped charging for about 45 seconds, then started back up again. This happend pretty much until we got to our target charge and left. Tesla Cus Svc had nothing for me. Anyone?
 
Having the charge stop in the middle for a few seconds OR go to a much lower level and then go higher again isn't all that uncommon. It's some sort of glitch in the SC electronics and has nothing to do with the popping sounds.
 
Thanks I actually
Having the charge stop in the middle for a few seconds OR go to a much lower level and then go higher again isn't all that uncommon. It's some sort of glitch in the SC electronics and has nothing to do with the popping sounds.


Thanks, it didn't happen the second time we stopped, but it wasn't a few seconds, it was almost a minute, 5 times