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Continuous Faint Humming Noise When Parked

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I've not noticed the real world mileage change since I do not drive that much. But, with the short drives of less than 50 miles, the actual miles used looks the same as the RM usage, i.e., if I drive 30 miles I lose about 30 miles off of my RM. This has always been the case as my lifetime average Wh/mi is about 287 (The car has 43K on it).

What's your Wh/mi and the car's mileage?

I average about 325 Wh/mi. Must be the heavy 21" wheels.
 
Also, as I described earlier, expect it to run more than once with the first occurrence longer the the second. Mine ran for about 10 hours the first time and about 5 hours the next day. No more since then. I would be interested to see your Rated Miles drop, if any. I got 7.5% decrease on my RM. That's significant.

As predicted, mine made the noise once, then again for a shorter period. Nothing since. I wasn't able to check the impact on range. I'm just glad there's nothing wrong with the car. I'm 15 months past my last service (4 year service) and I'm hoping to avoid service/repairs for some time.

I may not have even noticed the noise if I parked outside, so maybe that's what Tesla was hoping for.
 
Came to post the same. First time we heard the hum was this morning, so unsure when it started (plugged in at 9:30 pm last night but charging is scheduled to start at midnight). Hum was going even after car had charged up but RM was lower than usual (229 vs usual 234) on our 85D. Hum continued until the second half of the morning commute.

Interest timing and software note - my vehicle was at a Tesla Service Center Monday morning - Tuesday afternoon, at which point it was updated to 2019.16.3.2. No instance of the humming on Tuesday night or Wednesday. Will follow up if this doesn't follow the trend of a second hum and then no more.
 
Mine is doing the exact same thing. 2019.16.3 2014 85 vin 408xx. Interestingly the drive unit was replaced a few weeks ago and they said they checked the battery and no issues.

Looks like they run these BMS maintenance tasks on the older cars (mine is 2015). Not sure if the SC's know about this. Mine did not. I also believe lots of owners just don't notice the noise.

I also did a bug report. I wish they would just tell us why its doing this. Speculation can be bad for pr.

No one from Tesla has followed up with my bug reports and since I opened this thread. I doubt they will. But, when I was taking to Tesla support line and as the pump was running for the first time, I asked them if they see anything at their end that is being done on my car, they vaguely mentioned they see "something" and the cells' voltage show "ageing"!

Came to post the same. First time we heard the hum was this morning, so unsure when it started (plugged in at 9:30 pm last night but charging is scheduled to start at midnight). Hum was going even after car had charged up but RM was lower than usual (229 vs usual 234) on our 85D. Hum continued until the second half of the morning commute.

Interest timing and software note - my vehicle was at a Tesla Service Center Monday morning - Tuesday afternoon, at which point it was updated to 2019.16.3.2. No instance of the humming on Tuesday night or Wednesday. Will follow up if this doesn't follow the trend of a second hum and then no more.

This is definitely appears a post-2109.16.x maintenance routine. It looks like the voltage health checking of the battery modules/cells (mine run for 10 hours and 5 hours in two consecutive days) and make some SW adjustments an/or reconfiguration (my total RM has suddenly decreased by 9% since then), as well as data collection (there were lots of uploads during the time which I reported in this thread). The usable portion of my battery has definitely shrunk (9% RM loss). I think the BMS probably wasn't reporting the correct/safe total RM and charging limits before this and that Tesla is now readjusting it (for fire safety reasons as well???).
 
When my car was updated to 2019.16.2 the range was down about 4 miles for 2 days and then things returned to normal. I didn't notice any extra noises, but the weather was fairly mild here at the time so maybe the car didn't get warm enough to need to run the pumps or fans during the test.
 
When my car was updated to 2019.16.2 the range was down about 4 miles for 2 days and then things returned to normal. I didn't notice any extra noises, but the weather was fairly mild here at the time so maybe the car didn't get warm enough to need to run the pumps or fans during the test.

I never figured out if the pump(s) were running for that long to cool or to warm up the pack. I would say probably both to see how the cells were behaving at certain temperatures for the purpose of the tests.
 
Checking in with exact same occurrence. 2012 Model S. Charging at 32 amps concluded at 4a to 90 percent and battery cooling noise ongoing for past 4 hours. Seems like the same noise as after a long drive with ambient heat. Will let folks know any updates
 
Checking in with exact same occurrence. 2012 Model S. Charging at 32 amps concluded at 4a to 90 percent and battery cooling noise ongoing for past 4 hours. Seems like the same noise as after a long drive with ambient heat. Will let folks know any updates

Sounds like you are going through the same thing. Keep eyes on few things:

- Runs twice (first time longer than the second time)
- Runs off the main battery (chews up your miles while it's running)
- Your overall car's Rated Miles might decrease
 
I might have some technical info that explains this at least in part.

There are three coolant pumps in the Model S/X. Two for the battery, one for the drive train (motor/inverter). The reason there are two for the battery is that there are several valves that can redirect the coolant through the radiator or bypass, through the AC chiller or bypass and there is a combination where the loop is divided into to two strings, thus there needs to be two pumps to keep the fluid in motion.

I have seen the pump going on for hours or intermittently in my S many times. Unless there is a fan blowing at the same time, the intent to run the pump is not to cool the battery. With a battery that large, different sections of the battery can have different temperatures. Since internal resistance depends on temperature, a warmer battery will have lower losses than a cooler one. If individual cells in the pack operate at different temperatures, it eventually causes them to be charged and discharged slightly different from each other. The BMS will counteract to this by balancing the cell blocks. But of course you always want to have all cells to have the same temperature. If they are different, running the coolant will help even out those differences. This is why the coolant pump keeps running at random times.

10 hours of running the pump seems excessive. I bet this was caused by a bug in the software. Even large differences in temperature will be gone within an hour or running the pump.

Here is a screen shot showing the different cell blocks and the temperature difference between them.
Screenshot_2017-02-01-18-37-08.png
 
I might have some technical info that explains this at least in part.

There are three coolant pumps in the Model S/X. Two for the battery, one for the drive train (motor/inverter). The reason there are two for the battery is that there are several valves that can redirect the coolant through the radiator or bypass, through the AC chiller or bypass and there is a combination where the loop is divided into to two strings, thus there needs to be two pumps to keep the fluid in motion.

I have seen the pump going on for hours or intermittently in my S many times. Unless there is a fan blowing at the same time, the intent to run the pump is not to cool the battery. With a battery that large, different sections of the battery can have different temperatures. Since internal resistance depends on temperature, a warmer battery will have lower losses than a cooler one. If individual cells in the pack operate at different temperatures, it eventually causes them to be charged and discharged slightly different from each other. The BMS will counteract to this by balancing the cell blocks. But of course you always want to have all cells to have the same temperature. If they are different, running the coolant will help even out those differences. This is why the coolant pump keeps running at random times.

10 hours of running the pump seems excessive. I bet this was caused by a bug in the software. Even large differences in temperature will be gone within an hour or running the pump.

Here is a screen shot showing the different cell blocks and the temperature difference between them.
View attachment 419650

The good info you are providing makes sense. But this event was not a routine battery cooling exercise as it ran twice and for very long hours. Not a SW either as the intention was to collect data and for those who are reporting a significant range loss after 2019.16.x ""this was done to prolong the life of the battery and reduce the pack wear" according to Tesla. Read here .