Battery depletes rapidly when parked at low SOC

[TJtv]

I have a 2016 Model X 60D. Recently, on several occasions I've driven it to the point where the battery was <15% SOC and then parked the car. One time it showed there was 17 miles remaining when I parked, and when I came back 20 minutes later it was down to 1 mile! Luckily I was only 3 miles from my house and I was able to make it back home, but very scary. And yesterday I parked the car with 36 miles remaining, after an hour I returned and it was at 19 miles remaining.

When I drive with the battery in the 10% range it seems to deplete just like normal driving. It's only when it's sitting parked at low SOC that this rapid battery depletion occurs. Has anyone else observed this? It's very unnerving to think you have plenty of range to make it to your next destination, and then come out to the car to find you lost 17 miles or range in the span of being parked for under an hour.

 

[ngng]

What features do you have enabled in your car? How cold was it outside? I'm confused because you are talking about charge percentages but also citing displayed miles (which are inaccurate). What are the actual percentages you are seeing?

 

[TJtv]

I don't have Sentry and cabin overheat protection is turned off. Although those shouldn't matter anyway because they are supposed to not run when SOC is <20% regardless. Temperature was ~85F.

If I rewrite the original post solely in terms of percentages it looks like this:
One time it showed there was 10% remaining when I parked, and when I came back 20 minutes later it was down to 1%! Luckily I was only 3 miles from my house and I was able to make it back home, but very scary. And yesterday I parked the car with 20% remaining, after an hour I returned and it was at 11% remaining.

The battery should NOT be dropping 10% over the span of an hour while the car is sitting there parked.

 

[Tam]

...The battery should NOT be dropping 10% over the span of an hour while the car is sitting there parked....

I guess it's riskier to leave your car at a low SOC and wait a little longer before charging.

Thus, the sequence for low SOC is: Don't rest first. Charge first, then rest.

 

[Rocky_H]

I know this isn't going to make you feel better, and you're not going to like it, and I would agree that it shouldn't be moving quite THAT much, but it is going to have some fluctuations when the car parks and sits and the battery cools down. And that drop off does get much faster at the very low end. In my phone, when it gives me the 15% warning, I sometimes can't even get it plugged in fast enough within 30 seconds before it shuts down.

But anyway, here's an interesting counter example to show how temperature makes it shift. I drove from my house, where it had been in a cool garage about 15 minutes to a doctor's appointment. When I parked, it showed 100 rated miles. It sat out in the sun getting pretty hot while I was in at my appointment, and when I came out and started the car, it was now showing 104. It had "gained" 4 rated miles because the measurement saw the warmer battery temp. The same kind of thing would happen, when you've been driving, and it's warm, and then you park and it cools down, and it will drop a few rated miles.

 

[TJtv]

It just doesn't make any sense that if my battery is at 10% I could either continue driving it for 20 minutes or let it sit parked for 20 minutes and both of those actions have the same outcome of having the battery depleted to 1% after that 20 minute activity is over.

 

[tsxl]

I noticed my battery is also depleting way faster after the most recent major software update a few weeks ago. I noticed it now also attempts to adjust the air suspension often when it would have previously gone to sleep.

So i suspect the software update caused some issues... Bootup of the car is also much slower when starting up ... Have tried rebooting couple times already. And playing around with different energy saving settings in the display menu.

... So Looking forward to the next software update to fix it (and break something else!)

 

[randall_s]

Had a similar issue just today. Got home with 18%. Waited 3 hours before charging at it was at 11%. About 60 F in my garage. Hooked up SMT and took some readings in case they may become useful. I had 2 modules with around 18 mV cell imbalance, but don't know what to make that. Nominal remaining was 11.9 kWh. SOC Min is 18.6% with SOC and SOC expected at 11.3%. Hmm.

 

[randall_s]

I just wanted to add that I remembered (and posted here back in 2017) a similar incident when my car was less than one year old. I parked and lost about 5% over two hours. I'm guessing the BMS gets better readings as the battery cools and settles without load. So maybe this is typical behavior. This last time I got an advisement to plug in - as the battery would have less energy available as it cooled. I realize the battery is more efficient and can deliver more energy at higher temps, but that shouldn't affect the SOC. Hmm.