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Battery hot, confused, car sluggish, then fine

QUILTT

Member
Mar 23, 2021
6
5
Boston
I searched a bit to see if this happened to anyone else and couldn't find anything similar enough, so I thought I'd post it. Sorry if I missed anything obvious.
We have a two month old Model Y, two motor, extended battery. It has been great. We charge it mostly at home on a 220V 40Amp circuit. Per Tesla recommendations, we leave it plugged in when not in use and set the max to about 80%. We only last week had occasion to do a fast charge on a 300 mile trip we needed to make. We did our first 100% charge before we left. A few days later we took it out briefly at 9 am and all was fine. We came back and did not plug it in. We then went out again and from the start, the car seemed to have no acceleration power. It even struggled to get up moderate hills. It was making a fan noise from the front. We took it home and plugged it in. Even though the charge screen said it was at 220 miles and would take a couple of hours to charge to 80%, it indicated the it was charging at 0 miles per hour. We left it plugged in for a few hours and came back to find fan noise quite loud and garage had gotten hot on a 50 degree day. We drove it again and the acceleration problem had disappeared but when we returned it to the garage to plug it in, the same thing happened (after a few hours the hood was warm, the garage hot, the fan noisy, and the charge rate at 0 miles per hour). We tried a 1st order reset of the screen but that didn't help. So we unplugged it and left it overnight. Weather conditions during all this were mild in the low 50s. Next morning it was as if none of this had happened. We had made a service appointment but cancelled it when all seemed fine. It was troubling that the car could just suddenly become unsafe to drive with no notice. Would it happen again? Tesla roadside service said there can be software bugs that work themselves out, but they had no other advice and didn't recognize the issue.

Only explanation we could come up with was that the software got confused and thought the battery was terribly low, and went into starvation mode. But then it thought the car was overcharged and overheating its battery so it turned on the fan to cool it down and would not add more to it. Unplugging and leaving it overnight caused the car to power down which helped reset the software. Powering down seems to be a 2nd level kind of reset as far as I can tell from posts here. Or perhaps it was some kind of sensor problem that will return. Time will tell. It's fine now.
 
Oct 3, 2020
172
183
Seattle
It sounds to me like you have a temperature sensor issue that's making the BMS think that the battery is warmer than it actually is. This could be causing it to go into thermal protection mode, which severely limits the motors' maximum power output to minimize the load on the pack in an effort to reduce the temperature. I would make another service ticket and minimize how much you drive the car, even if it's behaving fine at the moment.
 
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QUILTT

Member
Mar 23, 2021
6
5
Boston
Thanks, that would make sense. It would be great if I could actually speak to someone at Tesla service about it to see if that would be worthwhile but they make it very difficult to do that. None of the automated interfaces give you the option to have a strange problem that doesn’t fit into their simple categories.
 
Oct 3, 2020
172
183
Seattle
I too felt that the app was over simplified when I first made a service request. However, after having put in several request at this point, I‘ve found that the ’other‘ category is appropriate to use if you find that none of the other categories apply. Just include enough details and you’re good. If more clarification is needed, they will reach out. If your service request is within the realm of a mobile tech visit, they will send someone to you instead.
 
Last edited:
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QUILTT

Member
Mar 23, 2021
6
5
Boston
Problem just recurred. After being away a week with car plugged in, it wouldn’t “wake up” to the phone app. Screen was dead. Did steering wheel/brake reset. Screen came back to life. Then it wanted to do a s/w update. Did that. Then went to drive it and it went into thermal protection mode. Now just parked and making fan noise. Have called roadside assistance for a tow. It’s not drivable. Did bug report as suggested by PT19713. Will update on what’s found.
 

QUILTT

Member
Mar 23, 2021
6
5
Boston
Back from service, under warranty replaced P/T Sensor high pressure(2) and low pressure(1). Apparently this was a recall fix that's not necessarily associated with the thermal protection mode problem. They felt that my problem may have been firmware related and that the latest release should have helped with this. Here's hoping it doesn't return.
 

QUILTT

Member
Mar 23, 2021
6
5
Boston
For what it’s worth, TMC has been ten times more helpful to me for issues resolution than Tesla. Thanks to all that contribute. Trying to do my part by following up.
 
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