Charging beyond the set limit, weird behavior in the last few days

[bjrosen]

I've noticed a strange behavior in the last couple of days, it's charging beyond the set limit. Friday I set the limit to 85%, in the morning the battery level was 89%. Last night I came home from a road trip and lowered the limit to 75%, in the morning it was 78%. I've had the car for four years and I've never seen this before, X% has always meant X%. An additional weirdness occurred after I got home and plugged in but before it started to charge (I have it set to do off peak charging). When I got home the level was 17% but when I looked at the app an hour later it was at 11%, where did that 6% go?

This feels like a software bug that was recently introduced but it could be a problem with the BMS in my car. Has anyone else seen this behavior? One more variable, I've only recently started using the off-peak charging settings, my utility just introduced off-peak EV charge rates. Is it something with scheduled charging?

 

[ATPMSD]

It is related to battery temperature. Just the other day, for example, I left the office after charging to 90% and a couple of miles down the road it read 94%.

I agree this seems to be a new behavior, my guess is the BMS firmware was updated.

 

[InquisHumble]

Same thing happened to me today went to 85 from st limit of 60%

 

[Wnuk]

I’ve seen this too for a few weeks now. It’s random and not really related to batter temp since I typically let the car sit for hours after driving before charging. Most times it’s plus or minus 3-5% from my set point.

 

[DblOSmith]

Same thing happens to me. Just today had limit set at 80%, consistently wake up at 83%. I'm not mad or anything, just an interesting quirk.

 

[mongo]

I’ve seen this too for a few weeks now. It’s random and not really related to batter temp since I typically let the car sit for hours after driving before charging. Most times it’s plus or minus 3-5% from my set point.

The battery temperature changes between the end of the charging cycle and your next drive. That can be a bigger impact than time from previous drive to start of charge cycle. Depends on conditions and charge current.

 

[StealthSabre]

My 2020 Model 3 has recently started doing this too. This past Saturday it charged to 100% despite a charge limit set to 80%. Last night, after the latest software update installed, it charged to 80%, stopped, then sometime later restarted and went to 90%, then stopped again and restarted then went to 98%. It seems to have stopped fully at 98%, but this is new, and concerning behavior, especially when it goes so much higher than the recommended daily charging limit. I've reached out for a service appt just to see what they have to say about it. I'll post back here if it's anything useful.

 

[StanMI]

Same here

 

[StealthSabre]

I got the following response(s) from Tesla support about this:

"Ok, perfect. So able to verify that the vehicle algorithm system is the one calculating incorrectly on the screen with the over charge circumstance."

"In most cases, this behavior is due to estimation accuracy of the algorithm that calculates state of charge (SOC) in firmware.
The SOC estimate is calculated differently when the battery is driving or charging than when the vehicle is at rest. The change you have noticed is a normal part of the battery pack adjusting it's estimate of how much energy is in the battery.
The design of Tesla's battery management algorithm prevents overcharging the lithium-ion cells in the pack; the phenomenon that causes the SOC adjustment cannot cause the pack to be overcharged."

"It will adjust on its own. Super worst case scenario that it does not have a few weeks or a month & constantly does it, make sure to make an appointment right away & note the recent time it has done it & we can continue from there, since we have a case on the vehicle already. But, like I said, that would be rare. Besides that, you are all set for now."

 

[PianoAl]

after the latest software update installed, it charged to 80%, stopped, then sometime later restarted and went to 90%, then stopped again and restarted then went to 98%.

I've seen strange charging behavior related to updates. I try to remember to monitor things after the update is complete.