Charging continues beyond SOC limit

[apacheguy]

I’ve noticed on recent firmware that my 3 will continue charging a few percent SOC beyond the limit I specify in the GUI. Doesn’t happen on every charge cycle, but maybe 1 out of 4 cycles it goes over by 3-4%. Anyone else notice this?

 

[Tam]

I’ve noticed on recent firmware that my 3 will continue charging a few percent SOC beyond the limit I specify in the GUI. Doesn’t happen on every charge cycle, but maybe 1 out of 4 cycles it goes over by 3-4%. Anyone else notice this?

Could it be that you don't charge your car to 90% every day?

See:

Battery Does Not Charge to Selected %

 

[destructure00]

I charge to 90% every night. Mine seems to over charge by 1-2% if it was run down fairly low the day before, like less than 15-20%. I just figured it was part of the battery management system.

On a normal day I'm only down to 70% or so, can't remember ever seeing it over charge in those cases.

 

[darth_vad3r]

I’ve noticed on recent firmware that my 3 will continue charging a few percent SOC beyond the limit I specify in the GUI. Doesn’t happen on every charge cycle, but maybe 1 out of 4 cycles it goes over by 3-4%. Anyone else notice this?

Does the notification that charge is complete tell you it has gone “too far” already at that point, or are you noticing later when you enter the car that it is “too high” after the fact?

The former sounds odd, the latter could be recalibration after the charge was over?

 

[apacheguy]

Could it be that you don't charge your car to 90% every day?

See:

Battery Does Not Charge to Selected %

Indeed, I charge to 70% daily. Although I’ve been doing that for years with my S and never noticed this behavior. Must be a different algorithm used in the 3 or something they changed in a recent firmware.

 

[Tam]

Indeed, I charge to 70% daily. Although I’ve been doing that for years with my S and never noticed this behavior. Must be a different algorithm used in the 3 or something they changed in a recent firmware.

Tesla has been working on its algorithm all the time and it looks like it has decided that 90% charge is how their system would use to calculate.

Anything less than 90% like 70% will increase the calculation drift.

 

[apacheguy]

Tesla has been working on its algorithm all the time and it looks like it has decided that 90% charge is how their system would use to calculate.

Anything less than 90% like 70% will increase the calculation drift.

State of charge is not based on a calculation. It is a measurement of the cell voltage. On my S, 70% is always right around 3.92 V.

 

[Sophias_dad]

Mine always stops at exactly 90%.... more surprising is the fact that after I disconnect, drive a quarter mile and let it sit unplugged for an hour or two, it occasionally has gained 3-4 miles and 1-2%(to 91% or more)

 

[pdx_m3s]

It’s just the BMS calibrating as it tries to determine the true SOC (easier said than done with Li-ion batteries).

I usually charge mine to 70%, but I recently did a charge from 20% to 90%. I got a notification that charging successfully completed at 90%, but it was 92% when I got in the car the next morning. I didn’t think much of it.

 

[edigest]

Another thing to consider is the temperature when the charge completes versus the temp the next morning. Similar to what @pdx_m3s experienced, when a charge completes early (when the ambient temperature is hotter) I frequently see one or two percentage points above the charge limit if the ambient temperature has goes down over the next few hours.

 

[darth_vad3r]

State of charge is not based on a calculation. It is a measurement of the cell voltage. On my S, 70% is always right around 3.92 V.

Nobody said SoC was based on a calculation. The displayed range that relates to your SoC is based on a calculation that can be recalibrated.