Stuck on “Calculating” at end of DCFC

[jeffnhelen]

I’ve taken our 2018 75D MX to fourteen Supercharger visits since taking possession. On a couple of these sessions I have actually charged up to 100% due to range or timing reasons. I understand 100% on DCFC is not optimal, but I have noticed an interesting issue. Both times I’ve attempted a full charge the vehicle gets to about 99% and then just sits on “Calculating” for an undetermined amount of time while it is figuring how much longer the session is going to take. The first time I sat for about 30 minutes while it still continued to push single-digit kW into the battery despite not adding any miles to the range. The second time was around 20 minutes. Each time it would have kept going, but I was no longer able to sit nor felt comfortable continuing to charge, so I ended the session.

I can’t say if I noticed the first time, but after this second time, I was able to drive for 6 miles before the range-o-meter finally started dropping in miles, so it’s almost as if it is still charging but nothing is added to the range. After creating a service ticket to discuss this with Tesla, they came back and said diagnostics determined it was a software related calculation behavior and no hardware issues were present. They then stated several 20%-90% charge cycles have been seen to possible resolve the behavior. This has been our typical charging cycle since purchase so not sure that’s going to do anything for us.

Has anyone else seen this stuck on “calculating” behavior? The handful of times I charged to 100% at home I didn’t see any indication of a similar issue.

 

[E90alex]

It’s balancing cells.

 

[jeffnhelen]

It’s balancing cells.

How long is it safe to leave it plugged in for this process? Would this not also happen when AC charging to 100%?

 

[E90alex]

You can leave it until it shows done but there’s no telling how long it would take. Could be 30 min or less. Could be an hour or more.

It should happen with AC charging as well but you might not notice it unless you’re sitting there watching it the whole time as it’s completing the charge.

 

[jeffnhelen]

You can leave it until it shows done but there’s no telling how long it would take. Could be 30 min or less. Could be an hour or more.

It should happen with AC charging as well but you might not notice it unless you’re sitting there watching it the whole time as it’s completing the charge.

Curious then if it was balancing the cells that 20-30min I was waiting, why did the range not go up after I stopped the charge session? Just sat at 209mi the whole time I was waiting.

 

[E90alex]

The pack was already full essentially, it’s just “topping off” the cells that were uneven with the rest of the pack.

 

[jeffnhelen]

The pack was already full essentially, it’s just “topping off” the cells that were uneven with the rest of the pack.

This makes more sense than Tesla’s response. So why did it not recalculate the expected range since I technically drove for 6 miles with it continuing to display 209 miles? Would think that it should have added in those unbalanced cells that were brought up and displayed 215 mi range.

 

[ucmndd]

All very normal and expected. It will eventually stop and say “charging complete”.

As for why the range doesn’t change much, as you note at this point it’s pushing single digit kilowatts into the battery, so not much energy to speak of.