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Please Explain This Charging Mystery

PianoAl

Active Member
Dec 15, 2019
1,039
700
Far Northern California
As usual, I had the charging (to about 240 miles) set for Scheduled Departure, departing at 8:00 AM. At 6:00 I see it isn't charging, it's at 217 miles. Granted it probably only needed another hour, so that made sense, but a look at the notifications shows "2:00 Charging started at 2:00 am with battery at 127 miles."

So, it started charging at 2 am but stopped at some point? There's no "charging complete" notification.

So, just to be sure, I chose Start Charging. I go back at 7 am and it's not charging and it hasn't reached the limit. There's notification that says "6:50 am Charging interrupted at 6:50 am with battery at 228 miles."

Questions:

1. Why did it start at 2 am, charge for a while, but not finish?

2. What might have caused charging to be interrupted?

Thanks.
 

Frank99

April 2018 Model 3 LR RWD, EAP, FSD
Apr 7, 2016
381
515
Arizona
Assuming that you’re charging at 32A from a 240v/50A circuit, the car can charge at about 32 miles of range for every hour of charging. At 7:00 AM, you were at 228 miles of range, meaning you only needed about 12 miles worth of charging to get to your 240 mile target. 12 miles of range should take about 25 minutes, so I’d expect the car to start charging at about 7:30 to finish by your 8:00 Scheduled Departure.
In other words, the car is behaving exactly as you told it to behave.

Scheduled Departure is mostly for people in cold areas in the winter. The intention is to finish charging right at the scheduled Departure time so the battery is warm; a cold battery has significant reductions in range and regeneration.
 

Sorny

Member
Jun 2, 2021
74
105
MN
32A charge rate is 9% and change per hour @ 240V on my '21 LR AWD, so around 30 "miles" per hour sounds reasonable.

Look to see if there are warnings/faults. You can find that stuff if you click the car, then go to service from the screen in the car.
 

Frank99

April 2018 Model 3 LR RWD, EAP, FSD
Apr 7, 2016
381
515
Arizona
If I had to guess, it started charging at 2:00 to make sure that it was MOSTLY done well before your scheduled departure, to make sure you had enough charge in case you left home early. It left 30 minutes worth of charging to be done just before your scheduled departure in order to warm up the battery.

But that's pure speculation. I don't know why it chose 2 am to start charging, because Scheduled Departure doesn't appear to be usable with Scheduled Charging for a start time.
 

GtiMart

Active Member
Nov 13, 2019
1,840
1,711
Quebec City, Canada
I'd say because charging isn't a precise science. When the car starts charging, voltage might sag and it won't quite go as fast as it would think. I would also say that in some areas, electricity is cheaper before 6AM. I remember this system actually stopping at 6AM at some point, even for locations that don't have variable pricing, without and configuration possible. I think there's a remnant of that, starting early to do most charging before 6AM and keeping just a bit of charge close to the departure time to heat batteries as someone else said.
 

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