Battery Capacity Calculation

[srankin1826]

Searched forum for this. Found some threads, but they seemed to over complicate what is a simple calculation (unless I'm missing something). So I decided to post my own.

To calculate your total battery capacity you will need to drive your Tesla for at least 15 miles, preferably 30. At the conclusion of the trip get the following 3 numbers from the energy app on the touchscreen.
A) Average usage in watt hours. If you drove 15miles, use the 15 mile tab, 30 for 30.
B) Miles to empty.
C) % of battery left (on the trip tab).

Battery capacity = (A*B) * (100/C)

Average usage * Miles to empty = the amount of usable battery you have left in watt hours.
Multiply times 100/(percent of battery left) gives you your total battery capacity when 100% charged.

For example from my morning commute:

(210 wh/mile)*(214 miles to empty)*(100/61%battery_left) = 73,672 watt*hour or 73.67 kW*hour

Rounding errors, particularly on the % of batter left will limit accuracy, so average several measurements. But it seems to give reasonably consistent results so far (3 days, 6 data sets).

Spreadsheet link for google sheets spreadsheet if you want to copy the formulas.
Model 3 Battery Tracker

Cheers,
Sam

 

[ran349]

That is correct. But you don't need to drive anywhere, just get in your car and take the readings at any time.

Also, you won't really get that range because the rated miles calculation includes the buffer, which is below zero on the battery gauge.

 

[Zoomit]

That is absolutely correct.

At best, this calculates what the car thinks is the available capacity between 100% and 0%, not the actual usable battery capacity from full to the car stopping.

 

[ran349]

At best, this calculates what the car thinks is the available capacity between 100% and 0%, not the actual usable battery capacity from full to the car stopping.

Yes, I edited my post probably after your response. The thing is, the car may stop right at zero, or several miles below zero, depending on many variables. So unless you're prepared for it, you shouldn't try to go below zero miles.

Edit: Actually, it does calculate the full capacity from full to when the car stops, but that full capacity is not all available unless you go below zero miles, which is not ever recommended.