Tesla Model 3 Unplugged – Summer edition

This is a follow up to my previous post about monitoring the phantom drain of my Model 3's battery as it sat parked for an extended period of time last winter.

Phantom Drain Summer 2019.png

Over 7 weeks this summer I remotely monitored the charge state of my car while I was away on vacation. During this time the state of charge dropped from 85% to 72%, meaning I saw not quite 2% of battery drain per week as the car sat parked in the garage.

The charge state was checked weekly using the Tesla app, thus allowing the car to remain at its low power sleep state for longer durations than during my last experiment when I took daily readings. I believe this explains why the drain was significantly lower this time around.

Car specification: Long Range Rear Wheel Drive Tesla Model 3, firmware version 2019.20.4, Sentry mode disabled.

Tesla Model 3 Unplugged – “phantom drain” when parked without plugging in

Despite Tesla recommending plugging their cars in when parking for extended periods I had to leave my Model 3 unplugged when I went to Sweden over the winter holidays.

Before heading to the airport I charged the car to 85% to make sure it wouldn't run flat. During my trip I tracked the so called “phantom drain” from the battery by taking a reading of the charge level every evening using the Tesla app.

Charge level vs. Day.png

After 42 days the charge level had only dropped by 28 points, to 57%. That's on average about ⅔ of a percentage point, or ½ kWh, lost per day. Based on this I wouldn't even worry too much about leaving the car unplugged for up to three months as long as I've charged it up beforehand. But plugging in while parked is of course always preferable as it lets the car run its battery management system.

An interesting data point to note is that one day after starting the experiment the charge level had increased to 86%. I suspect this was due to the battery recalibrating after the charging session.

Car specification: Long Range Rear Wheel Drive Tesla Model 3, firmware version 2018.42.4.

Environment: Unheated indoor garage in Seattle during December and January, temperature range 0 – 15°C (32 – 59°F).