Bjørn Nyland's 2013 Tesla Model S P85 is one of the oldest Model S in Europe and with quite high mileage: 8 years and over 350,000 km (218,000 miles).

In the battery degradation test, its second battery - installed after about a year and 86,000 km (53,000 miles) - noted quite good capacity retention of 89% (some 65.9 kWh out of 74 kWh when new) after 7 years and about 265,000 km (165,000 miles).

But how about the "vampire drain" - the discharge rate when the unplugged car stays parked for a prolonged time?

Well, according to the most recent test, over 13 days and 7 hours, the results are not so great. The battery State of Charge (SOC) decreased by 17% (from 83 to 66% SOC).

That's a lot. Considering about 65 kWh available, it's 11 kWh just for sitting idle. That's comparable to a small electric kettle, run for 2 minutes, every hour.

  • 17% or about 11 kWh over 13 days and 7 hours (up to 830 Wh per day average)
  • about 9% per week
  • about 1.3% per day

The same car with a new battery had a much lower vampire drain of about 5% per week, which means that now it's 80% higher, on top of the 11% lower range.

It's not terrible, but already high enough to take into account, especially as the car is used as an auxiliary vehicle to get test vehicles (it then sits idle for a week or longer).

In the case of the Tesla Model 3, it should be within 1.5-2% per week, while the LFP battery type was higher at about 2.8% per week.

The vampire drain rate depends on many factors, but its base is the energy used to keep the battery temperature in optimal conditions, battery self-discharge and on-board devices (computer, 12V auxiliary battery, some communication/updates and other energy losses in the electronics).

One of the biggest electric loads, when a car is idle, is the sentry mode (guarding and recording things around the car), but this was not used in this test (it can drain half of the battery pack within several days).

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