Battery losing 1 mile per hour when parked

I searched the forum and cannot find a discussion that matches this one so here goes:

I have had my Model S for just over two weeks now and it consistently loses 1 mile of range per hour when it is not plugged in. Considering that at full charge it is rated for 188 miles that is a 12.8% loss per day. At this rate of loss my car would be at zero miles in less than eight days. The owners manual says that the loss of range should be around 1% per day. When I called the Tesla service representative I was told that 1 mile per hour loss was normal and not to worry.

I am curious what losses other people are seeing. If there is already a discussion with this information I would appreciate being pointed to it.

Oops - posted wrong table above - here is the one with Electricity Costs:


You say that the parasitic losses should equal about 180 watts. Wouldn't those losses normally be measured in kWh? And for 14 rated miles at 308 w-h/m, the losses would be about 4.3 kWh, not 180 watt-hours.

Also, your input chart shows maximum charging at 20 kW. You might want to point out that this is with twin chargers. Most people have a single charger, which charges at half that rate.

Watts is *rate* of loss. kWh is *total* over a specified time period. If you run a 100 watt light bulb for 10 hours it uses 1kWh...and that is what you pay for!

So, applied to MS, the 180 watt parasitic load x 24 hours would be about 4.3 kWh - but that would double-count the "baseline" draw when driving. My calculations use non-driving time and estimated total of 123 kWh per month (never used 180 as total energy, just went into the calculation). Thanks for double checking!

True about charger max kW - only an issue for the HPC...home NEMA 14-50 is still under 10kW.

Yep, you're right! :)

... sleep ... sleep... must sleep ....zzzzzzzzzzzzzz

@Cliff - Great data. Thanks.

I've been trying to quantify the parasitic loss as well. I put a pair of power clamps in my breaker box directly on the two hot leads that go to the nema 14-50 in my garage. I'm able to track the kWh I put into the car on an hourly basis. I plugged in the 180W parasitic loss power that you derived, but I'm getting a smaller difference between kWh supplied and kWh driven than I expected. For instance, I took an odometer and kWh reading on 3/2 8am from the car. I did the same on 3/5 7am. The car says I drove 82 miles and used up 27.6 kWh driving (336 Wh/mile). The power meter in the breaker box says that I supplied 41.7 kWh. Assuming that the car was idle 23h/day, at 180 Wh, parasitic loss would be 12.2 kWh. So if the car had no parasitic loss at all, I would have supplied 41.7 kWh - 12.2 kWh = 29.5 kWh. This means a charging efficiency of 93%. So either the car is overestimating kWh driven, or the 180 W parasitic loss is closer to 140 W. The power meter I'm using is pretty accurate as far as I can tell. I've repeated these samplings 3 different times and I find the same outcome. I have a 85kWh model (rev 4.2) and I top it off every day at 240v 40A.

@jemarting - Depending on temperature/trend, I wouldn't be surprised if the parasitic could be as low as 140W - my measurements varied A LOT (I have one set of measurements on the spreadsheet at the URL above). You also can't count on the Rated Range being altogether accurate - and then there is the temperature-adjusted Rated Range. If you start your measurement when the battery is cold, it is artificially low.

Cliff, thanks for the numbers. A loss of 13 - 15 miles per day isn't that bad.

But for mine, I noticed that, in just over 1 hour, there was a 5 loss of 5 miles. And in two hours, there was a loss of 8 miles. This was when the temperature was around 35 degrees. I will keep track of how much these losses are over a period of time.

If the car was just sitting cooling, that may not be real. Just reporting what the chilled output would be if the battery didn't warm, which it necessarily would. It's an anomaly TM is working on.

I have been keeping a log for the past week and I am losing about a mile of range every 2 hours while parked.

I typically drive 40 miles a day. During the 24 hour period my miles remaining will go from 190 (standard charge) to about 130.

I have concluded that I get about two thirds of the range indicated by the miles remaining. Temp has been in the 40 - 70 degree range.

I am on v4.2 of the firmware.

My electricity cost with TXU is 12 cents per KWH. To charge from 0 to 230 range should take 60KWH and cost $7.20 and I should get actual milage of 153 miles. So my cost per mile is about 4.7 cents per mile. My previous car (Infinity M35) got 17.5 miles per gallon at $3.50/gallon for premium or 20 cents per mile. I am currently saving $185/month for fuel.

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