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Winter range

Winter range

I just did my first winter trip to Jaffery, NH, it was 11F in NH and a relatively balmy 17F back home in MA. I left with 91% in the battery, returned with 42%, used 49% of the battery capacity.

Trip stats,
100.2 miles
33KWh
326Wh/mile

33KWh/.49 = total capacity 67.34KWh
Maximum range 67340Wh/326Wh = 206 miles

Power per mile is almost exactly 100W/mile higher that this trip in the summer, that's the heater penalty. I never measured the battery capacity in the summer in this way but assuming the reported capacity of 75KWh is correct then cold weather diminishes the capacity by about 11%. All if this is as expected, winter range is 1/3rd less than summer range.

Mike UpNorth_ | 7 December 2019

Sounds about right.
When I drive like a maniac I can get the winter hit up to 40%+.
AWD non P.

Bighorn | 7 December 2019

The capacity shouldn’t change from summer to winter. More likely your methods.

bp | 7 December 2019

Thanks for the details and figures.

Bighorn | 7 December 2019

If you did the trip in two segments, you’ll get a low estimate of capacity due to unrecorded draws.

bjrosen | 8 December 2019

Bighorn@ The car sat for three hours at 11F, I didn't notice a drop in the % during that time but I also didn't record the values so it's entirely possible. I used the Since Last Charge screen to get my values, are you sure that they don't record the vampire drain on that screen?

I have a 60 mile trip coming up on Wed, I'll record the values on each leg for that trip. Will someone who lives in CA or in the South please post your values here for comparison.

The capacity of lithium ion batteries is reduced by temperature but Tesla heats the batteries to counteract that problem. Heating the batteries 11F weather would require a significant amount of power. It's would be interesting to find out how much power they expend when a car is just sitting in the cold and not plugged in or if their strategy is to just expend the energy when you start the car. In the couple blocks between our concert venue and the restaurant the trip computer screen reported over 1100W per mile, I'm assuming that this high draw was due to the battery heating as well as cabin heating. This high initial draw would be recorded on the Since Last Charge screen because it happens while driving.

BTW the Wh/mile had dropped to 300 by the end of the trip which reflects the steady state energy usage when it's merely maintaining cabin temperature as opposed to heating it in the first place.

whealey85 | 8 December 2019

What was your heat set at. I haven't taking any long trips yet in the cold ( I live in southern Mass) for the short trips I've been getting around 280 kwh if I drive around 30 miles half highway half back roads I get around 260. I keep the heat set at 68 recirculating and seat heater set at 1

whealey85 | 8 December 2019

Also awd LR

bjrosen | 8 December 2019

My seat heater was set to 1, the cabin heat to 69. If it were just me in the car I'd try and turn the heat off but my wife insists on having heat. I wear a fur hat, a heavy sweater and a parka so I'm very comfortable without heat in the car, but she's not. And here's the kicker, I grew up in Chicago, she grew up in Leningrad but she's the one who's cold. I keep asking here if she really grew up in St Petersburg FL instead of St Petersburg Russia.

Bighorn | 8 December 2019

The car only records energy usage while the car is “on”, so vampire drain and battery cooling, pumps, etc. don’t get accounted for. The early big number, 1100 Wh/m is more an artifact of the small 0.1 mile denominator and only represents 110 Watts. I’ve seen the figure as high as 8000 Wh/m when climate was going prior to departing. Meaningless in the larger scheme. After your first stop, you’ll also have a smaller capacity after the battery cools. Tesla puts a warning screen up to that effect below a certain threshold SOC so people aren’t caught off guard with insufficient charge. The battery heating draws about 7kW while stationary or up to 4 kW if you are NAVing to a supercharger. Climate control also draws about 6 kW for maximal heating.
Under any conditions, you should be able to arrive at a battery capacity (in kWh) equal to your rated miles times 234 Wh/m so 72.5 kWh for a 310 rated mile charge. This is only possible on a long, uninterrupted trip for the reasons stated above.

bjrosen | 8 December 2019

Bighorn@ Thanks, that's all great information. I'm going to continue to take readings to further my understanding of where energy is expended in the winter, I'll make sure to capture the readings at each step, when starting out, when I park, when I return to the car and then when I get home. I'm doing for my own amusement. Last night readings just confirmed the conventional wisdom which is that EVs lose 1/3rd of their range in the winter.

The temperature conditions were on the low end of a normal winter day here, most of the winter the temperatures are in the 20s or 30s but there usually is one week a year where it's below 0. My speeds last night were also on the low end, I was doing 35-45 for most of the trip because there are no superhighways in that direction, but the average energy per mile is likely to be similar on a highway because the lower heater cost/mile is balanced out by the higher motion/cost.