On 11/8 I attempted to replicate the route and conditions of an earlier trip, which I had kept careful notes of, to try to see what sort of range reduction is caused by reduced m/kWh due to lower temperatures, and what proportion of this reduction is due to reduced battery capacity. I did this on a dry day with windows up, without using the heater or windshield wipers. I believe that I got about 5% reduction in battery capacity, and a slightly larger decrease in driving efficiency (m/kWh) resulting in a total range reduction of over 10%. This is the same trip I made several times over the summer, and posted details of on this thread:
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My trip (each time with a 1 1/2 hour break at the halfway point (for a hike around Burney Falls) on 8/30 was 87.6 miles by odometer (85.5 miles by Carwings-see other thread for info on this 2.5% discrepancy) with between 5,000 and 5,500 ft. of total ascent and descent, carwings reports 16.8 kWh consumed and 5.1 m/kWh. I believe my total battery capacity after charging to 100%, was about 20.4 kWh.
When I made the (almost) identical drive on 11/8 of 88 miles (85.9 as reported by CW) CW reported 17.6 kWh consumed and 4.9 m/kWh. I believe my total battery capacity when I left home with a 100% charge was probably close to 19.4 kWh.
Both trips were made at about the same average speed, about 40 mph, and despite the elevation change, very little friction braking was required, on either trip. The main reason I think the cold weather reduction was slightly greater than 5% for the drive, is that I either had a window cracked open, or the AC set low, for much of the 8/30 trip. The difference in miles driven was due to a short detour I made for 50 minutes of L2 about 55 miles into the trip. In retrospect, this was probably unnecessary, as it looks like I would have made it home on 11/8 at about the “very low battery” warning, but that was not apparent at the time. I got a scant three bars from the charge session, and had almost one full bar showing when I got home.
Both initial charges were done to 10 bars, with a top-off to 100 % many hours later, and were all done in an open carport.
On 8/30 the overnight low was in the low 60’s, and the top off was done when the ambient temp had warmed to the mid 80’s , and my best estimate that the battery was probably in the 70’s at this time. The drive was done in temperatures of 80-95 degrees. I believe (but did not record) that the battery temp indicator remained at 6 bars for the entire trip.
The 11/8 top-up charge was done when the overnight low was 35. I doubt that the battery temp was much higher than this. The temperature during the drive ranged from 47 to 36 degrees. Battery temp showed 4 bars until the recharge session, and it was at 5 bars for the rest of the trip.
So this approximately 40 degree decrease in temp when charging, and 50 degree reduction when driving, resulted in about 10% recorded range reduction. I expect that If I’d done the 8/30 trip in “sauna” mode, with the windows up and AC off, it would result in more like 11-12%.
It gets much colder than 35 here during the winter, but I plan to start parking in my garage (unheated but insulated, and stays above freezing) once winter sets in, so I think this is pretty close to the maximum range drop I’ll see (until I turn on the heater and wipers...). I know lots of you will be driving in much lower temps, but I wouldn’t want to try a long no-heater test trip on a much colder day. I, like many others, have seen larger range drops in cold weather driving, but I think you have to look at other causes, such as the heater, rain and wet roads etc.