I’d like to share two examples of range estimate calculations under winter conditions that were verified by actual trips. I used the same method to estimate the range at the beginning of the trip, and compared with the actual remaining range on the dashboard at the end of the trip. In both cases, the estimate was very close to the final dashboard range.
First example was a 57 Km trip. Initial state of charge was 10 bars. Range chart estimates for 10 bars @ 80 Km/h were 137 Km. Temperature was -2C, meaning 22% drop in range. We planned to use climate control throughout the trip to avoid fogged windows, which I estimated would take another 15%. So The initial 137 Km range minus 37% quickly became an 86 Km range. If the estimates were correct, that would still leave us with 29 Km to spare.
At the end of the trip, we made it home with 28 Km of range on the dashboard.
– Round trip: 37 Km
– Starting charge: 10 bars
– Range chart estimate at 20C and 80 Km/h: 137 Km
– Outside temperature: 2C (-18% drop in range)
– Climate control on: -15% drop in range
– Final range estimate: 137 – 33% = 92 Km
– Estimate range to spare: 92 – 37 = 55 Km
– Actual dashboard range at the end of the trip: 55 Km (no kidding)
A couple of notes:
- I used the final dashboard range measured after putting the car in park. Estimated range in Eco mode would be a bit higher, but you have to consider the fact that the last kilometer of the trip was done at low speeds, so things kind of balance out at the end.
- The range chart estimate is based on constant speed, which was obviously not the case of either trip.
- Outside temperature was not necessarily constant.
- The method is clearly not very scientific but it gives me a fairly good estimate of what to expect. The formula will probably change once outside temperature dips below -20C, because that’s when the internal battery heaters kick in.