I'm going to preface this as speculative, but it does seem to make sense to me. YMMV
Now suppose I'm driving along at 65 mph and it says I have 100 miles left in the tank. Now lets say I immediately slow down to 30 mph and all the sudden my energy usage/mile drops. Now I should expect my range to jump up to 150 miles left in the tank. Now say a little bit later, I speed up to 80 mph. Now I should expect my range to jump down to 75 miles. But if you look at the graphs from Tesla, you see basically continuous lines and always too optimistic (up to the 400 milepoint). Now, you'd think if you were constantly monitoring the battery usage and the odometer, you'd eventually get the CORRECT slope or at least have data points which bracket the slope but yet it's consistently wrong. In other words you expect "-Rated Miles/Mile to be 1, but for the first 400 miles it's constantly too high. (Again as Kevin showed in an earlier email about the IGN report) http://i.imgur.com/5mHrgMu.png I'm going to suggest that they don't even track the "mileage" and instead the formula they use for rated miles is much simpler and something like this. Rated Miles = 265*(percent State.of.charge) * (C(Temperature) ) Where C(T) represents a function that allows the Rated miles to decrease as the temperature goes down. (There's another part about the S.O.C where they also seem to keep 5% in reserve) Now according to the NYT article the Temp started out at 30 F and according to Musk, the car's rated ranges started at 265 miles This would imply that C(30 deg F) = 100%. Now after the car sat overnight, the Temperature was reported at 10 deg F. Furthermore the range was reported at 20-25 miles. Now looking at the SOC data, it looks like only went down to 30%. S.O.C If you leave 5% in reserve this would indicate that C(10 deg F) = appx 33%. i.e. ( 22.5/(265*.25) So could the function for C(T) be something as simple minded as this?(assuming T in Fahr) 1.0 (if T>30) T/30 (if 0<T<30) 0.0 (if T<0) (It also might explain the peculiar and rather drastic change in slopes observed between milepoints 400 and 470 because the temperature was rising. ) Anyway it's just random speculation, but it seemed as good of explanation as any. It would indicate however that there is virtually no feedback back to the driver as to how his driving habits are affecting his range, but on the plus side it indicates what is feasible at any point in time. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130219/002f2368/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
