| stop trying to change the subject I'm not. The subject is whether or not the Tesla people gave Broder good advice. Obviously that depends on what information he gave them and what they based their advice on. You are basically saying that Broder asked them: "I can drive at 25 mph steady state, or do stop and go driving at an average speed of 25 mph; which will give me better range?" If that were indeed the question he had asked Tesla, you are entirely correct that "stop and go" would have been the wrong answer. But I believe the question Broder actually asked Tesla was more like: "I can drive at 50 mph on the freeway steady state, or do stop and go driving at an average speed of 25 mph; which will give me better range?" If that was the question he asked Tesla, "stop and go" could have been a correct answer. That's my point. According to the above, the energy recovered in the Model S is about 20% of that required to get the car to its present speed. The quote you gave referred to the Roadster; as far as I know the Model S uses regen on all four wheels [Edit: probably not--see below]. That would make it 48.4%, not 20%, assuming there are no other differences between the Roadster and the Model S. If the correct number is 48.4%, that makes e about 2; so my equation would look like this: E2 - E1 = [- c0 + 2 * c2 * v1^2] * D I agree this is less likely to be positive; I would have to see detailed numbers for the Tesla Model S to get a better estimate of c0 and c2. The Tesla people who gave Broder the advice presumably had such detailed data, so they would have been able to make a more accurate calculation of estimated range for each alternative. Science isolates one variable, the topic of study, and keeps everything else the same to the degree that's practical. Exactly: to the degree that's practical. Broder was not running a controlled scientific experiment; he was running a real-world test of a vehicle. [Edit: Looking at the Model S specs on the Tesla web site, they do say it's a rear wheel drive vehicle, and there's no mention of separate regen motors for the front wheels. If so, and if the 20% figure for energy recovery is correct, that would make it extremely unlikely that a calculation like the one I've done would give a positive number. If the Tesla people were basing their response on such a calculation, their numbers for regen energy recovery must be significantly higher than 20%, or they were estimating a significantly higher freeway speed than 50 mph, or (most likely) a combination of the two.] |