A few years back Drag Times reported these results on a Tesla S in the quarter mile:
"As you can see in the video below the Tesla’s total energy consumption was 1.1 kWh at 114 MPH and after the car slowed down using the regenerative braking .6 kWh was put back into the battery. This results in a net energy usage of .5 kWh for the 1/4 mile pass. Pretty amazing that the car can recover just over half of energy used and put it back into the battery using it’s regenerative braking." http://www.dragtimes.com/blog/tesla-...usage-and-cost This agrees with the range of vehicle ke recouped by regen that I have measured on my car by data logging battery current and voltage, taking their product to estimate power, and dividing by the 1 sec time between samples to estimate energy into/out of the pack during deceleration and acceleration. Also a few years ago I estimated the percentage of energy expended driving on level ground recouped by regen with the simplifications that deceleration rate = acceleration rate, and the vehicle travels at constant speed between stops. Note that this assumes the vehicle is brought to a stop using only regen, no mechanical braking, which may not be the case with some manufactured EVs. I put this in a spreadsheet and did "what if" scenarios varying things like vehicle mass and speed between start/stops each by a factor of 3 to estimate relative effects. See the summary of these below the "examples". The equation used is given for those who have an interest: The percentage of the energy expended driving the car on level ground that is regained through regen = energy gained by regen/(energy used at constant speed + energy used to accelerate), or: n*(K.E. – L)/ [(d – 2*n*x) * (Fd + Fr) + n*(K.E. + L)], for 2*n*x < d Where: n = number of acceleration/deceleration cycles, L = sum of average losses (need to average if travel at different constant speeds between stops, i.e. loss at 35 mph, loss at 50 mph… just assume one constant speed between stops for simplicity) d is total distance traveled x is the distance required to accelerate or decelerate to/from speed, so total distance driven at constant speed is d – 2nx assuming the same rate for acceleration and deceleration, and same constant speed between each acceleration and deceleration for simplicity. Examples: (1) My car accelerates at 6 mph/sec to 60 mph, drives 10 miles, then decelerates at the same rate to a stop, estimated percent energy regained is: 2.7% (2) Acceleration at 6 mph/sec to 35 mph and deceleration at same rate 10 times in 10 miles:12.7% (3) Acceleration at 6 mph/sec to 35 mph and deceleration at same rate 20 times in 10 miles:20.7% A more typical acceleration/deceleration rate might be 3 mph/sec, or 1.34 m/s (0 to 60 mph in 20 sec). Then the same three scenarios give 2.4%, 12%, and 20%, so a factor of 2 slower rate doesn’t change the result that much. At 2 mph/sec acceleration/deceleration rate the three scenarios give 2.2%, 11%, and 19%. Increasing total miles traveled, d, to 30 in scenario (1) gives 0.9%. Increasing stops in this scenario to 3, with 30 miles total, gives 2.7%. Increasing vehicle mass increases the percentage of energy recovered, but it’s a small effect for larger number of stop/starts. For example the first scenario goes from 2.7% to 3.8%, second goes from 12.7% to 14.7%, third goes from 20.7% to 23.2% if vehicle mass is doubled. *So I would expect the Tesla S to recover a bit higher proportion of total energy expended than my much lighter vehicle.* Decreasing losses in the motor/controller and drive train of course increases the energy recovered. For example, decreasing motor/controller loss to 15% in scenario (2) increases the energy gained from 12.7% to 16.5%. Increasing drag coefficient or area, A, reduces percentage of energy recovered, but it too is a small effect. * The largest effect is the constant speed between stop/starts.* Varying this from 10 to 35 mph results in a change in proportion of energy regained by a factor of about 2.5. So in heavy traffic that is creeping along at 10 mph or less, proportion of expended energy regained will be very small, and likely less than zero with climate control on. -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-EVLN-Upgraded-2016-Tesla-S-90D-is-the-first-300mi-483km-production-Electric-car-tp4681833p4681885.html Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
