The percentage of the energy expended driving the car on level ground that is regained through regen is:
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 2nx < 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. Here are some examples for my 2001 Suzuki Swift: (1) Accelerate at 6 mph/sec (26.8 m/s) to 60 mph, drive 10 miles, then decelerate at the same rate to a stop. Estimated percent energy regained is: 100 * 3.7e5 J*(1-0.377)/[(10 * 1610 – 2*135) * (64.1 N + 140.6 N) + 3.7e5*1.377] = 100 * 230510/3719901= 6.2% (2) Acceleration at 6 mph/sec to 35 mph and deceleration at same rate 10 times in 10 miles: 100*10*93600 J*(1-0.377)/[(10*1610 – 2*10*68) * (16.2 N + 140.6 N) + 10*93600*1.377] = 16.3% (3) Acceleration at 6 mph/sec to 35 mph and deceleration at same rate 20 times in 10 miles: 100*20*93600 J*(1-0.377)/[(10 * 1610 – 2*20*68) * (16.2 N + 140.6 N) + 20*93600*1.377] = 24.8% 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 5.5%, 15%, and 23%, so a factor of 2 slower rate doesn’t change the result that much. Increasing total miles traveled, d, to 30 in scenario (1) gives 2.2%. Increasing stops in this scenario to 3, with 30 miles total traveled, gives 5.5%. 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 6.2% to 7.3%, second goes from 16.3% to 17%, third goes from 24.8% to 25.6% if vehicle mass is doubled. Increasing drag coefficient or area, A, reduces percentage of energy recovered, but it too is a small effect. Seems numbers for most cars will be close to the above. Brake pads and shoes are comprised of some nasty stuff. Better to keep that off the roads where it drains into streams during rain storms. -- View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Fiat-500e-EV-close-to-perfect-tp4668392p4668520.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 For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
