Energy requirements are determined by rolling resistance, air resistance, and vehicle 'house' loads. At high speeds, air resistance usually becomes a large factor, because it increases by speed squared, though how large also depends on aerodynamics.
Somewhere (I don't recall where) I saw discussion of an optimization where using regen to quickly drop from high speeds to a medium speed will capture enough energy to drive further at medium speed (then coast to zero) than one would go by simply coasting down from high to medium speed, and down to zero. The idea is to lose less energy to air resistance in the high to medium speed range, then maintain medium speed via powered driving where the air resistance is much lower, and finally coast to a stop from the medium speed. On Tue, Aug 24, 2021, 07:32 Bill Dube via EV <ev@lists.evdl.org> wrote: > The round trip efficiency of the motor-inverter-battery-inverter-motor > is perhaps 50%. > The 15% number comes from the increase in range from having a car with > regen, versus one not having regen. In stop and go city driving, that > number can go much higher, thus the 25% increase in range. > Thus, regen efficiency is on the order of 50%, not 25% or 15%. > > Of course, you are always better off driving more efficiently and > coasting to a stop, but that is not always possible, or even legal. :-) > > Bill D. > > On 8/24/2021 10:12 PM, Jay Summet via EV wrote: > > > > > > On 8/24/21 2:56 AM, Martin WINLOW via EV wrote: > >> In an EV, much of the braking in stop/go energy can be recovered by > >> regenerative braking, thus the ’shed mass’ argument is severely > >> undermined. The same applies to hilly terrain. > > > > > > I can't let this statement go unremarked as it propagates a common > > misconception. Regen captures some of the power lost from braking or > > going downhill, but the efficiency is probably 15-25% of the total > > energy used to accelerate or climb the hill initially. So it > > re-captures "much" more than an ICE vehicle does using mechanical > > brakes that drop the energy as heat, but it is not a magic energy > > recovery system. (Unless you have your vehicle towed to the top of a > > hill, all of the energy re-gen captures came out of your vehicle on > > the way up the hill or acceleration curve.) > > > > Coasting without power is MUCH more efficient than stopping with regen > > and then re-accelerating in a BEV (or an ICE for that matter). > > > > > > Jay > > _______________________________________________ > > Address messages to ev@lists.evdl.org > > No other addresses in TO and CC fields > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > ARCHIVE: http://www.evdl.org/archive/ > > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20210824/b4f335b6/attachment.html> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
