I can assure you that the Model 3/Y Powertrain is way above 85% efficient.
85% might have been reasonable for a mechanically commutated DC motor, but
even modern non-Tesla powertrains are better than that!

On Tue, Jan 4, 2022 at 3:27 AM Cor van de Water via EV <ev@lists.evdl.org>
wrote:

> Reason you can't drive as conservatively as you'd like is simply: other
> traffic.
> If you are alone on a 45MPH road, nobody cares if you want to do 35,
> but if 2 lanes of traffic are storming at you doing 55-60 then it is
> mightily inconvenient if someone is blocking the road at 35.
> The other reason of course is your own time. While it makes hardly any
> difference if you are doing 55 iso 60 on a freeway in time difference,
> you are still taking an extra 5 min on an hour trip and sometimes that
> means missing appointments, so a higher speed may be necessary at
> times.
>
> BTW, I question the 85% efficiency. Not at max (acceleration) power,
> but I am under the impression that the majority of the driving is not
> done at max acceleration and at lower power levels, the efficiency of
> the drivetrain is usually higher. For example, doing a constant 55 on
> a flat freeway takes only 15kW while max acceleration is about 6 times
> that amount.
> 15kW is about 40 Amps while max current is either 200 or 250A
> depending on the vehicle. Running at 20% of max also means a Voltage
> drop of 20% so resistive losses drop to 4% of max losses when running
> at 20% power, so I presume that if max losses are 15% (=85%
> efficiency) then the losses at 20% must be much lower, as long as the
> *fixed* losses are orders smaller.
> Cor, happily regenning before every traffic light that is not green
> and for sharper turns.
>
> On Tue, Jan 4, 2022 at 3:04 AM EV List Lackey via EV <ev@lists.evdl.org>
> wrote:
> >
> > On 4 Jan 2022 at 22:40, Bill Dube via EV wrote:
> >
> > > Whatever the drivetrain losses, they at least double when you
> > > regeneratively brake.
> >
> > I see your point, but I think it's a bit academic.  Assuming your 85%
> > efficiency number, you aren't losing 30% on regen, you're losing 15%.
> > You've already spent that other 15% by the time the energy gets to the
> > wheels, so it's gone anyway.  And 15% loss is a lot better than the 100%
> > loss that you get burning it off in the friction brakes.
> >
> > > If you drive a bit more conservatively, you can avoid expending that
> > > energy extra energy in the first place,
> >
> > Here I agree with you completely.  Not using the energy in the first
> place
> > is better than using it and then recovering some of it.  Unfortunately,
> you
> > still have to use energy to move, unless your trips are all downhill. :-)
> >
> > My point is that regen id like partly  smoothing out the hills and
> valleys.
> > With good strong regen, properly used, your energy use for a given hilly
> > route is only slightly more than if it were flat.
> >
> > If you're not in a hilly region, I agree that regen is of less value.
> But
> > as you say, with modern controllers, you get it essentially free, so it's
> > always worth including and using.
> >
> > One other often forgotten benefit of regen is that it reduces friction
> brake
> > wear.  That not only saves you money, it has environmental benefits in
> > reducing vehicle particulate emissions.
> >
> > David Roden, EVDL moderator & general lackey
> >
> > To reach me, don't reply to this message; I won't get it.  Use my
> > offlist address here : http://evdl.org/help/index.html#supt
> >
> > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> >      We don't devote nearly enough scientific research to finding
> >      a cure for jerks.
> >
> >                            -- Bill Watterson, "Calvin and Hobbes"
> > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> >
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