Unlike an ICE, a more powerful electric drivetrain uses _less_ energy
under normal driving than a marginal HP drivetrain.
A large inverter and motor run more efficiently at low power because
they have larger conductors and less internal resistance than a smaller
inverter and motor. Driven side by side, a very powerful EV will be far
more energy efficient (Watts per mile) than a marginally powered EV.
Quite the opposite of what you might expect.
A gasoline engine is most efficient at near full throttle, and least
efficient at small throttle settings. Basically, when you throttle a
spark-ignition engine, you do so by restricting its intake, which
reduces the combustion pressure (and density). You are essentially
throttling the engine by reducing its efficiency. Thus, a gasoline
engine car would prefer to have its engine run at near full throttle,
which means that from an efficiency viewpoint, you want a tiny engine
that is just barely enough to propel it down the road.
I might add, that a diesel engine does not throttle by restricting its
intake. Its fuel efficiency is _not_ effected by engine size or by the
throttle setting. (Engine RPM is what dictates Diesel efficiency.) This
is why you rarely see diesel hybrids. They don't add much efficiency,
other than to capture the braking energy (regen.) On the highway, they
get the same mileage as non-hybrids. (This is also why manual
transmissions in diesel trucks have so may gears.)
Bill D.
On 11/5/2021 9:00 AM, Cor van de Water via EV wrote:
Don't knock vehicles with limited power, there is absolutely no
objective *need* for a family car with 400+HP.
My 1994 US Electricar (S10 factory conversion) has a 50kW induction
motor and a 250A limited inverter.
Original design had a 312V lead acid pack, but due to the inverter's
design with 450V components and specified 405V operational voltage
(90% derated) it is possible to use a full Leaf pack in the truck
which reduced weight from close to 5,000 to somewhere closer to 4,000
lbs.
The ~360V (under load) and 250A current limit give the truck a
theoretical peak power of 90kW but I hardly ever see the inverter
capable of delivering more than 200A so the actual peak is closer to
70kW and that makes this truck very peppy and fun to drive, much
better than when the Lead Acid pack was sagging below 280V and the
truck was both heavier and only wielding 50kW.
I have driven many low powered vehicles, including an original Trabant
during a visit to former East Germany, so I know how to handle a
vehicle that has just enough power to do what it is designed to do -
move people around at freeway speeds. My first car had an air cooled 2
cylinder 800cc engine into a continuous variable transmission. Not
fast or quick but very easy to drive ;-)
Cor.
On Thu, Nov 4, 2021 at 12:33 PM EVDL Administrator via EV
<ev@lists.evdl.org> wrote:
On 4 Nov 2021 at 11:52, David Nelson via EV wrote:
I don't know where to source a 40kWh (note it is not kw, but kWh,
kilowatt-hour) battery for a Leaf
Yup. KW measures the battery's ability to deliver power, not its energy
storage capacity.
But who knows? Maybe some Leaf owners really DO want 40kW batteries.
After accounting for efficiency, a 40kW battery would give a Leaf roughly
the power of a 1961 VW Beetle, in a car that weighs over twice as much - and
doesn't have a 4-speed transmission for torque multiplication.
Thirty or 40 years ago, 40kW was a typical small-car conversion - 96 volts
with a 400 amp controller. A 2500lb car with a forklift motor bolted to the
stock 4- or 5-speed transmission could usually manage a top speed of around
65mph, if you were prepared to give it the better part of a minute and
didn't have too much of a headwind.
In a 3400lb car with a single-gear transaxle, things might be a bit more
dicey. But maybe the OP is up to the challenge. :-)
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
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I said I didn't know.
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