Peter VanDerWal via EV wrote:
A few points:
1) Modern EVs all come with fixed ratio transmissions (no shifting)
2) The single most important specification for quick 0-60 acceleration
is ample torque.
3) In order drive up to a mountain pass, you need ample torque.
I agree with these point.
Quick 0-60 times are just a side effect of making a safe, single ratio,
vehicle that can handle highway driving. Remember, unlike a conversion,
you can't shift down for the mountains.
This does not quite follow from the above. It's a consequence of the
current strategy to use high-voltage packs, and a single AC PM motor.
Motor torque is proportional to current, so if the controller can
deliver the current, you've got the torque to climb hills. Speed is
proportional to voltage, so if it's high enough, you have freeway
speeds. Now you have a wide power band, and the resulting fast
acceleration. But you also have an expensive pack, an expensive
controller, and an expensive motor. It's hard to make inexpensive EVs
this way.
But there are alternative designs.
You can use a 2-speed gearbox. Even Tesla did this in some cars. It's a
*win* if the reduced cost of the batteries and controller saves more
than the added cost from the gearbox. Automakers are highly skilled at
making transmissions, much less so at making batteries and controllers.
Golf carts have plenty of torque to climb hills; but their low-voltage
packs limit their speed. The Prius solves this problem by including a
boost converter to raise the apparent pack voltage.
AC induction and DC series motors are capable of high speeds without
high voltages; but their torque is limited at high speeds. One solution
is to use *two* motors, and switch them in series or parallel. Series
for high torque, parallel for high speed.
I'm sure there are other options. I suspect that low-cost EVs will have
to evolve different design strategies to be competitive.
Batteries are still the heaviest part of the vehicle and most EVs mount
them on the bottom. This makes for a vehicle with low center of gravity
which means that cornering like a race car is another free side effect.
Well, it's not "free" -- it's just easier. It still costs more to
provide high-performance suspension, brakes, and steering.
Most non-Tesla EVs don't come standard with leather seats.
Heated (non-leather) seats adds very little to the cost of manufacturing
an electric vehicle.
Sure; this is true for almost all the luxuries that are loaded into
cars. But the luxuries come at a high price to the consumer. Automakers
routinely charge high profit margins on anything that makes the car seem
more "luxurious". The cheap car won't have them so there is an incentive
for the customer to buy a higher-priced car instead.
Modern EVs need a pretty sophisticated computer system and by federal law
all vehicles have to provide an OBD-II interface which pretty much requires
the automakers use a CAN bus system. CAN = Controler Area Network, so not
just one computer, but a network of them.
Are you sure that's true? I thought OBD-II was only required for the
engine and its emission control system. EVs don't have these.
Modern COWs (Computers On Wheels) require very little to add external
connectivity. So again, very little additional costs.
To the manufacturer, perhaps. But it's a big cost "hit" to the customer.
And... it will require monthly subscription fees. And when it breaks, it
will difficult or even impossible to fix. Guaranteed obsolescence.
If you're going to get the "common man" into EVs, you''re going to have
to make them cheap enough so the "common man" can afford them.
Cheap-Lee :-)
--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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