Electric Vehicles
Positive and Negative Attributes

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Notes:

I don’t think there’s any doubt that we can expect to see widespread use of electric vehicles in the future, both battery-electrics and hybrids - certainly within the time frame that we are discussing, and probably sooner.  I might have to come back in a few years and eat those words because there are still significant problems that have to be solved.  But from this perspective in time, it’s difficult to imagine a future without electric cars.

In my opinion, the electric power system, at least from a conceptual standpoint, is the ideal automobile power system.  The torque characteristics and wide speed band of the electric motor make it ideal for propulsion, and generally, a multi-ratio transmission is unnecessary.  Also, the energy loop is inherently bi-directional, so the energy used for acceleration can be reclaimed on deceleration using the same hardware.  You can’t do that with a liquid fuel without resorting to a separate system like a flywheel or an electrical generation and storage system.  In the case of BEVs, the vehicle itself has zero tailpipe emissions and operates at more than twice the onboard energy efficiency of a conventional ICE-vehicle.  And despite the talk about their high costs, a battery-electric car is potentially a very cheap vehicle to build.  It has an elegant simplicity that’s very appealing - conceptually, mechanically, and from a manufacturing standpoint. But there are a couple of spots on the wall.

The first problem with BEVs is the limited energy capability of the battery.  The second problem, which is less talked about, has to do with the practical limitations of pulling into a local service station for a quick fill-up of electrons.  I think the problem of limited energy capability has good prospects for being solved, but I’m not too optimistic about the prospects for solving the quick-recharge problem - and I’m referring to the ten-minute fillup, not the one- or two-hour recharge.  The battery-electric car will probably never equal the fast fill-up of today’s liquid fueled cars (on a time/energy-dump basis).  At least that’s the way it looks through my paradigm of technical feasibility.

Assuming an energy efficiency equal to that of the EV1, a 300-mile range BEV would need energy stores on the order of 65 kW-h.  A ten-minute, 65 kW-h energy dump at 70% efficiency (conversion and battery efficiency) would imply an input of over 1800 amps at 300 volts.  If we account for the lighter batteries of an advanced EV, the same range might be provided with a 45 kW-h battery, which would then reduce the ten-minute recharge to 1280 amps at 300 volts. Considering the limitations of conductors, batteries, and other associated realities, I’m not very optimistic about the prospects for a truly quick-recharge system for BEVs - at least not one that would equate to what we have with liquid fueled vehicles.

Although BEVs could ultimately approach the range of today’s cars, they will probably remain mostly limited to overnight recharging at home, with perhaps some topping off done at remote recharging sites.