On Tue, 3 Jan 2006 23:16:37 +0000 (UTC), Brimstone wrote:

Adrian wrote:

What's this 500mile capacity battery going to weigh? A ton? Literally?

Compare the size, weight, capacity and duration of a late 1980s/early 1990s
mobile phone battery with a current one.

There is a theoretical limit here. Lithium - being a light material - can
reach about one tenth of the energy density of diesel, used in batteries.

That sounds bad, but it is vastly alleviated by the fact that

- battey electric is 70-95% efficient overall, diesel is about 40% at best,
in a road vehicle.

- a 100 bhp electric motor is a lump of iron and copper about the size of a
watering can. BUT it needs no exhaust system, not a lot of shock mounting,
no radiator, no gearbox, no injection mechanism, no starter motor, no
starter battery, no air filter, no oil cooler, no turbo charger , no
intercooler , no heavy mountings for all of the above..., and les sound
insulation....In short there are huge weight savings to be made to offset
the battery weight penalty.

I am flying RC planes with this technology. We can esasily get the same or
more duratiion from a typical electric package at the same weight and power
as an IC engine. We can't get the absolute peak power to weight of a racing
2-stroke, but the overall package weight of e,g a methanol or petrol 4
stroke i, or a diesel, is broadly similar. A lot of that comes from reduces
structural weight as the vibration is far less severe. Peak power (albeit
for very restricted durations: 10 minutes or so) is up around a half bhp
per lb. say 1000bhp per ton. take that down to 100bhp per ton - a
respectable sort of middling car - and you get 100 minutes duration. At
full power. what speed would 100bhp do in a ton of car? 100mph? so about
170 miles range flat out...? The battery weight would represent about half
the total plane (or car) weight at that point.


AND batteries can be made of smaller cells, fited in the car anywhere you
like. Under the seats, behind the rear seat. Under the floor even.

The overall package is likely to - with 300 mile range LIPO batteries -
weigh little more than a conventional mid range car.

I think this is abou 3-5 years away frankly. And it will be expensive, and
I suspect it will be in short range luxury cars first - where the packaging
pluses plus the low noise, will make a rolls royce car seem easy, and the
immesense development costs can be met by selling the cars expensively.

At the other end of the scale expect to see cheap piddly 50 mile range
shopping trolleys coming out with nickel batteries - electric scooters are
here already. That will help prove the technology and get people used to
them: Then an expensive LIPO battery will net them nearer 200 miles range.

Aftre that the technology will extend into the middle ground I think. As
more and more fast charge batteries and fast charge stations get built.

Now a lot of this edepned son rnewable or nuclear electricity being
available - otherwise there is no net carbon gain to be had.

But that goes for fuel cells as well, and even old IC engines.