Jed wrote: <snip> The point that Mike Carrell has made about a very rapid recharge is that it would require the batteries to absorb energy much faster than they ever discharge it. Suppose you have a car with a 200 mile range that recharges in six minutes. The batteries have to absorb enough energy in six minutes to drive the engine at top speed for three hours, a 30:1 difference (900 hp in, 30 hp out). This is much more demanding than regenerative braking.
30 hp, by the way, seems a little low even for a lightweight electric car, based on the performance of my 40 HP Geo Metro. I think you need more like 70 to 100 HP, even with a light, aerodynamic car. The Honda Insight has a 73 hp engine and a 10 kW electric motor. The Toyota Prius has 110 hp, gasoline-electric combined. See: MC: I said *at the wheels*. I don't have the exact numbers at hand, but there are a lot of losses between the engine crankshaft and the wheels. One is the power necessary for the hydraulic system. It needs high pressure, which has to be generated constantly, so there is a bypass around the pump which wastes energy constantly. There is talk of future designs with 48 and 72 volt electric systems. At that level, magnetically activated brakes and power steering are possible and the hydraulic system is yesteryear. The deal with hydrids is that the engine provides the necessary power for cruising and battery charging while running at a constant speed for which it is optimized. The batteries provide the surges for acceleration, with some recovery in braking. The torque from electric motors and batteries can be very high. One hybrid SUV has the acceration of a sports car and is attracting customers on that basis. In a normal car the engine can provide more power for acceleration [inefficiently] than is needed for cruising, with no recovery in braking. Mike Carrell
