jbde

Chevy Volt: How It Stacks Up

you said:

"The reason the Volt could get the equivalent of 230 miles per gallon is that on many short trips, the gas engine wouldn't even be on."

if the engine is not on, the mpg would be infinite ..... but;

Before you jump on me, to determine the MPG of an EREV; first the car is driven from a full battery until it reaches charge-sustaining mode [engine on], then one more cycle is driven. If we use the highway schedule first from a full charge, the first 40 miles are electric covering the hiway course of 10.26 miles and continuing until the engine comes on to ready for the city course of 11.04 miles. If the Volt gets 50 MPG in charge sustaining mode, it will use .22 gallons of gas for that 11 miles. Thus 51 miles/.22 gallons = 231.8 MPG. Close to the GM quoted figure of 230mpg.

The real issue comes from Einstein - E=mc^2

Since there is no transmission, there is alway a direct relation to speed squared. Thus to sustain a faster speed over a given distance requires more energy [than if you covered it at a lower speed]. This is why the Volt is not good for long high speed trips. The real question is how fast you can go in charge sustaining mode, or even in charge draining mode - both with the engine running. Then produce a table for distances at various speeds so you can determine when you will be stranded.

What if you drain the battery below sustaining charge levels and continue to dirve? Of course you should be able to "idle" and recharge the battery as opposed to plugging it in - but that is real bad mpg! Like - zero.

Li-ion Batteries: A Speculative Field of Dreams

Whatever happend to storing energy kenetically in flywheels? Rev 'em up when plugged in and drive away by converting to electricity and driving motors on each wheel. Also motors could harvest breaking energy in a small bank of batteries that would assist in accelerating from a dead stop.