nitePhyyre wrote:Edit: I forgot that with gas cars you are going to be wasting fuel while you are stopped at red lights and stop signs. With an eclectic car, you won't be wasting anything. And when you stop our slow down in a gas car you are bleeding off even more of your energy as heat. With electric, you are recharging you battery.
That's why you have the drive train for the car be all electric, and only use a gas generator to make power as needed. Trains have done this for decades (well, with diesel instead of gas) and I've been wondering since the first parallel hybrids came out why the hell they were bothering with that instead of just sticking a gas generator in an otherwise all-electric car.
Something i have also wondered ever since i learned how a diesel-electric train works. The short answer is that it would make the car too damn heavy. Long explanation follows:
The engine would need to be powerful enough to power the car entirely when the battery is low or unable to produced the needed power to meet momentary demand of the motor. So you can't just have a tiny engine and trickle charge the whole time, or you're underpowered on hills and whatnot. But not only does this mean you need a large engine, it also means you need -two- large motors (the generator that the engine cranks must be able to match the power demand of the drive motor under the above conditions)
So already we have the engine that would be in the vehicle anyway, plus two electric motors which are each weigh half as much (or more) as the engine. The one place we are down here is a simpler (and therefore lighter) transmission: electric motors make asstons of toque at low RPM, and don't really lose anything as they speed up, so you only need one or two main drive ratios (or a nice CV transmission, but those are expensive and can be maintenance intensive).
Next we have the battery. Three options are lead, nickle, and lithium.
Lead is the heaviest, but it also provides the greatest working current ranges (both charging and discharging) and (when properly treated) has the best longevity.
Nickle has somewhat better energy-per-mass than lead, but has limited cycle life, more so at high charge rates (as a fraction or multiple of capacity) which limits the useful recovery of regenerative braking: either you can dump all the braking energy to the batts and cut their useful cycles down a quarter, or you can friction brake at heavier braking pressures and waste some of that energy. Nickel cells also waste volume because they must be cylindrical.
Lithium has astonishing energy density, and since lithium packs may be rectangular they are almost (but not quite) as volume-efficient as lead. Lithium is also capable of some truly terrifying discharge rates. the current generation of lithium batteries in use in today's RC model industry are capable of discharge rates upwards of 60C, that the maximum safe discharge rate exceeds 60 times the Ah capacity of the battery. That is, you could discharge the entire battery in a minute or less with no adverse effects. The most significant drawback of lithium though, is that it is tempermental as all hell. Forget a woman scorned, you ain't seen fury till you've seen an over-charged lithium-polymer pack go up like a fireworks stand. In addition, the fastest safe charge rate on most lithium packs is 1C, that is a one-hour charge rate. faster than that and you risk a fire, so forget regenerative braking entirely.
but yeah, the biggest thing holding electrically-driven, IC-generated cars and trucks back is the weight all that stuff adds. On a train, the weight of the locomotive is irrelevant, when you're pulling a vehicle that is over a mile long and weighs half a million tons or more, fifty tons of electrical generators and a hundred tons of batteries make fuck all difference there. On a passenger car that weighs just over one ton, however, adding five hundred pounds of motors and batteries (plus ancillary equipment like speed controllers and safety equipment) will entirely negate any benefit that would be gained from such a system.