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by prodmerc
3654 days ago
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I'm assuming all that weight still gets better mileage than what would basically be a petrol->kinetic->electric->kinetic convertor. Modern engines are pretty efficient, adding an electric stage would likely reduce that efficiency. |
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a) absorb braking energy - that's why I mentioned super-caps, because batteries can't ingest the vast amounts of energy that braking could theoretically produce (usually the brake power is 4x engine power, which means for a 250 kW motor a minimum brake power of 1 MW, and for sportscars likely muuuch more)
b) keep the engine, if not in idle (i.e. you're stuck in traffic), at its most fuel-efficient RPM range - this is something any cheap-ass scooter does, and every diesel-electro locomotive and ship, but no car! Not to mention it isn't just about fuel-efficiency, but also many exhaust gas treatments only work at peak performance under very specific driving conditions (esp. temperature).
The efficiency loss by conversion (97% and better in efficiency class IE4, see https://de.wikipedia.org/wiki/Elektromotor#Wirkungsgrad_und_...) is, taking especially the recovered braking energy into account, smaller than the efficiency delta gained by loss of hundreds of kg of weight (batteries are heavier, yes, but they can also replace "dumb weights" needed before to keep the car on the ground in the "elk test").
Also, less parts that are prone to (dirt) failure, e.g. the power-loaded joints on FWD cars, clutches, bearings, the entire gearbox system, differentials (in 4WD/multi-WD systems!). And you save on tires because in curves the individual motors can adjust speed. If done well, it should be pretty cost-efficient (less stops in the shop), too.