Quote:
Originally Posted by oil pan 4
The smallest hybrid battery I recall was from first Gen prius. It was about 0.4kwh, but that hybrid drive topped out at like 34mph.
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Pretty sure that was the usable capacity, while the actual pack was more like 1-1.3kwh.
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I think lower hanging fruit is in improving alternator efficiency. Not that you can't do both, which is the point of a hybrid. But every step in the system is lossy, even in hybrids.
With an alternator you're looking at ~50% losses (give or take) when charging, then ~20-30% losses putting it into the lead-acid battery. Discharge efficiency depends on how fast you discharge the battery, but could be as much as 30%, and then you're looking at another ~50% (I guess?) loss using the alternator as a motor.
That gives a round trip efficiency of... what, 13%? Give or take? That's before even sending it through the transmission and tires.
The system really needs a permanent magnet motor with a controller, higher voltage, (preferably) a lithium battery, and a DC-DC converter for supplying the 12v electronics. That probably gives 5-6x improved efficiency. Once there, you have a hybrid with two entirely separate electrical systems.
That's not to say you couldn't do it with a 12v system alone, but as-is, 12v systems are set up so that you're floating the charge on the battery, and only enough electricity is being generated to meet the immediate needs of the car, which masks a lot of its inefficiencies.
Mazda apparently thought this was inefficient enough that they decided to put a supercapacitor pack in parallel with the 12v battery, and simply turn the alternator off now and then.
https://www.mazda.com/en/innovation/...y/env/i-eloop/
I expect it's more of a gimmick, but better than nothing if you're trying to incorporate stop-start with a conventional alternator and no high voltage system.