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Old 08-22-2019, 09:22 PM   #11 (permalink)
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Originally Posted by mpg_numbers_guy View Post
Someone I know "overclocked" their alternator with a different pulley size. Might be consideration if you don't plan on using the alternator for normal driving. I surmise there would be a definite amount of additional load from doing that, but you might be able to get a bit more "regen".
No, NO, NO.

Spinning the alternator faster pretty much only produces more losses after a few thousand rpm. They're usually spinning at >2x crank speed, so you'll have most of it by 2000rpm at the engine. The limiting factor is the current capacity of the stator winding.

You can only increase output by increasing voltage or putting in a bigger alternator. With increased voltage you will need more rpm to let the alternator reach that voltage if the field coil is current limited.

The alternator will need to be run more than just when you brake unless you have a really huge battery that's being charged at home and depleted as you drive.

If it were me, I'd use about 30Ah @ 24V lithium titanate oxide batteries (~$500), a 24V regulator from a tractor alternator, and DC-DC converter (~$70), and a switch to cut the alternator out above a certain % throttle input (if the engine is at low load you might as well run the alt).

Using LiFePO4 is more troublesome since you'll need a lot more of them in parallel to accept a fast charge, like 70Ah worth (assuming 100A alternator - 30A ignition/ECU/fuel pump/lights) which gets quite pricey and bulky.

Last edited by serialk11r; 08-22-2019 at 09:40 PM..
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