small parallel hybrid via differential?

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MC Hamster
Joined: 07/08/2010
Points: 3

Greetings folks.. long time lurker, first time poster...

I've been pondering potential 'future projects' around lightweight, low-cost EVs for a while, and have come to a question.. well, an idea.. that I'm stuck finding a decent answer for.

Mental process has gone, like I'm sure it has for many, from pure EV, to 'what if you carried a portable generator to recharge it as you go' and all the difficulties in properly charging and maintaining batteries in that sort of situation of a series hybrid, to 'So just exactly HOW do parallel hybrids work, and would it be feasible to DIY one?'

My concern was how do you mechanically combine two separate power sources of uneven and varying power into a single output?

I've seen things like the XR3 Hybrid (from the creator of the Tri Magnum) which uses an ICE to power the front wheels, and an electric motor for the rear. I guess that would work, but it seems a little awkward to me.

Then I had a bit of a brainwave: A differential, of course! (forehead slap)

Just like the diff on the back of a RWD car, only reversed.. attach an ICE where one wheel would be, an electric motor at the other, and now you're powering the drive shaft off two independent sources. Whats more, with the ICE turning at a fixed speed (eg: at its optimal efficiency), any difference in output power requirements is offset mechanically at the electric motor, meaning that if you're using less power than the drive shaft requires, the diff can 'freewheel' to an extent, diverting power back into the motor, effectively allowing direct regenerative braking and eventually for the full output of the ICE to be diverted straight to the motor and hence batteries while the vehicle is stationary.

Is that a feasible way to go about doing things? Seems like it would be a more efficient way of running than with all the mechanical/AC/DC/chemical conversions.. though I guess you run into problems with using a motor as a generator... Are there specific motors/controllers/etc that would best deal with that sort of regenerative braking setup?

Or is (most likely) my genius idea one someone who actually is a genius came up with decades ago and have since discovered all the problems with and moved on from?


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