Modify Alternator Output Voltage
 

Alternator Secrets

That is a really interesting article on how to make an alternator output anything from 5VDC to 120VAC. So if anyone is thinking of making a hybrid setup like I was planning. Using electric drive as well as keeping the gas engine, one of the circuits described in that article lists how to make your own voltage regulator. So you can charge your 72V or whatever battery bank using the existing alternator.

One possibility is to periodically run the gas engine at an ideal speed to charge the batteries as efficiently as possible and drive on electric only so it acts as a serial hybrid. I am not sure if it would actually get you better mileage but once the alt is modified then it won't be hard to do a few experiments on what gives the best mileage overall. An alternator that can charge 12V as well as the higher voltage at the flip of a switch would give a lot more flexibility to what you can do.

very interesting. if i ever got something going i was just going to make a bracket and run a second alternator, as my aspire has no power steering. plenty of room. additional loss even if it was 5+mpg would definately be overcome by the ability to shut off ice and use electric, or even idle-2000rpm w/no load on drivetrain.

Using a gas engine to first charge a battery and then use the battery to drive the car is a lost cause. There are too many losses in the "loop". Actually more efficient to drive the car directly.

What you are missing is...

A small, highly efficient (efficiency above/before HP/torque) engine, too small to provide even a moderate level of acceleration on a FLAT roadbed. Now you use the engine, when no acceleration is required, to charge/recharge the battery. Then when you need to accelerate you throw the switch to bring the battery power online in parrallel with the gas engine and now you can accelerate, even "rapidly".

Guess what, add an e/CVT so the engine RPM can be independent of roadspeed during battery charge periods and now you have a Prius.