manual_tranny said:
I have a fantasy... that somehow electric drive could be hooked up to the rear wheels, and that the parking brake could be fitted to work as a regenerative braking command for the motor(s), that the electricity would be quickly and efficiently contained in two car-battery-sized ultracapacitor banks that could push as much power as the electric motor(s) could safely take. I imagine the hardest part would be engineering the part that would work as a regenerative brake and a centrifugal clutch for the rear wheels, while the second hardest design would be rear axles to centrifugal clutch. Control mechanisms would be available and since I wouldn't care what the prototype looked like, only a few parts and some fabrication would be expensive. I would be happy if my fully-charged ultra-capacitors had only 400-800ft of acceleration available, they would mostly function as a brake saving and fuel saving device, that as a side benefit, would allow manual control of fwd, rwd, and 4wd.
This sort of thing would be really handy when it came to getting up slippery slopes, getting un-stuck in deep snow, eliminating front brake wear (depending on driver use of rear motor as brake), and hybrid drive system without a computer telling you how to use it, how good you are at driving it, etc. The weight over the rear axles would increase, but having available drive back there would help things.
Hey ManualT: I just found this thread last night. I have been slowly working toward a lifted Jetta also.
I happen to be in the camp that off roading a VW is a terrible idea. But I am also a Jeep guy (and strongly disagree with your opinion on Jeep reliability, mine have been pretty bulletproof, but that's another discussion!) and I also understand having to work with what you have.
Specifically toward your electric AWD system. That's ironically on my list of to-dos. I work at a robotics company so I have a pretty reasonable idea about the workings of electric motors and the like. I also happen to have an Audi A4 so I have a vague idea how VW does their AWD bits, and as a Jeep guy so I have a penchant to f* with things.
My plan is to drop the rear end of a TT into my Jetta. It SHOULD bolt in pretty easily. Should. Plus I'll get to keep the same wheels and I think the brakes will get slightly larger in the rear. I run GTI bits now, but they are the same, just red (in the rear). For the record, it's never, ever a good idea to shrink your brakes. I'd stick with the 15" wheels and if you want to run bigger rubber, drop a spacer on and space the wheel out a bit to fit the larger rubber. I found my stock brakes adequate. I put on a set of GTI brakes, and measurably they are not that much bigger, but the stopping improvement was pretty serious. Brakes are more than just about 1 time clamping power. Especially don't forget all the extra stuff/weight and what not you have added to your car (coolers, racks, people, whatever).
As to the motor. That's a tough call, there is a lot of suitable stuff on the market and in junkyards. That's on you.
Batteries. No capacitors. That's not what you want. You WANT good old fashioned Lead Acid batteries. They'll be bulky and heavy but you can get better/smaller batteries if you so desire. Optimas, Braille whoemever makes nice lightweight batteries for a price. You don't want capacitors.
You have WILDLY over thought the regen. An electric motor does 2 things. It takes power and causes the armature to spin, or you spin the armature and the motor generates electricity. (yes, very simplified, but basically true) If you're smart, you'll spend the money on a GOOD controller for the motor. You'll then have a throttle which you can vary the power applied and the controller will automagically recharge the batteries for you. And you're done. Ta-daa.
If you want to be even simplier.. you can hook up a contactor, it's like a relay but works in the exact opposite. You turn it on and power is dumped to the motor, when the power is depleted from the batteries, the motors turn (from the wheels) and charge the batteries back up. Or you can slightly modify the system so the batteries are charged when.. blah blah blah, it's too much to type but pretty simple.
Point is, the hardest part is getting and fitting the rear part of the AWD system. But, everything you need is on a shelf somewhere waiting for you to pick it.