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So, I have been a really big fan of ev's for a long time, and hope to get a BMW i3 some time in the future. In the mean time I drive a Prius that I love ( but really wish I got the plug in version).
I am also a big Subaru guy (on my 9th now), and a big fan of all wheel drive. I was super excited to see the teasers for the new e-AWD Prius coming, but when the details were made clear, I was less than impressed.
I have accepted the fact that my Prius will always be incredibly slow, and it is honestly not worth the time or money it would take to make it into the Ken Block style, hardcore eAWD rally car I really want.....
But it got me thinking. I have a 2004 VW Beetle that is my "weekend toy". I have considered everything from audi quattro to Corvette C5 chassis and V8 swap for my Beetle, but I think it would be really cool to do a diy electric axle on the back to make it selective awd/rwd/fwd..
What I am thinking is to possibly run a fwd transaxle with an electric motor on the rear axle, and power it with a battery pack in place of the rear seat. Have the rear axle independently controlled from the rest of the car.

Has anything like this been done before on a diy level? I saw the wheel hub motors that were debuted at SEMA this year, but that was more just a proof of concept exercise.
I am very mechanically capable. Been an auto tech for nearly 15 years, but minimal experience with high voltage transportation.

My goals for the project would be to have a car that is well balanced, with drive on both axles at speeds from 0mph to ~65mph.
Selective assist from the rear with maybe a dial to adjust how much power goes to the rear depending on conditions. (Range from free wheeling, to 100% torque to the diff). EV only range would be cool, but that might be limited due to complexities with running AC, power brakes, and other amenities normally handled by the ICE.
Regen on rear axle would be nice, but depends on budget and complexities.
I am still only in the dreaming/planning stage of the project, but am trying to gather as much info as I can to see if I can make this a reality.
 

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Should be no real problem - think about a Leaf motor/transmission - maybe suspension - in the back

Look up the old "Twinny Minis"
 

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Discussion Starter #3
I definitely need to do a lot more research. Are there aftermarket solutions to control oem motors? I like the idea of the Chevy Spark EV drivetrain since the torque is so high.
 

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I like the idea of the Chevy Spark EV drivetrain since the torque is so high.
If you are using the motor complete with the original transaxle for reduction gearing, the motor torque doesn't matter - the Spark has a high-torque motor, but runs it at lower speed through less gear reduction than a typical EV, so the end result is the same.

If you are using the motor without the original transaxle, and only have the moderate gear ratio of a typical rear-wheel-drive final drive (differential) available, then the Spark motor is attractive.
 

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I'm right here with you slow03 except I joined this forum to start researching the same idea on a Ram Promaster van. I'll be following your progress for sure.
 

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An AWD would be really the best of the best I think.
But I would put the power distribution like Audi does. 70/30 or 80/20
That is 70% on the rear tires and 30% of the power on the front.
Or 80% on the rear and 20% on the front. This would give you much better power distribution what you could actually put on the road. It really isn't fun to have your front wheels spinning all the time because the power is to much.
 

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An AWD would be really the best of the best I think.
But I would put the power distribution like Audi does. 70/30 or 80/20
That is 70% on the rear tires and 30% of the power on the front.
Or 80% on the rear and 20% on the front. This would give you much better power distribution what you could actually put on the road. It really isn't fun to have your front wheels spinning all the time because the power is to much.
In general a rear bias is good, but it is far from that simple.

The desired balance depends on the weight distribution of the vehicle (put more power where weight provides more traction), the varying shift in load to the rear tires due to acceleration, and whether the vehicle is understeering (so drive force should be shifted to the rear) or oversteering (so drive force should be shifted to the front).

A practical consideration in this case is that the vehicle is to be a hybrid, with electric-only drive to one axle. That is a well-proven design, used (for instance) by Toyota in the RAV4, Highlander, Lexus NX, and Lexus RX, by Honda in the Pilot and Acura MDX and RLX, by Volvo in the XC90, and in various more exotic performance vehicles (in all cases, the hybrid version of these vehicles). The problem is that the power transmission path through the electric drive (including the engine-driven generator and the motor) is much less efficient than the power transmission through the transaxle to the normally driven wheels. For good reason, none of these vehicles put any power through the electric-only axle unless power is being used from the battery, or it is needed for traction and stability. The shifting of power distribution as they go through mode changes can make their handling awkward.

The AWD vehicles that continually put a high proportion of power through the rear wheels are doing it mechanically, not electrically.

Of course, if the modification only adds a battery and a rear drive - without adding a motor-generator to the existing powertrain - there is no choice: any electric drive goes only to the rear, and the front to rear distribution is essentially random. That throws balance out the window.
 

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'I am very mechanically capable. Been an auto tech for nearly 15 years"

A good start, but do you have a machine shop at your disposal?

What's your budget?

How much range on battery only?

FWIW, your idea of a hybrid is nice, but is a nightmare (scares me and I've been writing embedded code since the Intel 8008...OK, not totally "scares" -- I have better things to do with my time) in terms of the software you'd need to either write, or make happy from a donor car if you don't use all its pieces.

I'd go with a single drive motor in the back, around 20-30HP, and do the math for about 30-50 miles of range. Whatever your local typical daily trips are. You have an ICE up front to get you further.

Also, get a regen capable controller so you can charge the batteries with the ICE through the road.

Have three modes: ICE, Electric, and ICE with charging and drive. The system gets simplified to sensing gas pedal, brake, and mode switch.

Your most simple option, IMO, and a great fit to your skillset, is to get a crashed VW Golf EV donor and do a swap.
 

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FWIW, your idea of a hybrid is nice, but is a nightmare (scares me and I've been writing embedded code since the Intel 8008...OK, not totally "scares" -- I have better things to do with my time) in terms of the software you'd need to either write, or make happy from a donor car if you don't use all its pieces.
I agree that effective control of any hybrid, but especially an AWD hybrid, is complex and not easy.

Also, get a regen capable controller so you can charge the batteries with the ICE through the road.
Regenerative braking is good, but through-the-road charging is very inefficient, due to losses in both driving and driven tires. This is still using gasoline to drive the car, just doing it badly. ;)

Your most simple option, IMO, and a great fit to your skillset, is to get a crashed VW Golf EV donor and do a swap.
Two problems with that:
  1. it would produce a battery-electric front-wheel-drive EV, not the desired hybrid AWD, so it's completely wrong for this project
  2. the motor and transaxle swap is straightforward, but the battery is not, because the eGolf floor is different from a regular Golf to accommodate the battery pack, and the Beetle does not have this major modification
.
 

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Two problems with that:
  1. it would produce a battery-electric front-wheel-drive EV, not the desired hybrid AWD, so it's completely wrong for this project
  2. the motor and transaxle swap is straightforward, but the battery is not, because the eGolf floor is different from a regular Golf to accommodate the battery pack, and the Beetle does not have this major modification
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Do you piss on every post or did I just get lucky in being assumed to be a perpetual motion idiot? Try and get your brain into the context of the poster instead of creating your own interpretation to elevate your own genius or, if that wasn't your motive, don't empty your bladder on a post you should try to make work by adding to it.

What I am thinking is to possibly run a fwd transaxle with an electric motor on the rear axle, and power it with a battery pack in place of the rear seat. Have the rear axle independently controlled from the rest of the car.
Picking up the shot down pieces of my posting from a genius who doesn't get it, YES you can do that.

The reason I suggested an electric VW Golf is that the Golf is sized right, all the pieces interwork, you have almost every piece you need from ONE donor car, and it's a no-brainer for your skillset to put the FWD subframe (I assume it has one) of the Golf into the back of the Bug if you fix the tie-rods, which I think is what YOU had in mind and needed validation for. Pull the right size and electrical configuration battery pack and mount it into the back seat area or under seats, or wherever you can package it other than underhood with the ICE of course.

As we know, the motor, gearbox, and diff are already assembled and figured out and there's no hacking on axles because I think the track on the two cars is close, if not identical. The computers, chargers (you can also use CHAdeMO network with this approach) harnesses are all there. Above all, you have everything you need harvested from one bent Golf electric vs spending years shopping for pieces and figuring out how to make everything work together. You also get to study the fine German engineering that went into the Golf, and then get the chance to do it right.

You'll get all electric, all ICE, operating modes, and the ability to get yourself out of a snowbank or mudhole with "AWD" with something as simple as a mode switch and a pot on the dash to bypass the electronic pedal when it's in use with the ICE. You can get clever and rig the one "gas" pedal to work with the ICE and with the electric mode but not a good idea to use them both in AWD mode, which is why the pot switchover.

There. I now posted this twice. How "efficient".
 

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The reason I suggested an electric VW Golf is that the Golf is sized right, all the pieces interwork, you have almost every piece you need from ONE donor car, and it's a no-brainer for your skillset to put the FWD subframe (I assume it has one) of the Golf into the back of the Bug if you fix the tie-rods, which I think is what YOU had in mind and needed validation for. Pull the right size and electrical configuration battery pack and mount it into the back seat area or under seats, or wherever you can package it other than underhood with the ICE of course.

As we know, the motor, gearbox, and diff are already assembled and figured out and there's no hacking on axles because I think the track on the two cars is close, if not identical. The computers, chargers (you can also use CHAdeMO network with this approach) harnesses are all there. Above all, you have everything you need harvested from one bent Golf electric vs spending years shopping for pieces and figuring out how to make everything work together. You also get to study the fine German engineering that went into the Golf, and then get the chance to do it right.
Sorry, when I read that you were proposing a "simple option" which would match the skill set of someone with mechanical experience (and no fabrication or bodywork experience mentioned), and described it as a "swap" (which would logically mean swapping what is in the Beetle for equivalent bits from the e-Golf), I incorrectly assumed that you mean, well, a swap.

Using the drive unit, battery, and supporting components from an EV donor in the back of the Beetle would, of course, meet the desired hybrid target. The components could come from nearly any production EV.

There is an advantage to using a coordinated set of components, but I doubt there's much advantage on the controls and electronics side of using VW bits. It's not as if the Beetle's accelerator pedal can be just plugged into the e-Golf controller, for instance, because the EV components need to be integrated with the gas engine components to make a useful hybrid.

Mechanically, it is good to roughly match track dimension, but other cars would be close, too. It would be nice to have one brand of replacement parts, and front and rear wheels of the same bolt pattern and hub fit. But more importantly, the mechanical work is not the difficult part when using a complete subframe and suspension: the work is then in reworking the structure of the back of the car to fit an entirely different design of suspension.
 
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