[Jens Rekker]

Last year I converted a pickup / ute with a DC PbA set-up. Nothing special, vanilla variety conversion. Goes fine, quite heavy for driving on Dunedin hills, and limited range in the hills. Dunedin is also more than one battery charge away from anywhere else, and (you guessed it) it's ringed by steep hills. But you know how you hunger for what you don't have ...

My addictive EV day-dream is a plug-in split hybrid. By way of explanation, a split hybrid is a fossil fuel car diving one set of wheels augmented by an electric motor EV set-up driving the other axle. No need for planetary gearing or motor-generators such as in the Prius. Typically, the petrol engine drives the front wheels - normal front wheel drive style. The back wheels have the capability of being driven by an electric motor. Ideally, the motor would have Regenerative Braking feeding energy back into the battery pack to maximise the advantages of the combination.

What troubles me with pure EVs is the range limitation, acceleration limitation and hill-climbing power limitation. But, for 90% of the time in my EV I am coasting very efficiently around town during which I am entirely comfortable with pure EV. It's those times when I want shoot over to Mosgiel (which requires the climbing of not one but two 300 m hills, in each direction), or highway drive to the next city that I am completely stumped. You might say "you've just got to choose - ICE or EV". I could have two cars, or rent a car for the odd time that I need the range. But, what if I could have both in one car? Would that be too much to ask? Would it automatically have to involve enough cash to fund a moon mission or a superpower arms race? Or could it be done in a backyard conversion?

My musings have led me to the current idea:

• Subaru Justy or similar small All-Wheel-Drive hatchback
• Leave the petrol motor in place to drive the front wheels, disconnect the prop shaft to the rear diff
• Fit DC brushess hub motor on each wheel assembly, or
• Fit AC induction motor with direct drive differential and drive shaft out to each conventional wheel
• Fit motor controller(s) as appropriate
• Fit battery pack (probably need to be LiFePO4 for weight reasons)
• Set up dual accelerator systems for petrol and electric control

That configuration could give me an EV for around town driving sub-50km/hr, and a petrol option for steep hills, heavy acceleration or inter-city travel. I would have the zero-emissions on EV and very good petrol economy overall. It would be a compromise, naturally. I would probably need to lose the rear seat due to space and weight reasons. It would be an expensive captital cost for a small car, but then nothing about EV conversion makes economic sense quite yet.

Thinking about the details, the DC brushless hub motors with alloy rim and integrated brake discs are the most appealing. they are Chinese made and 10 kW capacity each wheel.

Brushless DC motors up to 72 V DC aren't too expensive, and rough pricing on the hub motors suggests similar pricing to a DC series motor to buy the two of them. The controllers are set up for Regenerative Braking. I think given the size of the Justy and sub-50km/hr city driving that the electric drive would give you most of your power requirements. Let's look at the opportunities -

• Use the electric drive for slow, low power driving
• Plug-in rechargeable for electric driving
• Able to slip into petrol driving on the fly
• Can combine the petrol and electric power capacity if needed
• Can use Regenerative Braking to recharge the batteries on long down-hills

I'm undecided whether a manual or automatic petrol transmission would work best. Manual would be simple and allow "crash starting" without using the starter motor. Automatic transmission would simplify the choice of gearing, and probably make driving the combined propulsion car easier.

I thought I'd share the day-dream and see what other folks thought of it.

[frederic]

Automatic transmissions do not like to be towed or pushed long distances without the engine running, because the automatic transmission cannot lubricate itself or generate hydraulic pressure without the engine running. This is why it's the common place for the manual to suggest not towing the vehicle with the drive wheels on the ground for long distances.

A manual transmission doesn't have this issue, so if you can tolerate the need to shift this would be your better option.

I like your idea a lot... with the Suby-type AWD vehicles they're actually FWD vehicles with the ability to drive the rear wheels, and if I'm not mistaken disconnecting the rear driveshaft entirely doesn't effect how the front wheels perform. If that is the case, you can then drive the rear axle directly with an electric motor, maybe with gearing or not, that you'd have to figure out of course.

I don't know if Suby's have hydraulic clutches or mechanical (cable or lever) clutches, but if it's hydraulic you can hold the pedal to the floor by inserting a "line lock" often used for drag racing applications. It's sometimes called a brake lock. Basically it's a hydraulic valve that if you flip a lever it prevents the hydraulic fluid from releasing when you take your foot off the brake pedal, so you can "stand" on the brakes without using your feet. It's a drag racing thing ;-) But one in your clutch line might be very useful because then while in EV mode you don't have to hold the clutch pedal down.

If it's mechanical, you'll have to devise something to hold it down of course.

I like your idea a lot actually... be green when you can and use gasoline when necessary. A friend of mine is building a hybrid Dodge Crewcab and where it's different than your idea (other than the starting vehicle is twice the size or more) is that it's getting a FWD Honda engine that will be driving a large generator, which can backfill the batteries. His first run at the math indicated that it will extend his range quite a bit, though he'll have to burn gasoline on a regular basis. He envisions a 30 MPG payback, far above the 8-9 that truck gets now.

[Jens Rekker]

Hi Federic
I tend to agree that manual transmission is simplest and therefore probably best. I hadn't thought about the inadvisability of electric driving with the petrol engine not running for an auto transmission. My ute has a standard manual box (transaxle to you) that changes easily with the DC motor. I expect that slipping the petrol engine transmission into neutral is going to be easy using a stab at the clutch. Might need a 'kill switch' like on a dirt bike to stop the petrol engine running in neutral. Wouldn't want to turn off at the ignition switch or you'd kill your accessory circuits that are definitely still needed!

When you want to fire up the ICE again on the fly, it might be as simple as slipping the box back into the appropriate gear and popping the clutch for a crash start.

[Renny_D]

I've been thinking about this for a long time but for a slightly different reason. I have three kids and their friends and the groceries and the gardening and the boat etc etc - you get my drift. We use a minivan for this - a Pontiac Montana. Their was an awd version available that hooks up to the same mounts as the standard two wheel drive - though I think a rearend out of alot of different cars could be adapted. I want the ability to lug around lots of people and the boat but use an electric to gain mileage or power as needed. I think an automatic would be ideal. I would have a varialble cable linkage made so that I can choose how much power I draw from either the electric motor or the ICE or combination. I would always have the ICE idling to run all the accessories - the transmission would just think you were always coasting down a big hill and shift up through the gears when choosing the electric as the prime mover. I am thinking of doing this on a dodge caravan as those can be had almost free and are really simple. I just seems like you can get the best of both worlds with a parallel hybrid set up like this. I know there would be lots of fabrication hurdles but I think it could be done and done well for relatively cheap. I would love to hear other peoples thoughts.

Thanks
Renny

[John]

I have wondered about a Nissan Cube as they made a version with electric 4WD. That is with a conventional FWD unit up front and an electric drive rear axle. I don't know if it would work but it might be worth looking into.

There was a guy who used to frequent this forum (Sharky I think) who built himself a pusher trailer out of the front half of a VW Golf. When he went on long trips in his EV he just hooked it up to his pusher trailer started it and put it in drive and away he went. He had it rigged with servo control of the throttle so he could control how much push it gave. This would save him carrying redundant weight when he didn't need it as the energy use of a vehicle is closely linked to its weight. You can read about it here http://www.mrsharkey.com/pusher.htm

[Jens Rekker]

Hi John. I've been a big admirer of Sharkey's pusher set-up. It has all the elements of a split hybrid if you think about it; the fuel power for hills and long range (over Santiam Pass to John Day is a feat in itself!), the ability to regeneratively charge the EV battery pack (thru a SepEx DC motor and controller), and the ability to intelligently switch between the fuels for optimum efficiency and convenience. In the case of the pusher, you even got to uncouple the weight of the pusher and leave it behind when pure EV driving is feasible.

One of the biggest challenges with a split hybrid would in fact be weight. With an EV conversion you get to ditch all of that engine, radiator, exhaust system and fuel tank weight. Not in the case of a hybrid! It means the electrical side of your hybrid needs to go on a crash diet to stay within GVM limits of weight. I suspect that means the batteries are not going to be lead acid. Lithium also allows those higher recharging currents if Regenerative Braking is included as well. The other way of dealing with weight is choosing a high GVM vehicle such as a pickup / ute. In Australasia I think one of the old Subaru Brumbies or a newer Proton Jumbuck would be the way to go as a donor ute.

[John]

Stumbled across this today. http://media.origin.popularmechanics...nts/ecomuscle/

[Duncan]

Hi Jens,
I like the pusher trailer
- nice and simple and you can leave it at home when you don't need it.

The VW was a diesel with automatic, not sure you need that you should be able to get away with a manual and some sort of solenoid to kick it into (or out of) gear then a hand throttle.

If you didn't need as much range a trailer with another battery pack could do it for Mosgiel but probably not much further

I like trailers - they convert my old station wagon into a large comfortable pickup whenever I need one.