[johnnyboy666]

Hi,

I've just registered in the hope that I might be able to get a bit of advice on a project I've been thinking about.

The donor car will be a front engined, front wheel drive diesel Peugeot 205. It's already slightly eco-friendly as it can run on Veg oil. Approx weight 850KG

My plan is to remove the rear suspension beam and fabricate some mounts to allow me to fit a complete rear axle/suspension assembly from a rear wheel drive Jaguar S-type.

I will then connect an electric motor to the Jag rear end. I intend to mount it above the axle rather than in front of it to save space, and this will also allow me to use a chain or belt drive, using different sized cogs to get the required ratio.

I can then add a second alternator to the engine to charge the batteries as I drive.

I also have power points at work which I can use for free. My commute is around 15 miles

I effectively want to achieve a car that is capable of the following:

-running the engine and the electric motor at the same time for AWD (more grip and more power) -max 80mph

-running only the electric motor for economy - max 60mph

-running the engine (but not in gear) as a range extender for the electric motor - max 60mph



I've got a couple of questions, as I haven't seen many hybrid conversions like this, they mainly seem to be all electric.

Is it relatively straight forward to charge the battery packs from an alternator that will be putting out around 14V?

My budget doesn't extend to the likes of Netgear motors, and I'll want something cheap to prove the theory before I dig deep. With this in mind, would a forklift motor be up to the challenge?
I'd like to aim for around 60HP from the electric motor if thats attainable?

And is there any glaringly obvious reasons why this won't work?

Thanks in advance

John


P.s. I'm a part time mechanic, so the nuts and bolts don't bother me. I've never built an EV before though, so this will be steep learning curve.

 

[johnnyboy666]

Apologies, I've just realised I've posted this in the wrong section :/ rookie error!

 

[jwiger]

Welcome to the forum! Here's a couple of issues:

If you have a good engine and FWD system, you're better off just driving long distance with that like normal. Driving an alternator or generator to charge batteries, to drive an electric motor is going to find a lot of energy loss. Your gallons of diesel will get you farther down the road driving the front wheels directly.

It's possible to use the electric motor to assist with braking (regenerative braking) this is a great way to capture energy to use later vs. making heat with the brakes.

Most forklift motors are DC motors with brushes and commutators. These hate to be turned for long periods with out electrical current going through them. Think of flat towing an automatic with out the engine running, the lack of lubrication burns up parts of the tranny. So if you used a DC motor you would want to have a clutch to disengage it, or risk burning it up and hurting your diesel mileage as well. AC motors could free spin without hurting brushes/comms.

Lastly DC motor speed is directly related to the voltage you put into them. I'm pretty sure most fork lifts run more than 12 volts, so a second automotive style alternator won't make enough voltage to spin it very fast at all. The exact voltage you'll need depends on the motor you pick.

 

[johnnyboy666]

Hi, thanks for the input.

Just to clarify, I would have a high voltage battery bank for the electric motor, and charge it at work. The added alternator idea would be to top - up the charge so to speak.

That's a good point about free spinning, I Could probably work some sort of clutch or freewheel into the arrangement

 

[miscrms]

Almost anything is possible, but its always a tradeoff between cost, complexity and performance.

I would say there is definitely a reason you don't see many hybrid conversions. Its fairly easy to do, but its really hard to do well. Most straightforward approaches (like what you've proposed) have been tried for decades, and generally yield pretty disappointing results. The major gains seen in the best production hybrids come primarily from very careful optimization of both the drive train and control software. For example in the Prius, the coupling of the Atkinson(ish) engine which has very broad high efficiency operating regions, but very poor on demand torque with an electric motor that has excellent on demand torque. Couple with that software and an innovative transmission that can keep the engine operating near peak efficiency under a very broad range of operating conditions and you can achieve pretty impressive improvement in overall efficiency.

Adding 500+ pounds of motors, batteries, gearing etc to an existing vehicle without removing any weight or optimizing its engine to complement the electric drive is probably not a recipe for significant efficiency gains. An alternator is not going to cut it for supplying electric drive power to the drive motor in a series hybrid like fashion, you're going to need 10s of times more power than even a high output 100A alternator can provide. Burning diesel just to recharge the batteries is going to end up being a very inefficient use of fuel.

You really have to look at what you are trying to build and why.

If you want a highly efficient commuter, why not just build a budget BEV conversion with modest range and performance and keep your traditional vehicle for longer trips?

If you really need one vehicle that can do both, its very hard to beat a used production hybrid. If you want to take it a step further in efficiency, adding a PHEV capability to an existing hybrid is likely a much more feasible and affordable solution than hybridizing a traditional vehicle.

Best of luck,
Rob

 

[johnnyboy666]

I feel I may have mis-described my intentions slightly. Although efficiency would be an added bonus, it would not be the main aim of the project.

As mentioned previously, I have the ability to charge at work, and the diesel engine can run on veg oil (ranging from cheap, to free) and is very efficient at 55 - 60mpg.
The engine in question is from a car that weighs 300kg more than the car it is now in, and has a larger turbo coupled with an uprated fuel pump, which allows it to make nearly double the stock torque figures. With that in mind, the added weight of the electric motor and batteries would cause minimal issues.

The alternator idea is not to run the motor with the alternator, but i thought it could be a sort of trickle charger for the batteries. In the same way that you can use solar trickle chargers to charge 12v car batteries.

The main benefit for me would be the ability to drive 4 wheels rather than two. There is only so much power you can put through a FWD car before it causes issues, so having some power from the rear should help to balance this

Imagine it like the KERS sytem used in formula one cars; a performance assistance to an ICE car provided by an electric motor

 

[dougingraham]

The alternator idea is not to run the motor with the alternator, but i thought it could be a sort of trickle charger for the batteries. In the same way that you can use solar trickle chargers to charge 12v car batteries.

The difference between solar trickle and an alternator driven by the ICE is with solar the energy is coming from outside of the vehicle. With ICE you are stealing energy from driving the wheels directly, doing about a 50% efficient conversion to electricity (Alternators suck for efficiency) and then losing another 10% to the boost and charger controller. Then you take that energy and lose 10% in the motor controller and another 10-20% in the electric motor which is driving the wheels. Driving the wheels directly with this energy is the only way to eliminate the losses in the alternator and charger controller. If you do this the best it is possible to do then you barely come out ahead. This is why Hybrids are so difficult to do right.

If you want to recharge the battery and your electric drive has regen, why not just switch it over to regen. You willl have less losses because the motor is better at regen than an alternator and you don't have the weight of the extra alternator and charge controller. Most people do see that running your ICE to move the vehicle and then turning on regen to recharge the batteries is not going to work to extend your range because when you are regenning it feels like you are putting on the brakes. And they know you cant run the motor as a motor and a generator at the same time. It does one or the other. Adding another alternator to the mix obfuscates the issue.

AWD with an ICE on two wheels and Electric on the other two is a difficult thing to do well. Using Life batteries you can estimate the weight at about 8 lbs per mile of range plus 150 to 200 lbs for the motor and controller. And you still need a differential and possibly a transmission for another 200 to 250 lbs. Lets say you want 50 miles of all wheel drive range. That is going to increase the weight of the vehicle by 850 lbs. How about doing an experiment before you go any farther. Load up your vehicle with 850 lbs of sand bags and see how that affects your mileage and handling. A passive load like this will show you what the vehicle will feel like when the batteries are dead.

The big challenge with be making the systems work together.

 

[johnnyboy666]

If you consider with a standard AWD setup, you would be taking power from the one engine two power both front wheels and rear wheels anyway, so I don't see the ~1/4hp loss caused by the extra alternator a big concern. I would be looking at at least a 30% power loss using conventional methods of achieving AWD anyway.
It's not set in stone, I just thought it could be a potential help. The alternator in question would be 120amps @14v

If the motor I end up with is capable of regen, then that of course is an avenue I could look into.

The rear suspension assembly I plan on using is complete with diff, and is only around 40kgs heavier than the standard axle, so then there's just the weight of the motor and batteries to consider. I could potentially make the batteries removable for long distance driving with ICE only without so much extra weight.

 

[Duncan]

Hi Johnny

It's not "electric" but the best way to get the benefit of your bigger diesel motor is to stick it and it's gearbox in the back to drive the rear wheels
Like the old "Twinny Minis"
http://www.minimania.com/Specs_and_Pictures_of_Twin_Engined_Cooper_S_1134

 

[dougingraham]

so I don't see the ~1/4hp loss caused by the extra alternator a big concern. I would be looking at at least a 30% power loss using conventional methods of achieving AWD anyway.
It's not set in stone, I just thought it could be a potential help. The alternator in question would be 120amps @14v

Assuming you can pull 120 amps at 14 volts the load on the ICE will be (120amps*14volts*2)/746 = 4.5 horsepower. But it will do that power level for only a few minutes before it catches on fire. An alternator of that size can do maybe 30 to 40 amps continuous without failing. At a 40 amp load the drain on the ICE would be 1.5 HP. By the time this energy gets to the wheels on the electric motor side you will be losing about 10% to the charge controller, 10% to the motor controller, 20% to the motor, 10% to the transmission, 5% to the differential and your 1.5 HP load on the ICE gives you back about 0.4 HP in drive at the wheels.

Not having the alternator would save you 1.1 HP (about 821 watts) in load.

 

[SHtruck]

The main benefit for me would be the ability to drive 4 wheels rather than two. There is only so much power you can put through a FWD car before it causes issues, so having some power from the rear should help to balance this

Imagine it like the KERS sytem used in formula one cars; a performance assistance to an ICE car provided by an electric motor

So... how are you going to control the rear motor in AWD mode? Matching the motor speed to front will be difficult as there is that front transmission. Assuming the 4th gear is straight (1:1), it would also be the only gear which could be used easily with the e-motor (if skinny pedal control is used). With other gears, without exact control of the electrics, rear would push or pull, making it death trap on icy or slippery roads!!
Probably you would need to use the output speed of the transmission instead of skinny pedal to control the e-motor. Now that I think about it, it wouldn't be too hard to obtain. Just a simple speed sensor, like the one used on ABS-systems, mounted on either of the wheel hubs or axle shafts. But there's a catch; differential. Again we come to death trap, as one sensor would work only on straight road. Curving either direction, left or right, would make the e-motor control difficult, as the motor would push or pull, more or less the tighter the curve is. You could use two sensors, but then you would need some electronics to get average value out of them. Best bet would be to take the speed from the ring gear, that way the motor control would be consistent to either direction.

 

[Duncan]

Hi
Don't worry too much - or at all about synchronizing the two systems
Effectively the ground does that for you - just like an open differential as fitted to 99% of the cars on the road

The old twinny minis were built with different sized and tuned engines - they all still worked fine

There was even a Twinny moke - which was offered to the Canadian army - they turned it down because of insufficient ground clearance

With either an IC engine or a motor powering the rear it will simply push the car forwards until the speed gets high enough to reduce the torque to zero

 

[johnnyboy666]

@Duncan - that has already been done. Tried , tested and proved. It essentially requires the entire front end of another 205 to be welded into the back of another one. Infinitely more complicated than what I have planned.

Regarding differing engine speeds, that will be limited by tyre grip. A lot of AWD cars send more power to one end of the car than the other without problems. If I use a single gear ratio at the rear, it should give a lot of assistance in lower gears, with the ICE doing most of the work in higher gears.

@Dougingram - I don't think your calculations for hp needed for the alternator take into account that the fywheel is keeping momentum going, as are the roadwheels. And considering the alternator can be turned with one finger, I really can't see much of an issue there. For example, you don't use the maximum of the engines power to increase from 60mph to 61mph. You use momentum and a small amount of power.

 

[Duncan]

Hi Johnnyboy

I hate to burst your bubble but grafting another "front end" into the back of your car is actually a LOT simpler than what you are proposing

 

[johnnyboy666]

Ok, in the interest of progress, let's just pretend that the engine in the front of the car doesn't exist. Otherwise we'll end up going round in circles.

Duncan. The jag axle can be bolted in, grafting in a front end requires a vast amount of welding, plumbing in coolant, electrics, exhaust etc etc etc.

 

[bigmotherwhale]

if you are going to do this i suggest you use a Lexus 450H rear diff, it already has a 68 HP electric motor mounted inside it, and can be had for very little at the breakers.

 

[Karter2]

if you are going to do this i suggest you use a Lexus 450H rear diff, it already has a 68 HP electric motor mounted inside it, and can be had for very little at the breakers.

Sounds good, .....but has anyone actually managed to hack the controls to make it work yet ?
J666.. If that Jag diff/ axle is what I think it is (inboard discs , cast link arms, etc?). Then it's way over engineered/ over weight, for your plans .
Look for something like a Ford or Suziki IRS

 

[bigmotherwhale]

it does not have any controls integrated into it, it just has a 3 phase output and a resolver.

 

[johnnyboy666]

Thanks bigmotherwhale, that diff has definitely gained my attention. A cursory glance on ebay puts them at around £350 or thereabouts, which sounds pretty reasonable for 68hp.
Could you point me in the direction of any projects already using it?

@karter2 - The jag axle would be the version with outbound discs and it would be going on a diet to remove unnecessary weight. Calipers and discs for example will be swapped for tiny ones, possibly motorbike alloy calipers. One of the sets of springs/dampers can be removed, as they have 4 as standard and I only need two.

I can't think of anything Ford based off the top of my head that isn't either leaf - spring based, or not in a suitable subframe type format for simplified swapping.

Suzuki vitara perhaps could work, but may require turret - ing the rear of the car

 

[bigmotherwhale]

remember you will need to find a suitable controller to work with that motor