[efeballi]

Hello all,

I'm Efe from Turkey, I'm new around here. Well if you disregard my long time lurking back in the days I had a Fluence EV. That poor thing learned to swim.

I wrote about this project of mine on a car forum for help regarding the mechanical side of things but that pretty much looks sorted now.

So, here's the idea.
My (Mk5 Golf platform) SEAT Altea is a FWD family car, and I'm thinking of buying the kit (subframe, diff, half shafts) to convert it to 4WD. Then, I'm thinking of installing a motor to the rear diff and have a parallel hybrid. At this stage I'm not considering any modification to the front half of the car.
The rear diff includes a Haldex coupling, basically a multiplate clutch capable of handling crazy amounts of torque. I'm planning to use this coupling when the battery is depleted, when I'm above the maximum speed the electric drive is capable of and when there's ESP intervention to make things easier for it.
I'm thinking of having a ~6 kWh battery pack, enough for about 15-20 km of driving which is 90% how the car's used. I'm not after a lot of power, 70 kph/45 mph would be enough as there's the engine for higher speeds.
I have a lot of experience with 16850 cells so I think maybe I can brew my own battery pack, to fit in the underboot area where you normally put your tools and things you carry all the time with the car. I'm open to suggestions on the battery pack, and one huge thing about it is not certain: VOLTAGE.

So, that brings me to the motor. As I said I don't need huge power, but I will probably need lots of torque as there's only the diff's reduction ratio between the motor and the wheels. The diff has a 1.6 reduction ratio. So, most electric motors fall out of my range as they have too high RPMs and too low torque for my work. A motor that will mount there directly would be AWESOME but so far I can't find it. The only other option would be to have a reduction gear between the motor and the diff.

I've never been in such a conversion so I'm a bit in the blind. I also have no idea what controller I'll use and how will I send throttle input to it. Integrating everything into the foot throttle sounds too hard. I think I'll go for two separate throttles for the ICE and electric.

Lastly, I'd LOVE to do engine off driving but then I'll need to substitute many engine-driven things with electric substitutes. Power steering, brake vacuum, lights and accessories, cooling/heating etc., in this order of importance. I've been googling for substitutes of these but found nothing. If this fails, I'll put the car on neutral and use the motor's own throttle to keep me going.

Thanks in advance,

 

[efeballi]

For the reduction thing, I found this:
http://www.electricmotorsport.com/ev-parts/power-transmission/gear-reducers/cast-iron-gear-reducer-5-1-c-face.html
This gives me a combined reduction ratio of 8:1.

I don't know of the torque rating of this reducer, I'll need to contact them for that.
With this out of the way, I'm eyeing the Azure AC24-LS motor with a DMOC445 controller. With the specs I'm seeing on the interwebz, the motor pushes 92 Nm, which means ~2300 N tractive force on the rear wheels, while allowing for some losses. With an all-up weight of ~1600 kg with all the batteries, this will be 1.4 m/s^2 of forward acceleration. Not bad, I guess?
I've also done a crude calculation in terms of hill starts, and it would take the motor ~21 seconds to reach 54 km/h on a 7% hill. This is a worst case scenario as I would normally use the ICE to start the car up hills. The only place where this capability would be necessary is during stop&go traffic up a hill. This is of specific concern to me as one of my main goals is to switch off the ICE in stop&go traffic, and believe me, Istanbul has a lot of'em.
For the battery, I'm hunting for Fluence ZE/Nissan Leaf battery packs from partouts/totaled cars but so far no luck. Another option is a Samsung ICR18650-HE2 battery pack, assembled to fill the underboot storage area(50L) and satisfy the minimum 288V requirement of the motor at 3.2 V/cell, which works out to be a 90S18P pack with a 0.7 volumetric packing factor, and 15 kWh if full capacity is used. But this entails LOTS OF painstaking work to assemble the battery pack, not to mention the pack costs ~$4500 if bought in bulk from NKON. I'm also in contact with my former employers to see if they are interested in selling me the Panasonic NCR18650B batteries we had laying around.

I'm not planning to use the full capacity of the battery, I'm doing my calculations over 50% of their rated capacity. With a CdA of 0.8 m^2 and a rolling resistance coefficient of 0.015, the car uses 8 kW of battery power at 60 km/h, considering motor and drivetrain losses. This equates to a range of 56 km, of course neglecting any accelerations. My guess will be that I will have around 30 km range all things considered, which is more than enough for inner-city work. Of course, the range depends on the final decision for the battery, $4500 is surely a whole lot for batteries and accounts for the single biggest expense for now, and I have not even accounted for the wiring and sensors to be added to the battery pack. Another reservation I have for the battery is safety in the event of a rear-end crash, lithium batteries burn spectacularly when punctured. I'm open for suggestions for the battery pack.

The integration of the electric drive to the rest of the car is minimal, as of now I'm thinking of having a separate throttle lever on the steering wheel to operate the motor. This is where I'll also command the regen, if I elect to implement it. Power accessories will be the only other thing, where I'm totally blind as of now.

The other small problems I'm currently considering is the operation of the Haldex clutch to disengage the electric drive for when the ICE is on or when there's a fault with the electric drive, and the need for gearbox oil circulation and cooling as the output shaft will be turning even when the gearbox is at neutral.

I've written a spreadsheet to calculate the 0-100 kph sprint time of the car with and without electric drive, and while corroborating the factory data of 9.8 sec with ICE only, I'm getting a 7.1 sec 0-100 time with both systems working at maximum.

The total costs involved look to be:

$500 AC24LS motor and DMOC445 controller
$500 5:1 reduction drive
$1200 rear subframe, differential and other bits&bobs to mechanically supply power to rear wheels
$4500(a lot!) battery pack
$500 charger
$500 labor, adapter parts and unforeseen costs

I'm really excited about this project now.

 

[brian_]

The other small problems I'm currently considering is the operation of the Haldex clutch to disengage the electric drive for when the ICE is on or when there's a fault with the electric drive...

Perhaps I've missed something, but I don't see a need for this clutch at all. There will presumably be a "kill switch" to remove all power from the controller, and once that's done the motor will freewheel, so any electronic or electrical failure is tolerable without a clutch. The mechanical portion of the electric drivetrain is simple, and so no clutch is needed for failures. Production hybrids don't include a clutch like this.

 

[brian_]

My (Mk5 Golf platform) SEAT Altea is a FWD family car, and I'm thinking of buying the kit (subframe, diff, half shafts) to convert it to 4WD.

I assume that it would be conversion like this:
Golf MK5 GTI DSG AWD Conversion
Correct?

It appears that the rear floor is raised in the AWD version, either eliminating the spare tire well and replacing with a temporary wheel & tire location sticking up above the trunk floor, or raising the spare enough to eliminate cargo space between the spare and the trunk floor.

I'm thinking of having a ~6 kWh battery pack...
I have a lot of experience with 16850 cells so I think maybe I can brew my own battery pack, to fit in the underboot area where you normally put your tools and things you carry all the time with the car.

Is that space really available, after the floor modification?

Also, with the motor ahead of the added final drive unit, there's the issue of space for a motor that the stock AWD doesn't have. This would normally be an issue for the fuel tank, but in the photo I found online the tank appears to entirely to the right-hand side. If the reduction box is used to offset the motor to the left side, this might work.

 

[efeballi]

Thanks for the replies brian. I'll try to go through all the points you mentioned:

The rear diff already comes with a clutch (google Haldex rear diff) and it would be a lot of work to remove it, so why not keep it and use it to good effect? It would also save wear for the motor.

The conversion is exactly like that, but this is the first time I'm seeing the modification of the underboot floorpan. Anyway, if there isn't enough space, I'll ditch the spare wheel.

As you probably know, there will be no driveshaft, and yes I was planning to shift the motor to the left by mounting the reducer rotated 90*.


Sent from my iPhone using Tapatalk

 

[brian_]

The rear diff already comes with a clutch (google Haldex rear diff) and it would be a lot of work to remove it, so why not keep it and use it to good effect? It would also save wear for the motor.

I can see leaving the clutch component of an integrated final-drive assembly, but you can probably get a final drive from another model which does not use the clutch. The photo that I posted is apparently from a conversion using one of these no-clutch units; I realize now that it is from a Nissan, but there may be a VW/Audi unit without the clutch; if not, the easiest approach is to keep the clutch.

If you do have the clutch, you need to keep it engaged, but you don't need to control it in any sophisticated way; it would be nice to avoid that wiring complication, and the small power consumption. It would make sense to open the clutch when the motor is completely turned off. There are aftermarket controllers for Haldex units which allow the factory AWD behaviour to me changed; one of these might give you the control that you need.

With a brushless motor, I don't see wear from spinning all the time as a concern. Do EV motor bearings and seals ever wear out?

 

[brian_]

The conversion is exactly like that, but this is the first time I'm seeing the modification of the underboot floorpan. Anyway, if there isn't enough space, I'll ditch the spare wheel.

The spare goes over the axle in these cars. With 2WD, the floor is as low as possible, limited by the suspension; with AWD, the floor is raised to make room under the front of the spare for the final drive unit and axles, leaving empty space under the floor behind the axle and final drive.

As you probably know, there will be no driveshaft, and yes I was planning to shift the motor to the left by mounting the reducer rotated 90*.

Reading about the conversion, it appears that the fuel tank is different, as well: the 2WD tank would presumably go across the car (instead of just one side), but would not be as tall. The AWD tank is designed to allow for the driveshaft, but would be needed to allow room for the motor.

 

[efeballi]

I've looked long and hard at other diffs to eliminate the need for a reducer gear, I've yet to see one that fits the subframe. If you happen to see a rear diff that doesn't have a clutch and fits, please let me know.

I'll try to make some sort of a switch to engage and disengage the clutch pack. There's a 12V oil pump and an actuator motor involved. The ideal system would engage the oil pump for just long enough to develop oil pressure then move the actuator to open or close the clutch pack. I think this is doable without using any controllers as I'll be commanding two very basic devices, but I'm not really sure. Perhaps two switches could be used, one to turn on the oil pump and one for the actuator.

And yes, I'll need to change the fuel tank to the AWD version but as of now I don't know if it will extend far enough forward to interfere with the motor and the reducer. I've looked into the boot floorpan and the spare wheel protrusion needs to be cut. Some applications have the entire floorpan replaced with a compatible one, some cut the spare wheel well and replace it with a flat plate. I suppose this cut would also be a nice place to get the battery-motor connection through. I'll try to keep the modifications and cuts to a minimum, so I'll go for the flat plate solution.

Another necessary modification is the exhaust, it needs to be rerouted through the AWD bits. I'm taking this as an opportunity for a better exhaust system. Before I get flamed, no, I won't de-cat or de-EGR it.

By the way, I was unaware of this entire floorpan thing, thanks for pointing that out

 

[brian_]

I've looked long and hard at other diffs to eliminate the need for a reducer gear, I've yet to see one that fits the subframe. If you happen to see a rear diff that doesn't have a clutch and fits, please let me know.

I'll certainly let you know, but it is highly unlikely that I'll find anything you haven't, since you've been looking.

While a suitable final drive without the Haldex diff might exist, I would not expect to find any final drive unit with a gear reduction ratio high enough to be suitable for typical motors. There's just no reason for them to exist, as no production vehicle with an engine would have a transmission output shaft speed as high as the upper operating speed of a typical motor.