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Discussion Starter · #1 ·
Hi,
I am a new member and this is my first post...please bear with me and go easy on my ambition here....
I want to convert my faithful, but beaten up, 2005 Volvo XC90 AWD SUV to electric. And I don't want to keep the transmission...want to connect directly to the drive shaft if I can. My aim is to have a range of minimum 100 miles (ideally 150) and highway capable. If I understand it right, this model has a curb weight o f about 4200 pounds. In connecting directly to the drive shaft, do I loose the AWD functionality of the car (if I am being illogical here, please bear with me). And also, would like to use the LiFexx batteries and not lead acid. Also, how does the car's computer system react to ripping off the transmission?
And what kind of budget am I staring at (rough ball park).

Thanks for your time.

Prism
 

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The XC90 has a transverse transaxle; it appears that you don't want to use that, and you want to connect a motor to only the shaft that goes to the rear. Yes, this would make it a rear-wheel-drive vehicle. Normally the XC90 drives only the front wheels, with the rear wheels getting some power when required; you would be putting all of the power to the rear wheels, all of the time. In a front-heavy vehicle, this doesn't seem like a good idea, but I suppose that it would be no worse than the many vehicles built this way for many years.

One detail to consider: the XC90 AWD system uses an electronically controlled and hydraulically actuated coupling on the front of the rear differential; you would need to remove that, or modify it to stay fully engaged all of the time. If you could fit a powerful enough motor in the location of the coupling, you could replace the coupling with the motor, so the shaft from front to rear would no longer be needed.
 

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There are two ways of implementing AWD in a front-engined vehicle:
1. Have a transfer case which takes input from the gearbox and has an output for each differential. This is what Landrovers use.
2. Build the front differential into the gearbox, connected to the output shaft. This is what Nissan's ATTESA drivetrain has used since 2000.

From what brian_ says, XC90 uses option 2.

For AWD in an gearboxless EV, you'll need a transfer case (or center differential, since front wheels travel further round corners than rear wheels), or one motor per differential.

I don't know of any EVs which have used the option 2 front differential without the rest of the gearbox.
 

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There are two ways of implementing AWD in a front-engined vehicle:
1. Have a transfer case which takes input from the gearbox and has an output for each differential. This is what Landrovers use.
2. Build the front differential into the gearbox, connected to the output shaft. This is what Nissan's ATTESA drivetrain has used since 2000.

From what brian_ says, XC90 uses option 2.
Yes, although the description of option 2 (which means that the transmission and front differential are combined into a transaxle) leaves out what makes it AWD.

For AWD in an gearboxless EV, you'll need a transfer case (or center differential, since front wheels travel further round corners than rear wheels), or one motor per differential.
You do need something to allow for the speed difference between front and rear. In many (probably most) current AWD systems that is not a centre differential, but instead is a clutch for one axle which slips to allow the speed difference. In the XC90 (as is the common practice for AWD vehicles which are derived from front wheel drive designs), the clutch is in the drive to the rear. In this case, it is the coupling mounted on the front of the rear differential.

I'm not suggesting this, but it would be physically possible to use one motor to drive both a front differential (which would need to be added) and the coupling input of the rear differential. This would be a control problem, because the XC90's control system certainly won't work without the engine and transaxle (without some substantial hacking), and it would not be trivial to build your own control computer for the rear drive coupling.

The few AWD EVs in production and shown as prototypes or concepts all (as far as I know) use separate front and rear motors - it's the only rational approach when not trying to re-use original components of an engine-driven vehicle.

I don't know of any EVs which have used the option 2 front differential without the rest of the gearbox.
I agree - it is not practical to use just the front differential (and rear drive components) of a transaxle, while removing the transmission part of the transaxle.
 

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Discussion Starter · #5 ·
Thanks Brian and Emyr for your insightful thoughts. Sorry didn't get back earlier as I was busy with other aspects. I am just beginning on this exercise and doing a bit of research to see if it is within me to carry out this project.

Thanks once again...would love to keep hearing yours and others thoughts if you folks think of something else.

Prism
 

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Hi everyone, thinking on running the same project. I have my xc90 still running very well but after thinking upgrading to a newer car, it would be better to make an electric conversion. What I am afraid, it is the compatibility of the AWD and the automatic transmission of the Volvo.
Just wondering if you got any advances with your conversion?
Thanks in advance
 

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If you want to retain AWD, you could use two Nissan Leaf motors - one for front and one for rear. Or two Prius motors (should be plenty of power with a pair of them).
 
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