2 motors, 1 controller?

2623 Views 18 Replies 5 Participants Last post by pengyou, May 25, 2021

pengyou

Discussion Starter · May 16, 2021

I started to piggy back on another person's thread but then realized that I was starting to hijack. I would like to convert a light to medium awd vehicle - Samari, Subaru, etc but would like to use one motor up front and one motor in the back. Would this require two controllors or one? I am guessing if I had 2 controllers that I would have to have a computer with a load balancing algorithm to to keep the wheels in sync. If I used one controller and, for example, 2 x 72v and 600 amp motors, I would need a controller that could handle 72v and more than 1200 amps? additional info is appreciated. I can make nice things out of wood but am just learning about this electricity stuff.

1 - 19 of 19 Posts

brian_

· #2 · May 16, 2021

In old-style motors (brushed DC) you might get away with one controller, but it won't work well. With AC motors, you need a controller (inverter) for each motor... and to do it well, they do need to be coordinated.

Reactions: 1

pengyou

Discussion Starter · #3 · May 16, 2021

brian_ said:
In old-style motors (brushed DC) you might get away with one controller, but it won't work well. With AC motors, you need a controller (inverter) for each motor... and to do it well, they do need to be coordinated.

I am guessing that there is no off the shelf item called a dual controller controller?

It would probably be easier to find a wrecked leaf with dual motors and strip the parts from that.

Duncan

· #4 · May 16, 2021

You will want two controllers - but don't worry too much about keeping them coordinated! - the ground - the road - will do that for you

Think about it they can't be worse than simply running one motor driving one end and that is what 95% of all cars do

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brian_

· #5 · May 16, 2021

pengyou said:
I am guessing that there is no off the shelf item called a dual controller controller?

Yes, there are inverter/controller combinations which package two of them in one unit, to control two motor/generators in a hybrid transaxle... but they're not set up for front and rear motors, and they are set up for their specific application so they are not easy for someone to use with different motors. You wouldn't want them physically together in most cases, anyway, because the length of the 3-phase cables from controller to motor should be kept as short as practical.

pengyou said:
It would probably be easier to find a wrecked leaf with dual motors and strip the parts from that.

A Nissan Leaf doesn't have dual motors. There are AWD EVs with dual motors, but there is no AWD Leaf. In AWD EVs with front and rear motors, the controllers are separate and each is mounted attached to or near the corresponding motor.

brian_

· #6 · May 16, 2021

Duncan said:
You will want two controllers - but don't worry too much about keeping them coordinated! - the ground - the road - will do that for you

True, as long as no wheel slips. When one does, running two controllers from the same accelerator pedal signal (using that signal as a torque request) is essentially like running an open centre differential. No one uses an open centre differential in production any more without brake-based traction control.

pengyou

Discussion Starter · #7 · May 20, 2021

brian_ said:
Yes, there are inverter/controller combinations which package two of them in one unit, to control two motor/generators in a hybrid transaxle... but they're not set up for front and rear motors, and they are set up for their specific application so they are not easy for someone to use with different motors. You wouldn't want them physically together in most cases, anyway, because the length of the 3-phase cables from controller to motor should be kept as short as practical.

A Nissan Leaf doesn't have dual motors. There are AWD EVs with dual motors, but there is no AWD Leaf. In AWD EVs with front and rear motors, the controllers are separate and each is mounted attached to or near the corresponding motor.

www.caranddriver.com

Dual-Motor Nissan Leaf Prototype Has AWD, 500 LB-FT of Torque

We think the upcoming Ariya electric crossover will be the first production car to use this powertrain setup.

www.caranddriver.com

brian_

· #8 · May 20, 2021 (Edited)

pengyou said:
Dual-Motor Nissan Leaf Prototype Has AWD, 500 LB-FT of Torque

We think the upcoming Ariya electric crossover will be the first production car to use this powertrain setup.

www.caranddriver.com

Yes, an AWD with a drive unit at each axle can and will be built with Nissan parts, just as it can with any EV drive units, and has been by most EV manufacturers.

pengyou said:
It would probably be easier to find a wrecked leaf with dual motors and strip the parts from that.

You're not expecting to find that Nissan test mule or a 2022 Nissan Ariya in a wrecker's yard, are you? You can certainly build your own AWD with two Leaf units... but they will come out of the front ends of two Leafs. CanadaLT28 is doing that right now: VW LT doka with Nissan leaf

Duncan

· #9 · May 20, 2021

brian_ said:
True, as long as no wheel slips. When one does, running two controllers from the same accelerator pedal signal (using that signal as a torque request) is essentially like running an open centre differential. No one uses an open centre differential in production any more without brake-based traction control.

True - but for the 50 years before that 99% of cars managed quite OK with open diffs and no brake based traction control

brian_

· #10 · May 20, 2021

Duncan said:
True - but for the 50 years before that 99% of cars managed quite OK with open diffs and no brake based traction control

Sure, if your project goal is to use current technology to produce the performance of the last century, that's fine.

MattsAwesomeStuff

· #11 · May 21, 2021

Damien has a Prius Gen 3 inverter dual-motor replacement controller I believe. Actually, there are 2 different types, one is for two different motors which I think you can just parallel, one is two separate inverters either slaved or with independent control? I forget the details...

It's hard to remember which project is which, which things are developed or in development.

Prius Gen 3 Inverter Logic Board Dual Motor

Electric Vehicle (EV) conversions of BMW cars and related technologies.

evbmw.com

I don't think it's a big deal either way.

brian_

· #12 · May 21, 2021

MattsAwesomeStuff said:
Damien has a Prius Gen 3 inverter dual-motor replacement controller I believe. Actually, there are 2 different types, one is for two different motors which I think you can just parallel, one is two separate inverters either slaved or with independent control? I forget the details...

Since a Prius (or any power-split hybrid) transmission has two machines (motor-generators) in the same housing, it makes sense to put both inverters in one housing. To drive front and rear motors in a vehicle, sharing an inverter housing doesn't make sense.

piotrsko

· #13 · May 21, 2021

Back in the day an EVnetics Shiva would drive 2 motors Siamese in a dragster. But if one motor is just a wee bit different, the Shiva will fry the entire motor system. Disconnected motors are going to be unbalanced and try finding or feeding a Shiva.

MattsAwesomeStuff

· #14 · May 22, 2021

brian_ said:
To drive front and rear motors in a vehicle, sharing an inverter housing doesn't make sense.

How big of a difference are we talking here, to have longer wires?

I don't think it would be noticeable or significant.

brian_

· #15 · May 22, 2021

MattsAwesomeStuff said:
How big of a difference are we talking here, to have longer wires?

I don't think it would be noticeable or significant.

Perhaps it wouldn't matter much. I would suggest looking at how motor cables the length of the wheelbase of the car work in production vehicles... but no one does that. I suspect that they have their reasons.

MattsAwesomeStuff

· #16 · May 22, 2021

brian_ said:
Perhaps it wouldn't matter much. I would suggest looking at how motor cables the length of the wheelbase of the car work in production vehicles... but no one does that. I suspect that they have their reasons.

OEM vehicles don't, because there'd be no reason to. Save on wiring costs if nothing else.

Well, what about the hybrid Highlander AWD? It has its inverter up front of the vehicle, and then the drive motor is in the diff at the rear.

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brian_

· #17 · May 22, 2021

MattsAwesomeStuff said:
OEM vehicles don't, because there'd be no reason to.

The reason would be the same as with a conversion, and the same as for having both MG1 and MG2 inverters in a common housing.

MattsAwesomeStuff said:
Well, what about the hybrid Highlander AWD? It has its inverter up front of the vehicle, and then the drive motor is in the diff at the rear.
View attachment 122699

The diagram is from the emergency response manual for the Highlander, and it does indicate the three-phase motor power cables running to the same front-mounted housing as contains the other two inverters. Good find.

Even if this is an example of an OEM vehicle-length motor power cable (and it may just be a sloppy high-level schematic, since the difference won't matter to emergency response), every other AWD EV has the opposite; for example, a Mitsubishi Outlander PHEV has a separate rear inverter in the rear. The Highlander and other transverse-engine Toyota AWD hybrids use the rear motor as little as possible; it may be that the design compromise was to sacrifice operating efficiency and effectiveness for inverter component cost savings as a result.

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MattsAwesomeStuff

· #18 · May 22, 2021

brian_ said:
(and it may just be a sloppy high-level schematic, since the difference won't matter to emergency response)

I tried to get an image of the damned drivetrain, that was the best I could dig up. Everything else was clearly stylized flow diagrams that revealed nothing. Even searching for high voltage wiring diagram.

The Highlander and other transverse-engine Toyota AWD hybrids use the rear motor as little as possible; it may be that the design compromise was to sacrifice operating efficiency and effectiveness for inverter component cost savings as a result.

In fact, the 4th gen has moved the MGR inverter to the rear of the vehicle apparently.

Reactions: 1

pengyou

Discussion Starter · #19 · May 25, 2021

Thanks! I would be fibbing if I said that I understood all of what has been said, but my fingers are working fast and furiously on google! A Suzuki Samuri or Sidekick is not a very long car. Is it possible to put the batteries, inverter and controllers towards the middle of the vehicle and then have a motor installed on each differential? That would be awesome for driving, from the perspective of the center of gravity.

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