# Nissan Leaf neutral gear?



## wjbitner (Apr 5, 2010)

GeorgeC said:


> What does the Nissan Leaf "neutral" actually do? It would appear that the motor is permanently connected to the drive train/differential, in which case how is the shifter "neutral" different to "drive"?
> 
> I am currently converting my 1982 Lotus Esprit S3 to electric using a Leaf motor/charger, but while I am developing the control electronics for the motor, I would like to be able to move the car and installed motor without turning the motor via the transaxle.


I'm not sure you have any choice. Turning the transaxle will turn the motor, assuming both wheels on the ground. It may be possible to turn the transaxle (with at least one wheel off the ground) and thru the differential, have the other wheel spin in the opposite direction without turning the motor. There is no 'neutral' in the sense of a manual/automatic transmission. I'm guessing that shifter neutral removes power for the inverter (or possibly tells it to not generate power). The motor is a permanent magnet motor, and power will be generated if the inverter is powered and the motor is spun. The early Leafs could charge the battery by getting a tow.


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## GeorgeC (Aug 4, 2020)

wjbitner said:


> I'm guessing that shifter neutral removes power for the inverter (or possibly tells it to not generate power).


Yes - that is what I assumed too, but can't really see the point of it.


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## wjbitner (Apr 5, 2010)

GeorgeC said:


> Yes - that is what I assumed too, but can't really see the point of it.


I'm assuming the point is to prevent overcharging of the batteries, either by too much current or letting the voltage get too high. Maybe to protect the inverter capacitors and such from too high a voltage. Maybe it simply makes sure no torque signals are sent to the motor. I'm guessing they had a reason, but who knows. Maybe to be more like the ICE machines we're all used too.


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## GeorgeC (Aug 4, 2020)

OK - thanks. I guess I'll have to disconnect one driveshaft to move it.


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## GeorgeC (Aug 4, 2020)

OK - my next question is how to put it "neutral" without the shifter/VCM. I assume there must be a CAN message to the inverter to do this?


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## kennybobby (Aug 10, 2012)

There is a locking pawl latch in the gearbox that is engaged when you go to Park position. If you can release the pawl, either mechanically or by energizing the actuator, then it will roll. Sorry i don't have the details of that circuit but might be able to look it up in the FSM. It can be found online and is quite handy for reference.

[edit: it is a motor driven actuator]


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## GeorgeC (Aug 4, 2020)

kennybobby said:


> There is a locking pawl latch in the gearbox that is engaged when you go to Park position. If you can release the pawl, either mechanically or by energizing the actuator, then it will roll. Sorry i don't have the details of that circuit but might be able to look it up in the FSM. It can be found online and is quite handy for reference.
> 
> [edit: it is a motor driven actuator]
> View attachment 120500


Thanks for the info - I have seen it online, but that actuator appears to only operate the parking brake - releasing it still leaves the transmission connected to the motor.


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## brian_ (Feb 7, 2017)

GeorgeC said:


> What does the Nissan Leaf "neutral" actually do?


It tells the controller/inverter to not power the motor (in forward or reverse), without engaging the parking pawl.



GeorgeC said:


> It would appear that the motor is permanently connected to the drive train/differential, in which case how is the shifter "neutral" different to "drive"?


Yes, the gearing connection is permanent. In Drive the controller/inverter can power the motor; in Neutral it does not. 



GeorgeC said:


> Yes - that is what I assumed too, but can't really see the point of it.


Neutral exists so that you can do exactly what you want to do, which is roll the car without power.



GeorgeC said:


> Thanks for the info - I have seen it online, but that actuator appears to only operate the parking brake - releasing it still leaves the transmission connected to the motor.


True. The information about the parking pawl and its actuator is just to help you ensure that you can freely roll the car, by getting it out of Park.



By the way, almost every production EV has a permanently connected single-ratio transmission like this, although not all have a mechanical parking feature.


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## GeorgeC (Aug 4, 2020)

Thanks to everyone for the useful information.

I still need to find out how to tell the inverter to go to neutral, though.


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## wjbitner (Apr 5, 2010)

GeorgeC said:


> Thanks to everyone for the useful information.
> 
> I still need to find out how to tell the inverter to go to neutral, though.


It may be as simple as commanding the motor to zero torque.


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## GeorgeC (Aug 4, 2020)

wjbitner said:


> It may be as simple as commanding the motor to zero torque.


I hope it's that simple, but I suspect there is a dedicated CAN command for neutral.


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## brian_ (Feb 7, 2017)

GeorgeC said:


> I hope it's that simple, but I suspect there is a dedicated CAN command for neutral.


Yes, but you don't need to get the controller into Neutral mode if it is producing zero torque... although the idea of glitch providing another torque command would make me nervous if I were pushing a powered car around the shop.


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## Dala (Jan 10, 2018)

To command the Leaf inverter to neutral (aka no creep), simply attack the NM demand message on the EV-CAN. Be aware that you need to modify the response message, otherwise you will trigger fault codes. Attach a CAN-bridge between the VCM and inverter, and go to town on the messages. MotorAmpTorqueRequest and MG_EffectiveTorque

More info here: Dala's Leaf buildthread (2015 Nissan Leaf) - Page 7 - Japtoys.net


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## GeorgeC (Aug 4, 2020)

I have come to the conclusion that "neutral" is just disconnecting power to the inverter.


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## brian_ (Feb 7, 2017)

GeorgeC said:


> I have come to the conclusion that "neutral" is just disconnecting power to the inverter.


If you turn to the motor with the inverter powered off, does it roll freely (great) or does it try to generate or "cog" (bad)?


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## GeorgeC (Aug 4, 2020)

brian_ said:


> If you turn to the motor with the inverter powered off, does it roll freely (great) or does it try to generate or "cog" (bad)?


Because of the reduction gearing, there is some resistance when trying to move the car.


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## brian_ (Feb 7, 2017)

GeorgeC said:


> Because of the reduction gearing, there is some resistance when trying to move the car.


Yes, there will be the significant flywheel effect of the motor: as you start it moving you're spinning the motor up, and when you let go the motor keeps it moving like any flywheel. It's like pushing a heavier vehicle: it doesn't take much more to keep it moving, but it's harder to get it going and to stop it. Without a mechanical neutral (and there definitely isn't one), there's no way around that. The issue isn't really the gearing, it's what the gearing is connected to.

If the motor is acting as a generator, there would be continuing drag or "cogging" (feeling like you're pushing past a series of bumps), in addition to the flywheel effect.


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## Duncan (Dec 8, 2008)

How about using a pair of these





Wheel Dollies 900Kg Pair (Set of 2)







www.savebarn.co.nz





Wheel dollies - about sixty pounds (sterling) a pair - and useful for all sorts of other things


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## JByrd (Oct 15, 2020)

GeorgeC said:


> What does the Nissan Leaf "neutral" actually do? It would appear that the motor is permanently connected to the drive train/differential, in which case how is the shifter "neutral" different to "drive"?
> 
> I am currently converting my 1982 Lotus Esprit S3 to electric using a Leaf motor/charger, but while I am developing the control electronics for the motor, I would like to be able to move the car and installed motor without turning the motor via the transaxle.


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## JByrd (Oct 15, 2020)

As a 2015 Leaf owner, I have observed that you can push the car forward or back by hand when it is in neutral. It is about as hard to push as an IC car (on a flat smooth garage floor). You have to have the motor "on" to keep it in N, as it automatically goes into P when you shut it off. The first time I drove it, I was surprised that it "creeps" ahead when you put it into drive, just like an automatic trans on an IC car. I assume the creeping and the existence of N is just so it behaves like cars we are used to. With a completely computer controlled motor, they can program it to behave however they want, so applying a bit of forward torque in D and no torque in N it is. It doesn't do regenerative braking unless you put it in the second D position, called B. I suspect if you towed it with the motor turned on and in B mode, it would charge the battery just like it would if you are rolling down a steep slope.
I have heard that the newer ones will come to a full stop when you take your foot off the accelerator, so my comments about creep may not apply to them.


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## brian_ (Feb 7, 2017)

A Leaf can regeneratively brake in "D", but "B" changes the logic and increases the amount of braking. "D" might not brake unless the brake pedal is pressed (I don't know) and in that case if it didn't creep then "D" would probably be as good as "N" for hand pushing.


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