Motors still driving wheels while stationary?

[user 3409]

Ok I have another question.

On my car, when in EV mode, I come to a halt at the traffic lights with my foot on the brake. The display show that there is no energy flow to the wheels and as I know that I will be stopped for a time I apply the electric hand brake so I can release the foot brake and not dazzle the driver behind. At this point the display shows that the motors are trying to drive the wheels and to stop this I dab the brake again and the drive is stopped. The car noticeably 'hunkers down' as the power is removed and it remains stationary held by the hand brake.

My questions are: why does it try to drive the wheels with the brake on and surely there must either be a clutch wearing out while dragging or are the motors straining but not moving, which can't be good for them? Or is there a torque converter not wearing out but getting hot while dissipating the energy?

 

[anko]

No clutch or torque converter between E-motors and wheels. Just gears with fixed gearing. All you do is convert battery charge into heat in the E-motors. Still not preferable, as it eats range.

Why don't you use the P switch ion the 'gear lever' instead of the handbrake?

 

[greendwarf]

Or swipe right into Neutral or would you leave any other automatic car in drive with the handbrake on?

 

[anko]

Or swipe right into Neutral or would you leave any other automatic car in drive with the handbrake on?

Indeed, although Neutral is a bit confusing in this case as there is no clutch involved. P button has the same effect as Neutral, plus that it prevents the car from rolling away.

Good to be aware of: for a normal automatic car, there would be no difference between applying the footbrake or the handbrake. For the PHEV there is a difference, as Topradio has noticed.

 

[user 1877]

Ok I have another question.

On my car, when in EV mode, I come to a halt at the traffic lights with my foot on the brake. The display show that there is no energy flow to the wheels and as I know that I will be stopped for a time I apply the electric hand brake so I can release the foot brake and not dazzle the driver behind. At this point the display shows that the motors are trying to drive the wheels and to stop this I dab the brake again and the drive is stopped. The car noticeably 'hunkers down' as the power is removed and it remains stationary held by the hand brake.

My questions are: why does it try to drive the wheels with the brake on and surely there must either be a clutch wearing out while dragging or are the motors straining but not moving, which can't be good for them? Or is there a torque converter not wearing out but getting hot while dissipating the energy?

You say you apply the electric handbrake. To be precise, do you pull up the “P” switch or do you press down the “Auto Hold” button immediately behind the “P” switch. The AutoHold behaves as if you have your foot on the footbrake except that it Auto releases as soon as you press the accelerator. Unless of course the Juro Commercial doesn’t have this feature. The Juro car does.

 

[user 3409]

Thanks for all the reply's. It is a little confusing as there seems to be multiple ways to stop the car from moving.
I don't think you can compare the car directly with a 'normal' auto as it has a completely different philosophy to any I have driven before.
When I come to a stop using the brake the power is immediately removed from the wheels (unlike either a TC or DC auto). I then apply the electronic hand brake and power is re introduced to the wheels. Why would they do that? I have discovered that if I press the brake pedal again the power is then stopped. So this is what I do.
I don't use the auto hold as there are pretty much no hills where I drive and I either move my foot from the brake and straight on to the throttle or apply the electronic brake and when I accelerate it comes off automatically.
TBH I haven't yet found what the P is for, I have been known to push it when I park but I usually use the hand brake.
I feel that at least one of the three parking devices is superfluous, I just haven't decided which one.
I still can't get my head around the neutral. When I move the lever to the right without moving it forwards or back it doesn't usually select N but I have seen it do it.
My weekend toy car is a DC auto and it pretty much behaves as an old fashioned TC auto while the Juro is completely different and almost like re-learning how to drive.

 

[jaapv]

The footbrake will hold the car against the torque of the motors. However, if you depress it more firmly, the current to the motors will be switched off completely.
Using "P" introduces a mechanical block in the transmission.

 

[greendwarf]

The footbrake will hold the car against the torque of the motors. However, if you depress it more firmly, the current to the motors will be switched off completely.
Using "P" introduces a mechanical block in the transmission.

So don't use it whilst moving (although probably the car won't let you :lol: )

BTW for the OP you need to hold it to the right to engage N rather than flick it.

 

[anko]

I think it is quite simple ;-)

There are three ways of cutting power (other than tuning off the car):
- Pressing the brake pedal (firmly, as Jaapv added). This will prevent the car from moving.
- Switching to N mode, by moving the gear lever to the right and holding it there for a while. This will not prevent the car from moving.
- Switching to P mode, by pressing the P button on the gear lever. This will prevent the car from moving.

Using the handbrake will prevent the car from moving, but will not cut power. Unless combined with either one of three above.

Not sure about hill holder, though. I think it will cut power until you press the go pedal.

 

[jaapv]

The footbrake will hold the car against the torque of the motors. However, if you depress it more firmly, the current to the motors will be switched off completely.
Using "P" introduces a mechanical block in the transmission.

So don't use it whilst moving (although probably the car won't let you :lol: )

BTW for the OP you need to hold it to the right to engage N rather than flick it.

Actually, if you are moving slowly you can introduce quite an interesting (and scary) "clonk" by pressing "P"

 

[jaapv]

I think it is quite simple ;-)

There are three ways of cutting power (other than tuning off the car):
- Pressing the brake pedal (firmly, as Jaapv added). This will prevent the car from moving.
- Switching to N mode, by moving the gear lever to the right and holding it there for a while. This will not prevent the car from moving.
- Switching to P mode, by pressing the P button on the gear lever. This will prevent the car from moving.

Using the handbrake will prevent the car from moving, but will not cut power. Unless combined with either one of three above.

Not sure about hill holder, though. I think it will cut power until you press the go pedal.

I can confirm that the hill-holding feature will cut power, but works only for a couple of seconds.

 

[user 3409]

Great info folks.

I used the auto hold today and that does seem to cut all drive to the wheels. I noticed that it doesn't work by applying the brake (as you can hear the motor for that) but seems to be able to lock up the wheels by some other means.

Just to clarify, when I stop by pressing the brake all drive to the wheels is removed but when I then apply the electronic brake the motors want to drive the wheels against the brakes. I discovered that pressing the brake pedal again briefly removes the power and the car 'squats' as the torque is removed.

So many ways to operate a vehicle, I suppose it comes down to personal preference.

@greendwarf many thanks for that I will try holding the lever for longer to select neutral.

 

[user 1877]

I don't use the auto hold as there are pretty much no hills where I drive and I either move my foot from the brake and straight on to the throttle or apply the electronic brake and when I accelerate it comes off automatically..

I strongly recommend you try the autohold. It’s not just useful in hilly areas but whenever you are in an urban environment or stop start traffic. The great thing is you only have to apply it once per journey and it then continues to work every time you stop.

The first time you stop, keep your foot on the footbrake and apply autohold. A light appears on the dash to say it’s on. Then you can take your foot off the brake but the brakes remain applied until you press the accelerator. Thereafter, every time you stop, autohold will automatically re-apply itself and illuminate the dashboard indication so you can take your foot off the brake straight after coming to a complete stop.
It’s a great feature once you learn to trust it!!!

 

[user 3409]

Thanks @WAH64, I have started using auto hold and it works well. The only downside that I can see is that there is a very slight delay between pressing the accelerator and drive being taken up.
It really is slight and I almost wonder if I am imagining it. This doesn't seem to happen when using the electronic handbrake but then I am anticipating it and allowing time for the brake motor to deactivate.

Next project will be to investigate a stiffer suspension setup as at the moment it handles like a barge floating in custard but I'm not complaining as I knew it would be like that.

 

[jaapv]

The main handling problem is by the factory-fitted tyres.

 

[user 3409]

The main handling problem is by the factory-fitted tyres.

Hi, can you clarify that. Are you saying that if I change my tyres the car will no longer wallow in corners like a drunken sailor?

 

[jaapv]

Mine was vastly improved after I switched to Contis

 

[greendwarf]

The main handling problem is by the factory-fitted tyres.

Hi, can you clarify that. Are you saying that if I change my tyres the car will no longer wallow in corners like a drunken sailor?

Don't understand either comment - I have Toyos and the car handles better and faster through corners than any car I have ever owned in 50 years of driving, which I put down to the low centre of gravity due to the battery.

 

[jaapv]

I found the car a bit unstable on the straight ( I guess that translates as "wallow"), especially if the road was uneven, on Toyos, so I have been using A-brand tyres:- Conti Crosscontact UHP in summer + Hankook winter tyres and now Vredenstein Quattro 5- ever since and it stiffened the roadholding up considerably - comfort on short bumps is better too.

 

[greendwarf]

The OP referred to cornering in his 2nd post - hence my comment. I can't say I 've noticed problems in a straight line either - probably due to our roads and standard of driving in UK is so poor, I don't have time to. :lol: