One Pedal Driving

[ElBobo]

My Trophy LR wouldn’t accept One Pedal mode yesterday @ 80%. mind you it was very cold. Odd though!

Mine wouldnt accept OPD today and my battery was 78%. It was frezing outside this morning though. I tried again after driving around for a bit when my battery was at 77% (and warmer) and it worked.

 

[Mchooligan]

My Trophy LR wouldn’t accept One Pedal mode yesterday @ 80%. mind you it was very cold. Odd though!

I think I can now say that temperature is the critical factor as OPD only comes on after a period of driving/distance travelled. So if it's cold it will take time for OPD to become available. Will now see if pre-heating the battery has an effect.

 

[crunchy]

This is really strange. Why it isn't possible to switch it on at higher SOC or very cold weather? 1-pedal driving should use only brakes then and when SOC decreases it can gradually add recuperation (like in my Leaf). Leaf is using (very weak) recuperation even at 99 % SOC.

 

[Brettus]

It’s cheap for a reason

 

[crunchy]

The price cannot be the reason. Use weaker recuperation for higher SOC. There is nothing to add which is not already available (SW or HW). Are they any other cars having 1-pedal driving and not permitting 1-pedal driving at higher SOC?

 

[NLMGSAN]

Depends on what you call high. Today I Ieft with 90% charge and -6 degrees Celsius. OPD was instantly available....but it showed a reduced braking power. In fact, it could not come to halt completely.
This was gone after about 5 minutes driving in city environment.

I have a Trophy Extended Range. So a 77kWh battery. At 90% effectively there is a 7,8 kWh gap to 100% (I was told this 74,4 kWh).
Maybe there is an absolute amount of kWh that should be left over to charge in the battery.
If this is set to the same value for each type of battery, percentagewise OPD should become available at lower percentages with smaller batteries compared to biggest one. That would suggest for the 64 kWh that OPD kicks in around 87%. For the 51 kWh this would be around 85%.
The other thing is definitely temperature. I think it also influence regen/recharge speed. In low temperatures simply regenerates less. Hence, my car did not come to a full stop with OPD in the beginning of my trip.
To sum it up: I expect an absolute limitation of battery (minimum recharge capacity needed) and a relative one associated to recharge speed.
Of course, this is just my two cents...

 

[Brettus]

The price cannot be the reason. Use weaker recuperation for higher SOC. There is nothing to add which is not already available (SW or HW). Are they any other cars having 1-pedal driving and not permitting 1-pedal driving at higher SOC?

Apart from the ability to control the (physical) brakes with some tact. That might not be in its repertoire. I’d imagine it’d need sensor data interpretation to figure out rate of slowing and such as pads wear it can’t work on pedal distance or whatnot. With the motor it’s predictable, -12% is always that.
Just my guess anyway, not worth the R&D investment effort for those few edge cases.

Remember the Phase 1 didn’t even HAVE OPD, it’s a relatively new addition at this point.

 

[Mchooligan]

Depends on what you call high. Today I Ieft with 90% charge and -6 degrees Celsius. OPD was instantly available....but it showed a reduced braking power. In fact, it could not come to halt completely.
This was gone after about 5 minutes driving in city environment.

I have a Trophy Extended Range. So a 77kwh battery. At 90% effectively there is a 7,8 kwh gap to 100% (i was told this 74,4 kwh).
Maybe there is an absolute amount of KWH that should be left over to charge in the battery.
If this is set to the same value for each type of battery, percentagewise OPD should become available at lower percentages with smaller batteries compared to biggest one. That would suggest for the 64kwh that OPD kicks in around 87%. For the 51kwh this would be around 85%.
The other thing is definitely temperature. I think it also influence regen/recharge speed. In low temperatures simply regenerates less. Hence, my car did not come to a full stop with OPD in the beginning of my trip.
To sum it up: I expect an absolute limitation of battery (minimum recharge capacity needed) and a relative one associated to recharge speed.
Of course, this is just my two cents...

Our second car (quadricycle) is a Citroen Ami which I use once or twice a week. Temperature definitely affects it at both ends of the battery's capacity - and the speed limiter (max 28 mph) will allow a downhill speed of up to 45mph because battery braking is non-existant for the first few miles until battery soc drops. I imagine the same physics apply for a 51kWh battery as it does for a 5.5kWh one regardless of sophisticated battery management systems.

 

[NLMGSAN]

Our second car (quadricycle) is a Citroen Ami which I use once or twice a week. Temperature definitely affects it at both ends of the battery's capacity - and the speed limiter (max 28 mph) will allow a downhill speed of up to 45mph because battery braking is non-existant for the first few miles until battery soc drops. I imagine the same physics apply for a 51kwh battery as it does for a 5.5kwh one regardless of sophisticated battery management systems.

I almost thought you were joking...as this is the Ami I know...

 

[crunchy]

In low temperatures simply regenerates less. Hence, my car did not come to a full stop with OPD in the beginning of my trip.

A full stop has nothing to do with recuperation. You always need physical brakes for a full stop. So this already exists in the OPD. The level of recuperation depends on the SOC. It does now. Do you really believe that the maximum degree of recuperation is the same at 87 % SOC or 50 % SOC? I doubt it, because it also changes in my Leaf (at 100% only the physical brakes are used).

The fact that the OPD cannot be switched on before starting the vehicle is nonsense. This must be a bug or MG is not able to brake smoothly at lower values of recuperation and higher values of physical braking (which I doubt).

I ask again: is there any EV where the OPD function cannot be switched on when the SOC is high? I'm talking about the OPD functionality, not the level of recuperation.

 

[NLMGSAN]

It could be that my English is bad because it isn't my native language, but I did not write that max degree of gen is the same at all SOC levels. Nor can it be concluded from what I wrote.
OPD on the MG can work fully on the regen system, but not in case of an emergency stop. It is similar to the Tesla approach. Proof? My front brakes squeak when cold when OPD and regen are both off. However, if the OPD is on there is no squeak whatsoever when I drive off in the morning. You can see it continues to regen until it comes to a full stop (which isn't an emergency stop).

Some info about temp, soc levels and regen with Teslas (2022):
"Tesla recently started offering a feature where it blends in the friction brakes on accelerator lift to compensate if the battery can't accept the desired amount of energy from braking, as the amount of energy you can regenerate depends on a number of factors, from motor design, to battery charge and temperature."

 

[crunchy]

It was written that your car did not come to a full stop with OPD. But then it is not an OPD, because the OPD should replace the brakes for non-critical braking (OPD is a mix of regenerative and classic braking). If higher deceleration is required, the normal brake pedal should of course be used.

I would like to know if there are any other cars that have an OPD option and where it cannot be switched on when the SOC is high?

 

[NLMGSAN]

The Teslas do a full stop on regen. They used to offer different levels of regen (like MG). levels.Then the they switched to max regen only. See my quote explaining that Tesla also could not regen at certain soc levels. Now they offer a mix of classic brake an regen.
Unless you mean something else, the full stop on the MG can work on regen only (the front breaks do not squeak). But maybe others could confirm or deny?

There are many different varieties of regen with OPD. Also some manufacturers use regen with mechanical brakes (porsche and toyota).
Could it be that your Leave works differently?

 

[crunchy]

Let me rephrase the question. Can Tesla and MG stop on a downhill slope with one pedal (without touching the brakes)? The Leaf can.

I think Tesla should be able to do it too. If it only uses regen, it can't stop the car on a slope. Why is that the case? When it stops, the braking force is zero. Consequently, there is no braking force from regen. Every electric vehicle has to brake with ordinary brakes at very low speeds if it wants to stop.
Another option would be sending current through the motor to generate braking torque, but it would consume too much energy.

 

[NLMGSAN]

If the force to stop a car exceeds the ability of the regen system to bring the car to a stand still, you need to use the brakes. Whether it is an emergency braking (already said that) or a down hill situation.
If it does not exceed the limits of the regen system, I experience a full stop by regen in my MG. And, if it has stopped it used Auto Hold automatically to keep the car in place.
You do not have to believe me, of course.

 

[Corindikev]

I use OPD all the time. When charged to 100% and then trying to set OPD a screen message says it is unavailable. I have never worked out the percentage of battery when it is available. I just turn it on after a few km of travel but then charging at home it always works from 80%.

The maximum Regen %age is 25% in both Regen level 3 and OPD. Regen 3 is nowhere near as severe as OPD when slowing from 100 to 110kmh and the car will never come to a complete stop. In OPD the brakes are applied as well and the car comes to a complete stop. Obviously if you are doing 110kmh and are close to a corner you will need extra manual braking.

I have no issues with OPD.

 

[Coulomb]

I think Tesla should be able to do it too. If it only uses regen, it can't stop the car on a slope.

It depends if you allow a rather looser use of the term "regen", e.g. to mean torque only from the electric motor, not from the mechanical brakes. In that case, you can pull power out of the battery, and arrive at a torque that just balances gravity. At least Teslas can do that because they have induction motors (for most models?). It would be pretty easy to do; just request the torque from the motor controller and if the power happens to be negative, then so be it. Then it's not really regeneration, but it's not using the friction brakes, either.

I don't know why you'd bother wasting that battery power just to say you're not using friction brakes though. Friction brakes are very efficient at standstill.

 

[crunchy]

If it does not exceed the limits of the regen system, I experience a full stop by regen in my MG. And, if it has stopped it used Auto Hold automatically to keep the car in place.
You do not have to believe me, of course.

Of course I believe you, why shouldn't I? I was only talking about stopping the car only by regen, let's say on some mild slope. This is impossible, since braking torque by regen is zero at zero speed. This is physics. You need friction, whether it is called brake or Auto Hold. Of course, inducing the external current to the motor will do as well, but this is not regen.

It depends if you allow a rather looser use of the term "regen", e.g. to mean torque only from the electric motor, not from the mechanical brakes. In that case, you can pull power out of the battery, and arrive at a torque that just balances gravity. At least Teslas can do that because they have induction motors (for most models?).

In fact, you can also brake with other types of motor by drawing power from the battery. The induction motor is a bit more problematic than other motor types because you have to create a rotating magnetic field (in the stator) to induce current in the rotor which creates torque. I think I read a few years ago that Tesla replaced the induction motors with other motor types, but I'm not an expert on Tesla EVs.
Anyway, I would still like to know the answer to my original question: Is there another car that prevents you from turning on the OPD function when the conditions are not right? I know that the OPD function can be switched on in the Leaf, BMW i3 and TM3 with no restrictions on SOC or battery temperature. I suspect that the MG4 is the only car (or MG the only manufacturer) that does not allow this in some cases, and would like to confirm this in this thread.

I'm just afraid we'll be revolving around whether the regen is strong enough and the like. I suspect there are not many users on this forum who (also) own other EV(s).

I don't know why you'd bother wasting that battery power just to say you're not using friction brakes though. Friction brakes are very efficient at standstill.

I agree 100 %. I wrote that above (that it would consume too much energy).

 

[ok86]

Made a video for people who haven't used OPD before.

 

[Rolfe]

I merged two threads with the same title. A quick scan suggests this shouldn't result in scrambled conversations, blame me if it does!