MG ZS EV ACC fix for use of regen.

[francisco.shi]

It is so annoying when the cruise control uses the brakes to slow down.
I also want one pedal driving.
Oh well it was only a matter of time before it got too much to bear.


I have been given permission by the big boss to fix this annoying problem.

[francisco.shi]

I have been doing a bit of work decoding the inverter communication between the VCU and the motor controller.
Today I finally managed to spoof the torque command.
The first test I did was to half the torque command coming from the VCU. The test was successful and the car drove with half the power.

The next test I carried out was to double the regen braking torque. The result is that KERS level 6 is now available.

There are two CAN buses and the one going to the motor controller does nmot have the ACC or pedal position information.
I will need to order another set of connectors to be able to splice into the wiring harness without cutting wires unwrapping the wire harness.
So it will be a while before I get further.
Barring any stupid design decisions from MG engineers I believe regen on ACC and one pedal driving are within easy reach.

[Nagaman]

I’m assuming that the warranty will be voided ?

[francisco.shi]

Only if you don't unplug the add on board when you take it for warranty claims.
I am getting the connectors so it can be installed without modifying the car.

[FyKnight]

Wow that's fantastic Francisco! Well done!

KERS level 6 would be amazing.

Presumably the BMS would protect against this, but I'd be a little worried about not putting too many amps back into the pack when it is nearly full or a bit cold.

I've noticed that I can get up to 120A back into it when on the highway, but it needs the brake pedal to be lightly applied. If you could get that just by lifting off the accelerator that'd be perfect.

Where did you manage to get the connectors from? I've only tried plugging in to the OBD-II port so far...

[francisco.shi]

Wow that's fantastic Francisco! Well done!

KERS level 6 would be amazing.

Presumably the BMS would protect against this, but I'd be a little worried about not putting too many amps back into the pack when it is nearly full or a bit cold.

I've noticed that I can get up to 120A back into it when on the highway, but it needs the brake pedal to be lightly applied. If you could get that just by lifting off the accelerator that'd be perfect.

Where did you manage to get the connectors from? I've only tried plugging in to the OBD-II port so far...

When I modify the torque command I need to limit the torque so the regen power does not exceed 50kw which is the maximum that the car puts onto the battery during regen. So what happens is as the speed increases the available regen torque drops.
Around about 20kph or less I can apply the full torque of the motor without exceeding 50kw. The maximum regen torque the car applies (while slightly pressing the brake) is about 38% of full torque.
Here is a plot of the torque command.

Torque command graph.

20220916_222859.jpg (1.35 MiB) Viewed 1464 times

On the graph you can see the torque dropping as the speed increases and the power is kept constant. When I take my floor off the accelerator the torque drops and it goes negative. Then when I press the brake the regen torque increases slightly.
You can see the torque remains constant and the regen power drops.

So if you are doing say 100kph the regen will be very light and as the speed drops the regen will get stronger.
I got the one pedal driving like what I did on the Imiev working but there is some problem with the communication and the inverter trips randomly. I still haven't worked out what the problem is but I will find the problem sooner or later.

Here is a video of the board.

[EvMe]

Are you planning on selling these? I'd be down if it can do KERS 6 and acc using regen. I am getting a 2022 model though, but from what I have read it is the same BMS.

[francisco.shi]

I am planning on selling the controllers.
I have been having some problems with timing and missing messages which I have finally solved.
So far I have got one pedal driving working with twice the regen braking torque and removed the delays.
If you are in sports mode and under regen and you floor it there is a very annoying delay. I have removed that and the response is amazingly quick.
I also need to get the brake lights to come on.
Also the gauge in the right is controlled by the accelerator position and the RPM. So I will need to also fix that.
And lastly I have not managed to find the CAN message that has the cruise control state.
I recently got a BYD and will be selling the MG. At the moment it is a race against time to finish the project before I sell the car.
It is a shame as it is so much nicer to drive with one pedal.
The BYD will be next.

[francisco.shi]

One pedal regen braking test.

[francisco.shi]

The no regen under ACC problem has been solved.
I finally got it working.
Now I just need to tidy up a few things and make the final hardware.
Still lots of little things to tidy up but nothing difficult. Mostly tedious little things left to do.
I did a video but it is very blurry. I will try to get a better video done and will post it later.

[Billy2Hats]

~~~ The BYD will be next.

I believe the BYD uses regen when the brakes are first/lightly applied. So not an issue with ACC.

Different story if you still want one pedal driving!

[francisco.shi]

BYD uses regen under cruise control but has very little regen on the accelerator below 40kph.
Adding 1 pedal driving to the Atto3 will make it a much better car.

[francisco.shi]

Here is a video done by Jon Day on the MG update.

[Billy2Hats]

Congratulations, brilliant! Will be interesting to see the general improvement to the range.

Do you have any plans to do these mods commercially, for either the two MG models or Atto 3?

[Nagaman]

I’d simply like more of a trigger sensitive brake pedal cancellation of cc, instead of needing (what feels like) more than 3cm to activate regen. Our Tesla’s brake pedal is super sensitive. Either way one pedal driving is the ants pants for us.
My theory is that paddles and coasting are simply ways of pandering to the old entrenched loyal customers and, in particular, those scared of ‘losing control’.

[francisco.shi]

Congratulations, brilliant! Will be interesting to see the general improvement to the range.

Do you have any plans to do these mods commercially, for either the two MG models or Atto 3?

I want to make an aftermarket kit. I need to wait to the end of Chinese New year tonsee if I can get the connectors and the parts.
I am also looking for someone that can help to set it up as a business venture.
I am hoping that I can do the same for the Atto3 but I am not being very hopeful. I watched a video the other day about the Atto3 and it looks like BYD decided to be different and put the VCU and inverter in the same box. This means that it may not be possible to do this to the Atto3 without modifying the boards. But in will have to wait and see how it goes.

[francisco.shi]

I’d simply like more of a trigger sensitive brake pedal cancellation of cc, instead of needing (what feels like) more than 3cm to activate regen. Our Tesla’s brake pedal is super sensitive. Either way one pedal driving is the ants pants for us.
My theory is that paddles and coasting are simply ways of pandering to the old entrenched loyal customers and, in particular, those scared of ‘losing control’.

The way I do the one pedal mode is not the same as what Tesla does. You get far more control over the regen than you do in a Tesla and it is very easy to coast without changing settings.
The Tesla (and all other one pedal modes) have the regen drop as the car slows down. The closer the car gets to a stop the less braking force you get. With my method you get the full braking force all the way down to a stop. Because of this you can get considerably more braking force than with conventional methods.
If you watch the video you will notice the front suspension sagging from the weight transfer which doesn't happen on the Kona or the Teslas.
The regen braking is so effective and controllable that someone sitting in the car will think you are using the brakes.

[Nagaman]

The way I do the one pedal mode is not the same as what Tesla does. You get far more control over the regen than you do in a Tesla and it is very easy to coast without changing settings.
The Tesla (and all other one pedal modes) have the regen drop as the car slows down. The closer the car gets to a stop the less braking force you get. With my method you get the full braking force all the way down to a stop. Because of this you can get considerably more braking force than with conventional methods.
If you watch the video you will notice the front suspension sagging from the weight transfer which doesn't happen on the Kona or the Teslas.
The regen braking is so effective and controllable that someone sitting in the car will think you are using the brakes.

Our Tesla’s regen transition to full used to be abrupt to the point of potentially dangerous in traffic due to phantom braking occurring, particularly if/when someone was tailgating ……imagine a cement truck.
Around a year ago it was modified to gentle initially but increasing to max right down to stationary. It’s sweetness personified, not as startling as before. Of course you can infinitely vary it via modulation of the go pedal.

[francisco.shi]

The problem with the conventional way if doing one pedal is that the amount of regen will depend on the speed of the car and the point where the neutral point is changes with speed. The end result is that at low speed you have very little movement of the go pedal to control the regen force so it has to get less as the car slows down. My method us not dependant on the speed of the car and the neutral point point is always in the same place. This means that it is very easy to control the amount of regen regardless of the speed. It is also a linear relationship between torque and accelerator position. This makes it much easier to control.
As an example, if you are stopped and press the accelerator you will have to get to maybe 50% to get full torque. But if you are doing 100kph on the highway you will have to hold the accelerator to about 50% just to keep the car at constant speed.
In my method you get 50% of the travel to control regen always regardless of the speed of the car.
In the video I took my foot off completely to let the car stop as fast as it can. I could have controlled the accelerator to slow down slower.
It is difficult to understand until you drive it. Once you have a drive it is clear why it can brake so much harder and still be easier to drive smoothly.

[Nagaman]

I simply don’t feel I’m missing anything in the Tesla in one pedal mode.
Numerous unaddressed ADAS failures are another thing however.

[francisco.shi]

I simply don’t feel I’m missing anything in the Tesla in one pedal mode.
Numerous unaddressed ADAS failures are another thing however.

You don't feel like you are missing anything because you haven't tried a better system. My daughter has a Tesla and when I drive it I most certainly notice the problem.
The ADAS failures I think are much more difficult to fix. They have to be overly sensitive to pass the ANCAP tests.