Speak EV - Electric Car Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
After 500 miles I have encountered some issues.

The car does not appear to use regen when using cruise control, whether its slowing due to adaptive or using the manual lever. Has anyone else noticed this? Seems odd it would only use the brakes.

Every now and then when I cancel the cruise with the stalk, I get a BONG! and a warning I cancelled it. Very irritating, any ideas why it only does it sometimes, would almost be better if it did it every time I cancelled, as the randomness makes me jump every time it happens. As aside to this it also has a mind of its own when setting cruise, sometimes it switches to the adaptive screen on the dash, sometimes it does not. Have not seen any pattern either.

The speed limit control also keeps turning itself on, and again it's random. If I turn it off, I want it to stay off.

Again, randomly, the time keeps switching from 24hr to 12hr clock. Very irritating...

All very minor but irritating much the same.
 

·
Registered
Joined
·
235 Posts
The no regeneration in cruise is well known. As for the rest, sounds like a glitchy flash on the ECU. Take it back to the dealer for a refresh.
 

·
Registered
Joined
·
276 Posts

  1. Do we know why there is no regen on cruise?
  2. The control software for this is provided by Bosch. I guess it depends on the specification they gave Bosch, or what software they purchased if it was "off the shelf".
The manual does mention the use of the brakes to slow the car when ACC is active. Will see if I can find the section where it is mentioned.
 

·
Registered
MG EZS 2020
Joined
·
4,261 Posts

·
Registered
Joined
·
19 Posts
It’s a shame as this defeats the point of having the feature. The one time I’d use it is on long trips which is the occasion I need the longest range.

Guess it’s something that will be sorted in future as standard on all EVs but there is no guarantee the ZS will ever get it.
 

·
Registered
Joined
·
843 Posts
It’s a shame as this defeats the point of having the feature. The one time I’d use it is on long trips which is the occasion I need the longest range.

Guess it’s something that will be sorted in future as standard on all EVs but there is no guarantee the ZS will ever get it.
Its not such a big deal - the effective loss of range can be estimated by simple comparison of lost kinetic energy when slowing in ACC mode.
As an example:
ACC cruising at 60 mph, slowing to 50 mph under ACC control, occurring 10 times in an hour.
Total ACC braking energy loss in the hour is about 1869 kJ (for 1700 kg vehicle mass) - this is equivalent to about 0.5 kWh.
For about 3 miles per kWh battery consumption, the lost ACC energy for the '10 occurences' scenario amounts to less than 1.5 miles, even at 100 % efficiency of the overall energy transfer process involving regen action / battery charging inverter and then back into the motor via another inverter process. In reality, possibly less than 1 mile of range 'loss'.
 

·
Registered
Joined
·
678 Posts
Its not such a big deal - the effective loss of range can be estimated by simple comparison of lost kinetic energy when slowing in ACC mode.
As an example:
ACC cruising at 60 mph, slowing to 50 mph under ACC control, occurring 10 times in an hour.
Total ACC braking energy loss in the hour is about 1869 kJ (for 1700 kg vehicle mass) - this is equivalent to about 0.5 kWh.
For about 3 miles per kWh battery consumption, the lost ACC energy for the '10 occurences' scenario amounts to less than 1.5 miles, even at 100 % efficiency of the overall energy transfer process involving regen action / battery charging inverter and then back into the motor via another inverter process. In reality, possibly less than 1 mile of range 'loss'.
I make your example 1.85kWh. In practice, on busy motorways it seems to intervene frequently (sometimes just trimming one mph and while still applying traction power, which is a complete waste of brake disc). You have to listen carefully, but it's like they have taken ICE ACC logic and applied it unchanged. It does the same on curving roads where it brakes while going round bends with no other cars around, which I have never known in any car.

The conversion efficiency one way of a modern battery/converter/motor chain should be c. 90%. You still have the losses when you draw power (whether it is previously regenerated or "new"), so you can't net that off as a "saving."

So even in your example, the effective energy loss is 5.1kWh per full charge (60mph @4mpkWh), or more than 10% loss of range. In practice on a busy or winding road I suspect it is worse.
 

·
Registered
Joined
·
276 Posts
The I-Pace records and displays energy recovered by regen during a trip.

On a 300 mile journey in the I-Pace, mainly MWay and A-Road, approx 10kWh of energy was regenerated.

If the lighter and less powerful MG ZS EV regenerated 50% of that, it would still be around 5kWh. That adds significantly to range. It's also a lot of energy wasted in friction braking.

The MG ZS EV is the only EV that I have owned that does not use regen during ACC operation. I was not aware that this was the case when I purchased the car - pretty sure the dealer would not have known either.

It does mean that when I want to get maximum range on longer journeys that ACC cannot be used.
 

·
Registered
Joined
·
19 Posts
Yes not sure where the 10 times an hour comes from, I rarely manage 10 times in 5 minutes with how busy the roads are when I go anywhere. Generally I’d use it in fixed speed area which means people often break as cars switch lanes.

I can see if you were travelling at night on an empty motorway it would make very little difference.
 

·
Registered
Joined
·
843 Posts
That's a bit of a cryptic post. Are you agreeing or disagreeing with the numbers?

E=0.5 m v^2

Mass in kg, velocity in metres per second squared.
Agree with formula...
These are the numbers I get :
At 60 mph, ie 26.8 m/s - the KE of a car with mass 1700 kg is 611. 53 kJ
At 50 mph, ie 22.4 m/s, the KE is 424.67 kJ.
The difference of KE when slowing from 60 to 50 mph is 186.86 kJ.
The equivalent kWh energy value is 186.86/3600 = 0.05 kWh

The 10 times occurences per hour is just an arbitrary example.
 

·
Registered
Joined
·
678 Posts
Agree with formula...
These are the numbers I get :
At 60 mph, ie 26.8 m/s - the KE of a car with mass 1700 kg is 611. 53 kJ
At 50 mph, ie 22.4 m/s, the KE is 424.67 kJ.
The difference of KE when slowing from 60 to 50 mph is 186.86 kJ.
The equivalent kWh energy value is 186.86/3600 = 0.05 kWh

The 10 times occurences per hour is just an arbitrary example.
Agree with your workings... I hadn't converted kJ back to kWh
 

·
Registered
Joined
·
843 Posts
Agree with your workings... I hadn't converted kJ back to kWh
So now that you agree with my calculation method, and comparing this result with your previous result, yours was greater by a factor of 3.7, consequently your previous estimate of energy loss of 5.1 kWh on a full charge should be reduced to 1.4 kWh...
 

·
Registered
Joined
·
678 Posts
Yes, for ten interventions in an hour. I can experience that in a few minutes on a busy or winding road.

I'll reset the counter in the Leaf, however it won't give a full picture as the Leaf doesn't seem to be so "jumpy", it's like the MG is driving looking only a short distance ahead.
 
1 - 18 of 18 Posts
Top