Guess-o-meter calculations. What is your true range and how much you should trust the car's Algo.

fshuk1 said:
Still sounds like you should be getting 4. The car's sweet spot is 40m/h stretches. May be ECO mode would help you as it just slows acceleration, which is the main culprit if you like your speed.
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I'm an engineer so should be able to work this out, but feeling tired and thick...

Does harder acceleration use more battery?? If we need to get from 0 to 60 for a 20 mile cruise on a dual carriageway with no stops, then DOES fast acceleration to 60 use more battery than slow acceleration? It feels like it does, but of course the cruise speed of 60 is reached faster, whereas a slow acceleration lasts longer while using the additional power to accelerate.

F = m a so more force is used if a is higher, but the higher force is needed for less time.

Anyway, anyone being less dopey than me that can give a quantative argument?

NB ignore the fact that you'll be at 60 a bit longer if you accelerate fast - that's why I suggested a 20 mile run at 60, so a few yards difference is negligible.
 
MartinSEsr said:
I'm an engineer so should be able to work this out, but feeling tired and thick...

Does harder acceleration use more battery?? If we need to get from 0 to 60 for a 20 mile cruise on a dual carriageway with no stops, then DOES fast acceleration to 60 use more battery than slow acceleration? It feels like it does, but of course the cruise speed of 60 is reached faster, whereas a slow acceleration lasts longer while using the additional power to accelerate.

F = m a so more force is used if a is higher, but the higher force is needed for less time.

Anyway, anyone being less dopey than me that can give a quantative argument?

NB ignore the fact that you'll be at 60 a bit longer if you accelerate fast - that's why I suggested a 20 mile run at 60, so a few yards difference is negligible.
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From the top of my head I would say if you travel a distance X, if you accelerate slowly vs accelerate fast means that your average speed over distance X will be lower than if you accelerate fast and then drive fast. Your average speed will be lower. Since average speed is lower , you have used lower power (for longer time but probably longer in the efficient range). Now if you want to take into account the second derivative of speed, time and force (checks his notes and quickly does a runner....)

siteguru said:
Can you not see signatures? ;)
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wow you guys read everything.....

Now if the car is Caliban and it's like her son then that makes her ....... a very fine lady.
 
Oh, sorry. I thought you were being sarky about the thread I started in General Chat about treating the car as a person or a pet. That explains the name, but the post does go on a bit.

Peace.
 
MartinSEsr said:
I'm an engineer so should be able to work this out, but feeling tired and thick...

Does harder acceleration use more battery?? If we need to get from 0 to 60 for a 20 mile cruise on a dual carriageway with no stops, then DOES fast acceleration to 60 use more battery than slow acceleration? It feels like it does, but of course the cruise speed of 60 is reached faster, whereas a slow acceleration lasts longer while using the additional power to accelerate.

F = m a so more force is used if a is higher, but the higher force is needed for less time.

Anyway, anyone being less dopey than me that can give a quantative argument?

NB ignore the fact that you'll be at 60 a bit longer if you accelerate fast - that's why I suggested a 20 mile run at 60, so a few yards difference is negligible.
Click to expand...
I think since the total change in kinetic energy is the same then it doesn't matter whether the acceleration is done quickly or slowly.

However, electric motors have an efficiency sweet spot for torque vs rpm. Good luck finding the data for our motor though. Here is one from an ID3:

1685951291104.png


I struggle to get my head around it but I think it shows that you should avoid stopping at all costs as the efficiency is greatly reduced when accelerating from a standstill but once moving at a reasonable speed it doesn't matter so much. I think the accelerator pedal position for a given speed moves the position vertically so accelerating gently does give a slight gain of maybe 3% at most.

The paper is really interesting apart from the fact that they completely ignored calendar degradation of the batteries so they are quite optimistic with their predictions of battery longevity. I would love for something similar for the MG4. I've attached it below.
 

Attachments

  • 1-s2.0-S2590116822000133-main.pdf
    3.1 MB · Views: 79
Also losses due to heating through internal resistance in cabling and battery increase with higher currents when Accelerating harder. It is not linear either sadly in the same way as air resistance builds as you go faster.
 
Without having to write a PhD. , I believe strongly that if watch your acceleration and keep to speed limits, MG4 fulfills our needs 90% of the time at around 2-3p per mile.
Cannot say fairer than that.
 
fshuk1 said:
Without having to write a PhD. , I believe strongly that if watch your acceleration and keep to speed limits, MG4 fulfills our needs 90% of the time at around 2-3p per mile.
Cannot say fairer than that.
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That depends on how much you pay for your electricity. At 34p per unit I'm more like 10p per mile - which is still a lot less than an ICE. (Circumstances mean that we can't time-shift heavy usage to utilise time-based tariffs).
 
As regards the question in the thread title, I wouldn't trust it at all. When doing lots of shorter journeys from home I'll plug in when the car gets down to about 50%. I'll also plug in the night before going on a longer journey.

Out and about, if my journey is going to take me close to my probable range before I get home, I've got a little map in my head of the rapid chargers on the various roads home, and if there's even the slightest question in my mind about whether I'm going to make it, I'm in there to add an extra 10 miles or so.
 
I remember when I was in my 20s some tourist asked me what is the deepest part of the river Thames. I thought, who cares man. Now that I am, shall we say more mature, I sometimes find myself wondering, WHAT is the deepest part of the river Thames.
 
MoDolph said:
I think since the total change in kinetic energy is the same then it doesn't matter whether the acceleration is done quickly or slowly.

However, electric motors have an efficiency sweet spot for torque vs rpm. Good luck finding the data for our motor though. Here is one from an ID3:

View attachment 18076

I struggle to get my head around it but I think it shows that you should avoid stopping at all costs as the efficiency is greatly reduced when accelerating from a standstill but once moving at a reasonable speed it doesn't matter so much. I think the accelerator pedal position for a given speed moves the position vertically so accelerating gently does give a slight gain of maybe 3% at most.

The paper is really interesting apart from the fact that they completely ignored calendar degradation of the batteries so they are quite optimistic with their predictions of battery longevity. I would love for something similar for the MG4. I've attached it below.
Click to expand...

Thank you for the interesting paper and charts. It looks like the motors are much more efficient at higher RPM, looking at the 0.58-0.96 graph, which is a pleasant surprise. Of course, faster motor = faster car, with higher drag (proportional to V squared) so power useage (proportional to V cubed) increases exponentially with speed, far removing any motor efficiency increases.

I still am not sure of my original Q though, if you plan to cruise at 60 for a long time (ie the extra time at 60 by getting there quicker is negligible) then does it use more battery to accelerate fast, compared to a long slow acceleration? I think they balance out now, with little difference. Which also means forget Eco and use Sport!
 
Rolfe said:
As regards the question in the thread title, I wouldn't trust it at all. When doing lots of shorter journeys from home I'll plug in when the car gets down to about 50%. I'll also plug in the night before going on a longer journey.

Out and about, if my journey is going to take me close to my probable range before I get home, I've got a little map in my head of the rapid chargers on the various roads home, and if there's even the slightest question in my mind about whether I'm going to make it, I'm in there to add an extra 10 miles or so.
Click to expand...

I'm really sorry Rolfe, I liked your original post, but then thoughtlessly hijacked the thread with a separate and now clearly unrelated question to do with power and energy consumption on acceleration... I should have started a new thread on that, apologies.
 
MartinSEsr said:
I'm really sorry Rolfe, I liked your original post, but then thoughtlessly hijacked the thread with a separate and now clearly unrelated question to do with power and energy consumption on acceleration... I should have started a new thread on that, apologies.
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That's normal for this forum. A lot of the threads go off at a tangent and some might even get back on topic. We like to keep Admin on their toes 😁
 
In answer to answer the OP. I suspect that my Trophy has a slightly non linear SOC scale. I seem to be able to go slightly further on the first 50% than the second 50%. It's not a problem as the difference is quite small.

I don't use the estimated miles on the GOM so I don't know how accurate that is.

Here are some examples as requested:

Reported: 100%-46% = 33.318kWh = 54%

Actual: 165.9/4.7 = 35.3 kWh = 57%

Consumption if reported SOC was true: 165.9/33.318 = 4.98 mi/kWh

1686037475240.png



Reported: 70% - 10% = 37.02 kWh = 60%

Actual: 164.5/4.6 = 35.8 kWh = 58%

Consumption if reported SOC was true: 164.5/37.02 = 4.44 mi/kWh

1686037739005.png



93% - 12% = 49.98 kWh = 81%

182.4/3.5 = 52.1 kWh = 84%

Consumption if reported SOC was true: 182.4/49.98 = 3.65 mi/kWh

It looks like the "Total power consumption" display is linked to the SOC and not the efficiency number.

1686039525564.png
 
Rolfe said:
If MG seriously think I can get 4.1 on regular journeys they are in cloud-cuckoo land.
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for journeys around my area I get 4.7 - 4.8 but then again nearly every road is 20mph but you are lucky if you get above 15mph just down to the sheer volume of traffic.

On motorways journeys I'm getting 3.4 - 3.6 depending on how heavy footed I feel
 
The journey above where I got 4.7 was a trip from hell down the M6 last Friday. The average speed was showing ~25mph by the time we reached Birmingham from Warrington. I remember thinking that I could almost have cycled it as fast.

When the motorway is clear this is more like what I see:

1686041749208.png
 
It's those pesky smart motorways and their speed cameras that seem to be everywhere around here. I only dare set the cruise control to 71-72 mph. The few places where they haven't ruined it yet I set it to 75 mph.
 

Are you enjoying your MG4?

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