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I think your calculation is not quite right Paul, I reckon the deceleration corresponding to 50 kW is higher - would you like to check it?
ah, I was tired, I was thinking of 50mph, which is about 25m/s


Force = mass * acceleration => a = f / m
Force * speed = power => f = p / s

so a = (p / s) / m => a = p / (s * m)

a = 50000 / (25 * 1500) = 1.3m/s^2

does that make sense? I'll correct my comment above if so.
thanks @davesul
 

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Yes, but that would happen if regen wasn't being counted, because power use during those times would read zero (rather than a negative quantity).
There's definitely something a miss with how it includes or doesn't include re-gen, I recently started a trip with a long downhill from over 1200 feet down into Wrexham, any other EV I've had would show some silly big mpkWh figure but the MG just 3.6 at the bottom of the hill.
 

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I'm also on about 500 miles in my first EV. The miles/kWh display seems the most useful measure of consumption, but it can take about 20+ miles to settle. Mine always starts at 3.1 and then goes up or down a little, about every half mile, depending on how I drive.

Do they always start at 3.1? Or does it eventually adapt?

Anyway, I've done a few test 'circular' runs (so the wind should cancel out) on A-roads and Motorways: Edit: All in Eco mode, KERS 3.

60mph 8.C 3.8m/kWh = 169 miles range.
65mph 8.C 3.3m/kWh = 146 miles range.
70mph 8.C 2.8m/kWh = 125 miles range.

My accumulated total displayed m/kWh is 3.6.

There're loads of roadworks on my local m-ways so plenty of scope to add 50 and 55mph tests.

Imagine how much fun I am at parties
I know the feeling well !.
I have heard my wife whispering to people at parties, “What ever you do, don’t get talking to him about electric cars, or you will be there all night, you have been warned !”.
 

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Discussion Starter #24
Some of the more experienced owners (had them the longest and done several thousand miles since October) have said you go further in normal mode than in eco. Normal mode range estimate is pretty much bang on, Eco mode is much more of a GOM.
Can you explain why this is?At first glance it makes no sense!
if this is true I’ll be pleased because having to manually set it to eco every journey is a minor hassle each time.
 

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Can you explain why this is?At first glance it makes no sense!
if this is true I’ll be pleased because having to manually set it to eco every journey is a minor hassle each time.

Eco mode is for last few miles when your running short, not entire trips. Car defaults to normal mode on restarting car, there is a reason for that.
 

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Discussion Starter #26
Eco mode is for last few miles when your running short, not entire trips. Car defaults to normal mode on restarting car, there is a reason for that.
I thought from the hand book it just dampened the throttle response?
 

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I thought from the hand book it just dampened the throttle response?
Think it cuts heater output too. It also clearly gives your made up range too, it should really say the same as normal mode but if you then subsequently drive more gently that range won't drop so quick. As it seems to give you higher than normal range but then fails to deliver it seems more of a placebo.

What I've found using eco mode in my Zoe is you tend to go slower, but spend longer holding higher kw for longer on the meter because the car is slower to accelerate and maintain speed etc. But in normal mode your flex your ankle more and speed up and then hold at neutral for longer.
 

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ah, I was tired, I was thinking of 50mph, which is about 25m/s


Force = mass * acceleration => a = f / m
Force * speed = power => f = p / s

so a = (p / s) / m => a = p / (s * m)

a = 50000 / (25 * 1500) = 1.3m/s^2

does that make sense? I'll correct my comment above if so.
thanks @davesul
Thanks Paul for explaining your method.
I looked at it a bit differently - based on Kinetic Energy of the vehicle.

Below are examples of deceleration values for 50 kW power, reflecting the variation for different speed drops compared to a starting speed of 50 km/h.

For speed = 50km/h, ie 13.9m/s, and mass = 1500 kg, the vehicle Kinetic energy (KE) : 0.5*m*v^2 = 144676 J, ie about 145 kJ. Then since W= J/s, this can be expressed as KE = 145 kW.s

Then for dropping to 45 km/h, the corresponding new KE is 117 kW.s and so the regen energy is the difference of the two KE values - about 28 kW.s. At a regen power of 50 kW, this corresponds to about 0.56 seconds for the energy to be absorbed by the regen system. The corresponding deceleration is then about 2.5 m/s^2.

For speed dropping to 30 km/h from 50 km/h, the corresponding new KE is 52 kW.s, the change of KE is about 93 kW.s and at 50 kW level this takes about 1.85 seconds with corresponding deceleration of 3 m/s^2.

To actually come to a standstill, the regen system would have to absorb all the original KE of 145 kWs, taking 2.9 seconds at 50 kW rate with deceleration of 4.8 m/s^2.
 

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1374 miles so far. 50% A roads 40% B roads 10% motorway. Usually in Eco mode. Can get between 2.8 and 4.8 on a trip but usually each trip settles at 3.1 - 3.4 miles/kW. Accumulated trip since new shows 3.2 miles/kW.
 

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Discussion Starter #32

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Winter ~3 mpkWh
Summer ~4 mpkWh

Driving style and limiting top speed can enhance this a bit more.

Wet roads will make it slightly worse.

Tyre pressures do very little unless overly soft ;-)

Is the same for most sub-2 tonne EVs
 

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To actually come to a standstill, the regen system would have to absorb all the original KE of 145 kWs, taking 2.9 seconds at 50 kW rate with deceleration of 4.8 m/s^2.
whilst you might average a 50kW KERS power recovery for a fixed deceleration, or average a deceleration of 4.8m/s^2 for fixed 50kW KERS, you don't get a linear relationship as the speed drops or as time progresses.

if you have constant braking/deceleration, then the power from KERS drops off with the inverse square of the speed (or time).
 

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whilst you might average a 50kW KERS power recovery for a fixed deceleration, or average a deceleration of 4.8m/s^2 for fixed 50kW KERS, you don't get a linear relationship as the speed drops or as time progresses.

if you have constant braking/deceleration, then the power from KERS drops off with the inverse square of the speed (or time).
Paul, I'm just about to send you a PM on the above, to avoid unnecessary clutter of the thread.
 

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I know the feeling well !.
I have heard my wife whispering to people at parties, “What ever you do, don’t get talking to him about electric cars, or you will be there all night, you have been warned !”.
Or at the Golf Club, or the supermarket checkout. My favourite is when I go into the petrol station for a car wash and am asked is there any petrol with that? Gotcha.
 

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For what it's worth. I've never seen Zoe give a higher regen value than -34 kW and that was downhill with slight pressure on the brake pedal.
 

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For what it's worth. I've never seen Zoe give a higher regen value than -34 kW and that was downhill with slight pressure on the brake pedal.
I've seen 40+ in my 22kWh model.... granted it doesn't last for long at that rate because your slowing down rapidly.
 

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Managed a 50mph run. Also at KERS 3 eco mode.

50mph 9.C 4.8m/kWh = 213.6 miles range.

I've edited this into my list of efficiencies at different speeds on page 1 post 3 of this thread. Just have the 55mph slot to go, though it looks as though it will be ~4.3m/kWh = 191 miles range.
 
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