How accurate is the % figure for battery charge in deducing potential range?

[CuriousIslander]

If this has been discussed elsewhere, please accept my apologies, and point me to the relevant thread (I have tried searching for it but have drawn a blank)


I am interested to know how much notice we can take of the battery charge indicator. For example, following a full balance charge I have just driven approx 60 miles on 25% of the battery. This would suggest a range of about 240 miles on a full charge equivalent. (SR model in ECO kers 3 pootling around the Isle of Wight). This I feel is very generous, if not fanciful! The GOM at full charge was 213 (with the car set to Eco mode), and adding the distance driven since charging to the GOM remaining, this has crept up to about 224. These different ways of estimating range therefore give a spread of about 213 to about 240. Which is the most reliable? I am disinclined to believe the GOM (certainly in isolation) but is the range based on % used actually any more accurate?

Have I read somewhere that the battery is more efficient at higher charge levels, ie you get more miles per % at higher levels than at lower levels, or have I dreamt it? If this is the case, then I think it suggests that not allowing the charge to drop below some magic figure (say 50%) and then charging, would give the best possible range. At the moment I tend to let it drop to about 35% before I recharge, but it would be no hardship to charge more often, and for a shorter time of course.

Is there any technical discussion about this anywhere? I would be intrigued to know.
Thanks

 

[Kithmo]

I think the GOM was said to be non-linear as well as only a guess.

 

[Fluffykins]

To quote Douglas Adams: "much that is apocryphal - or at least wildly inaccurate"

Actually it's not bad but the real life rate will vary day to day, depending on things like the amount of lead in your right foot, speed, temperature, water on the ground etc.

 

[Lguk]

I need to get acquainted with ACC because my right shoe seems to be made of cast iron. Trying to get into the habit of driving efficiently for when I need to drive long ranges or free charging at work ends.

 

[Jomarkh]

Hi, what is your m/kwh? During the summer i was getting 4.3 but only getting 3.4 currently.
The gom is based on your long term trip counter, so see what m/kwh that is showing.

 

[lebelinconnu]

Hi, what is your m/kwh? During the summer i was getting 4.3 but only getting 3.4 currently.
The gom is based on your long term trip counter, so see what m/kwh that is showing.

Yes, same here at 3.4. I do find that the battery percentage seems to decrease more rapidly once I get down to around 60%. I posted in another thread that after charging I can do up to 12 or 13 miles before the battery percentage drops at all- a couple of other owners have reported the same.

 

[Lguk]

Is that from 100% or any value? By the time I've got 3 miles up the road my SOC number has dropped.

 

[CuriousIslander]

the battery percentage seems to decrease more rapidly once I get down to around 60%.

That - or something similar - is what I thought I have read elsewhere, but can't find it.

 

[sido]

From my experience the % charge remaining is not any different to my ICE petrol guage, it gives you approximate readings. It’s only really accurate when you run out. I use the trip computer readings for information and checking miles per KWHr. The 100% on my 5 SR equates to 48 useable KW hrs. This give about 150 miles in the winter, so average a little ove 3 miles per KW hr.

 

[5teep]

I've done over 21k in my SR model now and things I know for sure... The gom is a placebo, it's generally meaningless. It tells me I have 208 miles with 100% soc when the temp is zero when I know for certain that at 0c I'll be lucky to get 150. So I ignore it. The actual state of charge drops 1% per mile from 100 down to about 96% after that it steadies out and is pretty accurate by my working. It does seem to drop faster once below 25% but that might just be me.

Working out available range is fairly easy for me, working on a range of 200 miles on a warm day (anything over is a bonus) my range should be about twice the remaining battery percentage. In colder weather if I want to check more accurately I look at miles driven by percentage used, 75 miles gone for 50% battery = 150 miles, 50 miles at 30% = 166 miles. I'm pretty good at mental arithmetic so it's not hard for me to work out other combinations.

General driving, I've stopped using kers 3 on the open road, it slows you too much and you use up any charge gained accelerating again, so kers 3 only in town, kers 2 all other times. Drive in eco mode all the time as it's plenty fast.
The AC uses a lot less power than the gom tells you (another reason to ignore it) I've tried driving with heating off, on and on high and I can hardly see a difference in my range.

 

[sido]

I've done over 21k in my SR model now and things I know for sure... The gom is a placebo, it's generally meaningless. It tells me I have 208 miles with 100% soc when the temp is zero when I know for certain that at 0c I'll be lucky to get 150. So I ignore it. The actual state of charge drops 1% per mile from 100 down to about 96% after that it steadies out and is pretty accurate by my working. It does seem to drop faster once below 25% but that might just be me.

Working out available range is fairly easy for me, working on a range of 200 miles on a warm day (anything over is a bonus) my range should be about twice the remaining battery percentage. In colder weather if I want to check more accurately I look at miles driven by percentage used, 75 miles gone for 50% battery = 150 miles, 50 miles at 30% = 166 miles. I'm pretty good at mental arithmetic so it's not hard for me to work out other combinations.

General driving, I've stopped using kers 3 on the open road, it slows you too much and you use up any charge gained accelerating again, so kers 3 only in town, kers 2 all other times. Drive in eco mode all the time as it's plenty fast.
The AC uses a lot less power than the gom tells you (another reason to ignore it) I've tried driving with heating off, on and on high and I can hardly see a difference in my range.

Great practical information I too have stopped using Kers3 same reason

 

[marsw2]

If this has been discussed elsewhere, please accept my apologies, and point me to the relevant thread (I have tried searching for it but have drawn a blank)


I am interested to know how much notice we can take of the battery charge indicator. For example, following a full balance charge I have just driven approx 60 miles on 25% of the battery. This would suggest a range of about 240 miles on a full charge equivalent. (SR model in ECO kers 3 pootling around the Isle of Wight). This I feel is very generous, if not fanciful! The GOM at full charge was 213 (with the car set to Eco mode), and adding the distance driven since charging to the GOM remaining, this has crept up to about 224. These different ways of estimating range therefore give a spread of about 213 to about 240. Which is the most reliable? I am disinclined to believe the GOM (certainly in isolation) but is the range based on % used actually any more accurate?

Have I read somewhere that the battery is more efficient at higher charge levels, ie you get more miles per % at higher levels than at lower levels, or have I dreamt it? If this is the case, then I think it suggests that not allowing the charge to drop below some magic figure (say 50%) and then charging, would give the best possible range. At the moment I tend to let it drop to about 35% before I recharge, but it would be no hardship to charge more often, and for a shorter time of course.

Is there any technical discussion about this anywhere? I would be intrigued to know.
Thanks

If this has been discussed elsewhere, please accept my apologies, and point me to the relevant thread (I have tried searching for it but have drawn a blank)


I am interested to know how much notice we can take of the battery charge indicator. For example, following a full balance charge I have just driven approx 60 miles on 25% of the battery. This would suggest a range of about 240 miles on a full charge equivalent. (SR model in ECO kers 3 pootling around the Isle of Wight). This I feel is very generous, if not fanciful! The GOM at full charge was 213 (with the car set to Eco mode), and adding the distance driven since charging to the GOM remaining, this has crept up to about 224. These different ways of estimating range therefore give a spread of about 213 to about 240. Which is the most reliable? I am disinclined to believe the GOM (certainly in isolation) but is the range based on % used actually any more accurate?

Have I read somewhere that the battery is more efficient at higher charge levels, ie you get more miles per % at higher levels than at lower levels, or have I dreamt it? If this is the case, then I think it suggests that not allowing the charge to drop below some magic figure (say 50%) and then charging, would give the best possible range. At the moment I tend to let it drop to about 35% before I recharge, but it would be no hardship to charge more often, and for a shorter time of course.

Is there any technical discussion about this anywhere? I would be intrigued to know.
Thanks

Hi I have a 72 mg 5 and run a spread sheet almost for each charge to compare predicted range vs actual and have come to the conclusion that....(Miles_Travelled/%age_used)*%age_remaining = most accurate prediction of actual range.for any given charge.

Yes there are multiple factors (driving style, temperature etc) that affect range but I find this formula gives best indication of what is "real"

 

[Anon70]

The battery charge indicator and the GOM are completely different indicators using a different set of metrics.

The GOM will be using the previous x number of miles of driving conditions and car settings to base it's calculations on, so if everything were to remain constant (no accelerating or decelerating, no changes in HVAC use etc etc) it tells you how far you can expect to travel on the remaining charge in the battery.

The battery charge indicator is the amount of charge left in the usable battery capacity (there is some leeway to allow you to get to 0% and keep moving and also for maintaining battery health). If you watch any YouTube video of "we ran these electric cars until they stopped" (which they never seem to do with ICE cars) then you will get an idea of what might be possible.

If you want some detailed stats have a look at some of the Bjorn Nyland videos as he connects up a data tracker to the cars he is testing

 

[Kithmo]

Hi I have a 72 mg 5 and run a spread sheet almost for each charge to compare predicted range vs actual and have come to the conclusion that....(Miles_Travelled/%age_used)*%age_remaining = most accurate prediction of actual range.for any given charge.

Yes there are multiple factors (driving style, temperature etc) that affect range but I find this formula gives best indication of what is "real"

Where do you get the % used from ?
I get mine from the amount put in on the charger less 10% for losses.

 

[marsw2]

Where do you get the % used from ?
I get mine from the amount put in on the charger less 10% for losses.

I run a spread sheet for roughly each charge.
And Register, %age charge, total miles, car estimate of range. Then when needed record %age left, new total miles, car estimate of range left. This gives info for spread sheet to calc miles per % as per formula for each drive. This then gives me real world range left for each drive based on archived miles/%

 

[5teep]

Where do you get the % used from ?
I get mine from the amount put in on the charger less 10% for losses.

The car gives you a percentage remaining, just subtract that from 100?

 

[marsw2]

The car gives you a percentage remaining, just subtract that from 100?

That only works if you charge to 100% which is why I record the %age charged to and the range the car thinks it going to achieve for that %age.

 

[5teep]

Got you, I do usually charge to 100% which is why I work it that way and growing up before calculators I had to learn arithmetic the hard way in my head so I generally have a good idea how far I can go before I need to charge.

 

[marsw2]

I grew up with quil pens and ink pots but I learnt to rely on the quage telling me reasonably accurately how much petrol was in the tank not how much further the car would go I could then work out when to fill up based on use of right foot. I have no trust in the electric range displayed but (right or wrong) I trust %age left and how many miles I have driven for each %... That said it's early days and i am impressed with electric traction. Think that's enough for me on this subject. All the best everyone

 

[5teep]

I grew up with quil pens and ink pots but I learnt to rely on the quage telling me reasonably accurately how much petrol was in the tank not how much further the car would go I could then work out when to fill up based on use of right foot. I have no trust in the electric range displayed but (right or wrong) I trust %age left and how many miles I have driven for each %... That said it's early days and i am impressed with electric traction. Think that's enough for me on this subject. All the best everyone

I could never do it accurately with a petrol car but a nice percentage gauge, that I can work with.