A missing mile.

[Kithmo]

When I bought my ZS in July last year the range shown on the GOM always showed 163 miles when charged. Then in the winter it went down to 157, fair enough HVAC used, same journeys. I had never reset the Accumulated totals trip.
When the car went for it's first service at the beginning of last month (July) for some reason the dealer had reset the trip, and when I charged it up it showed 162 miles.
Bearing in mind my GOM has always been fairly accurate and consistent, by my calculations I have lost 0.07% of my range.
Checking on the OBDII ZS EV app, the SOH is still showing 100%, I expected it to say 99.3% or similar.
I charged it up again a couple of days ago, expecting it to go back to 163, but it went to 162 again.
Where has my missing mile gone ?
Another thing I've noticed since resetting the accumulated trip is that two things are happening.
1. The actual miles travelled is slightly more than the miles dropping off the GOM (good).
2. My accumulated m/kWh is more than the average of my current journey trip works out to (?).
E.g. each 2.7 mile there and 3 mile back journey I've done every morning has shown 3.4-3.5 m/kWh, yet the accumulated trip shows 4.1.
How can the accumulated be more than the average, I thought that was how it worked it out ?

 

[Scriv]

For sometime I've used the figure of 4 m/kwh to calculate roughly the mileage range after charging, and this time of year I'm achieving about 4.6/4.7 on the display, so there's always a margin of safety.
Having nothing better to do, I decided to make some checks by using actual mileage and kwhs charged. I fully charged to 100% plus balancing, before and after a couple of journeys each of about 70 miles.
To my surprise each time the m/kwh figure worked out to be lower than that on the display, apparently indicating more kwhs used than in the display figure!
Kwhs used were checked against my Zappi charger and smart meter.
Has anyone else noticed this?

 

[Cocijo]

With any charge there are efficiency losses. The amount of kwh’s shown as used to charge will be different to the amount actually usable.

 

[Lovemyev]

When the car went for it's first service at the beginning of last month (July) for some reason the dealer had reset the trip, and when I charged it up it showed 162 miles.
Bearing in mind my GOM has always been fairly accurate and consistent, by my calculations I have lost 0.07% of my range.

Hi @Kithmo.
I had my service and BMS update on the 15th Jan 2021.
After a few charging hick up's, the car reported 162 miles and 449 - 450 volts after a full charge and balance.
This is when both trips have been reset, with foot off the foot brake when booting up.
Now 6 months latter, when in the default mode of normal and regen level 3, the voltage on the pack is still 449 volts but the predicted range on the GOM now hovers around the 156 - 157 miles mark.
I don't have a OBD dongle so unable to check my actual SOH.
The car is 18 months old and has covered 14,000 miles.
Some battery degradation ?.
I expect so, but in actual real term range lost ( if any ) is it SO small that it does not concern me too greatly.
I consider it a huge fail if my route calculations, requires that I need that missing 5 miles to get me to my actual destination !!.
Five miles is very unlikely to save your arse, if you got it THAT badly wrong ! .
There is more important things in life to worry about IMO.

 

[Coulomb]

Bearing in mind my GOM has always been fairly accurate and consistent, by my calculations I have lost 0.07% of my range.
Checking on the OBDII ZS EV app, the SOH is still showing 100%, I expected it to say 99.3% or similar.

My theory is that they call the factory provided SOH about 103%, but report anything over 100% as 100%. So you don't see any of the very high degradation in the first year or so.

Some variation in new capacity is expected, and cars can spend variable time and conditions before sale. If some cars reported 103.1% when new, and others 102.9%, then people would complain or feel bad. So this ploy avoids all that hassle.

 

[Gomev]

I like a good theory.

 

[Lovemyev]

My theory is that they call the factory provided SOH about 103%, but report anything over 100% as 100%. So you don't see any of the very high degradation in the first year or so.

Some variation in new capacity is expected, and cars can spend variable time and conditions before sale. If some cars reported 103.1% when new, and others 102.9%, then people would complain or feel bad. So this ploy avoids all that hassle.

I totally agree !.
The car will continue to report 100% SOC after a while of ownership, but the battery will not hold the same capacity as it did when new.
It reports 100% full, but your actual miles achieved will have decreased slightly due to the small amount degradation.
They don’t want owners banging in the door, reporting that they cars will not give them 100% when fully charged anymore !.
So they “fudge” the percentage figure slightly to account for the early degradation.

 

[Gomev]

My theory is that they call the factory provided SOH about 103%, but report anything over 100% as 100%. So you don't see any of the very high degradation in the first year or so.

Some variation in new capacity is expected, and cars can spend variable time and conditions before sale. If some cars reported 103.1% when new, and others 102.9%, then people would complain or feel bad. So this ploy avoids all that hassle.

I totally agree !.
The car will continue to report 100% SOC after a while of ownership, but the battery will not hold the same capacity as it did when new.
It reports 100% full, but your actual miles achieved will have decreased slightly due to the small amount degradation.
They don’t want owners banging in the door, reporting that they cars will not give them 100% when fully charged anymore !.
So they “fudge” the percentage figure slightly to account for the early degradation.

Does 2 people with the theory make it a conspiracy theory

 

[Bazzer44]

When I bought my ZS in July last year the range shown on the GOM always showed 163 miles when charged. Then in the winter it went down to 157, fair enough HVAC used, same journeys. I had never reset the Accumulated totals trip.
When the car went for it's first service at the beginning of last month (July) for some reason the dealer had reset the trip, and when I charged it up it showed 162 miles.
Bearing in mind my GOM has always been fairly accurate and consistent, by my calculations I have lost 0.07% of my range.
Checking on the OBDII ZS EV app, the SOH is still showing 100%, I expected it to say 99.3% or similar.
I charged it up again a couple of days ago, expecting it to go back to 163, but it went to 162 again.
Where has my missing mile gone ?
Another thing I've noticed since resetting the accumulated trip is that two things are happening.
1. The actual miles travelled is slightly more than the miles dropping off the GOM (good).
2. My accumulated m/kWh is more than the average of my current journey trip works out to (?).
E.g. each 2.7 mile there and 3 mile back journey I've done every morning has shown 3.4-3.5 m/kWh, yet the accumulated trip shows 4.1.
How can the accumulated be more than the average, I thought that was how it worked it out ?

Kithmo.
Been experimenting and mine has gone other way , answer to your question , I've got it

 

[Kithmo]

My theory is that they call the factory provided SOH about 103%, but report anything over 100% as 100%. So you don't see any of the very high degradation in the first year or so.

Some variation in new capacity is expected, and cars can spend variable time and conditions before sale. If some cars reported 103.1% when new, and others 102.9%, then people would complain or feel bad. So this ploy avoids all that hassle.

But shouldn't the ZS EV OBDII app report the actual SOH at over 100% when newer, when I used it last year, at a few months old, it reported 100% the same ? Or would the app take the SOH from the same source as the charging display ?

 

[mystreet]

I totally agree !.
The car will continue to report 100% SOC after a while of ownership, but the battery will not hold the same capacity as it did when new.
It reports 100% full, but your actual miles achieved will have decreased slightly due to the small amount degradation.
They don’t want owners banging in the door, reporting that they cars will not give them 100% when fully charged anymore !.
So they “fudge” the percentage figure slightly to account for the early degradation.

Does this mean another 'dieselgate' claim in 5 years. Those lawyers/solicitors will be making a fortune ?

 

[Simon S]

"Another thing I've noticed since resetting the accumulated trip is that two things are happening.
...
2. My accumulated m/kWh is more than the average of my current journey trip works out to (?).
E.g. each 2.7 mile there and 3 mile back journey I've done every morning has shown 3.4-3.5 m/kWh, yet the accumulated trip shows 4.1.
How can the accumulated be more than the average, I thought that was how it worked it out ?"

This second point has been puzzling me for a while. Same here About 3.5 m/KWh on the Current Journey for the first few miles, and about 4.5 m/KWh on the accumulated trip. The Current journey should also be going up and down like a Yoyo as you accelerate and decelerate in the first mile or two (as it does on my wife's Renault Zoe), but stays suspiciously stable (at the 3.5 figure). Any thoughts anyone?

 

[Coulomb]

Or would the app take the SOH from the same source as the charging display ?

That's up to MG. It looks like it comes from the same source.

The Current journey should also be going up and down like a Yoyo as you accelerate and decelerate in the first mile or two (as it does on my wife's Renault Zoe), but stays suspiciously stable (at the 3.5 figure). Any thoughts

In my Leaf, when I reset the usage, it just reports --- for a minute or two, then it shows actual values. I guess that Nissan argue that the yoyo-ing values aren't useful, so why confuse the driver with them?
So it looks like MG do much the same thing, except that they provide an actual value (guessed from what??), which I think is less honest.

 

[JodyS21]

That's up to MG. It looks like it comes from the same source.

In my Leaf, when I reset the usage, it just reports --- for a minute or two, then it shows actual values. I guess that Nissan argue that the yoyo-ing values aren't useful, so why confuse the driver with them?
So it looks like MG do much the same thing, except that they provide an actual value (guessed from what??), which I think is less honest.

That is a very interesting thought that it starts off at more than 100% SOH, it would be a sensible thing to do from a manufacturers perspective.
It's a well known fact that Teslas had a bigger battery capacity to what is advertised, they could then effectively allow this extra capacity to be used once the battery had started degrading a bit so it didn't look to/or affect the customer.

The only thought I have to make me think that it isn't more than 100% initially, is that this SOH data is supposed to be hidden to us customers, so there isn't any need to make it look better than it is. Also I'd have thought it would be necessary for MG technicians to read what the real SOH is, so there would need to be another "real SOH" bit of data that we don't know about.

It would be very good to know how the SOH 70% is measured for warranty purposes, one would think it would be the SOH data item that we know about and can access via OBD2.

@Kithmo, it could be how balanced the cells are to whether or not its saying 163 or 162 in the Guess O Meter. I always used to see 163 after fully charging, but on a couple of occasions I looked at it quite a few hours after it had finished charging/sat on the driveway and it showed 162, so it must loose a tiny little bit within a few hours sitting around.

I don't tend to get much mismatch between averaged trips and accumulated trip figure.
I do wonder though if one trip discounts any regen power used whilst the other doesn't.
I'm beta testing an App, that supposedly works out the power regenerated, so doing some data analysis at some point I may be able to make sense of it all.

 

[Coulomb]

I always used to see 163 after fully charging, but on a couple of occasions I looked at it quite a few hours after it had finished charging/sat on the driveway and it showed 162, so it must loose a tiny little bit within a few hours sitting around.

This might not be a whole mile "lost", though. It might be that you used to have 163.1, and now it's 162.9, truncated to 162 on the screen display. Or it might be 162.6 (rounds out to 163) versus 162.4 (rounds out to 162). Either way, it's only 0.2 mi of guessed range that is being lost. But that might be due to real degradation.

More likely, you are now right on a rounding or truncation boundary, hence sometimes 162 and usually 163, depending on temperature, balance, and other factors.

 

[JohnB]

A couple of things spring to mind.
1. The SOH reported is for the useable space. Initial degradation will be taken up in the buffer zone so range won't be affected.
2. For something lovingly referred to as a Guess-O-Meter, you seem to be expecting an accuracy that it probably doesn't warrant.

I'd go with the rounding explanation.

 

[Lovemyev]

This might not be a whole mile "lost", though. It might be that you used to have 163.1, and now it's 162.9, truncated to 162 on the screen display. Or it might be 162.6 (rounds out to 163) versus 162.4 (rounds out to 162). Either way, it's only 0.2 mi of guessed range that is being lost. But that might be due to real degradation.

More likely, you are now right on a rounding or truncation boundary, hence sometimes 162 and usually 163, depending on temperature, balance, and other factors.

I see a similar situation now six months after the BMS update and a few more miles added to the car !.
After a full charge and balance, I still see 449 volts on the pack ?.
But the predicted range is now around 156 - 157 in default mode and all trip meters reset.
The GOM is very fickle as we know.
If I forget to reset the trip meter and leave it with a very small number of 20 miles recorded, it will boast up the predicted range, even with a small number stored !.
163 miles f predicted range can become 157 miles at the flick of the okay button ?.
It will continue to inflate this predicted range each time the car is used.
Quickly you can be fooled to believe that your car will now travel +200 miles !.
This strange behaviour can fool some people and catch them out on a long trip.
Reset your trips before making a long trip IF you are running on the latest BMS update, would be my advise.
Just for the record, our car is over 18 months old and covered 14,000 miles enjoyable miles.
Drives and performs as it did when I collected it on Jan 6th 2020.
Hooked on EV driving that’s for sure, absolutely love it !.
There must be some battery degradation I think ?.
But IF so, there is nothing I can do to rectify this situation so move on, life is too short to spend chasing a few lost ( or not ) miles of range.
If I find myself bedding then few extra miles, then I have screws up badly or bought the wrong EV in the first place.
I will start to worry when it stops taking me to the places I have been accustomed to travelling too.
We have clocked more miles in this car over 18 months ( a two lock downs ) than we ever did in our previous car.
Why ?.
Simple, I enjoy EV driving and as OAP’s - it is VERY affordable to use.
Popped out for a “Little Drive” just after lunch yesterday, weather was good, ended up travelling over the Welsh mountains and returned home after clocking up about 125 miles and arrived home with about 79 miles remaining on the GOM.
Car reported 5.0 m/kWh on our return.
What more do you want !.
Oh ….. What is the predicted mileage on the GOM - Is it 163 or 162 or 157 - 156.
Bugger it, just charge / reset / drive and enjoy is my moto ?.

 

[JodyS21]

A couple of things spring to mind.
1. The SOH reported is for the useable space. Initial degradation will be taken up in the buffer zone so range won't be affected.
2. For something lovingly referred to as a Guess-O-Meter, you seem to be expecting an accuracy that it probably doesn't warrant.

I'd go with the rounding explanation.

That’s not the case, SOH isn’t usable space.
Via the OBD2 data we can see usable space/buffer, it’s the (real) SOC. The % charge shown to the driver is a calculated SOC that is based on usable capacity.

The GOM is just a guess as you say; however used at full charge with trip data reset, it is a way of seeing the “true” state of your battery without any OBD2 access.

 

[Kithmo]

A couple of things spring to mind.
1. The SOH reported is for the useable space. Initial degradation will be taken up in the buffer zone so range won't be affected.
2. For something lovingly referred to as a Guess-O-Meter, you seem to be expecting an accuracy that it probably doesn't warrant.

I'd go with the rounding explanation.

I had no expectations of accuracy on the GOM, but I was just wondering why it had been consistently showing 163 and now it shows 162. I agree the rounding off sounds the most plausible explanation.

 

[JohnB]

I had no expectations of accuracy on the GOM, but I was just wondering why it had been consistently showing 163 and now it shows 162. I agree the rounding off sounds the most plausible explanation.

True, without knowing what parameters the GOM is using it really is a black box. It could be anything from battery SOH, temperature, time-of-day, tyre pressure, previous usage just to think of a few. I think It's fair to say its precision is greater than it's accuracy.
It's effectively saying "nnn miles available +/- nn.nnn miles"