EV reports all having 100% SOH
Discussion
Seen a few cars some 5 year olds wirh 100k+ miles.
The reports all have 100% SOH.
How true is this? Are they actually same health as brand new? Or some sort of odd dodgy testing
https://www.autotrader.co.uk/car-details/202606163...
The reports all have 100% SOH.
How true is this? Are they actually same health as brand new? Or some sort of odd dodgy testing
https://www.autotrader.co.uk/car-details/202606163...
I have a vague recollection from years ago that some companies had a battery reserve that they released to offset degradation. Something like a physical size of say 76kwh, claimed useable is 70kwh. Over time the degradation reduces the 76kwh but they can still give a useable 70kwh. In practice this is just how high the voltage they chsrge too on the individual cells, which also helps preserve the battery as they generally don t like being charged to 100%. It s not like you have 3 battery cells which arent being used until the others die and the BMS manages it all.
Ive not seen this approach being mentioned for years, it was cars like the BMW i3 that did it which was different to Tesla who didn t, but if it is done by some today, it might explain it, although it makes those reports a little pointless as you ve no idea how much of the buffer has been released.
Ive not seen this approach being mentioned for years, it was cars like the BMW i3 that did it which was different to Tesla who didn t, but if it is done by some today, it might explain it, although it makes those reports a little pointless as you ve no idea how much of the buffer has been released.
Edited by Gone fishing on Monday 22 June 06:56
Almost certainly rubbish; 120k miles is going to be about 500 full charge cycles. Even if the battery has been treated perfectly in other respects, it's going to have lost more than half a percent of its capacity over that. Most likely it's hovering around the 90% mark in terms of actual cell capacity, although as above the firmware may large hide the range effect of that.
Edited by kambites on Monday 22 June 08:39
Ricky997GT said:
Seen a few cars some 5 year olds wirh 100k+ miles.
The reports all have 100% SOH.
How true is this? Are they actually same health as brand new? Or some sort of odd dodgy testing
https://www.autotrader.co.uk/car-details/202606163...
That is not a 'State of Health' figure, it is a capacity figure.The reports all have 100% SOH.
How true is this? Are they actually same health as brand new? Or some sort of odd dodgy testing
https://www.autotrader.co.uk/car-details/202606163...
The capacity of a cell depends on what end voltages are specified.
Without knowing what the voltages are, the capacity isn't the whole picture, even then it varies with the many different Lithium chemistries.
But shifting the voltages can only gain a relatively small capacity, so it's not dropping off a cliff.
It's a guide that suggests another 5 years and 50k miles and you'll still have a decent range.
It's not like buying a car which has barely enough range to start with.
Although it's high mileage, it's not very old. Time is a major factor in the demise of Lithium cells.
Time and deep cycling. But long range cars are less likely to get deep cycled.
Still lots of other bits with 120k miles on them though.
I got a 100% figure for my 82K mile '19 reg i3 from the model's leading UK specialists via the vehicle's onboard diagnostics as part of an end of warranty check. Said report was at pains to explain it wasn't a battery condition report, so I dropped them an email to ask what precisely it was showing me. No answer is yet forthcoming.
There's probably the buffer, some cars also do some adjustments where the SOH is related to expected condition for the age.
My 0.02€:
120,000 miles might mean brush replacement for the motor sometime during the next 100,000 miles, but based on what I read doesn't seem to be a big deal (FWIW, using the brushed design to allow true "neutral" and eliminate the need for permanent magnets sounds like a good - or at least understandable - trade-off to me!).
My 0.02€:
- Testing the actual battery capacity is always somewhat destructive process (you need to do a deep discharge)
- There's no "electron tank" that goes empty: the BMS switches the battery off when the voltage drops below the safe threshold, and the point at which the voltage limit is reached varies (temperature, possibly also ageing)
- As a bit of an apples and oranges comparison: my latest phone has been "driven" almost the equivalent of 100,000 miles (approaching 400 cycles). The reported SOH is 95%, with three percentage points lost during a two-week holiday when temperatures were close to 40%. This is without active cooling of the battery, so the usage pattern has been like a second-gen Nissan Leaf in driven in Southern Europe. I think cells have become more and more robust.
120,000 miles might mean brush replacement for the motor sometime during the next 100,000 miles, but based on what I read doesn't seem to be a big deal (FWIW, using the brushed design to allow true "neutral" and eliminate the need for permanent magnets sounds like a good - or at least understandable - trade-off to me!).
Danm1les said:
My model 3 has nearly 100k miles and last time I checked the battery it was 87%, there is no way any 100k mile EV can still have 100% useable.
that would suggest you have a full and detailed understanding of every current and future battery technology used by every manufacturer.Tye Green said:
Danm1les said:
My model 3 has nearly 100k miles and last time I checked the battery it was 87%, there is no way any 100k mile EV can still have 100% useable.
that would suggest you have a full and detailed understanding of every current and future battery technology used by every manufacturer.
kambites said:
OutInTheShed said:
That is not a 'State of Health' figure, it is a capacity figure.
The report thing specifically says "State of health: 100%". That may not be what it means, but it's what it says!It actually says
State of Health:
Percentage of original capacity currently available:
100%
The trick is, the available capacity was never the nominal capacity.
So the '100%' only tells you that the true capacity hasn't fallen below the 92% that the car made available in the first place.
Actual SOH of a cell would be % of measured new capacity under the exact same voltage and current conditions.
The measured new capacity might have been a few % higher than the nominal too, because the cells will have some variation and you'd want a very high % of cells to be > minimum.
A fairly good li-ion battery generally has something like 80% capacity after about 8 years if treated nicely, so >92% after 6 years and 126k miles is really pretty good. It shows progress over previous generations.
If you ever read the old i3 forums, BMW used to have to tweak the voltages to avoid warranty claims due to falling capacity. Batteries have improved, but so has carmaker's ability to manage the situation.
Also a huge great 80kWh battery has an easy life.
ix3 uses about 8% of the total as buffer, and (like Kia/Hyundai) they count SoH as percentage of usable capacity, not total.
So in effect that first 8% of degredation comes out of the buffer and the SoH will stay at 100% until it dips below.
For 126k miles in under 5 years it's probably been doing just over 100 miles each working day - if the first owner was sensible and ran it from (say) 20% to 80% then it's pretty gentle on the battery. Even then it's probably not sat at very low or very high charge for long.
So in effect that first 8% of degredation comes out of the buffer and the SoH will stay at 100% until it dips below.
For 126k miles in under 5 years it's probably been doing just over 100 miles each working day - if the first owner was sensible and ran it from (say) 20% to 80% then it's pretty gentle on the battery. Even then it's probably not sat at very low or very high charge for long.
OutInTheShed said:
kambites said:
OutInTheShed said:
That is not a 'State of Health' figure, it is a capacity figure.
The report thing specifically says "State of health: 100%". That may not be what it means, but it's what it says!It actually says
State of Health:
Percentage of original capacity currently available:
100%
kambites said:
Hmm, yeah fair point if it does keep the same usable capacity despite the actual capacity loss, but that would probably suggest a cliff-edge of actual usable capacity once they run out of buffer.
I though the usable vs nominal difference was because you can never fully discharge the battery. So that difference should be there for the entire vehicle life.
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