aart wrote:
God knows what in the coming years. Solid batteries, Sodium?
Hopefully batteries with a lesser fire hazard. And that is not only valid for EV but mainly for personal devices. LiIon and all this stuff is simply too dangerous and has to be replaced asap. Otherwise it is only a question of time until more catastrophic events are caused by those batteries.
I am not sure that study proves in any way the battery capacity doesn’t get adjusted for display purposes. Indeed, it states
On the one hand, it’s astonishing that some vehicles with that many miles [ 100k miles ] still have nearly 100% of their original usable battery capacity.
which one cannot believe literally.
But, regardless of the details, this is very good. And the fewer charges the better, so the big-battery cars do better.
The study is also not impartial: EV diagnostics company Aviloo released the results of thousands of battery health checks for 20 popular EVs. No way such a company would publish anything bad about the big players.
Peter wrote:
On the one hand, it’s astonishing that some vehicles with that many miles [ 100k miles ] still have nearly 100% of their original usable battery capacity.which one cannot believe literally.
It may well be that the actual capacity starts out at more than 100% of the advertised figure, but the car doesn’t use more than that.
Not sure what you mean by “use” but as I often say 
it looks like, in some mfg cases, they have extra capacity which is not shown.
That way, there is no visible capacity loss for first few years. Result: happy customers! As I often say, this is exactly what one does in other product design, and I’ve had customers ask me directly to do such things in custom designs.
Especially as one cannot display battery capacity accurately anyway. It’s in the chemistry, after all… you measure energy in, energy out, chuck in other stuff like terminal voltage, temp compensation, etc. Over time you learn how to do this well. But within say 1%? I don’t think so.
Peter wrote:
Not sure what you mean by “use”
I mean that charging will stop at the advertised 100% level even if the battery is capable of accepting a higher charge,
That’s the same thing as I wrote, in reality.
AFAIU the invisible reserve is on the bottom (empty) end because full is the only state that can be measured reliably. In order to bring every cell in a pack to the same state, also known as balancing, the BMS will slowly charge the whole pack to 100%. But writing this, I am realising that it’s probably more complicated and the software tries to keep the state of charge in the most healthy range and only once in a while charges to full capacity. What is shown to the user as SoC would then have no 1:1 relationship to the amount of energy stored in the battery.
Peter wrote:
I am not sure that study proves in any way the battery capacity doesn’t get adjusted for display purposes. Indeed, it statesOn the one hand, it’s astonishing that some vehicles with that many miles [ 100k miles ] still have nearly 100% of their original usable battery capacity.
which one cannot believe literally.
I think from what I see there are several factors which may well yield such results, even though 100% is something you see very rarely on those documents, more like between 90 and 95%.
First, most charger electronics today are highly advanced and the default level they charge to unless told otherwise is 80%. This is something that is also recommended for mobile phones e.t.c. but nobody does it unless the phone has this capability itself, which most don’t. Hence, the battery is charged very conservatively and therefore keeps higher percentages.
Secondly, quite a few people claim that the batteries which do charge to 100% as a rule have a 20% reserve on top, to again achieve the actually optimal 80%. That is also a very probabe variant how you can keep a battery healthy. And consequently, if they degrade with age the first 20% will not be documented as they will only measure the nominal value.
Quite a lot of things are going against human instinct in battery management so in order to overcome that, if they want longlivety for batteries, there are not much other chances than to “cheat” with capacities and with charging logic.
AFAIU the invisible reserve is on the bottom (empty) end because full is the only state that can be measured reliably.
That is very true. I used to design chargers but it was a while ago, and those were mostly NICD or NIMH. However it is true for all chemistries that full charge cannot be determined unless the battery is actually fully charged There are various indicators for various chemistries; some lithium cells show a dip in the terminal voltage when approaching that point, while with the oldest ones the only way to tell was to use embedded temperature sensors and you detect the point when the energy going in is just wasted into a temperature rise, versus external ambient.
I can well see cars do not routinely go to full charge, to achieve max battery life, but that also means the software is doing a lot of tweaking, because when you leave it to fully charge, eventually it will say “full” but it has to be lying. It is probably pretty complicated.
