Hi Matti,

On Thu, Dec 2, 2021 at 7:29 AM Vaittinen, Matti
[off-list ref] wrote:

(fast forward the stuff where we are in violent agreement)

What I was now considering is that maybe the capacity drop (in uAhs)
caused by the temperature change - is not the same for new and old
battery. It sounds more logical to me that the capacity drop caused by
the temperature is proportional to the maximum capacity battery is
having at that point of it's life. Eg, if new battery can hold 80 units
of energy, and drops 20 units of energy when temperature changes from T0
=> T1 - an badly aged battery which now only can hold 40 units would
lose only 10 units at that same temperature drop T0 => T1. I was
wondering if such an assumption is closer to the truth than saying that
bot of the batteries would lose same 20 units - meaning that the new
battery would lose 25% of energy at temperature drop T0 => T1 but old
one would lose 50% of the capacity. I somehow think both of the
batteries, old and new, would lose same % of capacity at the temperature
change.

So, if this assumption is correct, then we should give the temperature
impact as proportion of the full capacity taking the aging into account.

This looks plausible.

My problem here is that I just assume the impact of temperature is
proportional to the full-capacity which takes the aging into account.
Knowing how this really is would be cool so we could get the temperature
impact modelled correctly in DT.

I suppose we should check some IEEE articles to verify that this is the
case before assuming. I have access to them but no time to read :(

quoted

Yes there is some tight community of electronic engineers who read the
right articles and design these things. We don't know them :(

Right. By the way, I heard tha the TI has patent protecting some type of
battery internal resistance usage here. OTOH, ROHM has patent over some
of the VDROP value table stuff. Occasionally it feels like the ice is
getting thinner at each step here. :/

This is none of our concern. Patents are concerns for people shipping
devices, not for open source code. Also patents are only valid for
20 years and we are looking at longer times anyway. If we define
generic DT properties for this they will be used more than 20 years
from now. We even have patented code in the kernel, see:
Documentation/RCU/rcu.rst

Yours,
Linus Walleij