> My question is: what exactly makes 14.75 the last "full" capacity? > How is that determined? Does the code for hw.sensors somehow observe > the AC is connected, but it's not getting charged > for the last $N minutes, so this must be the full capacity > or is this just what the battery tells us via apcibat(4)? > Possibly via "hw.sensors.acpibat0.raw0=full"?
It is all embedded code inside chip on the board. OpenBSD reads it and nothing more, I think. This was done by IBM/Lenovo to support your battery in time and to be able to alert user for a battery replacement operation. I remember back there it was an utility for T40 model which let you "recondition" the battery. It was Windows only, basicaly it was changing your battery and drain it again, at least what the user was able to see. I think a capacity calibration was done also, but no option to "reset" the capacity to the factory one. Sorry.
