* Arthur D. <spinal.by@xxxxxxxxx> [200321 22:09]: > Hi. > > > Hmm I'm getting -EINVAL when I do echo 1600000 > charge_now but yet the > > value does get updated? > > Hm. I'm getting "Permission denied" when trying to do this. > Anyway, charge_now value is not supposed to be initialized by the user. > Only charge_full should be writable. Sorry I meant writing to charge_full :) Anyways, looks like echo -n works with no errors: # echo 1305000 > charge_full bash: echo: write error: Invalid argument # echo -n 1305000 > charge_full > > And I'm still not seeing capacity show up after that though even with > > full battery.. I think we should be able to calculate it if either a > > high or > > low value has been seen? > > There are two steps needed to calibrate the battery: to hit the "fully > charged" > state and to hit "battery empty" state. When the both states were hit the > driver > will initialize charge_full value. And it will start reporting correct > charge_now > and capacity (battery charge percentage) values. Hmm OK. So far no luck triggering that though. > Once the charge_full value is calculated it's recommended to be saved by the > user > to a permanent storage between reboots. > > Saving/restoring the value can be done in init scripts. > > For saving the calibration value just use the command like: > cat /sys/class/power_supply/battery/charge_full > /battery_cf > > To restore (after device reboot or power on): > cat /battery_cf > /sys/class/power_supply/battery/charge_full OK > This will allow the kernel to do fast calibration. I.e. you will > only need to fully charge _OR_ fully discharge the battery to start > seeing correct charge_now and capacity values. OK > > Also, we should have the driver default to using the charge_full_design > > value if nothing is written from userspace and we see a high or low > > value. > > I'd prefer to have charge_full value undefined until the battery is > calibrated. > This way the userspace can estimate current battery capacity using voltage > as a > fallback for uncalibrated battery. The voltage estimation will be way more > accurate than having charge_full = charge_full_design on pretty old Droid 4 > batteries. For example, my battery after calibration has about 1000 mAh, > while charge_full_design is 1740000. OK > > Maybe some pessimistic estimate could be used instead of just using > > charge_full_design if no value is initialized from the userspace? > > Something like (charge_full_design / 4) * 3 maybe? > > It's better to rely on voltage estimated percentage. > In Maemo Leste we patched upower to use the following formula, which gives > pretty > good results: > > percentage = (voltage - voltage_empty) / (voltage_full - voltage_empty) * > 100 > > Actually, the formula we use is a bit more complicated. OK > If you're curious, here's how it's actually done: > https://github.com/maemo-leste/upower/blob/master/src/linux/up-device-supply.c#L756 Thanks, I'll give the calibration another try. Maybe I did not wait low enough, I think I went down to 3.3V. Regards, Tony
