Hi! > >>>>> to introduce coefficients for temperature and discharge rate? > >>>> What do you mean? Nothing like that is used in current driver why do > >>>> we need to add it? > >>> > >>> Well, conversion between Li-ion's voltage and state of charge at 0 > >>> current is well known: > >> > >> We can’t measure at 0 current since the OMAP is driven from battery > >> and charger and may also draw some mA… > > > > Yes, but you know how many mA you are taking just now. So if you knew > > the internal resistance, you could compute the voltage at 0 > > current. (And it should also work during charging, as long as you know > > how much current is going in.) > > As far as I understand the twl4030 charger and MADC it is not possible to > separate these values. It is only reporting the inflow from charger to > battery + system. So you don’t know how many mA are supplying the system > and how many mA are left over for charging. > > You can only assume how much the system is drawing while running (something > between 50 and 600 mA but this depends on system activities, power state > of peripherald and e.g. backlight being switched on). > > I think your basic assumption that we know any time how many mA the system > is taking is not given. So.. you won't be able to get exact value while charging, but you get one while discharging, which is what really matters...? > > Yes, and that coefficient should be internal battery resistance ;-). > > But where do you know this value from to write it into a DT file? > Usually you can’t measure it easily and for some batteries you don’t have > a data sheet. > > Contrary, the calibration curves can easily be measured on the device > (assuming that the charge level decreases/increases linearly over time > between Full and Empty). If you can copy it from the data sheet, that's the easiest option. If not, you should be able to easily compute it from the charge/discharge curves or from measured voltage at different loads. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
