Inaccurate Battery Percentage (Fuze V2)

[coffeejunky]

Hi all,
First off, absolutely fantastic work, this has changed a great player into a brilliant player.

However, I seem to have noticed a bug with my V2 Fuze, the battery percentage given seems to be wildly inaccurate. It will randomly change +/- 10%.
For example right now it is reporting 51% charge remaining, just a second later it is showing 47%, then in a few minutes it will be 53%. In the last ten minutes I have seen it as low as 41% and as high as 54%. I can gain an approximation by this but it shouldn't normal behavior surely?

The OF shows battery life as steady and accurate, so it isn't a hardware failure, seems to be a calibration issue with Rockbox and my hardware.

I haven't yet managed to fully drain and recharge the battery (long battery life can be a tad annoying sometimes  ). Maybe that would help?

Anyone have any thoughts or can replicate this?
I am on the lastest stable rockbox build (3.71) with the latest Sandisk firmware.

[coffeejunky]

Just an update, did a full discharge/recharge cycle and this has not helped the issue.
I poked around in the debug section of the firmware under the battery section and in a 5 minute span the battery voltage fluctuates from 4.066v to 4.1044v and the voltage deltas for each minute seem to flit around a bit. I guess it's just a limitation of the way rockbox works out the battery % as it seems to be polled more frequently than the OF, meaning more fluctuation.

[Llorean]

The OF may also just refuse to update the display of battery percentage until a certain number of readings are more than a certain percentage from the last reading, rather than updating for every reading, in an effort to create a smoother apparent curve.

There's several ways that the OF could be "cheating" to provide a nicer looking (albeit technically slightly less accurate) display.

If it's that jumpy in Rockbox, it might actually be nice to look into it and see if there's a reasonable way to do something similar.