Battery calibration - Sansa c200

[tomkiewicz]

Hi, i just bought refurbished Sansa c250 - it works well, but... when i use rockbox, it turns off when battery is about 20-30% (after that, when i try to turn it on, player only displays empty battery icon). On the other hand, player won't be fully charged - I had charging c200 under rockbox whole night, after that I started original firmware - when rockbox says, the battery was 100%, OF says it was about 70% (and after connecting cable it charges to 100%).

Is there any way to calibrate battery? I guess, that rockbox have lowered voltage range - both max and min :/. When I had mobile phone Siemens SL45i, it was quite easy - I had to fully discharge battery, then save lower limit, after that I had to raise upper limit, fully charge (phone went off, when battery protection notices overcharge) and save limit a bit lower.

[saratoga]

Hi, i just bought refurbished Sansa c250 - it works well, but... when i use rockbox, it turns off when battery is about 20-30% (after that, when i try to turn it on, player only displays empty battery icon). On the other hand, player won't be fully charged - I had charging c200 under rockbox whole night, after that I started original firmware - when rockbox says, the battery was 100%, OF says it was about 70% (and after connecting cable it charges to 100%).

I don't think the c200 charges under rockbox, so you should use the OF.

Is there any way to calibrate battery? I guess, that rockbox have lowered voltage range - both max and min :/. When I had mobile phone Siemens SL45i, it was quite easy - I had to fully discharge battery, then save lower limit, after that I had to raise upper limit, fully charge (phone went off, when battery protection notices overcharge) and save limit a bit lower.

Yes, you need to provide a discharge curve for the battery.  See http://www.rockbox.org/tracker/task/8480 for an example of one taken from the e200.  Currently its also used for the c200, which is why the battery percentages are off.  

I have a standing offer to fix the c200 one as soon as someone gives me the discharge curve, but looking at the battery bench wiki page it seems someone uploaded on without telling me, so i'll try and commit that later today.

(fine i'll edit)

Edit:  I take that back, the one posted on the wiki is obviously wrong, so I still need a new one.

[tomkiewicz]

OK, I'll make some battery benchmarks (including OF playtime check) - it may take me about two-three days, then I'll put these on wiki and PM you

[Febs]

I'll do one as well so that we have multiple data points to work from.

[saratoga]

I don't really need the OF part, but its certainly interesting enough to put on the wiki if you do measure it.

[Multiplex]

I have a couple of C200 players which I can run the benchmark on if you want a larger data set to average up.

I'm assuming there are instructions somewhere.

They are both fairly new so it may be best to get a few more cycles in before measuring them. And I haven't invested in any Micro SDHC cards yet - that might be a consideration.

Just holler...

[tomkiewicz]

there is another issue - i cannot make complete benchmark - i tried twice in this way - it runs from 100% to about 50-60% and log file ends with 6-7 hours in column "Time left" - another words, it have logged about 5-6 hours, but really plays about 12... Semi-solution to this problem (my third try) is stopping and resuming battery bench every 2-3 hours, but i think, it affects results... May it be problem of low amount of songs played (about 10MB)?

Now I uploaded about 100MB of music and run fourth bench...

[pixelma]

another words, it have logged about 5-6 hours, but really plays about 12...

The battery benchmark plugin doesn't work correctly on the sansas. There is a quick hacky solution to it in the tracker - together with a little information to be found in/through the SandiskE200BatteryMeasurements wiki page. The same applies to the c200 as well, you would need to compile your own build with this patch applied.

[tomkiewicz]

argh... during the OF test my player just switched off at about 65% of battery :/

I think, that writing down every voltage change may decrease playtime - I have written another patch, and uploaded in that thread: http://www.rockbox.org/tracker/task/8070 - now I can finally make proper benchmark for rockbox

[saratoga]

argh... during the OF test my player just switched off at about 65% of battery :/

I think, that writing down every voltage change may decrease playtime - I have written another patch, and uploaded in that thread: http://www.rockbox.org/tracker/task/8070 - now I can finally make proper benchmark for rockbox

Is the log attached with your patch suitable for battery calibration?

[saratoga]

See FS#8868.

I welcome additional battery benches if anyone else has run them.  

[Multiplex]

Is there still a need for battery data?

I should be able to do some now if required (I also have a 3Gig card)

I can only do Rockbox runs - I don't think that the OF understands ogg files (and I have never used it except to set the USB mode and load Rockbox, and USB)

[saratoga]

I commited 8868 already, but if you're interested in improving it with calibration data from your Sansa, you can do a battery bench and update the patch I commited.

[Multiplex]

I've just updated to a recent build so I'll keep an eye on the batery meter so see how accurate it feels...