sansa battery life

[corvetteguy]

Sorry for thread digging but the OP had the same problem as me.

When plugged into the wall, the battery % reads 100%. After being plugged in for around 10 hours, i unplugged it and it read 84% and about 4 hours of runtime left. People here have said how inaccurate the read out is, but its funny because thats about how long it lasted. Without doing a battery bench, and just from timing it myself at school, the player lasted from about 9am to 11:30am, which is far from the 12 hours other people are getting. I also charged it using the OF to the same effect.

It can't be the battery because I only changed the firmware a few days ago after having this player since July 2006 and consistanly getting 17 hours of playback after charging for about 2 hours every morning.

I read somewhere about changing a text file to fix the meter but i know nothing about programming and am somewhat overwhelmed by massive notepad files 

I really hope I don't get another "Read the manual" response, or some sarcastic comment because i feel i have done my best to figure out the problem to no avail, and would really like to continue using RB.

[Llorean]

It's nearly physically impossible that you've had the same battery life since July 2006, because lithium based batteries decay over time. Please, do a proper test both in the original firmware on a full charge, and in Rockbox on a full charge, with equivalent settings (volume at the same loudness, equalizer, bass, treble, replaygain, crossfeed, etc all turned off).

[saratoga]

When plugged into the wall, the battery % reads 100%. After being plugged in for around 10 hours, i unplugged it and it read 84% and about 4 hours of runtime left. People here have said how inaccurate the read out is, but its funny because thats about how long it lasted. Without doing a battery bench, and just from timing it myself at school, the player lasted from about 9am to 11:30am,

I fixed runtime estimation the day before yesterday.  Upgrade your build and it'll give you a more realistic run time.  

Did you charge it in the OF?  I think rockbox doesn't actually charge the battery.  At least it sounds like your battery didn't actually recharge if its only reading 84% fresh off the charger.  That or its amazingly dead.

[P.Opus]

If you read some of the forums regarding Rockbox and Battery issues on the Sansa, then you would notice two things.

1. Rockbox is not optimized for PortaPlayer based players.  This is due to the Rockbox team not having all the information regarding the chipset.  As a result, they are unable to know what optimiztions can be made (i.e. what can be turned on and off) to help optimize battery life.

2. Rockbox and battery charging does not work will well.  It has been documented somewhere that while running Dropbox, the USB cable only draws 100mA vs, 500mA in original Firmware.

This means that battery charging time under rockbox is 5 times longer and if you are actually running Rockbox during the charge, you might be barely breaking even if not actually trickle discharging.

So as it stands, the suggestions from the Rockbox team is to use Original Firmware for not only USB transfer, but also for battery charging.

There may be some future build which modifies the Rockbox USB charging routine, at which point we'll be able to use Rockbox while charging and actually be charging the battery.

[corvetteguy]

Yes I read all that before. The thing is, even though they are not getting an accurate estimate people are still getting around 12 hours from a full charge, which i know is down from the 17-20 in the OF. I went from getting about 16 hours to 3 hours, so I just want to know how to get close to the 12 hours others are getting.

I have been charging under OF, overnight sometimes, so its not because of trickle charging.

[saratoga]

I went from getting about 16 hours to 3 hours, so I just want to know how to get close to the 12 hours others are getting.

http://www.rockbox.org/twiki/bin/view/Main/SandiskE200BatteryMeasurements

[corvetteguy]

Maybe the problem is that it shuts off at 40% charge. My friend recently bougth an e280 and is getting the exact same 3-4 hours i am getting. Is there any way to chane the % at which it shuts down or is that a dev thing?

[saratoga]

See battery_level_shutoff in \firmware\target\arm\sandisk\sansa-e200\powermgmt-e200.c.

However, unless your battery is significantly different then the standard one, I doubt that is going to help you.  

[P.Opus]

so I just want to know how to get close to the 12 hours others are getting.

I have been charging under OF, overnight sometimes, so its not because of trickle charging.

And what are you doing in Rockbox.  With OF, I simply played my music, pretty straight forward.  However, with Rockbox, I play solitaire, Bubbles, Doom, etc.  All this stuff takes more processing power and hence more power than simply playing music.  Also realize that playing games, the backlight stays on constantly, where as in OF it rarely is on unless you are choosing an album, or otherwise navigating.

While there is no doubt that Rockbox in simple playback mode has approx 30 to 40 percent lower battery life in strict playback.  Rockbox does indeed change the way you use your player, so you must keep that in mind.  

[corvetteguy]

Ya i know that. The 3-4 hours was strictly music, and most of the time it was just playing, no nav. Iccaisionally i had tostart the song again cuzit would stop for no reason, buti assume thats a bug.

[Icarus]

Are you using an official Sansa cable?  I'm not, and I'm having the same damn problem.

[corvetteguy]

I'm using the one that came with the player.

[scharkalvin]

I wasn't getting only 3-4 hours, but I was getting less than 12 (maybe 6).
Then again, I bought a reconditioned player, which might have come with a used battery!
Could try a new battery from an official sansa source.

[AutobahnSHO]

It can't be the battery because I only changed the firmware a few days ago after having this player since July 2006 and consistanly getting 17 hours of playback after charging for about 2 hours every morning.

Batteries are finicky- they do deteriorate over time and especially if you went from a low-drain situation to a higher-drain it could affect battery life.

Try fully discharging/charging a couple times?

The battery kit from Sandisk is only $20.

[Chronon]

Try fully discharging/charging a couple times?

That shouldn't affect anything.  Li⁺ batteries don't suffer from memory effects like NiMH batteries do.  I would lean more toward deterioration, as you suggested in the first sentence.  Wikipedia estimates a 20% drop in capacity per year for Li⁺ batteries.