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is it possible to recalibrate the battery indicator?


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#1 OFFLINE   ahahah

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Posted 05 March 2013 - 04:59 PM

hello

when i full charge the battery it stay a long time with "100%" before decreasing.

 

then it decreases normally (or a little bit too fast).

 

and last time after a game session i had the message that says the pandora will shutdown because 5% was reached, and the red LED blinked.

 

when the day after i powered the pandora on, it indicated 24% :blink:  (i have not recharged it)

so i could use it normally for some time.

 

so my question is: is there something to do to have a more accurate indicator?



#2 OFFLINE   SNESFAN

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Posted 05 March 2013 - 05:42 PM

Mine has gotten more or less more accurate in time... pandora info shows im on my 30th charge cycle 100% - 0% - 100% Im sure someone is going to chime in and point to the thread explaining the % readout and how its calulated and calabrated automatically. I know my phone acts the same way but it doesnt take nearly as many cycles to calabrate

#3 ONLINE   Linux-SWAT

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Posted 05 March 2013 - 05:46 PM

Maybe discharge almost totally, then do a full recharge a few times.



#4 ONLINE   Binky

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Posted 05 March 2013 - 05:47 PM

When using sysinfo on my unit, I can get up to around 4600mAh, yet it claims full is 3800mAh

Same problem?


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#5 OFFLINE   Askarus

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Posted 05 March 2013 - 07:39 PM

I wish I had your battery.

 

Would be great to be able to get 4600mAh.



#6 ONLINE   Binky

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Posted 05 March 2013 - 08:14 PM

When using sysinfo on my unit, It claims I can get up to around 4600mAh, yet it says full is 3800mAh
Same problem?

 

FTFM (fixed that for myself)


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#7 OFFLINE   ElGecko

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Posted 05 March 2013 - 08:45 PM

"Forgot the Fraggle Manual"? B)

Could be that the TS's problem is related to mine. Battery-related topics are popping up on other forums in the last 2 days, it seems.

Greetz from Germany,

ElGecko

 

 

Edit: Yep, I just checked. Turned the system of with bat at 62% and charging, removed it, turned it back on and violĂ : 92%. Strange.



#8 OFFLINE   ahahah

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Posted 06 March 2013 - 09:38 PM

i always wait the almost full discharge before full recharge it.

 

i add that the battery indicator of xfce doesn't show the same values than the system info app one. (73% displayed in the xfce taskbar vs 69% displayed in the system info app).



#9 OFFLINE   WizardStan

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Posted 07 March 2013 - 12:33 AM

Fully charge to 100%, turn it off and leave it for 5 hours. Fully discharge (make sure that "cat /sys/class/power_supply/bq27500-0/voltage_now" returns about 300000), turn it off for 5 hours. That's the process for recalibrating the fuel gauge.

#10 OFFLINE   ElGecko

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Posted 07 March 2013 - 01:01 AM

Many thanks, that's good to know!



#11 ONLINE   Neelix

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Posted 07 March 2013 - 06:01 AM

Why 5 hours? I don't understand the mechanics of what makes such a delay necessary.

 

- Neelix


This is the Internet, ffs - Everybody has an opinion, everybody publishes their opinion, and nobody listens to anybody else.


#12 OFFLINE   WizardStan

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Posted 08 March 2013 - 12:47 AM

It tells the BQ chip "this is full/empty" as opposed to just a blip in the charge cycle. After sitting at approximately the same capacity for the necessary length of time, the BQ firmware records it.
In actuality, one of the directions only requires one hour to mark it, but I can't remember if it is charging or discharging and I'm too lazy to look it up, so I just say 5 hours both ways.
It's not exactly that simple, if the measurement is way off it may take a couple of cycles to get it right.
I also forgot to mention, a full charge is when, while charging, "cat /sys/class/power_supply/bq27500-0/voltage_now" reads around 4200000 and "cat /sys/class/power_supply/bq27500-0/current_now" reads around 800000. If the meter reads 100%, make sure to check these two files to ensure it's actually FULL. Realistically a charge current below 100000 is close enough.

#13 OFFLINE   _wb_

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Posted 08 March 2013 - 12:39 PM

You can also check the voltage and current in System Info (it gets the info from the same place, but it's slightly more human readable than those bare numbers in microVolt and microAmpere.

 

Your battery is "really" full when the voltage is around 4.2V, and it is "really" empty when the voltage is around 3V. During discharge, the voltage gradually drops. Voltage alone is not enough to reliably tell the exact charge percentage though.

 

Differences between what System Info reports and what anything else (like the battery indicator of xfce) reports are explained as follows:

 

- System Info gives two percentages: % of design charge and % of "full" charge, where "full" is some estimate of your battery capacity. The design charge is 4240mAh for everyone, the full charge will depend on your battery wear level, e.g. mine is 3874mAh at the moment (although that number is probably not a good estimate). All other indicators give only the percentage of "full". The percentage of design charge will of course always be lower.

 

- System Info gets the current battery charge to initialize its values, and it keeps looking at that reported value, but it also meanwhile monitors the power consumption based on the measured voltage and current. As long as the reported charge is close to the computed charge, it will "believe" the reported charge, but when the computed charge becomes too different from the reported charge, it will give you the computed charge. The reported charge is always clipped between two values, e.g. on my unit it is always between 38mAh and 3915mAh, so it can happen that the percentage you see is 100% and the reported charge does not go up, but the unit is still charging; in that case the computed charge of System Info will probably be closer to the truth. It can also happen that the reported charge is at the minimum (0% or 1%) and stops going down, but the unit is still discharging. In that case the computed charge of System Info will keep going down, and can possibly go negative too, which is of course not what the actual charge is, but it means that the initial reported charge was not correct because of miscalibration.


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#14 OFFLINE   ahahah

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Posted 08 March 2013 - 03:38 PM

when you talk about a fully discharge, there is something special to do or i just discharge it in using the pandora as usual?



#15 OFFLINE   WizardStan

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Posted 10 March 2013 - 06:43 AM

Just use it as usual. When the voltage_now command (shown above) reads 3000000 then you're empty. It will quickly drop from 3100000 to 30000000 so be sure to pay very close attention when it is getting close. The instant it hits 3v shut it down, if you keep using it beyond that mark you'll risk damaging the battery. This shouldn't be a problem, the lower bound is hard coded, once it hits 3v it should show 0% and you can shut it down, but in the event there is something amiss and it reads 0% before reaching 3000000 then just hit cancel every time it tries to shut down. Pay very close attention to the voltage, I cannot stress this enough when recalibrating. If you're at 3.2v you will reach 3.0v within minutes and the instant it does you need to shut down without hesitation.

edit: also as mentioned, the battery is really "full" when it reads 4.2v, but it's not really REALLY full until it reads 4.2v and the charge rate drops below 80ma. That's what the "current_now" command is looking for, checking the charge rate to see if it crosses the magic threshold.

Edited by WizardStan, 10 March 2013 - 06:52 AM.


#16 OFFLINE   _wb_

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Posted 10 March 2013 - 07:12 AM

How carefully do you have to be about not going below 3V? I've occasionally tried to see exactly how far it goes before there's just not enough juice left to keep going, and on my unit it seems to go down to about 2.85V before the screen goes black. When you get it that low and then plug in the charger, it takes a while before it even starts booting. I hope I didn't damage my battery by doing this - it still seems to work fine as far as I can tell.


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#17 OFFLINE   WizardStan

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Posted 10 March 2013 - 07:48 AM

Just don't do it. 3v should be the hard cutoff, below that you risk doing serious damage to the battery. It's probably fine, there are other safeguards in place, but it's still not a very good idea.

#18 OFFLINE   ahahah

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Posted 10 March 2013 - 10:34 AM

with the file manager i've searched the "/sys/class/power_supply/bq27500-0/voltage_now" file and when i want to open it i have this error message "failed to open the document: failed to map file '/sys/class/power_supply/bq27500-0/voltage_now': mmap() failed: no such device."

 

at any rate: xfce indicates 100% but system info indicates 92~93% with 3910mah. it seems that it doesn't continue the charge process.



#19 OFFLINE   ahahah

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Posted 10 March 2013 - 10:42 AM

lol ok i've used the terminal^^

 

ok so i have 417500 for the voltage_now and 433000 for the current_now



#20 OFFLINE   ahahah

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Posted 10 March 2013 - 12:38 PM

voltage_now is stabilized around 4165000 and current_now is now around 180000 which is far from the 800000 you indicated.

 

are that values normal?

 

can i consider the charge is full?

can i power the pandora off for 5 hours now?




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