Extended "screen-on" time by battery gauge tricks - Huawei MediaPad, T-Mobile SpringBoard

Sorry for long story but might be interesting for developers.
Some time ago I have flashed OSIMood ROM to my Mediapad. After flashing I had brand new "Battery Gauge" showing percentage values (circular icon), but after some time it was.... lost(!!!)? I do not know what happened but it just has disappeared. At the same time device stopped displaying warning about "automatic shutdown" because of the low battery level.
Then.... I started to use alternative battery monitors (like Battery Monitor Widget) and it read very strange battery levels from system. According to what it read battery went down to 0% in 1-2hours of "screen-on" and it stayed at 0% even for 5 hours of "screen-on" time until device switched off because battery was empty.
The Battery Monitor Widget showed clearly that MEDIAPAD switches off without warring when the battery is empty (usually about 3250mV, lowest level reached was 3100mV). Switch off at ~3200mV is not devastating to battery as I have monitored many recharge cycles and battery was able to recharge back to 4199-4200mV every time.
The battery condition is fine - when it was recharged overnight I could EASILY reach over 6 hours of "screen on" watching online video (with WiFi on). I think this is perfect.
I have tried to recalibrate battery but it did not help. The battery monitors have always read level 0% and stays at 0% much too early.
I was NOT complaining about missing "automatic shutdown" - in my opinion this was triggered much too fast (when there was still lot of battery left). I could use my Mediapad much much longer, In my opinion this was huge ADVANTAGE(!!!).
I have tried to investigate and found somewhere that FuelGauge interprets 3900mV as 100% and 3400mv as 0% while Mediapad tab can still work intil it drops down to 3200mV(!!!). Moreover I have noticed that pad gets quickly down to about 3500mV~3450mV and this is a time when "automatic shutdown module" triggers "force close". But.... this feature was gone/borken in OSI MOD allowing tab to work for nex few hours (!!!) great
Now..... I wanted to get "overcloked kernel" and "touchsceen filtereing" and flashed CleanICE ROM and.... my tab gets dow to 0%in 2 hours + I suffer from "automatic shutdown". I miss the OSI MOD now and miss 6 hours of screen-on working.
THIS IS A MESSAGE TO ALL DEVELOPERS.
1. Could you please reveal how to REMOVE/DISABLE standard "automatic shutdown" feature? It will allow our's mediapads to run for 6 hours instead 2 or 3 hours.
2. Could you please fadjust the fuel gauge, by setting up the 100% for 4000mV and 0% for 3200mv. I think this will give much better battery level estimations.
Who know how to do this? Implementing this this would be great contribution for all Mediapad user community.

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maybe yor battery is worn...before I replaced battery, it jumped from 15% to 0% almost immediately, now with new one I can go up to 7 hours of screen-on+wifi (CM10 rom)...it takes about 40 minutes of using to drop from 2% to 1%

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441Excelsior said:
maybe yor battery is worn...before I replaced battery, it jumped from 15% to 0% almost immediately, now with new one I can go up to 7 hours of screen-on+wifi (CM10 rom)...it takes about 40 minutes of using to drop from 2% to 1%
Click to expand...
Click to collapse
Where did you buy the new battery from?

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441Excelsior said:
maybe yor battery is worn...before I replaced battery, it jumped from 15% to 0% almost immediately, now with new one I can go up to 7 hours of screen-on+wifi (CM10 rom)...it takes about 40 minutes of using to drop from 2% to 1%
Click to expand...
Click to collapse
can you tell me step-by-step how to open back cover? thankyou

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I have a similiar problem in ALL custom rom i tried. My mediapad is hooked up in my car dashboard, so
ignition on -> charging (and normal use)
ignition off -> standby and airplane mode
many mornings instead of waking up automagically, I found mediapad shutted down. When I turn it on it shows suddently something like 70% charge! This issue *doesnt* appear in huawei rom, so it seems to be a custom rom/cyanogen issue
feel free to ask me info and please provide procedures for log and debug, I whould be very happy to solve this issue

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danisukses said:
can you tell me step-by-step how to open back cover? thankyou
Click to expand...
Click to collapse
you must remove two black covers then unscrew 6 screws (3 under each cover), then remove speakers cover and then carefully remove screen (use knife or something thin but be very careful cause you can damage wires or PCB with knife...it is not so hard to open it but you must be extremely careful

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441Excelsior said:
you must remove two black covers then unscrew 6 screws (3 under each cover), then remove speakers cover and then carefully remove screen (use knife or something thin but be very careful cause you can damage wires or PCB with knife...it is not so hard to open it but you must be extremely careful
Click to expand...
Click to collapse
Excuse me.
Where did you buy the new battery from?

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I bought it from one man who had 2 months old mediapad lite with broken screen so he was selling its parts

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thankyou brother

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MediaPad is only using ～40% of its battery power
I too observe the same behavior. It's quite obvious that the MediaPad is only using ～40% of its battery power.
The MediaPad would scream battery low and shut off (after around 3 hours of use) at around 3.75v, but there is still a lot of juice left in the battery! I can confirm this by continuing reboot into recovery mode (ie, screen on full brightness, no battery management), while the MP body becomes quite warm due to high power draw, it lasts another 3 hours before the battery protection kicks in and shuts off the power (~3.2V).
I found that if I plug in again and turn on the Mediapad, the battery gauge would stubbornly stay at 0% for around 2 hours (even though the battery is sucking power @ 1.3a and recovering in voltage) and then starts to move upwards (at around 3.95v). After another 3 hours, the battery is fully charged.
I can replicate this behavior in the official rom or any other roms that I have tried. So, it's seems to me that there're something REALLY WRONG with the MP's battery gauge and I would repeat eses1234's request:
THIS IS A MESSAGE TO ALL DEVELOPERS.
1. Could you please reveal how to REMOVE/DISABLE standard "automatic shutdown" feature? It will allow our's mediapads to run for 6 hours instead 2 or 3 hours.
2. Could you please adjust the fuel gauge, by setting up the 100% for 4000mV and 0% for 3200mv. I think this will give much better battery level estimations.
Who know how to do this? Implementing this this would be great contribution for all Mediapad user community.

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buddylu said:
I too observe the same behavior. It's quite obvious that the MediaPad is only using ～40% of its battery power.
The MediaPad would scream battery low and shut off (after around 3 hours of use) at around 3.75v, but there is still a lot of juice left in the battery! I can confirm this by continuing reboot into recovery mode (ie, screen on full brightness, no battery management), while the MP body becomes quite warm due to high power draw, it lasts another 3 hours before the battery protection kicks in and shuts off the power (~3.2V).
I found that if I plug in again and turn on the Mediapad, the battery gauge would stubbornly stay at 0% for around 2 hours (even though the battery is sucking power @ 1.3a and recovering in voltage) and then starts to move upwards (at around 3.95v). After another 3 hours, the battery is fully charged.
I can replicate this behavior in the official rom or any other roms that I have tried. So, it's seems to me that there're something REALLY WRONG with the MP's battery gauge and I would repeat eses1234's request:
THIS IS A MESSAGE TO ALL DEVELOPERS.
1. Could you please reveal how to REMOVE/DISABLE standard "automatic shutdown" feature? It will allow our's mediapads to run for 6 hours instead 2 or 3 hours.
2. Could you please adjust the fuel gauge, by setting up the 100% for 4000mV and 0% for 3200mv. I think this will give much better battery level estimations.
Who know how to do this? Implementing this this would be great contribution for all Mediapad user community.
Click to expand...
Click to collapse
Hi, I'm not a developer but I think this can be a real HUGE and fantastic improvement for out MP. Googling around I've found this (maybe can be useful):
in BatteryService.java ,when the battery lvl is too low (0%, lower than 3.4v), the service will call shutdownIfNoPower to shutdown system. The complete file path is services/java/com/android/server/BatteryService.java in android_frameworks_base.

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Thats really some interesting facts.
I did some googling an came to this point:
I downloaded the latest rom from after_silence and extracted it to my hard disk.
Then i took the "/system/framework/services.jar" and disassembled it with the apktool.
After that i digged into the folders and found the BatteryService.smali in "com\android\server".
Im not a developer as well so im not able to go any further right now, but as far as i can see it should be possible to modify the BatterService, compile the services.jar and sign it again to push it back to the MediaPad.
Im stuck to the "shutdownIfNoPowerLocked" i think this is the variable which is forcing the shutdown.
Someone else with some more information?

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I did some more experiments about the battery problem and found the following facts. I am not a developer myself, but I'd really be grateful if someone can at least disable the shutdownIfNoPower mechanism.
buddylu said:
At first when I found this problem, I thought that’s my battery dying and its power output characteristics are dropping, so I changed to a NEW battery. While it's better than the old one, the MediaPad only see and use about half of its juice.
I even went to the extreme, put 2 NEW batteries in parallel circuit (in theory providing twice the juice, with the same voltage and better power output curve characteristics), and changed the battery protection circuit to a new one. Same thing - the MediaPad stubbornly only see and use ~ half of the juice. Plus the aforementioned observation of the cut off voltage @3.75V in Android system and @3.2V cut off in recovery, I come to the conclusion that MediaPad’s power gauge is faulty.
Click to expand...
Click to collapse

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Any improvements in this subject???

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no sorry, the only thing you can do to extend battery life is undervolting

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441Excelsior said:
no sorry, the only thing you can do to extend battery life is undervolting
Click to expand...
Click to collapse
Thanks but undervolting does not help in the main problem that mediapad switches off at high battery voltages.

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mine switch off at 3.55-3.6V

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Hiero said:
Thats really some interesting facts.
I did some googling an came to this point:
I downloaded the latest rom from after_silence and extracted it to my hard disk.
Then i took the "/system/framework/services.jar" and disassembled it with the apktool.
After that i digged into the folders and found the BatteryService.smali in "com\android\server".
Im not a developer as well so im not able to go any further right now, but as far as i can see it should be possible to modify the BatterService, compile the services.jar and sign it again to push it back to the MediaPad.
Im stuck to the "shutdownIfNoPowerLocked" i think this is the variable which is forcing the shutdown.
Someone else with some more information?
Click to expand...
Click to collapse
I had a look into it from the kernel side. The battery percentage shown is read directly from a battery monitor chip (TI bq27510). The percentage is calculated by the amount of charge that the battery provided to the pad (coulometer). The sysfs driver lives in /sys/power, its source is in drivers/power/bq275x0_battery.c.
The function that reports the battery percentage is this one:
Code:
/*
* Return the battery Relative State-of-Charge
* Or < 0 if something fails.
*/
int bq275x0_battery_capacity(struct bq275x0_device_info *di)
{
int data=0;
// int data2 = 0;
if(BSP_FIRMWARE_DOWNLOAD_MODE == gBq275x0DownloadFirmwareFlag)
{
return 30;
}
#ifdef BQ275x0_DEBUG_FLAG
get_remaining_capacity(di);
get_full_charge_capacity(di);
#endif
data = bq275x0_i2c_read_word(di,BQ275x0_REG_SOC);
BQ275x0_DBG("read soc result = %d Hundred Percents\n",data);
return data;
}
If you want it to report something else, maybe based on the voltage, this function could easily be changed to something like:
Code:
/*
* Return the battery Relative State-of-Charge
* Or < 0 if something fails.
*/
int bq275x0_battery_capacity(struct bq275x0_device_info *di)
{
int data=0;
// int data2 = 0;
[B]int voltage = 0; // Voltage in mV[/B]
if(BSP_FIRMWARE_DOWNLOAD_MODE == gBq275x0DownloadFirmwareFlag)
{
return 30;
}
#ifdef BQ275x0_DEBUG_FLAG
get_remaining_capacity(di);
get_full_charge_capacity(di);
#endif
[B]voltage = bq275x0_battery_voltage(di);
data = some_cool_function_that_magically_converts_the_voltage_into_a_good_percentage_estimate(voltage)[/B]
BQ275x0_DBG("read soc result = %d Hundred Percents\n",data);
return data;
}
Although one should check first that this does not interfere with charging the battery correctly (I guess it won't).
I have no working toolchain ready to test this atm (quite busy...). If I find some time I will give it a shot and ask around who wants to play the guinea pig
mblaster

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Hey mblaster,
that sounds really interesting!
So with this function we can reduce the shutdown voltage by manipulating the variable, right?

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any news?
my pad keeps dropping its capacity by 20%+ in no time when its active/ in use
when in standby it works like it is supposed
any news would be much appreciated