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shut down voltage in rafpigna kernel

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By viper2097, Senior Member on 23rd February 2011, 01:00 PM
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Hi Guys!

Sorry for posting this here, but with less than 10 posts i'm not allowed to post in development threads.

i'm using rafdroid 3.1 and really love it, it's a great build!
but my battery lasts only for about ~12-18 hours on normal usage. This is really a problem for me, it should last at least 24h, better 30h in normal usage. cause when i have to use it more, i need to go to ~12h without any problems...

i noticed that the shut down voltage in the used kernel is @ 3.6V, could somebody confirm this?
A li-ion battery can be discharged to 3.0V (maybe lower) without any problems. I'm into r/c planes so i have a lot to do with batteries and i know this is true, also look here: http://en.wikipedia.org/wiki/Cutoff_...oltage_cut-off

So is it possible that i set the shut down voltage for myself to 3,2V or 3,0V?
Maybe this would bring the extra hours i'm searching for...

switching to a none sense build isn't a solution for me, i love sense and use it a lot (the dialer is really near to the best thing i can imagine, i also love friendstream and the weather widget with the fullscreen animation...)

We are dischargin with a maximum of 0,2C (~240mA) so when you look at this chart at the red line:

we are nearly wasting the half battery time when shutting off @3.6V. with a shutoff @[email protected],2C i think we would have a 1/4 more use time. with a shutoff @[email protected] in standby mode (4mA) the battery would maybe stand 2 times longer?
but in fact of the fast downgoing voltage i would prefer to go to 3,2V to be on the safe side...

sorry for my bloody english, i hope everyone can follow me
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23rd February 2011, 01:15 PM |#2  
E90 Commie's Avatar
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I think this is a very interesting question. I have calibrated my battery but it seems like my ROM/kernel (imilka Vision Sense 4.1) is thinking that 3.6 V is the same as empty and shuts down. It initiates the shutdown procedure at that level approximately. After that it can be restarted some times before the battery is completely empty.

What I am looking for is a solution to change the shutdown voltage to 3.2 V instead of 3.6. It would be a good addition to the battery life.

If there´s some kind of configuration file that can be changed it would be good to have it done.

It seems like calibration doesn´t solve this configuration problem. It still shuts down at too high level.

I hope this thread can provide a solution.
23rd February 2011, 04:37 PM |#3  
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That's really interesting. But I think it is a protection feature for the battery itself. So I don't know what might happen if you go down to 3.2V.

I'm not sure but this might be a driver or even something deeper in our phone that causes the shutdown so early. So I guess it's not very smart to touch this piece of the system and I don't know if it is possible anyway. But please, someone who knows better should let me know
23rd February 2011, 06:00 PM |#4  
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As far as i know, the hardware cut off in the batterie is around 2.6v, so there would be no caution to the batterie itself. I also read that the software shutdown is in the kernel.
So the question is, if there is a posability to change the voltage myself or if this have to do a kernel chef?
The danger to destroy the batterie with this experiment would be very smal, and if, an original htc batt cost @ amazon ~20€...
23rd February 2011, 08:09 PM |#5  
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Actually I think if you look at the post about Battery stats bin file, there is talk about the actual cut off without harm to the battery, and I think I remmeber seeing that 2.6 is the cutoff, is there a way to see what WinMo cuts off at? this way we are sure of the same cutoff, cause I agree the battery doesnt last nealy as long as winmo and that would be a good reason why.
24th February 2011, 10:51 AM |#6  
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It would be great if some of the devs could also say something to this thread
24th February 2011, 06:29 PM |#7  
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hopefully the devs notice this thread.

honestly this is the best (better most exciting) idea i have heard since magdlr came out did you allready ask in the irc?
#htc-linux, #htc-linux-chat on freenode
25th February 2011, 07:06 AM |#8  
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sorry, I'm not usin irc, maybe someone else could do this
25th February 2011, 07:44 AM |#9  
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I like this idea too especially since most batts have some juice left till 3.2 Volts and all the extra bits of minutes we can squeeze out of it is nice.

BUT, I wonder if this is not being done on purpose. Who says our beloved phone works under a certain Voltage treshold?
I have no schematic so I can't check on what Voltage the components and probably the Voltage regulator work.
25th February 2011, 11:16 AM |#10  
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There´s a sign that we should be able to get some more juice from the battery. When the device switches itself off there´s sometimes power left to do atleast 2-3 reboots almost until full boot (with other it switches off first when the home screen is supposed to be shown).

That is an indication that there should be some more power left in the battery which means the shutdown can be delayed somewhat in theory. When the battery is really depleted the HD2 switch itself off after one second of showing the bootscreen. But before it can almost complete 2-3 reboots.

In Windows Mobile it´s a little bit different - it can do one reboot before calibration but with Android it´s able to do more reboots before depletion. I would guess that 3.3 V would be a proper shutdown value when those reboots is considered. Unfortunately I don´t know how the voltage when it has been emptied down to "immediate shutdown" because it indicates 3.6 V after the first successful boot with charger connected.
4th May 2019, 04:17 AM |#11  
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My phone is dying at 30%... Started to happening when I changed the ROM. I managed to drain the battery to 7% with 3.4 V... At this point I can't keep de phone on to drain the rest. Tried all "calibration" methods.. not working
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