Lowest battery charge until N900 turns off? - Page 2 - maemo.org

x-lette | # 11 | 2010-11-11, 12:45 | Report

Originally Posted by Matan View Post

Did you use hostmode? is BME running? I think BME is responsible for shutting down when battery level is low, so when it is not running, you don't have that protection.

No, not using hostmode yet.
BME? Don't know about it. I didn't stop it but also didn't take care if it's running.
...

Code:

ps ax|grep bme

shows

Code:

/usr/sbin/bme_RX-51
/usr/lib/hal/hald-addon-bme

Is it that?

RobbieThe1st | # 12 | 2010-11-11, 12:55 | Report

Thing is, the actual shutdown stuff is based on voltage. If you ever look at battery-eye's voltage logs, you will see the voltage all over the place during normal usage. The "percentage" is just a rough estimate, barely more than a guess based on current use and voltage.

This also means that if you use your n900 heavily until it shuts off, the voltage will have been pushed lower than "normal" by the heavy usage; letting it sit before powering it on will give ot a chance to recover a bit and go back over the poweroff threshold.

To use a different metaphor, it's like a car battery: crank the engine until it stops turning over, wait for 10 minutes and you'll be able to get some more cranking out of it.
Run it dead with a smaller load - like leaving your headlights on - and you probably won't.

Matan | # 13 | 2010-11-11, 12:56 | Report

bme_RX-51 is bme. If you did not stop it and did not run hostmode which stops it, it is probably running. Do you know how the widget finds the remaining capacity? From hal, which is the value that BME uses, or directly from the hardware?

dr_frost_dk | # 14 | 2010-11-11, 13:26 | Report

To sum this up:
The phone shuts off at 3.3V on the battery
The battery manager you refer to is not that accurate, it says 0% at about 3.6V
In mine i use a custom "script" for QBW

Code:

hal-device | grep voltage.current | awk '{printf "%1.3fV - %3.0f", $3/1000,($3-3300)/9}{print "%"}'

with this "script" the phone turns off seconds after it shows 0%

At 3.3V the battery is about empty, if you where to use it after this it would be a matter of minutes before it would hit 2.0V and that will kill the battery completely.
But luckily the phone has a batt manager that shuts it off at 3,3V, and the battery has a circuit that shuts it off at 3.0V.

Last edited by dr_frost_dk; 2010-11-11 at 13:31.

The Following 2 Users Say Thank You to dr_frost_dk For This Useful Post:
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x-lette | # 15 | 2010-11-11, 13:39 | Report

Originally Posted by Matan View Post

bme_RX-51 is bme. If you did not stop it and did not run hostmode which stops it, it is probably running. Do you know how the widget finds the remaining capacity? From hal, which is the value that BME uses, or directly from the hardware?

It's the standard script from DCEW:

Code:

hal-device bme | awk -F"[. ]" '$5 == "is_charging" {chrg = $7}; $5 == "percentage" {perc = $7} END if (chrg == "false") {print perc "%"} else {print "Chrg"}'

x-lette | # 16 | 2010-11-11, 13:41 | Report

Originally Posted by dr_frost_dk View Post

To sum this up:
The phone shuts off at 3.3V on the battery

Tthat's quite the answer I was looking for. So it's voltage-triggered and for best watching the status I'll add current voltage to desktop.
Thanks!

dr_frost_dk | # 17 | 2010-11-11, 15:11 | Report

glad to help

try the code i submitted then you will know when it dies.
there is just one thing, 3.5 to 3.3 volts goes quite fast, witch you can see when looking at the capacity graph for litium batterys.
since im one off those EV freaks, i know first hand to what to do and what not to do with litium batterys.