[ltp] R40 Battery life

[Eben King]

On Sat, 26 Feb 2005, John M Flinchbaugh wrote:

> I have a 1.4GHz R40 and probably average 4 hrs on battery, though I've
> seen 5.
...
> I also try to keep my LCD brightness turned down, though I'm not sure
> how much that really affects power drain.

You can find out with something like:

cat /proc/acpi/battery/BAT0/state ; sleep 10 ; \
cat  /proc/acpi/battery/BAT0/state

With the backlight at maximum:

before: present rate:            14466 mW
after: present rate:            14271 mW
average: 14368.5 mW = 14.3685W

or

before: remaining capacity:      70600 mWh
after: remaining capacity:      70560 mWh
average: 40 mWh/10 s
       = 0.040 Wh/10 s
       = (0.040*3600) J/10 s
       = 0.040*360 W
       = 14.4 W

Not too far off.  I'd trust the first result more.

With the backlight at minimum:

before: present rate:            13153 mW
after: present rate:            12372 mW
average: 12762.5 mW = 12.7625 W

or

before: remaining capacity:      70200 mWh
after: remaining capacity:      70170 mWh
average: 30 mWh/10 s
       = 0.03 Wh/10 s
       = (0.03 * 3600) J/10 s
       = 0.03*360 W
       = 10.8 W

20% or so off.  Again, I trust current meters more than I do
remaining-charge estimates.

So it looks like turning the backlight up from min to to max would reduce
your runtime by about 37 minutes.

-- 
-eben    ebQenW1@EtaRmpTabYayU.rIr.OcoPm    home.tampabay.rr.com/hactar
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