On Thu, May 17, 2018 at 05:08:42PM -0600, Chris Murphy wrote:
> Check this out. After fully charging from this morning?
>
> [chris@f28h ~]$ upower -i /org/freedesktop/UPower/devices/battery_BAT1
> native-path: BAT1
> vendor: Hewlett-Packard
> model: PABAS0241231
> serial: 41167
> power supply: yes
> updated: Thu 17 May 2018 04:59:54 PM MDT (14 seconds ago)
> has history: yes
> has statistics: yes
> battery
> present: yes
> rechargeable: yes
> state: fully-charged
> warning-level: none
> energy: 29.1522 Wh
> energy-empty: 0 Wh
> energy-full: 29.1522 Wh
> energy-full-design: 38.115 Wh
> energy-rate: 0 W
> voltage: 8.671 V
> percentage: 100%
> capacity: 76.4848%
> technology: lithium-ion
> icon-name: 'battery-full-charged-symbolic'
>
> [chris@f28h ~]$
>
> How does capacity go from 82.68% this morning to 76.48% this
> afternoon? This laptop is ~18 months old.
Doesn't make sense, unless this morning it was "percentage" that was 82.68,
not "capacity". (I've certainly misread things like that, and this stuff
is hard to understand because there are no explanations given.)
>
> [root@f28h ~]# cat /sys/class/power_supply/BAT1/cycle_count
> 0
>
> That's obviously bogus. I'd say 75% of the time I'm working on power,
> the other 25% or less of the time it's running on battery. It gets
> battery usage once a week or so.
I think what that means is that the battery design was such that when
new the battery would hold 38.115 Wh, but it has now degraded so that
it only holds 29.1522 Wh.
if you divide 29.1522/38.115 you get 0.764848, hence the "capacity"
now that it has aged a year and a half, is 76.4848% of the original 38.115.
You'll notice that "capacity" is 100%, which means it's fully charged
for its current place in the battery lifetime curve, i.e., 29.1522 Wh.
Lithium Ion batteries age like that, its normal. Eventually you get
fed up with it and buy a new battery or a new laptop (or phone or
whatever gizmo we're talking about). The very reason why after a lot of
customer furor, Apple agreed to replace iphone batteries cheaply rather
than raking all those customers of the coals of overly-priced replacement
batteries.
--
---- Fred Smith -- fre...@fcshome.stoneham.ma.us -----------------------------
God made him who had no sin
to be sin for us, so that in him
we might become the righteousness of God."
--------------------------- Corinthians 5:21 ---------------------------------
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