kern/173414: [acpi] ACPI battery time incorrect
Kevin Oberman
rkoberman at gmail.com
Thu Apr 17 05:20:01 UTC 2014
The following reply was made to PR kern/173414; it has been noted by GNATS.
From: Kevin Oberman <rkoberman at gmail.com>
To: bug-followup at FreeBSD.org, jb.1234abcd at gmail.com
Cc:
Subject: Re: kern/173414: [acpi] ACPI battery time incorrect
Date: Wed, 16 Apr 2014 22:11:16 -0700
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Im most systems, ACPI does not return the battery lifetime when on AC
power. The actual remaining time is calculated by the EC BIOS and is
calculated mostly be taking the discharge rate in mW and the current
capacity in mWh. As far as I know, no OS attempts to calculate the time. It
is simply read from the the EC via ACPI. When plugged in to AC, the
discharge rate is 0, making the calculation undefined (division by zero).
Even the remaining battery time reported by ACPI is, at best, a very rough
guess as discharge rate can vary dramatically depending on system load.
On FreeBSD you can see detailed information on batteries with the
acpiconf(8) command. "acpiconf -i N" where 'N' is the battery number; 0 if
only one battery is present.
My system on battery:
esign capacity: 50540 mWh
Last full capacity: 46660 mWh
Technology: secondary (rechargeable)
Design voltage: 10800 mV
Capacity (warn): 2333 mWh
Capacity (low): 200 mWh
Low/warn granularity: 1 mWh
Warn/full granularity: 1 mWh
Model number: 42T4795
Serial number: 2654
Type: LION
OEM info: SONY
State: discharging
Remaining capacity: 96%
Remaining time: 2:12
Present rate: 20460 mW
Present voltage: 11652 mV
And after plugging in to AC:
Design capacity: 50540 mWh
Last full capacity: 46660 mWh
Technology: secondary (rechargeable)
Design voltage: 10800 mV
Capacity (warn): 2333 mWh
Capacity (low): 200 mWh
Low/warn granularity: 1 mWh
Warn/full granularity: 1 mWh
Model number: 42T4795
Serial number: 2654
Type: LION
OEM info: SONY
State: high
Remaining capacity: 96%
Remaining time: unknown
Present rate: 0 mW
Present voltage: 11648 mV
Looking at the raw sysctl when on battery shows hw.acpi.battery.time: -1.
This is normal. I don't see that ACPI
--
R. Kevin Oberman, Network Engineer, Retired
E-mail: rkoberman at gmail.com
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<div dir=3D"ltr"><div><div><div><div>Im most systems, ACPI does not return =
the battery lifetime when on AC power. The actual remaining time is calcula=
ted by the EC BIOS and is calculated mostly be taking the discharge rate in=
mW and the current capacity in mWh. As far as I know, no OS attempts to ca=
lculate the time. It is simply read from the the EC via ACPI. When plugged =
in to AC, the discharge rate is 0, making the calculation undefined (divisi=
on by zero). Even the remaining battery time reported by ACPI is, at best, =
a very rough guess as discharge rate can vary dramatically depending on sys=
tem load.<br>
<br></div>On FreeBSD you can see detailed information on batteries with the=
acpiconf(8) command. "acpiconf -i N" where 'N' is the ba=
ttery number; 0 if only one battery is present.<br></div>My system on batte=
ry:<br>
esign capacity:=C2=A0=C2=A0=C2=A0 50540 mWh<br>Last full capacity:=C2=A0=C2=
=A0=C2=A0 46660 mWh<br>Technology:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 sec=
ondary (rechargeable)<br>Design voltage:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=
=A0 10800 mV<br>Capacity (warn):=C2=A0=C2=A0=C2=A0 2333 mWh<br>Capacity (lo=
w):=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 200 mWh<br>Low/warn granularity:=
=C2=A0=C2=A0=C2=A0 1 mWh<br>
Warn/full granularity:=C2=A0=C2=A0=C2=A0 1 mWh<br>Model number:=C2=A0=C2=A0=
=C2=A0 =C2=A0=C2=A0=C2=A0 42T4795<br>Serial number:=C2=A0=C2=A0=C2=A0 =C2=
=A0=C2=A0=C2=A0 =C2=A02654<br>Type:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =
=C2=A0=C2=A0=C2=A0 LION<br>OEM info:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 S=
ONY<br>State:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 disch=
arging <br>Remaining capacity:=C2=A0=C2=A0=C2=A0 96%<br>Remaining time:=C2=
=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 2:12<br>
Present rate:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 20460 mW<br>Present volt=
age:=C2=A0=C2=A0=C2=A0 11652 mV<br><br></div>And after plugging in to AC:<b=
r>Design capacity:=C2=A0=C2=A0=C2=A0 50540 mWh<br>Last full capacity:=C2=A0=
=C2=A0=C2=A0 46660 mWh<br>Technology:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =
secondary (rechargeable)<br>
Design voltage:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 10800 mV<br>Capacity (=
warn):=C2=A0=C2=A0=C2=A0 2333 mWh<br>Capacity (low):=C2=A0=C2=A0=C2=A0 =C2=
=A0=C2=A0=C2=A0 200 mWh<br>Low/warn granularity:=C2=A0=C2=A0=C2=A0 1 mWh<br=
>Warn/full granularity:=C2=A0=C2=A0=C2=A0 1 mWh<br>Model number:=C2=A0=C2=
=A0=C2=A0 =C2=A0=C2=A0=C2=A0 42T4795<br>Serial number:=C2=A0=C2=A0=C2=A0 =
=C2=A0=C2=A0=C2=A0 =C2=A02654<br>
Type:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 LION<br>OEM i=
nfo:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 SONY<br>State:=C2=A0=C2=A0=C2=A0 =
=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 high <br>Remaining capacity:=C2=A0=C2=
=A0=C2=A0 96%<br>Remaining time:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 unkno=
wn<br>Present rate:=C2=A0=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 0 mW<br>Present vo=
ltage:=C2=A0=C2=A0=C2=A0 11648 mV<br><br></div>Looking at the raw sysctl wh=
en on battery shows hw.acpi.battery.time: -1. This is normal. I don't s=
ee that ACPI<br>
-- <br><div><div><div><div><div><div dir=3D"ltr">R. Kevin Oberman, Network =
Engineer, Retired<br>E-mail: <a href=3D"mailto:rkoberman at gmail.com" target=
=3D"_blank">rkoberman at gmail.com</a><br></div>
</div></div></div></div></div></div>
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