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Date:      Thu, 17 Apr 2014 05:20:00 GMT
From:      Kevin Oberman <rkoberman@gmail.com>
To:        freebsd-acpi@FreeBSD.org
Subject:   Re: kern/173414: [acpi] ACPI battery time incorrect
Message-ID:  <201404170520.s3H5K02i079943@freefall.freebsd.org>

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The following reply was made to PR kern/173414; it has been noted by GNATS.

From: Kevin Oberman <rkoberman@gmail.com>
To: bug-followup@FreeBSD.org, jb.1234abcd@gmail.com
Cc:  
Subject: Re: kern/173414: [acpi] ACPI battery time incorrect
Date: Wed, 16 Apr 2014 22:11:16 -0700

 --047d7b10cf8b0fcbe604f736106a
 Content-Type: text/plain; charset=UTF-8
 
 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@gmail.com
 
 --047d7b10cf8b0fcbe604f736106a
 Content-Type: text/html; charset=UTF-8
 Content-Transfer-Encoding: quoted-printable
 
 <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. &quot;acpiconf -i N&quot; where &#39;N&#39; 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&#39;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@gmail.com" target=
 =3D"_blank">rkoberman@gmail.com</a><br></div>
 </div></div></div></div></div></div>
 
 --047d7b10cf8b0fcbe604f736106a--



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