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.Dd March 17, 2010
.Dt ACPIBAT 4
.Os
.Sh NAME
.Nm acpibat
.Nd ACPI Battery
.Sh SYNOPSIS
.Cd "acpibat* at acpi?"
.Sh DESCRIPTION
The
.Nm
driver supports
.Tn ACPI
batteries.
.Pp
The battery status is made available through the
.Xr envsys 4
.Tn API .
The battery information can be displayed also with the
.Xr envstat 8
command:
.Bd -literal -offset 2n
$ envstat -d acpibat0
                Current  CritMax  WarnMax  WarnMin  CritMin Unit
       present:      ON
design voltage:  14.400                                        V
       voltage:  16.267                                        V
    design cap:  74.880                                       Wh
 last full cap:  48.260                                       Wh
        charge:  47.910                      5.000%   0.414%  Wh (99.27%)
   charge rate:     N/A
discharge rate:  16.641                                        W
      charging:     OFF
  charge state:  NORMAL
.Ed
.Pp
Depending on the battery, the unit of measurement is either watt-hour
.Tn Pq Wh
or ampere-hour
.Tn Pq Ah
for the capacity related information.
From these the
.Dq charge
is usually the most interesting value,
but it is possible to derive useful information also from the other values.
For example, when
.Xr acpiacad 4
is disconnected, the
.Dq discharge rate
gives a coarse approximation of the current power consumption.
The ratio between the design capacity and the last full capacity
on the other hand reveals the overall
.Dq health
of deteriorating lithium-ion batteries.
.Sh EVENTS
The
.Nm
driver is able to send events to
.Xr powerd 8
daemon when a capacity state has been changed.
The new state will be reported as the
.Em fourth
argument to the
.Pa /etc/powerd/scripts/sensor_battery
script.
If a custom capacity limit was set via
.Xr envstat 8 ,
the
.Nm
driver will report a
.Em user-capacity
event to the same script when current capacity limit has been reached.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr envsys 4 ,
.Xr envstat 8 ,
.Xr powerd 8
.Sh HISTORY
The
.Nm
driver appeared in
.Nx 1.6 .
.Sh BUGS
The
.Tn ACPI
specifications make a distinction between
.Dq control method batteries
and
.Dq smart batteries .
The
.Nm
driver only supports control method batteries.
Furthermore,
.Nm
does not yet support some additional battery information introduced in the
.Tn ACPI 4.0
standard.