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ACPIBAT(4) BSD Kernel Interfaces Manual ACPIBAT(4)
acpibat -- ACPI Battery
acpibat* at acpi?
The acpibat driver supports ACPI batteries.
The battery status is made available through the envsys(4) API. The battery information can
be displayed also with the envstat(8) command:
$ envstat -d acpibat0
Current CritMax WarnMax WarnMin CritMin Unit
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
charge state: NORMAL
Depending on the battery, the unit of measurement is either watt-hour (Wh) or ampere-hour
(Ah) for the capacity related information. From these the ``charge'' is usually the most
interesting value, but it is possible to derive useful information also from the other val-
ues. For example, when acpiacad(4) is disconnected, the ``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 ``health'' of deteriorating
The acpibat driver is able to send events to powerd(8) daemon when a capacity state has been
changed. The new state will be reported as the fourth argument to the
/etc/powerd/scripts/sensor_battery script. If a custom capacity limit was set via
envstat(8), the acpibat driver will report a user-capacity event to the same script when
current capacity limit has been reached.
acpi(4), envsys(4), envstat(8), powerd(8)
The acpibat driver appeared in NetBSD 1.6.
The ACPI specifications make a distinction between ``control method batteries'' and ``smart
batteries''. The acpibat driver only supports control method batteries. Furthermore,
acpibat does not yet support some additional battery information introduced in the ACPI 4.0
BSD March 17, 2010 BSD
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