NAME

acpibat — ACPI Battery

SYNOPSIS

acpibat* at acpi?

DESCRIPTION

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
       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

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 values. 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 lithium-ion batteries.

EVENTS

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.

SEE ALSO

acpi(4), envsys(4), envstat(8), powerd(8)

HISTORY

The acpibat driver appeared in NetBSD 1.6.

BUGS

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 standard.