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.