be negative; there is no empty or full value. It is only useful for
relative, time-based measurements.
+CONSTANT_CHARGE_CURRENT - constant charge current programmed by charger.
+
+CONSTANT_CHARGE_VOLTAGE - constant charge voltage programmed by charger.
+
ENERGY_FULL, ENERGY_EMPTY - same as above but for energy.
CAPACITY - capacity in percents.
+CAPACITY_ALERT_MIN - minimum capacity alert value in percents.
+CAPACITY_ALERT_MAX - maximum capacity alert value in percents.
CAPACITY_LEVEL - capacity level. This corresponds to
POWER_SUPPLY_CAPACITY_LEVEL_*.
TEMP - temperature of the power supply.
+TEMP_ALERT_MIN - minimum battery temperature alert value in milli centigrade.
+TEMP_ALERT_MAX - maximum battery temperature alert value in milli centigrade.
TEMP_AMBIENT - ambient temperature.
+TEMP_AMBIENT_ALERT_MIN - minimum ambient temperature alert value in milli centigrade.
+TEMP_AMBIENT_ALERT_MAX - maximum ambient temperature alert value in milli centigrade.
TIME_TO_EMPTY - seconds left for battery to be considered empty (i.e.
while battery powers a load)