The ACPI (Advanced Configuration and Power Interface) daemon provides battery information in Linux and is installed by default in most Linux distributions. /sys filesystem stores all the battery information monitored by ACPI.
You can view your battery information by viewing the content of the files in the battery section of the /sys filesystem. The filesystem could be hard to navigate, but a few userland applications such as upower and acpi can assist in viewing your battery information.
You can view battery information via /sys filesystem, upower, or acpi in Linux from the terminal.
$ ls /sys/class/power_supply/BAT0/ alarm charge_full_design device present technology voltage_now capacity charge_now manufacturer serial_number type capacity_level current_now model_name status uevent charge_full cycle_count power subsystem voltage_min_design
$ cat /sys/class/power_supply/BAT0/capacity 100
$ upower -i /org/freedesktop/UPower/devices/battery_BAT0 native-path: BAT0 vendor: Samsung SDI model: DELL TXF9M6C serial: 34075 power supply: yes updated: Fri 05 Jul 2019 11:27:48 AM +08 (91 seconds ago) has history: yes has statistics: yes battery present: yes rechargeable: yes state: fully-charged warning-level: none energy: 54.0968 Wh energy-empty: 0 Wh energy-full: 54.0968 Wh energy-full-design: 61.9932 Wh energy-rate: 0 W voltage: 8.504 V percentage: 100% capacity: 87.2625% technology: lithium-polymer icon-name: 'battery-full-charged-symbolic'
$ sudo apt update && sudo apt install --assume-yes acpi #Ubuntu and Debian
$ acpi Battery 0: Full, 100%
$ acpi --battery --details Battery 0: Full, 100% Battery 0: design capacity 8157 mAh, last full capacity 7118 mAh = 87%
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