Battery Forensics on Debian: Inspecting Your Power Stats with upower

So I’m currently selling an older Lenovo ThinkPad on eBay — and, unsurprisingly, one question keeps popping up in my inbox:

“What’s the remaining battery capacity?”

Now, instead of guessing, hand-waving, or saying “it still lasts a few hours™”, let’s do this properly — with actual numbers, straight from the system.

If you’re the kind of person who thinks /sys/class/power_supply is light reading before bed, then this one’s for you.

In this guide, we’ll install upower on Debian, query battery stats like a proper terminal dweller, and extract the one metric that actually matters: remaining battery health.

🔧 Installing upower on Debian

sudo apt update
sudo apt install upower

Enumerate power devices:

upower -e

/org/freedesktop/UPower/devices/battery_BAT0
/org/freedesktop/UPower/devices/line_power_AC
/org/freedesktop/UPower/devices/line_power_ucsi_source_psy_USBC000o001
/org/freedesktop/UPower/devices/line_power_ucsi_source_psy_USBC000o002
/org/freedesktop/UPower/devices/DisplayDevice

🔋 Querying Real Battery Data

upower -i /org/freedesktop/UPower/devices/battery_BAT0

Here’s the actual output from my ThinkPad T490 (no fake data, straight from the terminal):

native-path:          BAT0
vendor:               SMP
model:                5B10W13906
serial:               6714
power supply:         yes
updated:              Mi 08 Apr 2026 13:45:43 CEST (5 seconds ago)

battery
  present:             yes
  rechargeable:        yes
  state:               discharging

  energy:              35,52 Wh
  energy-full:         44,13 Wh
  energy-full-design:  50,45 Wh

  energy-rate:         10,576 W
  voltage:             11,87 V
  charge-cycles:       363
  time to empty:       3,4 hours

  percentage:          80%
  capacity:            87,4727%

  technology:          lithium-polymer

  charge-start-threshold: 75%
  charge-end-threshold:   80%

🧠 What Buyers Actually Want to Know

The key values are highlighted above:

• energy-full-design: 50.45 Wh → original factory capacity
• energy-full: 44.13 Wh → current real capacity
• capacity: 87.47% → this is the money shot

➡️ This means the battery still retains about 87% of its original capacity. And that’s exactly the number you can confidently put into your eBay listing.

⚡ Runtime Snapshot

energy:      35,52 Wh
energy-rate: 10,576 W
time to empty: 3,4 hours

At ~10.5W power draw, the system behaves exactly like you’d expect from a reasonably optimized Linux laptop.

🛡️ Bonus: Battery Longevity Mode

charge-start-threshold: 75%
charge-end-threshold:   80%

This prevents charging to 100% and significantly slows down battery wear — a classic ThinkPad pro move.

📊 Final Verdict

• Battery health: 87.47% ✅
• Charge cycles: 363
• Power usage: ~10.5W

Conclusion: This battery is still in solid condition — and now you have hard data to prove it to even the most skeptical buyer.