Written 28 Aug 2026. This is a how-to, not a product card.

See if the old laptop is actually plugged in

Before you trust the old laptop overnight, confirm it is drawing wall power. A dying battery is not a reason to buy a UPS.

You left the old laptop on. This morning ads are back, or SSH hangs. The lid was shut. The charger looked seated. The old laptop still ran on its own battery and died. Look first. You are not buying a house battery box for this.

Skip until SSH works

If you cannot log in from the couch, stop. That is SSH from the couch. This note assumes you can type commands on the computer from the couch.

Skip if the computer is a desktop

An OptiPlex, EliteDesk, or mini PC has no laptop battery. It is on when the wall plug is in. Skip this note. Come back only if this computer is a laptop.

What this is

An old laptop has two power stories. Wall power is the charger in the brick. The battery is the small pack inside the laptop. Linux people call that pack BAT0 or BAT1. You don't need the code. You need the check. This is not the same note as don't let the old laptop sleep (that is the lid) or is the computer still on? (that is a knock from the couch). A house battery box is later, and usually not this weekend: you don't need a UPS yet.

See the power names

SSH in from the couch, then run:

ls /sys/class/power_supply/

You want a name that starts with BAT, often BAT0 or BAT1. A desktop prints no BAT name. That is your skip. Names like AC, ADP, or ACAD are the wall plug the computer can see.

Ask if it is charging

Swap in the BAT name you saw:

cat /sys/class/power_supply/BAT0/status

Charging or Full means the old laptop is on wall power. Discharging means it is running on the battery. That is the loose charger, the dead brick, or a battery that no longer holds a charge while unplugged.

Optional battery room, same BAT name:

cat /sys/class/power_supply/BAT0/capacity

That is a percent. Under about 20 and still Discharging means the old laptop will go dark soon. Seat the charger now. Don't buy a new battery this weekend if Charging works once the brick clicks in.

If it says Discharging

Look at the old laptop, not a store page. Click the barrel or USB-C charger all the way in. Confirm the wall brick has a light, if it has one. Ask status again. If it flips to Charging, you are done. If it stays Discharging, try another charger you already have before you shop. An old laptop that only lives on wall power is still a lab. Leave it plugged in. That is enough.

What next

The lid stays don't let the old laptop sleep. Air stays don't cook the computer. If ads came back this morning, knock first: is the computer still on?. A cable still beats Wi-Fi: a cable beats Wi-Fi for the computer. Skip a UPS this weekend: you don't need a UPS yet.

Skip

• Skip this note if the computer is a desktop or a mini PC.
• Skip this note if SSH from the couch does not work yet. That is SSH from the couch.
• Skip a new laptop battery this weekend if Charging works once the brick is seated.
• Skip a UPS for this. That later skip is you don't need a UPS yet.
• Skip a new mini PC because the charger was loose once.