"The battery is dead" covers at least four different faults, and only one of them is fixed by a battery. The tests that separate them are quick, and the first one is free.
Test One: Ask the Battery What It Thinks
Windows will tell you the battery's own view of itself. From a command prompt:
powercfg /batteryreport
That writes an HTML file, usually to your user folder, and it is the single most useful thing in this whole diagnosis. Three numbers matter.
Design capacity is what the pack was built to hold. Full charge capacity is what it holds now. The ratio is battery health. A pack at 80% of design after a few years is normal ageing. A pack at 40% is worn out and a replacement will fix it.
Cycle count is how many full charge-discharge equivalents it has been through. Most laptop packs are specified for a few hundred to around a thousand cycles before meaningful loss. A high cycle count with low health is an honest worn battery. A low cycle count with low health is a pack that failed early, which is worth knowing if it is still in warranty.
On macOS the same information is under System Information, Power. On Linux, upower -i /org/freedesktop/UPower/devices/battery_BAT0 gives energy-full against energy-full-design.
If health is high and the machine still will not run on battery, the battery is probably not your fault. Keep going.
Test Two: Separate the Battery From Everything Else
If the battery comes out, take it out and run the machine on mains alone. If it runs normally, the charging path from the wall to the board is fine and your problem is the battery or the circuit that charges it. If it still will not run, the battery was never the issue.
On a machine with an internal pack you can do the same by taking the bottom cover off and disconnecting the battery connector, though at that point you are already inside and may as well inspect the pack while you are there.
Test Three: Rule Out the Charger and the Jack
Chargers fail more often than people expect, and the failure is usually partial rather than total.
- Try a known good charger of the same wattage and connector. A lower-wattage charger may run the machine and refuse to charge it, which produces exactly the "plugged in, not charging" symptom people blame on the battery.
- On USB-C, the cable counts. A cable rated for data but not for high-wattage power delivery will charge slowly or not at all. Swap the cable before condemning anything.
- Wiggle the plug at the jack with the machine on and watch the charging indicator. If charging cuts in and out with movement, the DC jack or its solder joints have failed, which is a board-level repair rather than a battery one.
- Check the charger brick's own LED if it has one. No light usually means the brick, not the laptop.
Test Four: Look at the Pack
Take the pack out, or the bottom cover off, and put it on a flat surface.
A swollen battery is a fire risk and the diagnosis stops there. The signs: the pack no longer sits flat and rocks on a table, the laptop's bottom cover bulges, the trackpad has started clicking oddly or sitting proud, or the case seams have opened. Any of those and the machine should be powered down, unplugged and the pack removed or the laptop taken to someone who can remove it safely.
Do not press it, do not puncture it, do not continue to charge it, and do not put it in household waste. A swollen lithium pack is in thermal distress and it does not get better.
What the Symptoms Usually Mean
| What you see | Most likely | Next step |
|---|---|---|
| Runs fine on mains, dies instantly unplugged | Worn pack, confirmed by low full charge capacity | Replace the battery |
| "Plugged in, not charging", battery holds a level | Charger wattage, cable, or a charge threshold setting | Try a known good charger, then check vendor battery settings |
| Charges only at certain cable angles | DC jack or its solder joints | Board-level repair, not a battery |
| No power at all, with or without battery | Charger, jack, or power delivery on the board | Test the charger first, then it is a board diagnosis |
| Charge level jumps around, 60% to 15% in a minute | Failing cells or a confused gauge | Replace the battery |
| Bottom cover bulging, trackpad sitting proud | Swollen pack | Stop, power down, remove or get it removed safely |
| Health fine, runtime still poor | Not the battery. Software, screen brightness or a background load | Check what is drawing power before buying anything |
That last row catches more people than it should. A machine that gets three hours where it used to get seven, with a battery reporting 92% health, has a software problem or a brightness problem, not a hardware one.
Charge Thresholds Look Exactly Like a Fault
Most business laptops now ship with a setting that deliberately stops charging at 60% or 80% to extend pack life. Lenovo calls it Conservation Mode, Dell puts it under Battery Settings in Dell Power Manager, ASUS and HP have equivalents.
If your battery charges to 80% and stops, check that setting before anything else. It is working as designed and it is the single most common false alarm in this whole area.
When to Stop and Get Help
A swollen pack, a machine that shows no sign of life on a known good charger, or charging that depends on physically moving the connector are all beyond a parts swap. The first is a safety matter and the other two are board work.
Everything else, once the report and the charger test point at the pack, is a battery purchase, and the next question is which one. How to find the right replacement laptop battery covers the model code and the voltage gate that decide it.
Related on Consumercarts
- Browse laptop replacement batteries
- Is Your Laptop Worth Repairing? A Parts and Value Guide
- How to Find the Right Replacement Laptop Battery
- Laptop Battery mAh vs Wh: Why the Bigger Number Often Means Less
- How to Judge Laptop Battery Life (and Why Watt-Hours Beat Marketing Claims)
- Panel, Backlight, Cable or GPU? How to Diagnose a Dead Laptop Screen
Common replacement packs: Dell 4GVMP, 68 Wh, HP HT03XL, 41.9 Wh, ASUS C41N1906, 90 Wh, Lenovo L23C4P70, 90 Wh.