Every laptop battery wears out eventually. The hard part is telling ordinary wear, which you can live with, from a battery that is unreliable or unsafe. These are the five signs that matter, what causes each one, and how to confirm the battery is really the problem before you buy a new one.
Sign 1: Runtime has dropped a lot
If a laptop that once lasted six hours now manages two with the same kind of work, the battery has probably lost a large part of its capacity. Confirm it with numbers rather than impressions: compare full-charge capacity with design capacity in Battery Health Checker or the Windows battery report.
There is no universal cut-off. Many manufacturers rate batteries to keep about 80% of their capacity for a set number of cycles, so falling below 80% means noticeable wear. Whether that justifies a replacement depends on how long you need the laptop to run unplugged. If runtime has fallen far more than the capacity figure suggests, look at software first: a new background app, a brighter screen, or a higher refresh rate can do that on their own.
Sign 2: Sudden shutdowns at 10%, 20%, or more
An aged battery has higher internal resistance. When the laptop suddenly asks for more power, for example when opening a heavy app, the voltage sags below the shutdown threshold even though the gauge still shows charge left. The laptop switches off without warning.
An inaccurate charge gauge can cause similar symptoms. A single calibration can help if the problem is only the gauge; if shutdowns continue afterwards, the battery itself is the likely cause.
Until the battery is replaced, keep the laptop plugged in for important work and save often. Repeated sudden shutdowns can corrupt open files.
Sign 3: Swelling or a deformed case
This is the one sign that requires immediate action. A swelling lithium-ion battery pushes against the parts around it. Look for:
- A bottom panel that bulges or no longer sits flat on the desk
- Gaps opening between the case parts
- A trackpad that is raised, hard to click, or clicks on its own
- A keyboard that lifts in the middle
Stop using and charging the laptop, shut it down, and keep it away from heat and flammable materials. Do not press on the swelling, puncture it, or try to remove a glued battery yourself. Take it to an authorised service centre and recycle the old battery at a proper collection point.
Swelling is caused by gas from internal side reactions. The usual triggers are age, sustained heat, long periods at full charge, physical damage, and manufacturing defects.
Sign 4: Charging errors and warnings
- “Plugged in, not charging”: first check whether a charge limit is turned on (for example Conservation Mode or an 80% limit). That message is normal when the limit is reached. If no limit is set, try another power outlet and the original charger, then reinstall the battery driver: in Device Manager, under Batteries, uninstall Microsoft ACPI-Compliant Control Method Battery and restart. Windows reinstalls it automatically.
- Manufacturer warnings: utilities such as Lenovo Vantage, MyASUS, Dell SupportAssist, and HP Support Assistant, as well as some BIOS screens, can report a battery as “Poor” or recommend replacement.
- No battery detected (a battery icon with a cross): the battery or its connector may have failed.
Sign 5: The battery area gets unusually hot
Laptops get warm under load, but the battery area should not become hot while the laptop is idle or doing light work. Heat that you have not felt before, particularly while charging, can indicate a failing cell. Treat it like swelling: stop charging and have it checked.
Loud fans alone usually point to a busy process or dusty vents rather than the battery. Check Task Manager first.
How to confirm it is the battery
1. Check the capacity figures
Record design capacity, full-charge capacity, and cycle count with Battery Health Checker or powercfg /batteryreport. The report’s Battery capacity history shows whether the decline was gradual or sudden.
2. Rule out software
- Look at Settings → System → Power & battery → Battery usage for apps that use unusual amounts of energy.
- Install Windows, BIOS, and chipset updates from your laptop maker.
- Restore default power plans with
powercfg -restoredefaultschemesin an administrator terminal if you have changed advanced settings.
3. Run the manufacturer’s hardware test
Most laptop makers include a pre-boot diagnostic that tests the battery: Dell ePSA/SupportAssist diagnostics, HP PC Hardware Diagnostics UEFI, and Lenovo Diagnostics are common examples. Check your model’s support page for the key to press at startup. Also try a known-good charger with enough wattage, since a weak or damaged charger can look like a battery fault.
Replacement options
Original (OEM) battery
Matched to your model and firmware and usually the most reliable choice. It costs more, and some models need a technician to fit it.
Third-party battery
Cheaper, but quality varies widely. Buy only from reputable sellers, check the exact part number, and look for recognised safety certifications. A very cheap battery with no clear brand is a genuine safety risk.
Authorised service
Recommended for laptops with glued-in batteries, for any swollen battery, and while the laptop is under warranty. Check your warranty terms first: many laptop warranties treat normal battery wear differently from defects.
In short
Swelling, heat, and sudden shutdowns are reasons to act now. Gradually shorter runtime is a reason to plan. In every case, check the capacity figures and rule out software and the charger before you buy a battery.