How to tell if your phone battery is failing (6 warning signs)

One of these can be a fluke; several together is a clear verdict:

• It drains far faster than it used to, even on light use
• It shuts down suddenly — often in the cold or while showing 20–40%
• The percentage jumps around (e.g. 40% → 15% → 30%)
• It charges slowly or struggles to reach 100%
• The phone runs hot during normal use or charging
• The back or screen is lifting/bulging — a swollen battery

Your phone can often tell you directly. On iPhone, go to Settings › Battery › Battery Health & Charging and look at Maximum Capacity — below about 80% means the battery is worn and due for replacement.

Android varies by brand: many show battery information under Settings › Battery or Device Care, and some surface it in a diagnostics menu. If yours doesn't expose a clear figure, the symptom checklist above is a reliable substitute.

If the back cover or screen is being pushed up, the battery is swelling — a safety issue, not just a performance one. Stop charging, avoid pressing or puncturing it, and don't keep using the phone. A swollen battery should be replaced promptly and handled by someone equipped to do it safely.

Before replacing, rule out the look-alikes: a failing charger or a worn charging port can mimic battery problems, and a runaway app can drain a healthy battery in hours. If charging behaviour is the main symptom, work through the port-vs-cable-vs-battery checks first so you fix the right part.

Battery quality varies wildly. Cheap, low-grade cells are the most common cause of a 'new' battery that fades or swells within months. iTweak fits quality cells with a warranty, for Apple and Android, and runs an 80-point check so you're not paying to replace a battery when the real fault was elsewhere — and if we misdiagnose it, you don't pay.