A new battery can make a two or three year old phone feel new again, for a fraction of the price of a new phone. But replace it too early and you waste money; leave it too late and you live with a phone that dies at lunchtime. Here is how to tell when it is really time.

The short answer

Most phone makers treat a battery as worn out when it holds less than about 80% of its original capacity. Google, for example, recommends replacing a Pixel battery when its capacity is below 80%, or at around 1,000 charge cycles on Pixel 8a and later (about 800 on older Pixels). OPPO, realme and vivo all flag 80% maximum capacity as the point where battery life drops noticeably. For most people that point arrives somewhere between two and four years, depending on heat, charging habits and how hard the phone is used.

7 signs your phone battery needs replacing

  1. Battery health is below 80%. If your phone shows battery health or maximum capacity in Settings and it reads under 80%, you are in replacement territory.
  2. It no longer lasts the day you need. If you used to finish the evening with 30% and now need a midday top-up with the same use, the battery is the likely cause.
  3. It shuts down with charge left. A worn battery cannot deliver peak current, so the phone may switch off at 15 or 20%, especially in the cold or when you open the camera.
  4. The percentage jumps around. Dropping from 40% to 10% in minutes, or stalling at one number, often means the cells are aged.
  5. The phone feels slower. Some phones reduce peak performance to avoid shutdowns when the battery is weak.
  6. It gets hot doing very little. A battery with high internal resistance turns more energy into heat. Rule out apps first; see why your phone gets hot while charging.
  7. The battery is swollen. A lifting screen, a back panel that bulges, or a phone that rocks on a table is a safety issue. Stop charging it and take it to a repair centre now.

How to check your battery health first

Before paying for a battery, get a number. Where to look depends on the brand:

  • Google Pixel 8a and later: Settings > Battery > Battery health. Pixel guide.
  • Samsung Galaxy: Samsung Members phone diagnostics shows Normal, Weak or Bad, and some models show a percentage under Settings > Battery > Battery information. Samsung guide.
  • OPPO, realme and vivo: maximum capacity under the Battery health page on supported models. See the OPPO, realme and vivo guides.
  • Motorola: Settings > Battery > Battery info on some models. Motorola guide.
  • Xiaomi and OnePlus: varies by model. See the Xiaomi and OnePlus guides.

If your phone shows nothing, bCare's battery health check measures the real capacity in mAh from normal charges and compares it with the design capacity. Read the cycle count guide too: a high health figure with a high cycle count means the battery is close to the end of its rated life.

Is it the battery or something else?

Fast drain is not always a worn battery. A new app, a system update, high brightness or a weak signal can halve battery life on a perfectly healthy battery. If your health reading is above about 85%, work through why your battery drains fast on Android before you replace anything. If health is below 80% and drain looks normal, a new battery is the fix.

Replace the battery or the phone?

A battery replacement usually makes sense when:

  • The phone still gets software and security updates.
  • The rest of the phone, screen, camera and storage, still does what you need.
  • The replacement costs a small fraction of a comparable new phone.

A new phone may make more sense if updates have ended, the phone is also too slow or full, or the screen is damaged too, since screen and battery repairs together can approach the price of a newer phone.

Where to get it replaced

Most modern phones have glued-in batteries, so replacement is a job for a service centre. The manufacturer's own service or an authorised repair partner uses genuine parts, keeps water resistance seals where possible, and on some brands lets the battery health readout work correctly afterwards. vivo, for example, says the maximum capacity reading resets to 100% after a battery replacement at an official service centre, and realme warns that a non-official battery can stop the health readout working. A non-genuine battery can be cheaper but may hold less than claimed.

Make the new battery last longer

bCare's health score tracks the habits that wear a battery, such as time spent hot, holding a full charge and deep drains, so you can see what to change while the battery is still young.