5 Signs Your Phone Battery Needs Replacing
How to tell if your phone battery is failing — and what to do about it before it causes bigger problems.
Phone batteries degrade over time — it’s unavoidable. Every charge cycle reduces capacity slightly, and after two or three years most batteries have noticeably less life than when the phone was new. The question is knowing when the degradation is bad enough to warrant a replacement.
Here are the five most common signs we see at MTM IT.
1. The Battery Drains Much Faster Than It Used To
This is the most obvious sign. If your phone used to last a full day and now struggles to reach mid-afternoon, the battery is losing capacity. A healthy lithium battery holds close to 100% of its original capacity when new; by the time it reaches 80%, many people start to notice the difference.
On iPhone: Go to Settings → Battery → Battery Health & Charging. If Maximum Capacity is below 80%, Apple recommends a battery replacement.
On Android: Most modern Android phones don’t have a built-in battery health display, but apps like AccuBattery can give you a good estimate of current capacity.
2. The Phone Shuts Down Before Reaching 0%
If your phone powers off unexpectedly at 15%, 20% or even 30% battery, the battery can no longer reliably deliver the power needed at lower charge levels. This is a classic sign of significant degradation, particularly common in colder weather when battery performance drops further.
This fault tends to get worse over time and can make the phone unreliable for everyday use.
3. The Battery Percentage Jumps Around
A battery showing 45% and then suddenly jumping to 20% — or back up to 60% when you plug it in — is a sign of an ageing battery with calibration issues. The phone can no longer accurately measure how much charge remains.
4. The Device Gets Very Warm During Normal Use
All phones generate some heat during intensive tasks like gaming or streaming. But if your phone gets noticeably warm just from browsing or making calls, the battery may be working harder than it should to maintain power output. This can also indicate a software issue, so it’s worth getting a free diagnostic.
5. The Back of the Phone Is Bulging
This is the most serious sign and should be acted on immediately. A swollen or puffed-up battery is a lithium battery that has begun to off-gas — a chemical process that poses a real fire risk if the battery is punctured or continues to expand. If you notice any swelling, don’t charge the phone — bring it to us straight away.
What to Do
Most battery replacements are quick and affordable. At MTM IT in Tiverton, iPhone battery replacements start from £39 and take around an hour. Samsung and Android batteries are similarly priced.
A new battery often makes an older phone feel significantly faster — particularly on iPhones, where iOS throttles CPU performance on degraded batteries to prevent sudden shutdowns.
If you’re unsure whether your battery needs replacing, bring your device in for a free diagnostic. We’ll test the battery health and give you an honest assessment.