Every MacBook battery wears out eventually — most are designed for around 1,000 charge cycles before capacity drops noticeably. The good news is that a failing battery gives clear warnings before it becomes a real problem. Here are the five signs we see most often in our Brentford workshop.
1. Battery life has fallen off a cliff
A gradual decline is normal, but if your MacBook has gone from lasting a full afternoon to dying before lunch, the battery chemistry is degrading fast. Check the cycle count under System Settings → General → About → System Report → Power. Anything over 1,000 cycles combined with poor runtime is a strong signal.
2. macOS says "Service Recommended"
Click the battery icon in the menu bar or check Battery settings. If macOS shows "Service Recommended" (or "Service Battery" on older versions), the system itself has measured the battery's health as below spec. It won't fail overnight, but it's on borrowed time.
3. Sudden shutdowns with charge remaining
If your MacBook switches off at 20 or 30 percent, the battery can no longer deliver stable voltage under load. This is more than an annoyance — repeated hard shutdowns can corrupt files you're working on.
4. The trackpad clicks strangely or the case is bulging
This is the serious one. Lithium batteries swell as they fail, and in a MacBook the battery sits directly beneath the trackpad. A trackpad that feels stiff, clicks oddly, or a case that no longer sits flat often means a swollen battery pressing from inside. A swollen battery is a safety risk: stop charging the machine and have the battery replaced as soon as possible.
5. The Mac only runs when plugged in
If your MacBook dies the instant the charger is disconnected, the battery is either completely exhausted or has been disconnected by its own protection circuitry. Either way, it needs replacing — running permanently on mains isn't good for the machine and defeats the point of a laptop.
What replacement involves
A professional battery replacement takes one to two hours for most models. At Computer Expert Brentford we fit high-grade batteries matched to original capacity, run a full health calibration afterwards, and recycle the old battery responsibly. Every replacement is covered by our 90-day parts and labour warranty — and if you're not sure whether the battery is really the problem, diagnosis is free.