What’s the difference between battery capacity and battery life?
Battery capacity is the amount of energy a battery can store, while battery life is how long a device runs before needing a recharge. Understanding the distinction helps people compare devices, estimate charging needs and recognise when an ageing battery may need replacing.
Capacity is usually measured in milliampere hours for phones and power banks, and watt hours for laptops; battery health describes how much of its original capacity remains. Google says Pixel devices such as the Pixel 8a are rated to retain up to 80 per cent capacity after 1,000 charge cycles, which could mean a replacement after about 2.5 years with one full cycle a day. Real-world battery life also depends on power use, screen size, temperature and hardware efficiency, while charging a phone from a power bank typically loses 20 to 30 per cent of energy.
- Capacity measures stored energy; battery life measures runtime.
- Battery health declines as charge cycles accumulate.
- Usage, efficiency and charging losses affect real-world performance.
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Battery capacity and battery life sound similar but mean different things. Capacity is how much energy a battery can store, measured in units like milliampere hours for phones or watt hours for laptops. Battery life is how long your device will run on a full charge before needing to be plugged in.
A battery with high capacity does not necessarily mean your device will run for ages, because how quickly that energy drains depends on many factors. Screen brightness, demanding apps, temperature, and how efficiently your device's hardware is built all influence battery life. Understanding both metrics helps when comparing devices or recognising why an ageing battery may eventually need replacing.
Batteries naturally weaken over time and with repeated use. Manufacturers estimate how much capacity a battery will retain after repeated charging; phones are often rated to keep around 80 per cent of their original capacity after 1,000 recharges. Once capacity drops substantially, the battery may need replacing to restore the device's battery life.