“My battery is terrible” can mean two different things. Either the phone dies before dinner today, or it holds much less charge than it did two years ago. The fixes are different, so let’s take them one at a time.

Getting through the day

These settings make the biggest difference on most phones:

  • Screen brightness. The display is usually the biggest drain. Leave auto-brightness on.
  • Refresh rate. Phones with 120Hz screens often let you drop to 60Hz, which saves power with little visible difference outside of games.
  • Location access. Apps that check your location in the background drain the battery quietly. Set most of them to “while using the app”.
  • Weak signal. A phone straining for one bar of reception works hard. In a basement or on a plane, Wi-Fi or airplane mode helps.
  • Low power mode. Turn it on earlier in the day, not at 5%. It cuts background activity you won’t miss.

Keeping the battery healthy for years

Phone batteries are lithium-ion, and they wear out with every charge cycle. Two things speed that up: heat, and spending long stretches at a full 100% charge.

Heat is the bigger one. Apple says its phones are most comfortable between 16°C and 22°C (62°F to 72°F) and warns that temperatures above 35°C (95°F) can permanently damage battery capacity, with charging in high heat making it worse. In practice:

  • Don’t leave the phone on a car dashboard or in direct sun.
  • If it gets hot while charging, take it out of a thick case.
  • Avoid gaming or navigating while fast-charging on a hot day.

For the full-charge problem, use the phone’s built-in protection. Apple’s Optimized Battery Charging learns your routine and can hold the charge at 80% overnight, topping up shortly before you usually unplug. Many Android phones offer similar settings, often called adaptive or protective charging.

Charging myths to drop

  • “Let it drain to zero first.” That advice belongs to old nickel batteries. Battery University, a long-running guide run by battery-testing company Cadex Electronics, notes that lithium-ion batteries don’t need full discharges and partial charges are fine.
  • “Charging overnight ruins the battery.” With optimized charging turned on, overnight charging is fine.
  • “Only use the original charger.” Any good-quality certified charger is safe. Cheap, uncertified ones are the risk.

Storing an old phone

Putting a spare phone in a drawer? Apple recommends leaving it at about 50% charge, switched off, somewhere cool, and topping it back up to 50% every six months.

Find the app that is draining you

Before changing a dozen settings, check what is actually using the battery. On iPhone, go to Settings, then Battery, to see usage by app over the last day or ten days. On Android, the same list is usually under Settings, then Battery, then Battery usage. If one app you barely open sits near the top, its background activity is the problem. Restrict its background refresh, turn off its location access or simply delete it.

When it’s time for a new battery

Every lithium-ion battery wears out eventually, no matter how carefully you charge it. iPhones show a Maximum Capacity figure under Battery Health, and many Android phones show a similar health reading in their settings or diagnostics app. Warning signs include the phone shutting down while it still shows charge left, slowing down under load or lasting only half a day with light use.

A swollen battery is different. If the screen starts lifting or the back of the phone bulges, stop charging it and get it looked at right away, because a damaged lithium-ion cell can overheat.

A battery replacement from the maker or an authorized repair shop typically costs a small fraction of a new phone and can make a two- or three-year-old handset feel new again.

What we think

If you remember one thing, make it heat. A phone that spends summers on a car dashboard will lose capacity faster than any charging habit could cause.

Turn on optimized charging, keep the phone out of the sun, and stop worrying about the rest. Battery wear is normal, and a replacement battery is far cheaper than a new phone.