It is four in the afternoon, you are still out, and your phone is at 12 percent.
We have all felt that small panic while hunting for a plug point.
The battery is never quite enough, and it quietly gets worse every year you own the phone.
Three settings do most of the work, and none of them take a minute.
Should I switch off auto-brightness?
No, and this is where the old advice has changed.
Phones now read the light around them better than we do, so leaving auto-brightness on usually saves more than switching it off.
What actually helps is dragging the brightness slider lower than feels normal, and letting the phone adjust from there.
Then turn on dark mode.
If your phone has an OLED screen, a black pixel is simply switched off and draws no power at all.
On a cheaper LCD screen dark mode still looks nicer at night, but it saves very little.
On iPhone: Settings -> Display & Brightness -> Dark.
On Android: Settings -> Display -> Dark theme.
Low Power Mode / Battery Saver
This is the single biggest switch on your phone.
It pauses the work your phone does when you are not looking, like apps refreshing, mail fetching, downloads and constant location checks.
On iPhone: Settings -> Battery -> Low Power Mode.
On Android: Settings -> Battery -> Battery Saver.
Do not wait for the 20 percent warning.
Switch it on in the morning if you already know it is a long day out.
Screen Auto-Lock
Your screen keeps glowing after you put the phone down, sometimes for a full minute or more.
Bring that down to 30 seconds.
On iPhone: Settings -> Display & Brightness -> Auto-Lock.
On Android: Settings -> Display -> Screen timeout.
Why is my two-year-old phone so much worse?
Heat, mostly.
Our summers are hard on batteries, and a phone left on a car dashboard or charging under a pillow ages much faster.
Take the cover off while fast charging, and keep the phone out of direct sun.
Many phones now let you cap charging at around 80 percent, which is kinder to the battery if you charge overnight anyway.
Look for the charging options under Settings -> Battery on either phone.
An iPhone shows your battery health on that same screen, and newer Android phones are starting to show it too.
Once it drops near 80 percent, a new battery will do more for you than every setting above put together.
Things to Remember
- Leave auto-brightness on, but keep the slider low.
- Turn on dark mode, especially on an OLED screen.
- Switch on Low Power Mode early, not at 20 percent.
- Set Auto-Lock to 30 seconds.
- Keep the phone cool, and check battery health once a year.