How to charge your phone during a power cut, safely

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In a power cut, charge your phone from a power bank, or from a car or generator used outdoors only, and make the charge last by turning on Low Power Mode on an iPhone or Battery Saver on Android. Ready.gov says to keep phones charged before a power cut and to plan for alternative power, such as a portable charger or power bank.

Quick answer

Turn on Low Power Mode (iPhone) or Battery Saver (Android) as soon as the power goes. Charge from a power bank, following its instructions. If you charge from a car, Ready.gov says to run it in a well-ventilated place outside, never in a garage. Generators go outdoors only, at least 20 feet from windows and doors.

How do I make my phone battery last longer?

Turn on your phone's battery saving mode first, then cut back what uses power. Apple says Low Power Mode reduces background activity to extend battery life, and Google says Battery Saver turns on Dark theme and limits or turns off background activity.

On an iPhone:

  1. Open Settings and tap Battery.
  2. On iPhone 15 and later, tap Power Mode, then turn on Low Power Mode. On iPhone 14 and earlier, turn on Low Power Mode on the Battery screen.
  3. Or swipe down from the top-right corner to open Control Centre and tap the battery icon.

Apple says Low Power Mode sets Auto-Lock to 30 seconds, reduces display brightness, pauses iCloud Photos, and turns off automatic downloads, email fetch and Background App Refresh. The battery icon turns yellow while it's on, and it turns off by itself when you charge to 80% or higher.

On Android:

  1. Open the Settings app.
  2. Tap Battery > Battery Saver.
  3. Choose a schedule for Battery Saver, or set it to turn off automatically.

Google notes that some of these steps work only on Android 13 and up, and that not every phone has Battery Saver, so check your phone maker's support site. Its other battery tips are to turn on aeroplane mode if you don't need the mobile network, use Wi-Fi instead of mobile data when it's available, turn off Bluetooth and location, reduce screen brightness and let the screen turn off sooner.

For what still works at home without mains power, see does Wi-Fi work in a power cut?

Should I change my iPhone's charging settings before a power cut?

Only if you want a full battery sooner. Apple's Optimised Battery Charging, on by default, can delay charging past 80 per cent in certain situations to reduce battery wear. When it's active, a Lock Screen notification says when your iPhone will be fully charged. To charge fully now, touch and hold that notification, then tap Charge Now.

On iPhone 15 and later you can also set a charge limit between 80 and 100 per cent at Settings > Battery > Charging. Apple says your iPhone charges to within a few percentage points of the limit and then stops. On iPhone 14 and earlier, you can turn Optimised Battery Charging on or off at Settings > Battery > Battery Health & Charging.

Is it safe to charge from a power bank?

Power banks are one of the alternative power sources Ready.gov suggests planning for. Electrical Safety First, the UK electrical safety charity, gives this advice:

  1. Read the manufacturer's instructions and follow them.
  2. Buy from a reputable retailer rather than a third-party seller online, and register the power bank so you can be contacted about a recall.
  3. Use only the cables provided with the battery pack and your phone.
  4. Keep it away from heat, direct sunlight, humidity and water, and don't leave it in a parked car where it could get very cold or hot.
  5. Charge it uncovered in a well-ventilated place, unplug it once it's charged, and don't charge it overnight or while you're out.
  6. Keep it away from coins and keys in a pocket or bag, which could short-circuit it.

If a power bank is too hot to handle, or you notice odd smells, sparking, smoke, swelling, cracks or damage, unplug it and contact the retailer or manufacturer. Don't take it apart or try to repair it. Electrical Safety First also notes that most power banks can't charge and discharge at the same time.

Can I charge my phone in the car?

Yes, if the car is outside. Ready.gov says that if you use your vehicle as a source of power or warmth, run it in a well-ventilated place outside, and never leave a vehicle running inside a garage, even with the garage door open. It also suggests making sure the tank has plenty of fuel before predicted extreme weather, in case there's a power cut.

Is it safe to charge my phone from a generator?

Only if the generator itself is used safely. Ready.gov says it's important to know how to use generators safely to prevent carbon monoxide poisoning, and describes carbon monoxide as a colourless, odourless gas that can kill you, your family and pets. The rules from Ready.gov and the US Consumer Product Safety Commission (CPSC):

  1. Run generators outdoors only, at least 20 feet (about 6 metres) from windows, doors and attached garages.
  2. Never run one inside a home, garage, basement, shed or other enclosed space. The CPSC says opening doors or windows won't provide enough ventilation.
  3. Install working carbon monoxide alarms with battery backup on every level of your home.
  4. Keep the generator dry. Touching a wet generator, or devices connected to one, can cause an electric shock.
  5. Connect appliances with heavy-duty extension cords, and let the generator cool before refuelling.

The CPSC says never to ignore a carbon monoxide alarm: get outside immediately, then call the emergency services (999 in the UK).

Ready.gov also says not to use a gas stove or oven to heat your home during a power cut, because it raises the risk of carbon monoxide poisoning.

How do I get ready for the next power cut?

Ready.gov's emergency kit list includes a mobile phone with chargers and a backup battery, and its power cut sheet says to keep phones and other electronics charged before a power cut. It also suggests finding out whether your home phone will work in a power cut and how long any battery backup lasts.

When the power comes back, Ready.gov says it may return with momentary surges or spikes that can cause damage, so disconnect electronics during the cut. There's more in how to protect electronics from a power surge and what to do in a power cut.

More questions

Does Low Power Mode turn off by itself?

Yes. Apple says Low Power Mode turns off when you charge your iPhone to 80% or higher. If your iPhone supports Adaptive Power and it's on, Low Power Mode turns on by itself when the battery drops below 20%.

Does aeroplane mode save battery?

Google lists turning on aeroplane mode, when you don't need your mobile network, as one way to stretch a low Android battery. Turn it off again when you need to make a call or use mobile data.

Can I leave a power bank charging overnight?

Electrical Safety First says not to charge power banks overnight or while you're out of the house, to unplug them after charging, and to charge them uncovered in a well-ventilated place.

Can I use any charger to charge my phone?

Google recommends the power adaptor that came with your phone. It says other adaptors and chargers can charge slowly or not at all, and can damage your phone or battery. Electrical Safety First says to use only the cables supplied with the battery pack and your device.

Is it safe to run the car in the garage to charge my phone?

No. Ready.gov says never to leave a vehicle running inside a garage, even if the garage door is open. If you use the car for power, run it in a well-ventilated place outside.

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