Decide what needs charging
List the devices you need most: usually a mobile phone first. A USB power bank is not a substitute for a professionally planned backup for vital medical equipment, and it will not normally run mains appliances.
Read the specifications
- Check output ports and the charging standard your phone supports.
- Match the cable to both the bank and your device.
- Look for a reputable seller, clear safety information and a meaningful warranty.
- Check the physical weight and whether you can easily read the charge indicator.
The capacity printed in mAh is normally measured at the internal cell voltage. Conversion losses and your phone’s battery size mean you should not expect a simple one-to-one comparison or a guaranteed number of full charges.
Practise and maintain
Charge your own phone from the bank before putting it away. Keep the right cable attached or stored beside it. Follow the manufacturer’s charging and storage instructions. Stop using a swollen, damaged or overheating battery; arrange appropriate battery recycling. Do not leave a power bank in a hot car or cover it while charging.
National Grid: being prepared ↗
Check the linked guidance for updates. Follow local instructions during a real incident. This site does not provide live emergency information.