A sudden interruption in power is one of the most common causes for a damaged memory card in a mobile phone. That means smartphone users should never take a battery out of an operating device, but power it down first, reports German telecommunications website Teltarif.de.
Don't remove the memory card unless the device is turned off either. If it has to be done when the device is on, at least turn off all apps and processes first. To protect memory cards or backups cards while they're out of the phone, store them in the small plastic boxes in which they are sold.