PORTABLE POWER BANKS ARE EXTERNAL BATTERIES FOR RECHARGING THE INTERNAL BATTERY OF CELLPHONES, TABLETS, AND SIMILAR USB-TYPE MOBILE DEVICES. ALSO KNOWN AS BATTERY BANKS, THEY ARE A RESERVE POWER SOURCE FOR REPLENISHING THE CHARGE OF A DEVICE WHEN USERS EITHER DON'T HAVE OR CAN'T USE THEIR STANDARD CHARGER. POWER BANKS ARE RECHARGEABLE TO ALLOW REUSE.
