How to use a portable battery charger
This video describes how to recharge your smartphone when there is not access to a power outlet or any other means of recharging.
The portable battery charger can be pre-charged at home and then taken on long trips, where the cellphone battery is likely to run out of power.
When the phone is low on charge, simply connect the portable charger to your phone and it will start recharging it immediately.
Depending on the charger, it may be possible to recharge your smartphone more than just once.
This is especially helpful when you are taking a lot of pictures and videos during the day or are using the phone's GPS functionality.