With the recent Hurricane Arthur moving up the east coast of the US, power becomes something to worry about and a mobile connection can prove a lifeline for many people in the path of such storms. Keeping a tablet or cell phone alive during a disaster is paramount, but portable power is also handy for mundane times like travel and camping.
Backup batteries are not scarce on the market, you can find any number of them if you look. The real question is, what do you need? Ideally, you want the maximum mAh you can afford, as it will provide the most charges -- remember that battery in your phone is rated, and is usually somewhere in the 2,000 to 3,000 range. Use that number to compare to what you are buying to get a rough estimate of the amount of times you will be able to recharge. If you live in a household with multiple members then that should also be taken into account.
betanews/ full read here/ http://betanews.com/2014/07/05/hyperjuice-plug-is-enough-backup-power-for-any-traveler-review/