Spending a lot of time in waiting rooms and hospital wards I depend upon my phone/kindle/internet access to amuse and distract me but they always run out at the most inopportune moment! I purchased the Poweradd Pilot X7 20,000 mAh as it (£18.99 including delivery with Prime) has good reviews. This external power battery bank is suitable for most brands of tablets and phones including Samsung and Apple. It charges my Apple Ipod ITouch 7 times before it needs recharging itself. It has dual USB output ports so can charge two devices at the same time.
I have 3 external power batteries, I can then rotate them when needed. If I am in hospital I will have on in use and someone will bring me a newly charged one so I can swap when it runs out. They remove the inconvenience of batteries running out when I am just at a good bit in my book or in the middle of playing a game. I just plug my device in to the charger and I can continue.
I purchased this myself and the views expressed in this blog are my own.