I cannot tell you how many chargers I've had to buy over the years due to impromptu nights or similar when that moment of fear kicked in at 'low battery'. I had dabbled with a Juicy Cube charger which was useless. I would charge it, carry it around in my bag but every time I'd go to use it there would be no charge left in it. I'm not sure if I had a faulty one but it made me skeptical of other offerings.
Taking to Twitter I had lot's of 'I'm interested to know this too' when I pleaded for recommendations but none were forthcoming. The one or two I found on my investigations seemed expensive and I wasn't sure I wanted, nor was it necessary to spend so much. As much as I've need chargers on my travels on a typical basis I'm stuck in an office so can easily charge up at my desk.
I can't remember if it was a recommendation from someone or I stumbled across the EasyAcc Portable Charger on Amazon, nonetheless after reading the reviews it seemed liked the best option being both lightweight and affordable at less than £20. Departing for Florida in a matter of days I placed the order and hoped for the best.
I'm pleased to report my gamble paid off and this charger saved many a low battery situation during my trip. I used my iPhone as a camera during my trip and found that for a full day I only had to recharge early afternoon and I could go the rest of the day. Plugging in to charge is simple using the yellow lead which is long enough to make holding both units easy but not too long you're tangled in wired.
A Nokia / Blackberry charger is used for the Power Bank so it does mean two different plug socket chargers are required but it's a small price to pay. I now keep the Power Bank in my handbag at all times and it's saved many a low battery situation without having to hunt down a supermarket or similar and buy another charger. Dramatic, but it's been a life saver!