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I bought this power pack specifically for a 30 hour flight to New Zealand from UK. With a 3 year old in tow I had loaded my iPad with films and cartoons in case the in-flight entertainment wasn't to his taste. I was also carrying my iPhone and Kindle - all of which charge via USB. With the time and distance involved I was worried that these items would run out of charge during the journey.
This super little (12.5cm x 7.7cm x 2.4cm) unit (I chose the gloss white one, although it comes in black too) holds enough power, when fully charged, to recharge an iPhone, from flat to full charge, approximately 7 times - and delivers just about a full charge to an iPad 3.
At just 318g it is nice and lightweight too - but feels chunky enough not to be flimsy. It comes with it's own slightly padded carry bag (quite a snug fit) to give it some protection in your bag.
It comes with a built in torchlight - which I thought seemed a bit odd when I purchased it - and it certainly wasn't a feature I was looking for in an external battery pack. However, in the middle of the night in an aircraft with dimmed lighting and a sleeping child next to me, it was an ideal lightsource for looking for something in the depths of my bag and then locating the headphone jack point in my armrest. So, just goes to show that sometimes you do unexpectedly find something useful.
This power pack charges via USB - it comes with it's own charging cable but not a plug, although I was able to use my iPhone plug to plug the USB 'end' into for charging direct from the mains. Alternatively you can plug into your computer USB port and charge it that way - but I found that a bit cumbersome (mainly due to the positioning of the USB ports on my particular computer and the shortness of the charging cable). Charging via the iPhone mains plug was much more convenient - and I think quicker too - but that will depend on your computer. Charging from the mains is much quicker and took, from totally flat to full, about 9.5 hours - so you do need to plan ahead and not leave it to the last minute before setting off on a journey.
In order to charge your item from the power pack you simply plug your USB charger for that item (eg, your iPhone charger cable) into one of the 2 USB ports on the power pack - you can charge two items at once as there are two USB ports - although one is 1A and the other is 2A - so one will be delivering charge more quickly.
When your battery gets low on your device (iPad etc) you can plug in the power pack and it will deliver charge as you are using your device - so you do not have to wait for it to charge up before carrying on with what you were doing.
A drawback is the level of charge held in the unit is shown by 4 illuminated bulbs on the top of the unit - it's not very specific - I would find it more useful to have a digital readout (for example) showing the specific amount of charge left (eg, 25%) - the instructions tell you, when charging the unit, to remove the power source as quickly as possible once the 4th light is lit - but not knowing how long, or how close to the end you are, makes this a bit tricky - I ended up watching it like a hawk for about 40 minutes until that last light lit.
A second drawback is the positioning of the on-switch for the torch - it is a very large button on the top of the unit and I was concerned that if I did not pack it carefully in my bag that the torch would switch on and drain power. Although the carry case is padded it is not padded enough to stop this accidental switching on happening. I was just very careful about how I packed it.
The final drawback is that it comes with it's own charging cable, as described above, but not it's own mains plug - having one supplied would have been a big bonus for me.
However, for me, the convenience and performance of this power pack far outweigh the minor drawbacks.
In order to charge your iPhone/Pad/Kindle etc you just use the USB power cable supplied with those items - although obviously this adds to the number of items you need to pack.
I was glad that I packed a packing cube in my hand luggage with all of my electrical items and associated cables together - it made going through the various security check points very straightforward as I was able to simply pull that one bag out of my handluggage for inspection. I discovered that there is a limit on the airlines I travelled on, for the number of lithium batteries each passenger could carry - I had the above electrical items plus a Leappad and Nintendo DS it's surprising how quickly you add up to the limit. It was very convenient to have it all to hand when needed.
I found this power pack to do the job it promised very effectively - although I will be interested to see how it fares over time once it has been re-charged a few times ... watch this space.