Product Round-up Everyone with a smartphone knows how frustrating it can be to reach the afternoon with diminishing batteries. While it may be a relief to lose access to your phone when you're away on a camping trip, for many it's an inconvenience we could do without.

However, with the price of external juice packs falling quicker than smartphones themselves, theres's little excuse not to avail yourself of a back-up power source.

Here's a look at some of the external packs on the market and how much they charge - both financially and in terms of phone replenishment.

Avantree Universal Portable Power Pack

This tube of juice comes with a purple felt carry bag, a retractable cable with various connections for a range of phone ports.

A small green LED hidden behind the plastic end - the body is aluminium - glows when in use and flashes when in charge mode. It was lit when I took it out the box and unfortunately the tiny power button alongside failed to function. Even on charge, pushing the pin did sod all.

The tube gets hot fairly quickly when charging too. On the positive note, this means it does double up a decent hand-warmer for those British winters. It's comparable in size to a pack of Trebor Extra Strong Mints as well, so slots in the pocket with ease.

Energenie Chargegenie 200

Green-focused energy management firm Energenie has started to roll out external chargers and to mix it up a bit, I thought I'd throw in its super high-capacity pack, the Chargegenie 200.

The hardback book-sized block comes with a snazzy neoprene zip bag, an AC transformer power plug to charge from the mains, and two adaptor cables with practically every connection under the sun. While it is obviously rather heavy, the high capacity means this beast will replenish laptops too, and with two output ports, can boost other devices at the same time.

A small blue LED display shows how much power remains, as well as information such as how many volts it's pumping. This can be adjusted to suit your tech, pushing the power button to switch between a range of voltages: 8.4V, 9.5V, 12V, 16V, 19V and 24V.

Of course, a charger of such magnitude is more of a camping accessory than an everyday companion, but it will sit in laptop bags comfortably and could come in extremely handy for long stretches of time away from power sources. It does seem like a high price to pay, but I have yet to see any other chargers out there with such a mental amount of power.

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