Despite the improvements in battery life in many devices, a portable battery pack can still come in useful, especially when out and about.

About the size of a small packet of fags, the Powertraveller Powermonkey Discovery is a metal-cased compact battery pack.

It charges from USB and has a USB port to charge up your tablet or smartphone. It comes with an array of different tips to charge up most devices, including the essential iPhone plug.  It is also compatible with e-readers, Sat Navs, handheld games consoles, portable GPS systems and more!

According to the company that supplies these, the device will recharge an iPhone twice, standard mobile phones 3-4 times, or give iPods / MP3 players up to an additional 120 hours playtime.

In our tests, it managed to recharge our test iPhone to full from flat and then again to around 50 per cent.

The construction apes Apple’s design ethos although looks and feels slightly cheap next to an iPhone.

This minor point aside, the build quality is good enough and does a great job in doubling battery life when out and about.

At around £39 from Amazon, it works out a lot cheaper than the Morphie Juice Pack PowerStation.