Smartphone battery life has marched backwards, or so it seems: my ancient HTC Desire still lasts longer on a full charge than my newer Nokia Lumia 620 or Sony Xperia T. Another problem is tablets: battery life is decent compared to a laptop, but it is easy to get caught towards the end of the day or on a plane with an exhausted battery.

The solution, if you cannot get to a charger, is one of those pocket chargers for topping up your device. These are popular promotional giveaways, which means I have a drawer full of them (or would if I had kept them); but many are rubbish: bulky, fiddly with lots of assorted adapters to cope with different phones, and some with pointless adornments like solar panels.

I make a partial exception for a PowerTrip charger I received recently, which has an impressive 5700mAh battery, but it is still ugly, comes with three cables, and has silly extras like a solar panel and ability to work as a memory stick.

By contrast, the Innergie PocketCell is the first charger I have seen which has immediately impressed me with its design.

There are only two pieces you need to carry with you, the small battery pack itself and a clever three-in-one cable in which the adapters snap together, so you can charge a device with Mini-B or Micro-B USB (the two popular types), or an Apple 30-pin dock connector (if you have an iPhone 5 or another device with the new Lightning Connector you are out of luck unless you have an adaptor).

The same connector also serves to charge the PocketCell, using one of the many USB mains chargers you almost certainly already possess, or by plugging into a PC or Mac. The PocketCell has a USB Type A socket for output, and a Micro-B for input, so you cannot easily get it wrong.

On the side of the PocketCell is a button which you press to discover the current charge. It lights up to four LEDs, to indicate the level of charge remaining.

Battery capacity is 3000 mAh; not as good as a PowerTrip, but decent considering that it is less than one-third the size and much lighter (72g/ 2.5oz).

I tried the PowerCell on an iPhone 4 with a fully expired battery (at least, expired to the point where it would not switch on).

The phone charged successfully, during which time the PocketCell got somewhat warm, but with impressive speed of charge. After the charge the PocketCell was pretty much exhausted.

The PocketCell supports 2.1 amp fast charge, which means it is fine for charging an iPad or other tablets with USB power.

The small size, nice design, and effective charging of the Innergie PocketCell means this device might actually find its way into your bag. The downside is that it is more expensive (especially in the UK) than some other portable chargers with equal or greater capacity, but its elegance and usability is worth a bit extra.

While I recommend the device, check that 3000 mAh is sufficient for you before purchase. I have also heard that the three in one cable is a little delicate, though you can get replacements if necessary or use a standard USB cable.