Japanese mobile giant DoCoMo is showing off its Ultra-Rapid battery solution over in Tokyo at the CEATEC expo, one that it states offers a charge time of just 10 minutes.

The system works through a battery case, rather than directly to the phone's internal battery; DoCoMo were demoing the system on an NEC Android handset but the aim is to provide cases for a wide number of handsets.

The battery case pulls in power at a much higher rate; up from around 0.55amps to over 5.5amps, meaning that the charge time is significantly reduced.

The battery case, once fully charged, offers your usual battery life on top of what your phone's internal battery is capable of and you can also hold down a button to charge your internal battery should you want to ditch the case. This would take around 2 hours.

We've used similar, if somewhat slower, battery case options such as the Mophie Juice Pack before, but we have to say that the 10 minute charge time is a brilliant USP and would be incredibly useful if, like us, you're the type of smartphoner who is always running out of power.

We questioned the DoCoMo rep as to why the tech couldn't simply be embedded within a phone and the answer was that the phones are just too small. Plus a typical mini or micro-USB charging point only offers a pass-through of around 1.8amps, albeit with other connectivity functions.

There's no plans for a release yet, in Japan or elsewhere, as its just a prototype for now. Great idea though.