The original 3DS model has always had one weak point over previous generations of Nintendo handhelds: battery life. This shortcoming opened the door for all sorts of battery expansions for the original 3DS, from the excellent Nyko clip-on unit to our personal favourite, the Mugen replacement battery. This accessory was an entirely new undercarriage for the original 3DS that housed a power pack around three times the capacity. As we found in my 3DS Battery test of the 3DS Mugen battery, it took the system to around 15 hours.

Strangely though, there are very few bigger battery options for the newer 3DS XL. Perhaps this is testament to the device's already improved duration, or its already larger size. Mugen is one of the first companies to answer the call of the super-long-lasting 3DS XL; it has just released the 3DS XL (or LL if you're in Japan) version of its battery replacement, again tripling the size of the power lurking below those two screens. Keen to put it to the test, we got hold of one.

First off, you need to get hold of the battery pack that matches (or possibly complements) the colour of your 3DS XL. We've got a pearl white 3DS XL and were expecting this less common colour to be hard to match. However, Mugen was able to supply a matching back panel with no questions asked.

Upon arrival it took about five minutes to fit. Just unscrew the two upper screws on the rear of the 3DS XL, then with some careful wiggling (we think that's the technical term for it) you can flip it off. From there you can pop out the existing battery, insert the bigger Mugen cell and screw on the new rear cover.

First impressions are that this greatly increases the size and weight of the 3DS XL. Now, where as we quite liked the diminutive size of the original 3DS and were a little reticent to make it any bigger, the XL is already a monster so making it larger still feels like less of an issue. The rear housing of the Mugen is a surprisingly good fit for the pearl white upper of the 3DS XL — it looks as if it has been manufactured with the big battery already in it. The lines of the upper case are matched a bit better than they were with the old Mugen 3DS battery, which went for an industrial-bevelled look rather than smooth lines of the 3DS XL unit.

In the hands it feels solid and well built; we could happily hold it without discomfort, although perhaps would be less inclined to play it standing up for too long – preferring instead to rest it on the lap or a table.

The real news here is how long the 3DS XL now lasts; whereas we used to get between 4 to 6 hours of gameplay we're now seeing between 14 to 16 hours (or even 20 hours with all the power saving switched on). If you're like us then you probably have a habit of charging your 3DS XL every night, but now we've found we can almost get through a week without even thinking of charging.

It will be interesting to see how well this performance keeps up, but first impressions of both build and duration are excellent. The Mugen 3DS XL battery is available from the Mugen website now.