A few months back I reviewed the Brando Power Jacket case for the Nokia Lumia 920. A case with a built-in battery, it could potentially double the battery life of the Lumia 920 – a dream for gamers. But the Brando case didn’t perform all that well as a charger, limiting its usefulness.

Enter Mugen Power, makers of many external batteries and cases. At long last, Mugen now offers an extended battery case for the Nokia’s original flagship Windows Phone 8 handset. The Mugen Power Battery Case for Lumia 920 comes in black or white, as well as two different battery capacities: 3000 mAh and 4700 mAh. The 4700mAh model offers 2.35x extra power on top of the 920’s built in battery. I’ve spent the last few weeks using that version as my case in order to bring you this detailed review.

Mighty Mugen Power Ranges

Mugen Power Battery Case for Lumia 920 review

The Lumia 920’s built in, non-replaceable battery holds 2000 mAh of power. The Mugen Battery Case comes in both 3000 mAh and 4700 mAh sizes. The price difference between the two is only ten dollars, making the choice between models come down mostly to size and weight. The larger capacity case is a few millimeters thicker than the smaller one, and presumably heavier too.

Even the 3000 mAh case will provide more power than the Brando Power Jacket, which has a capacity of 2200 mAh. At 3000 mAh, you’re looking at 150 percent extra power on top of the 920’s internal battery – more than doubling the available power, in other words. The 4700 mAh case I’ve been using exceeds the phone’s standard battery by 235 percent, basically tripling the power it has to work with.

How well does one of these cases extend the 920’s battery life in practical terms? An unenhanced Lumia 920 will likely get 2-3 hours of playtime from a graphically intensive game. After that, you’d better plug in or you’re going to miss some calls.

With Mugen’s 4700 mAh case, I played Temple Run 2 for five hours (yar, a tad boring) without fully draining the case. The phone itself showed some battery drain; these cases can’t eliminate the fact that 920s sometimes use power faster than they can charge. But the case certainly helps!

Retraction action

Mugen Power Battery Case for Lumia 920 review

The Mugen Battery Case connects to the Lumia 920 in a most unusual way. Unlike the Brando Power Jacket, this case doesn’t cover the bottom of the 920 where the phone’s micro-USB port calls its home. The bottom of the phone remains largely exposed while inside the case. The bottom-left side of the case houses a retractable micro-USB plug that provides power to the phone.

A hole at the bottom of the case holds the plug snugly when not in use. Pull the plug out of the hole and you’ll find a thin, coiled wire about three centimeters in length. The wire is built into both the micro-USB plug and the inside of the case itself. It allows just more than enough room to connect the case to the phone’s power jack.

After plugging the Mugen Battery Case’s male connector into the power jack, the case automatically starts charging the phone. No pressing a button to switch to charging mode here; connecting the case while it holds a charge is just like plugging in a charger. One won't get into situations where the case is charging itself but not the phone (both can charge simultaneously), unlike the Brando Power Jacket which often stopped charging the phone.

Mugen Power Battery Case for Lumia 920 review

However, the retractable plug betrays some significant design flaws. The cord itself is quite thin and can’t be replaced if it breaks on either end. Cut or tug too hard on it and your hundred dollar case drops to a value of zero. The charging plug itself is too fragile as well. It sticks out from the phone, completely unguarded during use. If the plug is bumped too hard or the phone gets dropped and lands on it, the plug will bend or break - possibly even damaging the phone's micro-USB port in the process.

That fragility of charging plug and cable means you shouldn't leave the case charging your phone all the time, as nice as the constant power supply is. When you’re walking around with the phone in-hand or in-pocket, you’ll probably feel a lot safer with the plug retracted inside of the case. Not a tradeoff we should have to make. At least Mugen Power offers a one year warranty, but those don’t usually cover damage from dropping and other accidents.

Big is beautiful

Mugen Power Battery Case for Lumia 920 review

Power connector issues aside, the Mugen Battery Case is mostly a good case. It adds a significant depth to the phone and a noticeable amount of weight. The extra size doesn’t make the phone too hard to pocket or anything, though it’s certainly hard to miss when looking at the phone.

The extra weight could be a concern for some users, but not this guy. As a gamer, I’m used to holding controllers that weigh just as much as a 920 with the 4700 mAh case on. I find it perfectly comfortable; it doesn’t fatigue me a bit.

The Battery Case has cut-outs for all of the buttons along the right-side of the phone: volume, power, and camera. A little behind the volume buttons, you’ll find the micro-USB port used to charge the case itself. A tiny red light next to the port comes to life when the case is charging.

On the rear of the case, a conical cutout allows the camera and flash to work unimpeded. Four LEDs and a button occupy the bottom rear of the case, just below the Mugen Power logo. Pressing the button will light up the LEDs and indicate the case’s remaining charge. I like that the lights only come on when checked instead of wasting power on them all the time.

Not the full wraparound

Mugen Power Battery Case for Lumia 920 review

If the Mugen Battery Case has one more flaw, it’s how much of the phone it actually covers. The case does not cover the top or bottom of the phone, although it does extend about a millimeter beyond the phone’s borders on those sides. This provides some minimal protection to the top and bottom areas, but not much. More egregiously, the case does not cover the front of the phone and the screen at all. The 920’s most fragile side - the one that most needs protection – is the only side that gets none.

Overall Impression

The lack of protection to the front of the phone belies the Mugen Power Battery Case’s strange design ethic. The number one reason anybody buys a case is to protect their phone. This case offers more protection than no case at all, but not to the all-important screen. I dropped my phone and got several new scratches that wouldn’t have happened had I kept using the Brando Power Jacket. The fragility of this case’s charging cable and plug is also worrying, especially given the high cost of the case.

On the other hand, the Mugen Power Battery Case for Nokia Lumia 920 is one hell of an external battery in either power capacity. I absolutely adore how much extra playtime and usage I get from my 920 with this thing attached. When I’m not gaming, I can go an extra day or two without plugging into a wall. And when I do game, I can play for as long as I want without being tethered to a charger.

For me, the benefits of the case’s voluminous power supply just outweigh the protection I give up from other cases. But I might feel differently if my Lumia 920 was at the beginning of its life instead of the tail end. If you’re looking to extend your 920’s day-to-day gaming life and you don’t have trouble keeping your phones free of bruises, give Mugen Power’s solution a look.

  • Mugen Power Battery Case for Nokia Lumia 920 – 3000 mAh – $89.99
  • Mugen Power Battery Case for Nokia Lumia 920 – 4700 mAh – $99.50 – Mugen Power Store Link (all varieties)