Mophie Juice Pack for HTC One.

Mophie's usual quality shines through with this HTC One battery case, but you've got to be prepared for a major increase in size

Let's get this out of the way: The Mophie Juice Pack takes the svelte HTC One and bulks it up. A lot. It's a big case full of battery -- 2,500 mAh, to be precise -- that takes an already lanky phone, makes it even taller and fills it out like a blogger at a buffet. You need to know this before hefting this the Juice Pack.

But those of use who have used the Juice Packs before know that this is the trade-off for having a combination case and battery, an amalgamation that was made popular by the iPhone and has become that much more important as more phone manufacturers seal the batteries inside.

And now we've got a Mophie Juice Pack for the HTC One. Our thoughts, after the break.

If you're new to this, here's the deal. The Mophie Juice Pack is a hard-shell case with a 2,500 mAh battery tucked inside. It plugs into your phone the same way a charger would plug into your phone. It's also relatively new to Android phones. The Juice Pack has long been a must-have for the iPhone, but we were fairly disappointed with the Galaxy S3 Juice Pack we tested. (All four of them we tested, actually.) Sharp edges and a couple other minor (but noticeable) manufacturing details led us to not recommend the Mophie for the GS3. Another deciding factor was that the Galaxy S3 -- like its successor, the Galaxy S4 -- still has a removable battery, and you can get a replacement cheaper than you can a Mophie Juice Pack.

For the HTC One, we're going the other direction. The issues we had with the Galaxy S3 case are nary to be seen here, and what we've got is a solid battery case that theoretically doubles the amount of time you can use your HTC One.

Mophie Juice Pack for HTC One - the case itself

It's arguable which part of a Juice Pack is more important -- the case or the battery. We'll start with the former, however. Like we said, this case is big, adding some six-tenths of an inch in height. Know how the dual speakers make the HTC One taller than a lot of phones out there? This case adds to that significantly. The Juice Pack also nearly doubles the thickness -- the HTC One was 9.3 mm at its thinnest -- but theres a gentle curving toward the edges that tempers that somewhat. 

Mophie Juice Pack for HTC One.

By the numbers, you're looking at the following:

  Height Width Thickness
HTC One naked 5.41 in. 2.68 in. 0.37 in.
Mophie Juice Pack for HTC One 6.06 in. 2.88 in. 0.67 in.

It's a pretty stark difference. But at the same time, I actually like the increased thickness. I've never really enjoyed the anorexic trend smartphones have taken the past couple years, with thin-at-all-costs dominating design. The increased thickness with the Mophie Juice Pack actually makes things feel more proportional. I may be crazy, though. I might just like junk in the trunk.

Mophie's soft-touch plastic remains excellent, though it's prone to showing off the oil from your hands. Seating the phone in the case is a no-brainer. You squeeze the sides of the top section of the case (that's the short part) and slight it straight up to remove it. The HTC One then slides down into the main body, with the microUSB plug hitting the port on the phone, almost like the whole thing is on rails. Mophie did a really nice job with getting that fight right. Then you replace the top section, and you're all set. 

Mophie Juice Pack for HTC One.

On the back of the case you'll find four LEDs with a button to briefly turn them on. That shows how much juice the Juice Pack has left with which to juice. There's a small toggle switch next to that. Flip it to green, and the phone charges off the Juice Pack battery. Leave it red, and the phone's on its own power. 

Mophie Juice Pack for HTC One.
The IR blaster hidden in the HTC One power buttons still works even with the Mophie Juice Pack attached

The Juice Pack has cutouts for all the microphones and ports and cameras and what not on the HTC One. The volume rocker works with buttons on the Juice Pack itself, and they're OK. The power button on the Juice Pack actually sticks out a little more than on the HTC One itself -- that's a good thing, actually -- but it's a little soft. Hardly a deal-breaker, especially when you take into account that the IR blaster that's built into the HTC One's power button still works even with the Juice Pack attached.

Also, NFC still works, too. Nice.

Mophie Juice Pack for HTC One.

The bottom of the case has a microUSB port. That's where you plug in the Juice Pack to charge. But you don't have to remove the HTC One first. In fact, if you just plug in everything at once, you'll simultaneously charge your phone and the Juice Pack. The metal contacts down there are for a desktop dock that we've been hearing about for months but still haven't seen.

All in all, the case is very nicely done. no sharp edges or ill-fitting parts that we saw on other models. It's big, but this is a battery case. Not a slim-fit case.

Charging the HTC One with the Mophie Juice Pack

Mophie Juice Pack for HTC One.

The other side of this rather large coin is charging your phone. It is, after all, why you bought the Mophie Juice Pack. It's a little important to set expectations here. The HTC One has a 2,300 mAh battery. The Juice Pack brings another 2,500 to the table. Theoretically, that's double the battery life. You'll probably find you don't quite get that in real life, however, because you'll still be using your phone while it's charging. You'll learn to get the feel for it soon enough. There's really no one answer to "How long does it take to charge my phone." It depends on what you're doing with it in the meantime. (If you're looking to only charge your phone, we'd recommend an external battery with greater capacity anyway.)

Mophie rates the Juice Pack's output at 1.0A. So, again, this isn't some miracle rapid charger cure-all. It's meant to be a steady stream of power when your phone runs low. The Juice Pack is rated at 500 charge cycles -- that's 500 full charge-discharge cycles for the battery case itself, not your phone. Mophie recommends charging your phone as much as you need, then switching the case back to standby.

From dead to charged, though? Figure a couple hours at least. And that's assuming your Juice Pack is completely charged the minute you hit that toggle switch. There will be some wiggle room here. It also takes a few hours to charge the Juice Pack. (The LEDs on the back turn off after a few seconds, so you won't be kept up at night with you leave it charging.)

The bottom line

At the time of this writing, the Juice Pack runs $99 on Mophie's website. (It's currently available in black; a silver version should be ready by mid-May.) That's not an insignificant sum, given that another 2,500 mAh of power is about a third of what you can get from an external battery at one-third the price. But this is battery and case in one package. It's arguably more convenient to carry. Plus it protects your HTC One without sacrificing features. (You Ingress players will love it.)

You just have to be willing to accept a pretty significant size bump in the process.

Check out these other great HTC One Cases

If you're looking for a more traditional case for the HTC One, has you covered.