Matrix PowerWatch review: The smartwatch you never need to charge

The Matrix PowerWatch’s unique selling point is very simple: you don’t have to charge it.

Ever.

Thanks to a thermoelectric generator (TEG) inside, the watch converts your body heat into energy, meaning you’ll never glance down at your wrist and find your trusty timepiece is about to run out of juice, a daily experience with smartwatches like the Apple Watch Series 3 and Fossil Q Control.

Sadly, such a device was always bound to come with its share of compromises. You don’t get a vibrant, high-resolution screen and the PowerWatch won’t even display smartphone notifications, though this feature is coming on the forthcoming PowerWatch X. It tells the time, naturally, but doesn’t do an awful lot else: all you get is step, sleep and calorie counting, and a stopwatch.[gallery:6]

At £200, it’ll also set you back considerably more than a fitness tracker like the Fitbit Alta (£100) but with one of those you don’t have the PowerWatch’s cutting-edge TEG technology to boast about.

Buy the PowerWatch from Matrix now

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PowerWatch review: Design

The PowerWatch is a striking device. The best way to describe it is that it looks a bit like a real-life Action Man watch. At 46mm across and 15.5cm thick, it’s BIG. It has a part-plastic, part-aluminum body, which sadly doesn’t look quite as attractive in the flesh as it does in the company’s promotional material, and there are two buttons and a crown for navigating the watch’s interface, but no touchscreen. [gallery:1]

Because the crown is on the right side of the casing it makes for very fiddly navigation if you prefer to wear the watch on your right wrist, like I do. The buttons also need to be pushed quite hard before you feel any kind of feedback, which again isn’t great if you’re left-handed and need to reach around to the other side of the watch. Otherwise, the buttons and crown work as you’d expect them to, letting you navigate the watch’s various menus.

It comes as no surprise a low-powered device like the PowerWatch has a monochrome display. It might not be bright and pin-sharp, but it’s easily visible in most light. Sadly, the only thing hindering this is the hardened-plastic front, which picks up a lot of fingerprints and quickly becomes smeary. For when it’s dark, there’s a backlight but because all energy must be carefully rationed, you can only use it up to four times an hour. That in itself isn’t so bad, but I found it so underpowered that it was only just enough to check the time in a pitch black room. That can be a good thing if you want to check the time without a flood of blue light hitting the back of your eyes and waking you up in the process but in some situations, I imagine it’s almost redundant.[gallery:8]

One pleasant surprise was that the watch isn’t as heavy as it looks. It’s listed as 50-60g on the website, which is lighter than the similarly chunky 62g Samsung Gear S3. It’s also deceptively comfortable, despite having a tough nylon strap that feels stiff and quite rough to the touch. I had no problems wearing it all day long and even when I left it on at night, I wasn’t overly aware of it.

Matrix PowerWatch review: Features

The PowerWatch’s main feature is its thermoelectric generator. Whenever there’s a difference in temperature between your skin and the watch’s casing, it’s then generating energy and the greater the difference the more energy it makes. A cursory glance down at the device tells you these temperatures and by simply turning the crown, you can see the “real-time power” that’s being generated, which is represented by a chart around the watch face.[gallery:2]

In the event that you take the watch off your wrist, it still shouldn’t run out of battery because after 45 minutes the watch automatically enters Power Save mode and turns off the screen. If fully charged, Matrix claims it can remain in this state for one year or more. I didn’t ever see the watch enter Power Save mode but it’s encouraging to know it’ll ensure you always have some battery at times when you need it.

Pressing the Mode button once loads the PowerWatch’s Daily Activity menu. Here, you can see your total step count and distance walked along with the number of calories you’ve burned. Unlike other wearables, the latter figure is calculated using not only your activity stats but also the temperature data gathered by the PowerWatch. Matrix’s website claims this is “inherently more accurate than fitness monitors that calculate calories based on step counting or other activity-based approaches” but without the means to empirically test how many calories I’ve burned, I’ll have to take them at their word on this.

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Scrolling the crown in this mode then displays a summary of your sleeping data. Although the website’s promotional shots shows this screen with details of deep and light sleep , I was disappointed to find that the model I was sent only showed the total amount of sleep. Unlike many fitness trackers, this feature isn’t automatically enabled, either. You need to press the Set button for three seconds to enter sleep tracking mode, and the Powerwatch can then detect when you’re no longer sleeping, and logs your total sleep duration.[gallery:5]

In terms of sports tracking apps, the watch only has a “Running Mode”. Essentially, this works as a separate step, distance and calorie counter accompanied by a timer, so you have an idea of how long you’ve been working out and the distance you’ve covered. There’s also a pace reading but you can take this with a pinch of salt since there’s no way it can accurately track your pace without GPS – unlike some smartwatches, it doesn’t even use your phone as a crutch. The watch is also waterproof to 50m, so you’ll have no problems jumping straight in the shower or pool after a workout but though you can take it for a swim, it won’t count lengths or strokes.

To build a long-term picture of your overall activity levels, the PowerWatch needs to be synced with its counterpart smartphone app to log step, distance, calorie and sleep data. To do this, you simply open the watch’s settings menu and then press Set to initiate a sync. The manufacturer recommends only doing this a couple of times a week, not least because it drains the battery, but also because the watch can store up to seven days of data on it at a time.

Strangely, when I synced the watch with my phone, I saw higher step and distance counts for that day than were showing on the watch itself, so I’m not sure if it was estimating my total activity based on what I’d done so far. Even more bizarrely, I found the sleep data didn’t sync to the app at all.[gallery:10]

Matrix PowerWatch review: Verdict

It’s impossible not to find the technology in the PowerWatch appealing. After all, how many other smartwatches can you say will never need to be charged?

However, even with the lowered expectations that come with knowing it charges from your body heat alone, the PowerWatch’s features are still underwhelming. You can get all of the functionality of the PowerWatch in the Fitbit Alta, which costs much less at only £100. It might need charging every five days, but it also has considerably less bulk and will display notifications on your wrist, too.

That’s not to say the technology isn’t worthy of celebration. It absolutely is and, for some people, there will be an appeal to owning a fitness tracker that doesn’t look like everyone else’s. However, as wearables become more power efficient and batteries more effective, I find it difficult to see a device that’s as necessarily big and bulky as the PowerWatch winning in the long run. I wish it all the luck in the world because I love the idea, but Matrix has a monumental challenge on its hands.