• The LightInk watch offers 400 days of battery life
• It does this by stripping back features and using an E Ink display
• It also adds solar charging to stay topped up on the go

From the Apple Watch Ultra 3 to the Google Pixel Watch 4, customers looking to adorn their wrists with one of the best smartwatches tend to look for wearables that offer excellent battery life — after all, there’s no point in shelling out on a device if you spend more time charging it than using it. If battery life is a priority for you, you might want to check out the LightInk watch.

That’s because with 400 days of juice on a single charge, it blows past the competition in terms of battery longevity. How does it achieve that figure? Well, this is no ordinary watch — it’s powered by solar energy to keep itself constantly topped up, meaning you can start charging it even when you’re miles from the nearest power outlet. As long as the sun is beaming down on you, the LightInk’s battery is getting topped up.

But you’ll get 400 days of battery even before solar charging is taken into account, the project’s creator claims. How? Well, one way is through cutting the feature list right down. As its name suggests, the LightInk uses an E Ink display instead of an AMOLED display, unlike some rival smartwatches. E Ink technology is incredibly efficient on the battery, helping you eke even more life out of this product.

And because it’s an open-source project, there’s no fee to obtain one. You just need a 3D printer and a few off-the-shelf components to make it yours.

Extreme battery savings

Of course, the LightInk isn’t all sunshine and roses — there are a few downsides to it. Its E Ink screen might grant it excellent battery life, but it comes at the cost of visual fidelity. The LightInk’s display is monochrome and low resolution, so you shouldn’t expect any eye-catching graphics here. It doesn’t even show seconds.

And if you’re a fitness nut or believe in the ‘quantified self,’ you’ll want to look elsewhere. You won’t get any of the health and fitness sensors and metrics you find in most smartwatches — the LightInk can tell the time, occasionally connect to Wi-Fi and GPS, and that’s about it.

You also can’t just go out and buy the LightInk at your local shopping mall. As we mentioned before, you need to have a 3D printer on hand to craft many of the required components yourself, then assemble and solder them into a finished product. You’ll also need to be comfortable with building your own firmware based on the resources provided on LightInk’s GitHub page.

Still, the LightInk doesn’t make any claims of being a high-end, flagship device — it’s a deliberately basic product, as this is what allows it to put all of its energy into maximizing battery life.

It’s definitely not for everyone, but if your priority is staying away from your charger for as long as possible, it could be just what you’ve been looking for.

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Alex Blake has been fooling around with computers since the early 1990s, and since that time he's learned a thing or two about tech. No more than two things, though. That's all his brain can hold. As well as TechRadar, Alex writes for iMore, Digital Trends and Creative Bloq, among others. He was previously commissioning editor at MacFormat magazine. That means he mostly covers the world of Apple and its latest products, but also Windows, computer peripherals, mobile apps, and much more beyond. When not writing, you can find him hiking the English countryside and gaming on his PC.