Battery Powered

Thomas Schoffelen
2 min readAug 22, 2022

Last weekend, I got my Oura Ring. Although it’s too early to tell whether it will help me adequately track my sleep and activity, or whether I will be able to commit to wearing this device on my hand 24/7 for the next months, it did make me realise one thing: batteries have come a long way.

The battery in my phone being the battery I tend to think about the most, I’ve always thought that small battery technology hasn’t moved that much in the last couple of years. No matter the fact that smartphone batteries keep improving, it never seems like my phone keeps a charge for as long as I would ideally like it.

Of course, that’s a fallacy: whilst batteries have improved, the phone’s power consumption has continued to rise. Better, brighter screens with higher refresh rates, faster connectivity through new technologies like 5G and increased usage have meant that I will keep using my phone’s battery to the maximum of its capacity, even if that capacity increases over time.

Credit: 9to5Mac

The battery capacity of the iPhone 13 is almost three times that if the original iPhone, in the same package size, if not smaller!

The thing that drove this point home for me is the battery in the Oura Ring. The ring has such a small form factor — 0.3 inches wide and 0.1 inch thick — that you almost forget there’s even a battery inside.

It’s located in the flat part at the top of the ring and is a tiny, flat, lithium polymer battery with a capacity of 21mAh.

That capacity is nothing compared to an iPhone of course (less than 1% of the capacity of an iPhone 13), but enough to make the ring last anywhere from 4 to 7 days.

This is mainly due to very efficient power management and low-usage components, but still fascinating to think about when you realise how tiny it is.

The battery used by the Oura Ring is developed by a company called Grepow, which specialises in all sorts of these batteries for unusual applications.

Here’s a great video showing what that looks like inside the ring:



Thomas Schoffelen

Entrepreneur tech kid, co-founder of NearSt, Londoner, open source enthusiast and aspiring spare time literature geek.