Smart watches nowadays are known for poor battery life, which is a fact that has plagued mobile technology for at least ten years as processors have increasingly become more hungry for power. The people at Sequent say “No more additional charging from socket-outlets, or coin cell batteries is required”. They have proposed the idea that we charge our smart watches with the kinetic energy of the wrist and as of writing this, the project has raised 774,755 US Dollars or 751,202 Swiss Franks.
It’s much like those old kinetic watches from Seiko, I presume. Except, rather than being like Seiko watches where it just tells the time, this watch reads your heart rate, tracks you with GPS and even handles notifications.
I find my own smart watch to sometimes be frustrating in its lack of battery life, so this is welcome news. Here is the Kickstarter video, so you understand what this watch is or at least what it claims to be.
Sadly, when browsing their page, I found lacking information on the battery capacity and when I eventually found some battery estimates with the smart features turned on they weren’t rated at infinite battery life at all.
I decided to get in touch with the team at Sequent so my mind could be put at ease and I was informed that the watch could generate 2000 to 3000mj (millijoules) in a single day from exercise.
If you don’t understand how much power that is you could be mistaken for thinking this is a significant amount. 3000 millijoules are equal to 3 joules of energy, and 1 joule is how much energy it takes for you to lift an apple up by 1 meter. If you think that this is enough energy to power a computer, then it is not.
After doing some digging, I found that an average persons day with one of the old Kinetron micro generators will generate roughly 600mj. The battery capacity on the watch is supposedly 150 mAh. Ideally, you would want to be able to fill the watches battery before the time it takes to drain for this to be called “infinite”, and we’ll be generous.
Let’s say you exercise every day and produce those 3 joules every day. To calculate this, we will use this equation 1000 x Wh / V = mAh.
psst, you can skip this if you want The upshot is that I calculate that it takes approximately 94 days to charge a 150mAh battery when doing tonnes of exercise and 402 days to charge the same battery assuming an average charge per day with the old generator.
3 joules per day needs to be converted to joules per hour so, 0.124 joules per hour is 0.00027777777777778 Watt hours and the charging voltage of a lithium ion battery is 4.2V so 1000 x 0.00027777777777778Wh / 4.2V = 0.066137566138 mAh.
0.066137566138 x 24 = 1.58 mA per day. 150 mAh divided by 1.58 is roughly 94 days to charge the battery to full. But, this is with exercise.
so, let’s assume the baseline 600mj which gives us a whopping 0.39 mA a day making it take 402 days to charge this watch fully with low energy.
The reason that most regular kinetic watches work is that they use very little power and this means they can have batteries as small as 34 mAh. Seiko claims you can charge 1 day of power on their watches with 12 hours of movement and that the battery will last 3 months from a full charge, this is confirmed by my calculations.
But we aren’t talking about a regular watch here because this one has a small computer inside so discharge time (battery life) could be less than 94 days or heaven forbid 402 days meaning the device could lose charge faster than it can gain it. On comparable watches like the Nokia Steel HR the battery drains in 28 days, the watch has a tiny screen, but it doesn’t have GPS like the Sequent watch, and GPS is incredibly power consuming. Even the Nokia Steel (the model down) without a heart rate monitor or a small screen or GPS will discharge in the space of 8 months (roughly 240 days), and that has a battery capacity of 163 mAh.
If I wanted a rough estimate of the battery life of the Sequent watch with the GPS and Heart rate monitor off, I could use the Nokia steel as a comparison. The difference in mAh is 13 which is 8% so we should expect roughly an 8% drop in battery life. So the battery life will be approximately 221 days with GPS and heart rate off. Given It takes 94 days of running around to charge this thing to full or 402 days of casual movement. You can charge the sequent “infinitely” with the smart features turned off and will presumably be getting ultra fit in the process. (keep in mind these are my estimates).
The graph shows that having all features except time, step counting and Bluetooth turned off and exercising every day, you can potentially infinitely sustain this watch.
To demonstrate that the watch is self-charging in every scenario the black would have to entirely overlap and fill the red. Overlap means “infinite” power.
As soon as you turn on those features that make it a smartwatch, the battery will not be able to sustain itself for more than a month let alone a day even with you attempting to charge it by running.
I think it is dubious to claim this watch is the worlds first self-charging smartwatch with infinite battery life up front but then backtrack into saying it will last only a day with most features turned on, which turns out to be worse battery life than an Apple Watch series 2. All that has been proved here is that smart watches will have to wait until they can last more than a few days without a charge. If you want this product to last infinitely all you have is a slightly fancy watch.
To show how much how much battery the smartwatch portion of this watch actually has according to the sequent team themselves, here you go, and it’s tucked away inside their own Kickstarter page.
So why write this article? One of the fundamental things I’ve learned from backing several Kickstarter projects myself is that when investing money, you should always understand the technical limits of the creators of any product that is still in development. I’m sure that the developers of this project are lovely people that just want to create a great product for people to enjoy. If you think the self-charging watch portion of the product is worth your money I say you should back it because frankly, the design team did a fantastic job of making this watch look amazing.
I welcome criticism of my writing so please feel free to comment and demonstrate where I may have gone wrong.
Edit: My maths may be slightly incorrect as with most things like this I’ve needed to make plenty of assumptions and if it is I apologise, but the maths of the watch makers shows that it won’t last much longer than a day with everything turned on.