Apple Watch 7 – New Battery tech & new design could boost life by 25%

Must Read: Apple Watch 7 Predictions

There’s a lot of chit chat amongst industry commentators about next week’s new Apple Watch 7 screen being a little bit larger, even more chat about the redesigned case format and further speculation that the old straps might fit the new Watch 7.

Unless there is some new screen tech then a bigger game-changer could be with the battery. Here’s why.

New Battery Tech hits the market.

The new WHOOP 4.0 band hit the headlines today and ships this month. The general chit-chat about WHOOP today was its new HR sensor. The chit-chat tomorrow will be founding members complaining that they will have to start paying a subscription in September 2023.

A much more impactful conversation would be about the battery tech that WHOOP 4.0 uses.

For the first time ever, a wearable’s Li-ion battery uses a silicon-based anode rather than a carbon-based one. The bottom-line for this tech is that the same capacity can be maintained by a 17% smaller battery ie about 20% more capacity for the same space if you do the math.

The battery maker is Sila Nanotech who received significant VC funding earlier this year to expand R&D. Ultimately Sila is gunning for the electric vehicle market but it seems to have taken a lucrative side road into wearables. I would imagine that the Sila Nanotech sales rep contacted all the big wearables companies and asked to pitch. I’m guessing that s/he had heard of Apple and made the call to them too!

It’s inconceivable that Apple & Garmin’s R&D doesn’t know about this. Whether or not they’ve bought it for the Apple Watch 7 or the next Garmin Venu 2 is, of course, speculation.

The like-for-like 18-hour battery life of the Apple Watch 6 would be boosted to 21-23 hours and the Garmin Venu 2 would see GPS+battery life raise from 22 hours to c25-27 hours should either of them use this tech.

Hold that thought.

A Bigger Apple Watch 7 screen also means a bigger case

Doh!

Apple Watch 7 will be larger, now coming in a 45mm version rather than the existing 44mm.

There’s also going to be more space for a larger battery or some other component in the Apple Watch 7.

To estimate how much larger the battery could be, we need to know the internal volume and the current battery size. We can base estimates on these sizes

 

I guestimate the existing internal size of the 44mm AW6 is 38x32x6=7296mm3.

Increasing the length and width for the AW7 by1mm gives 39x33x6=7722mm3. That’s 426mm3 more or a 5.8% bigger volume

Let’s look at this teardown of the AW6 and see the battery in the bottom left of the image.

 

Conservatively, I’d say the battery takes up 1\8th of the volume. ie 7296/8=912mm3

If we assume that ALL the new space is used by the battery then the battery can now be increased by 426mm3, the number we found earlier ie 912+426=1338mm3 or 46% more!

This translates to another 8 hours more battery life – from 18 to 26 hours. Add in the silicon anode and we get 31 hours.

There’s also talk of other internal space savings being made with a double-sided CPU plus the CPU and other components could become slightly more energy efficient which itself extends the battery life.

 

Apple Watch 7 Battery Life?

Whilst the headline spec of the Apple Watch’s battery life has stayed at 18 hours for several years, the reality is that judicious use of GPS, SpO2 and HR can easily give a day and a half battery life.

Put that all together and the bottom line is that realistic battery life for the Apple Watch 7/8 could exceed two days/2 sleep cycles and a realistic best-case scenario could hit 3 days with a few features disabled.

 

What works against that?

OK, there’s a lot of assumptions there on every level.

I would further assume that any case changes made this year will be here to stay for several more years to come and yet I haven’t even considered the use of alternative screen tech and sensors that use less energy.

I would point out that Apple probably plans to incorporate the Rockley Photonics sensor in AW8/AW9 to measure lactate, blood glucose, hydration and other vitals via laser-based, IR spectrophotometry. That sensor is a working prototype but it looks quite big.

 

Maybe some of the extra space is intended for that component? Then again, the laser should be more energy-efficient than LEDs…

What does this mean for Garmin?

Whilst extra battery capacity would be welcomed by any wearable company, the impact on Garmin watches will be much less than the pure smartwatches made by Apple, Samsung, Fitbit/Google and others.

Garmin Venu 2 already has a multi-day battery life based on realistic/normal usage. Even adding an extra day won’t change Garmin’s marketing or your usage patterns too much. It wouldn’t be the same kind of game-changer that it could be for Apple.

 

Should we be excited for Apple Watch 7

Hmm. Probably not!

I originally expected a slight increase in battery capacity and a slight increase in component efficiencies to deliver a slight increase to the overall battery life.

The most realistic expectation about how Apple can deliver a (small) step-change increase in battery life lies in the availability of more internal space rather than the unrealistic use of cutting-edge tech. Apple tends to use well-proven tech.

Must Read: Detailed Apple Watch 7 Predictions