Battery Improvements in Apple Watch Series 2


The latest Apple Watch (Series 2) used only 46% battery for a 3 hours, 35 minutes run vs the first generation Apple Watch that drained most of the battery on a similar run last year. Both the watches are 38mm in size.

Some data from last year:

During a 20 mile run last year (9/19/15), Apple Watch (first generation) drained almost 99% battery.

Apple Watch (2015): Post 20 mile run. Battery at 1%.

Apple Watch (2015): Post 20 mile run. Battery at 1%.

The 20 mile run was in preparation for the Chicago marathon, and based on above data, I knew that Apple Watch won't last for the full marathon at my pace. On race day, I decided to not bring my iPhone so I could carry enough energy gels instead. This meant all of Apple Watch tracking was done using the built-in accelerometer. Surprisingly, I found Apple Watch to be way more reliable than a Garmin Forerunner that went erratic around tall city buildings. Unfortunately, with no paired phone, it also drained 100% battery in the first 16.3 miles.

For my spring 2016 marathon, I discovered power saving mode that disables heart rate sensor during workouts. I verified it during a 20 mile run and used it for the marathon. It worked great, and while the battery lasted for the entire race, I have no heart rate data from that run. It was a hot and humid day to run a marathon and heart rate data would had been an effective way to analyze how I faded off during the last 8 miles.


Same run with the new Apple Watch Series 2:

Last Saturday (9/17/16), I did the same run, a bit longer (21 miles), mostly along the same course, with Apple Watch Series 2. Here are some screenshots taken before, during and after the run,

A quick side experiment:

This was the final long run of my training cycle for Chicago marathon, so I did not want to risk not bringing my phone along and possibly lose or have inaccurate data for it. While I still carried my phone, I decided it was safe enough to do a little experiment at mile 19 and turn off the phone. In the presence of a paired phone, Apple Watch relies on phone GPS reception for better signal and to conserve battery. So I was curious to see how the watch (specifically built-in GPS) would react, when a paired phone disappears in the midst of a run.

The transition was flawless. Apple Watch GPS took over seamlessly when the phone was turned off. This was verified with a course map generated from accurate location data for the whole run.

Not surprisingly, the built-in GPS did use more battery. In the last 20 minutes, battery availability dropped from 57% to 48%. That's 9% for 20 mins with built-in GPS vs 39% for the first 182 mins with a paired phone.

Again, this was mostly to test how well the watchOS and Workout app is built/tested for random GPS source switching. It's impressive that the watch GPS picked up without any glitch and it tracked the remaining run with no issues. In retrospect, considering I didn't want to mess with my data for this run, shutting the phone down was a risky move. I am glad that watchOS and iOS could pick up and sync nicely when the phone was back online.

Results – Battery improvements by numbers:

At mile 19, while still paired with a phone, the new Apple Watch had drained only 39% battery (that's about 41% for 20 miles *). This is substantial improvement over first generation Apple Watch that drained almost 95% battery for the same 20 mile run, done last year.

Mapping the above numbers to total running duration: first generation Apple Watch drained most of the battery for a 3 hours, 35 minutes run, where as the current Series 2 model needed only 46% (**) for the same 3 hours, 35 minutes run. That's over 7 hours of running time on one charge with still some battery power left. (Apple's official tech specs suggest 8 hours of workout from a full battery charge)

Even by including the variance caused due to the above side experiment, 48% for first 21 miles without power saving mode means I can run with the new Apple Watch Series 2 for a full 26.2 miles and still collect all the useful heart rate data.

This is great news for me as a runner and I am sure for many runners out there. If you are looking to buy a new running watch, I would highly recommend Apple Watch Series 2.

Battery was at 96% at start and 57% at mile 19. That's (96-57)/19 = 2.05% per mile.

** Battery drained for 182 minutes was (96-57=39%). That's about 46% for 215 minutes.

Tempo v1.0

Tempo is now available in the App Store. If you run with your Apple Watch, please do check it out.

You can read Tempo’s story here. To celebrate the launch, here are some more fun facts that I edited out of the original story,

  • I sketched up Tempo’s original screen last year, during a sleepy morning, while staying up with my newborn. It was probably around 5am.
  • That sort of got me into sketching habit during early mornings. Most of them now are before my long runs on the weekends.
  • Many Tempo features have been devised during miles and miles of training on Newton hills and other parts of Boston marathon course along Comm. Ave.
  • During its initial prototyping phase, Tempo was called Runlog.
  • Tempo has been my only running log for my last 2 marathon training cycles.
  • I have been building it for almost a year; crafting it slowly and carefully as my go to running log. As I have said before, I love running and building software, and building Tempo is now my favorite way to do enjoy both!
  • Tempo is the very first project launched under Indie Computing Labs, LLC.