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Suunto Ambit External Battery Experiment – Test 02

This is the second part in a three-part series of experiments investigating the use of an external, USB battery pack with the Suunto Ambit GPS Watch in order to extend its useable field life.  That is: can a Suunto Ambit user record a high-detail log/move longer than the 16hrs the internal battery allows?

While the rationale for this experiment was outlined in the previous post, in short we want to determine whether we can record beyond 16hours at 1sec/1sec  intervals (high detail mode) for activities such as Ultra Running and other activities with a longer duration.

Test 02


1 x Suunto Ambit (and charging Cable)

1 x Sony External USB Battery Pack


1. Turned on the watch in “Cycling Mode”, set to 1sec recording intervals and 1sec GPS fixes.

2. Drove from one part of Victoria to another, approximately 108km (75minutes)

3. Let the Ambit record for another 7hours approx.

4. Connected the USB charger and let the Ambit run for another 15hrs approx.

5. Turned it off.

GPX/KML files available here (click the respective file type)



1. The recorded log was 23hrs 19minutes @ 82.41km

2. As per experiment 01, there was clearly no issue with the USB Battery Pack extending the field life of the Ambit.  When I turned off the recording, the battery was above 80% and the USB Battery Pack still had charge (though how much, exactly, I couldn’t determine)

3. Given the approximate distance from where I started recording to the location where the watch stopped travelling is approximately 105km yet the recorded distance is 82km, I would assume that the circular design of the Ambit’s memory system (i.e. once the memory is full it will start to overwrite older logs) means that once a unique log fills the memory, it will start to overwrite itself.  This will clearly affect the data uploaded to Movescount, but will it affect the Total Distance from Start (TDS) as displayed on the device?

Roughly speaking, the TDS could either be:

A) A Realtime calculation performed by the Ambit based on every recorded distance increment, or;
B) An independent variable that increase every time the Ambit records a distance increment.

While B seems much more likely (as it would require far less processor capacity and therefore less battery power), I’m yet to confirm this.


1. Unfortunately this experiment was fundamentally flawed in that I didn’t independently record:

a) the total distance travelled after the watch stopped moving (e.g. with pen and paper)

b) the exact time and location that I commenced recording (e.g. using a known location and another clock)

c) the total recording time, independently of the watch (e.g. on another stop watch)

2. While I believe that the final distance recorded during this experiment to be LESS than the total distance travelled (i.e. the TDS has been REDUCED as new data was recorded), without the data mentioned above it is impossible to be conclusive.

3. A third experiment is therefore required wherein these flaws are addressed.

4. Tentative findings would suggest that the limitation of the Ambit won’t, as initially suspected, be battery life. Rather memory capacity seems as though it might enforce an upper limit on usability and the ability to track TDS above 16hrs.

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