John Galea's Blog

My blog on Gadgets and the like

Fenix 6 Pro distance and wheel sensor

I’ve seen some posts that made me wonder if my Fenix 6 pro distance measurements were accurate and it sent me down a rabbit hole. So first of all I went on a road ride, somewhat flat somewhat straight and took along an Edge 305 as well as Strava running on my iPhone XS. I put both Garmins in per second GPS mode. The Fenix 6 uses a different, Sony GPS chipset and battery estimates indicate Garmin have played around with normal GPS settings to improve battery life. The results were spot on identical. 15.16KM for the Edge 305 Vs 15.17KM for Fenix 6 pro but Strava running on the phone clocked in at 16.35KM or about 7% on the high side. Other phone apps might be even worse.

I contacted Garmin about issues I was having with wheel sensor accuracy and they told me what the process is for a wheel sensor. I have a Wahoo Speed sensor. Unlike past sensors that require a magnet on the spokes this simply straps to the wheel hub and broadcasts over bluetooth and Ant+. It uses the standard CR 2032 battery has over a year of battery life.

So why should you care? Well if your on twisty trails like mountain biking, even per second GPS can be inaccurate. How inaccurate? 10-15% is what I’ve seen in the past. So according to Garmin the process is to add the sensor to the Fenix, add it in auto mode (which is the default) and go for 3 rides of approx 1 mile in as straight and as level as possible. At the end of each ride note the size of the wheel that the Fenix calculated. First time up it will announce when it’s found the wheel size. You can see what size it has calculated by going into settings, sensors, find your sensor and slide on down to wheel size and note it. Rinse and repeat three times in all, then average the numbers. Then change the wheel size from auto to manual and enter the average size. If you have previously used the device, delete it from the fenix and add it back and start again. You will now have the most accurate size you can hope for that will account for inflation, your weight etc. So what kind of difference does this make. I headed out and did a mountain bike ride and compared with the Edge again. The Edge got 28.45 KM Vs the wheel sensor with the Fenix that got 31.67 Km or a difference of 11% pretty much spot on what I would expect.

July 16, 2020 Posted by | Fenix | Leave a comment

Fenix watch face power consumption

I’ve often wondered, and have seen a number of people wondering, do non Garmin watch faces take more power? So I thought, heh this sounds like a good topic for a blog post. Garmin do not seem to evaluate the power consumed by watch faces, leaving it up end users to figure out why there battery life seems to have gotten shorter.

So to start out with I decided on a procedure to measure battery consumed by the watch face. There are lots of things, like pulse ox, GPS, heart rate monitor, notifications that consume reasonable amounts of power. So to eliminate them, I note the battery level and time before I go to sleep, take the watch off, then note the power level when I wake up, the watch is in do not disturb so it should be as quiet battery wise as possible. I do three runs to hope to eliminate other extraneous power blips. The watch is on Software version 9.0. I used defaults on all watch faces. I chose some of my favorite watch faces for my Garmin Fenix 6 pro.

So let’s start out with a default Garmin watch face, this one:

Power consumption was %/hr: 0.057142857, 0.125200642 and 0.113793103 averaging 0.098

Next up SimpleCassieWF01

Power consumption was 0.255319149, 0.021052632 and 0.120437956 averaging 0.138513514 or 40% more than the stock Garmin

Next up Instinct tactical

Power consumption was 0.161073826, 0.152542373 and 0.166666667 averaging 0.1599073 or 62% more than the stock Garmin.

Last but not least Retro Quartz digital

Power consumption was 0.19, 0.23 and 0.258064516 averaging 0.225255973 or 128% more than the Garmin. This is a busy watch face with seconds changing, so not a surprise it’s noticeably higher. Changing options can of course reduce power consumption.

So what can we learn? Yes watch faces do seem to vary a LOT. You can also see getting stable results is challenging. Of course I have zero knowledge of the actual coding of the Fenix that might explain the variations. BUT, and this is a BIG BUT, from the highest power consumption to the lowest the difference in 24 hours would be like 3%, so in all … find the watch face you like and rock on!

July 9, 2020 Posted by | Uncategorized | Leave a comment