so much for a 935 lasting for a full Ironman

Hmmmm, that's pretty weird then indeed... Some rogue process in the background perhaps?

Sucks indeed about the timing, guess a restart of the watch would have fixed it. Notice any unusual drains still? Otherwise the forced close-down (and restart) of the watch probably did just that... fixing it.

Looking some more at the FIT file, there seems to be time alerts every 1 to 4 mins in the run. Did that involve any bleeps? What would they be I wonder on non uniform intervals?

Also lots of "rider position change" events on the bike. Wonder what they are?

You appeared to be using HRM-Tri, Garmin Vector pedals, and some sort of foot pod. None of these should cause excessive battery drain though.

The battery drain graph is actually fairly linear with about 10% drain every 1.5 hours. It seems it started from 95% though.

Looking one of my recent outdoor rides with GPS (only - I think), HRM-Tri, power meter then I had 10% drain in about 1 hour 35 mins so actually fairly similar.

Interestingly when did a ride with HRM-Tri and cadence sensor but no PM managed to get 2 hours 20 mins for 10% drain.

Not done much running of late but last one got 7% drain in 1 hour 5 mins so again that is around same 10% every 1.5 hours.

So is anybody getting much better than 10% drain every 1.5 hours?

Not me it seems...

I ran little over an hour yesterday i(1:08-is) n GPS only 1-sec mode (removed the battery connectIQ field I usually have) so no connect-iq fields, no pods/bluetooth and it used between 5 and 6 percent of battery.

Will anaylyze the fit file for exact details later today

Another thought is your backlight settings. As I mentioned above there seem to be several hundred "events" (seemingly alerts) during your race which if they turned on the backlight every time is definitely going to consume non trivial amounts of battery life. For maximal battery life in a daylight event, I would definitely recommend ensuring all backlight settings are off so it would only come on with a manual press of the backlight button (top left).

The 1 min and 4 min alert was a run/walk alert - 4 min run/1 min walk. Yeah it beeps at me every time - plus runs the back Light for about 10 seconds. I?m thinking this is what really did me in - but there isn?t any corresponding drain on the battery when it was going on.

I dont know what the rider position changes were.

the footpod is the Garmin footpod that I?ve used for years.

another thing that I forgot to mention was that when it was charged up and rebooted- it only then told me that I was now upgraded to 6.0. I?m wondering if that upgrade process was the something going on in the background that caused excessive battery drain...

So I analyzed my files a bit more in depth:

1. Half marathon (although distance was short) in 1:23:41.

FIT file shows battery going from 0.84 to 0.77 over 1 hr and 20 minutes. I used the battery level connect iq field for that and it shows 84.20% to 77.45% in 1:23:42. So that would be just short of 5%/hr of tracking. This is 1sec, GPS only, OHR enabled, battery level connect iq field.

2. 12k last evening, removed the connectiq field to see if that mattered.

FIT file shows battery going from 0.52 to 0.47 over 1 hr. Same settings as above, just no connectiq field with battery (and thus not more detailed info). All in all the connect iq field doesn't seem to matter though and I'd say I'm getting 5% an hour of activity with gps only and 1-sec.

THe half marathon was during day and the 12k after dark so that might skew things a but (backlight settings are set to brightness at 10%, keys-on, alerts-on and movement-after sunset so I did use the backlight a bit more at the 12k)

The upgrade may have contributed to starting at 95% not 100% which might be up to an hour of battery life and the backlight coming on so often may have been 1 or 2 more hours. Otherwise it seems your battery consumption does not seem a whole lot different to mine. Of course it does not really matter much for me as I don't think I have ever done anything over 6 hours continuously with a Garmin device.

Not much consolation now but I suspect if the backlight was not coming on each time, it would have lasted the whole course.

Thanks timgrose I appreciate the info and feedback.

I just wish that upon shut down due to battery life, that the file wouldn't be lost. You should at least be able to keep what you have done up to that point. Now I have absolutely no info from the run portion of my Ironman... I really wanted to find out the info about where my HR was vs calorie consumption as well as some other info... Just really a bummer... It seems like badly designed software. It would seem easy to run a file save command upon detecting a low battery level before it dies...

Yeah something not right there. With Garmin devices over the years I have sometimes run out of juice and the watch has always saved the file up to that point OK as far as I can recall. Similar thing happens if you have an unsaved activity and then you connect to your computer.

I'll try to have another look in the FIT file to see if there is any info on the run that could be useful.