Battery drain is a recurring problem. Not sure why it does it, but I have been caught by it many times, having fully charged it, then turning it on sometime later only to get the low battery warning. Then there are other times I have been able to use it every day for a week or more and find it still has 40% battery life left. Mysterious, but I generally keep it plugged in until I absolutely need it if I am going to an o-meet with it.
The only time I've had a surprise battery drain with my 310xt is when I plugged it in to recharge and, unbeknownst to me, it accidentally turned on when I connected the watch to the clip (which happens if the contacts don't connect solidly right away).
Looks like I'll see both of you tomorrow. Hope it's not a death march at the end.
This
link on 310 issues begins with the mysterious turning on. Maybe a firmware issue? It never happened with the 305. Maybe just plain black magic:).
Death march or not, I didn't enter. I think BHT days are over but BG in the spring for sure and Highlander or bust in the fall. May the force be with you!