Garmin Forerunner 405CX battery life?

[Deleted User]

I've had my Garmin 405CX for about 3 years now and went out for a 2:20 LSR last week, the battery was at 65% when I left and died just moments after my run. Have just entered the Loch Ness Marathon with a goal time of 5 hours and now worried that the battery won't last!

Would a new battery help do you think or does the 405 just have a short battery life?