Garmin 305 battery life & long races

I have not done a IM yet but have thought of what to do and you have a few options.

1.) One, is turn of the GPS function for the swim/bike and use a standard bike computer and then turn on the GPS for the run only.  The battery life is significantly longer when not in GPS mode.  This way you get total time but pace on the run.

2.) You could try and find someone with a 305 that is not using and see if they will let you borrow if for part of the race and use yours for the rest.

3.) Go under 10 hrs

Just turn off the GPS, what I intend to do at IMAZ.  You've got markers every 5 miles or so on the bike, and every mile on the run, not like you need to figure out where you are..... And I don't intend on having speed or pace even showing, so loss of that info is irrelevant

x2.  I didn't use my Garmin on my first IM and I didn't even have a bike computer on my bike either.  I actually didn't know what my time was until I was on my second of three laps on the run.  In the end, I was running my race based on my RPE and not having the pressure of some semi-arbitrary time goal was liberating.

I turned my on in T1 and it lasted the whole day. It beeped low batteries on the run but never shut off. For me, it lasted over 11 hours

I also left GPS on, had it calculate my 10 mile bike splits, 1 mile run splits and set a 20 minute reminder for nutrition on the bike 

I kinda realized my first reply/post didn't really answer your question.

I think the short answer is that you can't really get it to last 12-17 hours.  Theroetically (although not very practically), you could have a solar USB charger for it and have it charge up while you are on the bike (it'd need to be in the cradle of course), but not likely you're going to want to have one of those during a race.

You'll just have to pick if you want it on during the entire bike segment and likely have it run out on the run (it will retain all the info when the batteries run out) or just use it on the run.  I've also found that my batteries don't last as long as they used to.  Maybe only a bit over 6 hours now when I used them in my last ultra.  Also, Garmin's don't seem to retain charge as long as other devices when unplugged (but not on).

Thanks guys! 

Wonder if Garmin realizes the opportunity? 

From what I've read about the 405, apparently they don't. It supposedly has less battery life. For mine, I used my wife's for the bike and mine for the run. Kinda handy to have two of them.