Gps watch / running watch for a 24hour race

ironically the 205 seems to last for ever...  I know it's a bit retro, but the battery life is astounding compared to my 305.  I too want an ambit as that would see me through the longest events I ever do. 

I'm sure I read somewhere (think dcrainmaker's site, but can't find it now with a quick look) that you can get one of those things which takes a couple of batterys (AA I think) and has a usb connector, and plug that in to recharge say a 305. Trying to remember exactly what he said, but I'm pretty sure that you couldn't see the screen whilst it was charging, but it would keep recording the data.

I'm sorry I'm not being very specific, but might be an option worth exploring!

Is it a timed 24 hours or a course that takes about a day ? Cos surely if its the former- then any running watch will tell you how long you have left ? 

Andy, im a garmin fan and have been running ultras for a number of years now. My trusty 205 typically last s for 16hrs (although it screams low bettery from about 12!). The way Ive got through either 24hr or 100mile races id by borrowing a friends to supplement mine from the midway point.

However, the cheaper more brick like series, the 105 maybe? with the batteries? is a really goo shout over ultra distance. a friend uses his over long ultras as you can change the batteries and it still recalls your current run etc when the new batteries are put in.

It's not the 105 you are on about - no such thing, it's the 101. I've got one, but have never tried a long continuous session with it, but you certainly get a good few hours with a decent set of batteries. I do know they are used by some ultra runners because of their battery life. I suppose if the batteries did run out, you could change them for a new pair, and it would only take a few seconds to do. Might need to do it before they actually ran out, reset the watch, then change them and start a second session - be best to work it all out before race day.

I used 2 x garmin 305's for the lakeland 100. First one went after about 14hrs..

my 305 low battery warning comes on after around 6.5 hours!!!

The new Magellan Switch Up has the ablity to add an extra battery - not sure what time that extends to but dcrainmaker has a review.  Not Garmin but functionality is very similar.

Exiled you're right the Forerunner 101 with the disposable batteries will run over 20 hours on brand new duracells and will continue to record the run during a battery change. I have an old one and a newer 305 which is a better watch for short stuff (as you can download routes etc) but for anything longer than 8 hours I will use the 101

That's frustrating. I bought the 310xt because it was supposed to have a long battery life (up to 20 hours claimed by Garmin). Longest I've used it continuously so far is 10 hours (and I forgot to switch it off for a couple of hours after that); it managed three shorter runs before the battery went, so about 16 hours including 14 hours of running & heart monitor, which would hopefully take me through Lakeland 50 but not through a 100-mile race  and now you're telling me I'd be better off with a 101???!!!

Debra I had the same problem, I got sick of buying batteries for my 101 and bought the 305, the most I ever had was about 9 hours, then dead flat. The 101 goes on longer and doesn't lose the run when you change, it has most of the features except HM and it's not got the download facility but more reliable on a long trek.

I think the maximum time Garmin state is without the HRM and things like auto scroll, light, bleeps and vibrate turned off.

Have seen someone running around with a USB battery pack in an arm band and a  cable to there Garmin. However, I read somewhere whilst it works the screen just says charging so not sure how much use that is if you want to keep to a pace. 

EG Graham: Ah, swings and roundabouts: I could get a 101 and have distance & pace throughout, or use the 310xt and have HR and be able to download afterwards. Or I could see if I could borrow a second 310 xt from someone in my club for the weekend when I get to doing a 100-mile race, like mr f suggests above. 

James Joy: I'll have to try turning off vibrate and see if I can make it last longer. I don't have it beeping nor use autoscroll. I would want to be able to turn the light on during the night part of the race, I think (although I'd be wearing a head torch, so maybe not. HR is interesting data to have afterwards, but not essential (well, none of it's essential, but...). What about the GPS? Can that be set to sample less frequently to save battery life? After all, I want to use it for a 100-mile trail race sometime, not a track run.

To be fair, when I got the 301xt, I was thinking Lakeland 50 would be about my longest race (and it should cope with that) - doing a 100-miler wasn't on the horizon. Now I've done my first 50-miler and I just know I'll go longer sometime!

Plugging a 305 into a charger unit works. I did the NDW100 week before last and was going along with 2 fellas who were using that. Basically they'd bought a £10 or so charger unit at Amazon that takes a couple of batteries, plugged the USB cable into it, zip tied the 305 to the charger cradle, turn on the 305 when it starts charging, away you go. See the DC Rainmaker article here;

http://www.dcrainmaker.com/2009/07/going-really-really-really-long-with.html

HowFar??? Pity that won't work for the 301xt (different charging system, not USB) - and if I'd known about that option I could have just bought the 305 and the charger system. Oh well.