ultrarocker: I've seen that link before - but when I connect up my 310 to the recharger, it goes blank except for showing the "battery charging" symbol, so I presumed it wasn't possible to do the same thing with thr 310 (which made me irritated becaue the only reason I'd got the 310xt rather than the 305 was for the longer battery life, and here someone was showing how I could have paid less and got a longer-lasting gadget). That's why I was interested to see slaneuk say he's adapted his 310.
Of course, the longest race I've got in mind at the moment is the Lakeland 50, and it -should- see me through that, I hope, if fully charged before I start, but I know I'll go for a 100-miler sometime and I want to be prepared!