Since the thumb boost i get something like 4 days, but i really don't use my N900's very heavily, for just GPS?, don't know, all i have used it jspeed to measure speeds from time to time.

So it is not that i need to make a bike charger, thou it is very simple when you have battery power, i can just put a DC-DC circuit in and set it to 4.2V and plug it in my DIY charge port that you can see in my battery thread.