Yes, sorry that was muddled thinking on my part.
So I can't do very low power with arduino alone. It's tricky though because I am not yet up to making a datalogger out of an XLP chip like those.
I'm confident I can get the datalogging working on arduino, I just need to figure out how to switch it on with a low power "clock" or pulse generator every 15 mins.
The RTC clock on the arduino shield will log the real time, so the pulse generator doesn't even have to be that precise in keeping time. Maybe I could use clockwork XD
But seriously, I think I could use a low-ish power chip (~1 mA) just to produce a pulse every 15 mins and switch the power to the arduino (maybe via a flip-flop) then the last thing the arduino does is switch itself off, until another pulse is applied.
Is there such a chip that doesn't require a lot of programming knowledge, ie is suitable for a relative beginner?