No Ah rating on these batteries. Funny, the package says "performance guaranteed" without indicating what the performance should be. The batteries I used were enercell 9V alkalines. That's a cool idea writing to an SD card jensvanhoof. I think I'm going to try that when I'm further along working with rechargeables and solar panels. I'm glad I decided to work on a project dealing with power efficiency. I'm a beginner at this and looking at efficiency has been forcing me to look at many different aspects of the arduino and microprocessors that I would've otherwise been unaware of.