That's why I would suggest you try checking eBay to see if you can get some of the original HyperMac models. They all use Li-Ion batteries, so no memory effect - though clearly the battery can still be abused. In any case, I have the 60 Wh model that I use with the MBA and also the 150 Wh model that I used to use with my MBP. They work quite well. I would caution against the accuracy of time estimates used by Hypershop, as my experience isn't quite as positive. Nevertheless, and extra few hours of battery life, which these units do deliver, can be quite helpful when flying, etc.