http://www.nature.com/nmat/journal/vaop/ncurrent/full/nmat3623.html Only excerpt and first few diagrams available without subscription, but there's enough to see what they are getting at. I think it's only for LiFePO4 batteries (3.2V) as opposed to the 4.2V ones in cellphones and computers. Bob --=20 http://www.fastmail.fm - Send your email first class --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .