An interesting and useful "Battery Charger Solutions" outline app note from LT. High and OK res 24 page PDFs on this page http://www.linear.com/designtools/BatSol.jsp All their "solutions" are far too dear for my current application, but all interesting. RM -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist