On 21 February 2012 09:11, Neil Cherry wrote: > On 02/20/2012 02:50 PM, Denny Esterline wrote: > > There's an Energizer powermat charger "demo set" available at Walmart f= or > > ~$30: > > > http://www.walmart.com/ip/Energizer-Flat-Panel-2X-Induction-Charger-Wii-W= ii/12510641 > > > I've really got to wonder what the transfer efficiency is for one of > those things. > > There really is very little to the basic system. Amp turns into resonant coil. Well coupled resonant pickup. Vout is set by the voltage you choose to use as long as you take out less energy than available,. within reason. I have a dual XBox battery inductive charger that I got from ?Sparkfun? . I looked at it to see if it seemed to do anything radical and it was about as expected. Efficiency should be in the 50-80% efficiency range without undue care and the inductive power transfer foundation (proper name escapes me and rushing ....) are talking about over 90% for their better configurations. Over 90% very doable if gap small and dimensions free. Charts available. See Microchip AN I cited to start. I can provide quite a few refs ... Russell -- --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .