On Tue, 15 Sep 2009 15:22:06 -0400, you wrote: >On Tue, Sep 15, 2009 at 1:33 PM, John Fields ><[email protected]> wrote: >> On Tue, 15 Sep 2009 10:30:56 -0400, you wrote: >> >>>These people claim they can improve over direct connection charging: >>> >>>http://www.wipower.com/ >> >> --- >> I have trouble following a long thread once it starts getting snipped >> and top-posted to so, if you don't mind, I'll continue this one by >> bottom posting: >> >> I couldn't find where they made the claim; do you have a link, please? > >Sorry, Google defaults to top-posting. I think it is an ADA thingy. > >Here is one reference: > >http://www.fastcompany.com/magazine/132/big-green-and-juicy.html > >"And according to WiPower, inductive charging systems work with about >80% to 90% efficiency -- roughly the same as plugging directly into a >wall socket.
--- According to WiPower's white paper at: http://www.wipower.com/PRESS_Files/WiPower%20White%20Paper.pdf (Sorry, for some reason I can't copy the text) A tightly coupled inductive system can have 90 to 95% DC to DC efficiency, while a loosely coupled system can send 300 watts plus at > 80% efficiency. The tightly coupled (because of its internal transformer) system is the conventional switching supply which connects to the mains and charges the load's batteries, while the loosely coupled system is WiPower's approach to eliminating the electrical connection between the load and the charger. However, according to the video, WiPower's device can only do 74%, and that's DC to DC, without considering the AC to DC conversion and smoothing required to get the DC input to the transmitter. --- >That blows away the industry average for wired chargers, >around 40%. So wireless juice is not only less messy, it's less >hungry, too." --- It's not less messy since it has to meet the same FCC radiation intensity spec's as anybody doing switching supplies with crispy waveform edges has to, and it's 74% efficient instead of 95%, it's not less hungry either. --- >But, as you say, there is no technical support that I can find. --- Yup. :-(
