This appears to be entirely based off of the OpenEVSE. Yes it can be used to charge a model S. I have built one and currently using it to charge at work. Keep in mind that it is not UL listed and if you burn your house down with it, your insurance will probably not cover you. I built mine because I wanted a very custom setup for at work charging. But, if you just want another charger to backup your UMC, you are better off buying another UMC because the UMC is less expensive ($480) and more capable (40 Vs. 24A). You can upgrade it to 80amp, but you need to buy a larger relay, larger enclosure, and larger charge cord. In that case you might as well buy the stuff directly from OpenEVSE (Chris Howell) so you don't get the extra stuff you can't use (such as the 24amp charge cord and small enclosure).
That said I like the one I built. Works fine, although I have found the processor (Ardruino Duo) will crash at temps below -20* I have found out during this Wisconsin cold snap. Just unplug it and plug it back in to reboot it and it works fine. Another note: I only operate mine at 16amps even though it is capable of 30amps for 2 reasons. First, at work I can only get 16amps at 240volts with the outlet they let me use. Second, the "30amp" relay and connections got too hot for comfort when I was testing at 30amps at home. I am not really sure the relay OpenEVSE suggested to use was rated for continuous duty at max amperage. Also be very carefull to have good secure electrical connections as high resistance connections will cause it to burn potentially.
Any other questions about it let me know.
Update: One nice thing about this thing is that it will give you flexibily to plug into any 60hz power source, be it 110V, 208V, 240V with any combination of amperage (although the model S will only charge at a max of 16 amps when running at 120 volts). So if you have to plug into a weird outlet that Telsa does not make an adapter for (which was my issue when charging at work) you just make your own plug for it.
