I think that in my spare time I will try to make one. An instructable will be made for anyone else who wants to attempt to make one.
I am (slowly) working on my own charger, mainly as a way to learn about it.
My goal is a portable charger that can be used when going to a friend's house either for a few hours (i.e. to share a meal) or overnight. To keep light and compact, I decided to design it for a 30Amp circuit (24A continuous). In a typical house, the laundry area is near or in the garage, so I picked a cloth dryer as my plug of choice.
This is a very basic but safe unit: it has a GFCI, and it implements the full diode check protocol.
Parts wise, I ordered a 30A cable from a supplier in Arizona which name's escape me at the moment. I was about $300~$400. I'm using a 30A contactor, from Digikey. The GFCI is a "donut" model meant for a hot-tub (available from any hot-tub and spa supplier). I have a tiny power module that takes anything from 90VAC to 240VAC and outputs 24V. From there I create +/-12VDC and +5VDC to power my processor. The "brain" is an Arduino Mini-pro. I have most of the code written which takes only a few KBytes. There is a relay under control of the Arduino that can control the main contactor, in series with the GFCI: as a result, for power to be present, both the GFCI and the J1772 protocol must be happy.
The whole thing fits in a outdoor grade box (meant to be used for industrial control boxes), sourced from McMaster-Carr. I think it is 7" x7" x5". There is no user interface other than the GFCI reset and test buttons. I figure most cars have plenty of indicators built-in to let the user know what is happening. A possible extension would be a Bluetooth serial port module that would allow me to use my mobile phone as an interface... I figure I'd get the basics right first and the bells and whistles later!
I will post some updates and pictures here soon.