The device you are describing is called a "micro-inverter". Typically they are designed with "anti-islanding" proteciton, so they require a system (the grid) already making 240v sine waves before they add 240 VAC back to the grid. You can purchase microinverters without this protection, but it may be easier to "simulate" your own grid with a small battery and a true sine wave inverter.

I think your easiest solution is to have a "traditional" solar system set up with it's own (small?) battery bank and inverter, and just use each component in the "normal" way. (e.g. Solar cells feeding a charger that charges the battery bank, and an inverter that produces 120 (or 240?) VAC to use to charge your car.

Perhaps you could find/use a specialty inverter/charger combo box specifically made for the solar industry, but depending upon size of your system, it may be cheaper to use a separate 12v inverter and one (or more) 12 volt solar charge controllers.

A single 12 volt battery may be enough if you are primarily going to be charging your car while the sun is shining and have more solar PV panel wattage than the car charger draws. The battery will give you a little buffer to provide for brief clouds, etc

If you had a slightly larger battery bank on your solar system, you could also use it to run a fridge overnight, etc...

Jay


On 10/06/2017 09:39 AM, Robert Bruninga via EV wrote:
I want to develop a way to charge an EV from a Solar array when the grid
is down cheaply.

My thiking is that typical modified sine 12v/120VAC inverters do their
inversion first from 12VDC to high voltage DC first, and then they chop it
to make it modified sine.

If that is the case, it should be possible to inject high votage DC from
the solar panels at that same point and produce the same 120VAC.  This
then can drive any standard 120v EVSE.

We can tap into solar panels in increments of 30 VDC and should find one
close.  The problem will be the starting process to bring the VOC down to
the Vmax that matches the HV in the inverter..  That can be done with a
trivial big resistive load a few caps and then transfer relay maybe.

Thoughts?
Bob
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