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.

There are several different topologies used for 12vdc-to-120vac inverters. Some have two stages; they boost 12vdc to 180vdc, and follow that with an inverter. Others have a single stage that chops the 12vdc into AC, and steps that up to 120vac with a transformer. There are several other less-common topologies as well.

The big issue is finding a schematic for any of them. Without one, it's going to be a challenge to reverse-engineer it sufficiently to make it work for your purpose.

Another option: If this is for emergency use, how about a motor-generator? I have one from the 1980's for my Elec-Trak. 36vdc in, 120vac at 600w out. Not the most efficient (around 80%) but reliable, and simple as dirt. They also produce a perfect sinewave, and can handle very high peak loads (for starting motors, etc.) Many sizes have been made, and can be found in surplus outlets pretty cheap.

You can also hack one together out of stuff you have. Any 120vac induction motor can be used as an induction generator; just hang capacitors on the AC bus to provide its leading PF excitation current.

In computing, the mean time to failure keeps getting shorter. (Alan Perlis)
Lee Hart, 814 8th Ave N, Sartell MN 56377,

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