Aha! Interesting stuff!
A big thanks to the photo posted by JSantala and the Instructables link from Joe.
I forgot about the fact that the hand-shake signal is using an AC signal! When thinking about transformers, I'm usually thinking about big ones for the main power! I completely overlooked a little tiny one for for creating 20V AC for the hand-shake.
Swapping out that little transformer for a 240V one would be an easy and permanent way to do a simple 240V conversion, at the expense of NOT being able to do 120V anymore.
The Instructables information was interesting, although not quite as well documented as I would like. I'll have to go through it very slow and deliberately to get the best understanding out of it. For me, having a level one charger that can run at 240V, but still be able to do 120V through a custom power adapter would be a good solution. I already have a nice Level 2 charger in my garage, I almost NEVER have a reason to use the level one (but it's nice to have as an emergency backup), and there's a location I'd like to charge on a semi-regular basis which has 240V power, but I can't permanently leave a charger.
I think I'll open up my charger and take a look inside. It will be fun, and I like voiding warranties.
I also have an friend who has a Volt. His old level one charger died, and he offered it to me. I plan to get it so I can take it apart. If I can fix it, hey, free charger! If not, it's still a fun learning experience. Perhaps I can fix up the broken Volt charger AND just permanently convert it to 240V. That way, I would have both a 120V Level 1 Charger AND a 240V Level 1 Charger!
It still makes me wonder how the EVSE upgrade allows the charger to run on either 120 OR 240?!
What can be used in place of a small transformer to create 20V AC from either 120 OR 240VAC? Is there an electronic device similar to a DC/DC converter that will allow for a broad AC voltage in and always send 20VAC out? Sorry, I'm just not that familiar with electrical components to know if such a thing exists. If it does, it seems reasonable the in the EVSE upgrade, that they replace the transformer with something different for creating the hand-shake signal from either (or a range) of voltages.
Looks like I'll be taking apart some EVSE in my near future.
PS: If anyone wants a free "Pro" membership for Instructables.com, please just message me. I believe I have 44 years worth of free Pro memberships. The Pro gets rid off all the ads on the site, which is nice. I place and win in contests all the time on that web page, so they just keep throwing free memberships and t-shirts my way. I had to check back on the last photo I posted in this thread. Yup, I'm wearing an Instructables t-shirt!