Sent Mark @ evseupgrade an email to clarify, as in their FAQ (https://evseupgrade.com/?main_page=faq_info&faqs_id=26
) it states this:
Some of our upgraded EVSE's are capable of 24 amps when used on a 30 amp 240 volt outlet, and this gets you 5.76kW which is 4 times faster than the original Level 1 capability!
If I can get 5.76kw charging, then I'm pretty happy with that as that's almost 90% max charging rate for my Leaf...
24a is NOT for the Leaf, trust me I got mine upgraded and it's only 20a max. The limiting factor is the J1772 cord which is 12 gauge and 20a is the max it can safely carry. The '15's and on only have 14 gauge wire hence the 16a max charge rate.
If you want more than 20a ability to limit the current and low cost then I might suggest the Zencar EVSE I have listed in my sig, a little less than $400 shipped direct from China and I had mine configured to the output amps I most use.
Finding a 30a portable EVSE(that also works on 120v) is quite hard to fine, Clipper Creek(CC) makes portables but are strictly L2(208-240v) and non adjustable output, that is if your Leaf can draw 27.5a and you have a 40a CC it will, regardless of your circuit. The Zen I bought can be dialed down to as low as 12a and works on 120-240v. It comes in handy at campgrounds that only have a TT-30 plug(the old RV standard) which is 120v 30a, a CC EVSE would not work on this and EVSEupgrade would only give you 12a @ 120v. A cheap 16a L2 EVSE like the ones I mentioned in my other post charge 16a at any voltage, including 120v but note there is no way to dial them down, if your car can draw 16a(yours can) the EVSE will even if it's only on a 15a circuit and will more than likely blow your breaker/fuse.
I had my EVSEupgrade'd but it does have it's limitations which is why I've kind of moved onto other options most of the time.
Tony Williams(one of the sellers of the cheap 16a portables) also sells a much nicer higher amp EVSE that automatically adjusts the current depending on what type of outlet you have, it's more expensive than any of the EVSEs I've talked about but it's also very nice, check out his web page for more info(I believe it's priced somewhere North of $700).