I don't recall seeing anything limiting the number of EVSEs (or cable heads for that matter). Instructions for Form 8911 (01/2022) | Internal Revenue Service
I claimed the credit for a whole stack of receipts for wire/conduit/connector/equipment purchases spread out over 2020 and 2021, and I suppose technically 1½ EVSEs because I also installed a proper, front-of-the-garage, additional 240 volt circuit that I can plug my portable EVSE into (which I purchased in 2019, but didn't claim the credit for). This is in addition to the primary 40A wall-mounted EVSE. I show them both in the link in my sig.
Thing is, I've got the stack of receipts in my tax folder, but I didn't get audited, so I can't say which of these decisions I made the IRS might have frowned upon.