One of my OpenEVSEs is 70' from a Ubiquiti UniFi UAP AC Long Range but there's a lot of metallic stuff in-between, and my signal strength was terrible:
I've actually seen -90 at one point. While everything still worked -- even with the old ESP8266, when I recently replaced the 8266 with a shiny new Huzzah ESP-WROOM32 (unfortunately, purchased 18 mos. ago and resting in a box for a long while), when I tried it out my signal was no better. Well, that wasn't really a surprise, but I had a bit of free time, so I added an external antenna, with good results:
I used someone else's work for inspiration, and purchased a pair of antennas & leads for $9 all-in.
I drilled a 1/4" (6mm) hole in the cover's top, midway in both axes. The display's spacer that this older model uses had to be notched via Dremel to clear the antenna's lead, which is quite inflexible in this area.
Interestingly, when first installed and powered-up, the signal strength displayed did NOT change, and I was quite disappointed. The next day, I looked again, and saw a significant difference. I did log out/log in twice, and reloaded several times, two different devices, etc., and the screen did dynamically refresh every ten seconds or so, so I have no explanation of that behaviour.