The stock antenna has a u.fl connector. For the metal enclosures you will need an external antenna.
this u.fl to rp-sma
https://www.sparkfun.com/interface-cable-rp-sma-to-u-fl.html
and this antenna would be a good option.
https://www.sparkfun.com/2-4ghz-duck-antenna-rp-sma-large.html
It would not likely be water tight so it could be mounted on the bottom between the power cables like EmotorWerks did on some models or the side if the station is indoors.
This might work:
TE ANT-2.4-WRT-MON-UFL
Dome/Puck Antenna, Single Band, Bluetooth / ISM / Zigbee,
--
225 in stock at DigiKey $18.
But a drain hole's a good idea anyway to allow humidity transfer.
Bryce Nesbitt
For JuiceBox units that came without WiFi,
is there a suitable antenna for the OpenEVSE upgrade kit, that can be retrofitted in?
What's the exact connector type of the stock antenna?