The manual states the following:
Please only use the supplied AC/USB power supply unless you are plugging the openSPOT2 to a power bank, a computer or your vehicle's built-in USB power adapter. The usage of inappropriate power supplies voids the warranty.
I have one (well, a few) of these Anker desktop chargers, similar to this:
https://www.anker.com/products/variant/powerport-5/A2124112
I've powered my original openSPOTs with it, but after reading the above statement in the manual, wanted to check to make sure I'm not voiding my warranty.