Parts-People here actually list a 65W adapter for your system. However if the adapter wattage cannot be determined make sure you are using a genuine Dell OEM adapter and not a compatible adapter. A non-Dell adapter will cause that problem. Also a bad DC jack or a problem with the charging circuit on the MB. A 100W Dell genuine adapter will not harm the system but I would not suggest using a non-Dell adapter. 
Good day honorable community,    I've got following issue with my XPS13 L322, few weeks ago notebook showed "Can not determine power adapter wattage, can not charge battery". Even though it continued to work at minimal processor power very slowly with adapter still connected. I ordered new power adapter same 45 wattage, dell compatible and issue still persisted. Issue persists if I disconnect battery. I had bios upgraded to latest version through official download page, it did not help. Then I went to local repair center and they sayed it was power socket and had it replaced. After that it still showed same error with both of its power adapters and with adapter I borrowed from HP notebook, but it worked fine with power adapter they had in repair workshop, it looked massive I suspect it must be something like 100 watts. Could this be some internal issue with charging on motherboard ? I'm scared to use 100W power adapter even if it will work fine, it could fry something. Any advice is appreciated. Kind regards, Iulii
XPS 13 power falure