PT are you saying that setting the Magnum to 15a input is the same thing as plugging a 125 amp charger into a 15a receptacle in a 15a circuit?
The 100 amper was pulling 122.7v, 15.57a , reading 1910VA and the watts with that was 1854. PF 0.97
Scaling up to 125 amps output, that 15.57 input would be 19.46a
I don't know why the Magnum quit when set at 23a running the 127a charger output. 19.46 is way under 23.
Were there other 120v loads on the Magnum besides the charger?
Did the Yamaha 3000 (23.3? ) pop or was it just the Magnum at 23 that popped?
My Honda 3000 (23.3) runs my 100 amper (15.57) and my 55 amper (11.06) total 26.63. I don't know how it can. I guess the combined load pulls down the input voltage more than it is when they run individually, so the combined VA is lower than the individual VAs added. Anyway it runs.
So really, the Yamaha at 23 should have run the Magnum's charger at 127 amps no sweat. Perhaps it is all about that Magnum (which was the duff one? )