Hi. Once testing electric palnel for industrial machine i needed to perform high voltage testing similar to this. It involved a special DC high voltage (2000V) probe. In your case, 275A does not tell much if we don't know at what voltage.
I sure am an "industrial" engineer. I don't see why you think i don't know what you want to test. The problem is that you talk of an amps test without mentioning anything about your connector. Perhaps if i was having its impedance it would help me better to advise you. Personally i like capacitors bank do make current testing as they can produce more than battery, but it may not work for all test (especially if you want a sustained amps to see a thermal reaction and in such case simple AC ). A down voltage transformer with a 9 ratio will be able to give you 275A from a 30A circuit (at 13V AC). You have to calculate the load resistance accordingly to not trip the breakers and you need proper wire size and resistance dissipation size (as i assume the connector is almost negligeable resistance internally).
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