[rickst29]

Thanks for your comment! My wiring will be 3S-2P, with about 64 volts V-disconnected (PWM mode). With my "solar power into MPPT using the bargman" trick, I have already run the BN-3215 at maximum output current for extended periods.

Your 1500w was a lot closer to the "3x" max rating for s single controller, which could theoretically put out only about 545 watts as 13.6 volts with 40A current. (higher power or lower voltage than I have could have reach your 40A limit, causing MPPT "issues under" great sunlight into only one controller). My 800 watts into a single smaller one is only slightly worse than than your "two controller" configuration.