Did AC300 UPS mode change to online UPS?

On my recently purchased AC300, I noticed a couple of behaviors that seem different than previous reports on the forum.

  1. With 120V grid input connected, full AC output (3000W) is available and is not limited to the grid input’s power limit. In Bypass Output-D mode, if output power load exceeds the grid input current limit, AC300 draws grid input power at input current limit and supplies the remaining power from battery.

  2. In both Bypass Output-C and Bypass Output-D modes, even though the grid input has neutral bonded (at my main service panel), AC output still has floating neutral.

It seems that AC300’s UPS mode now behaves like online UPS mode instead of offline UPS mode. This is a pleasant surprise.

I bought a second AC300 and observed a different behavior. On this second AC300 (which has older serial number than the first AC300), in Bypass Output-C and Bypass Output-D modes, AC output has neutral bonded (the neutral bonding of the grid input is “passed” to the AC output).

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The reported the behavior of the second (older serial number) AC300 to Bluetti tech support, and they determined that the unit needed to be replaced. They replaced the unit, and the problem was resolved. The replacement unit’s AC output has floating neutral (even when connected to neutral-bonded grid input) as expected. I suspect the AC300 with the older serial number (that “passed” the neutral bonding of grid input to the AC output) was a “first generation” AC300 that had the neutral bonding problem.