Split-Phase Power Issues. AC300 with two B300, x2, with Fusion Box

I have two AC300 with two B300’s each, connected with Fusion Box. During operations as Split-Phase, I have found that the system runs one battery to 10% and then shuts down (leaving the other at 50-70%).

I also have numerous and repeated errors that cause the AC Output to shut off, that are listed as “BMS Communication Error”

@ProfGrizzlyJon Please check the details below:

  1. Check whether the input current of the two AC300s is consistent
  2. Reset the AC output voltage of the next two AC300s and make them consistent
  3. Reset the UPS mode of the next two AC300s and make them consistent
    Kindly notice that the 240V load is carried by two AC300s, and the 120V load is carried by only one AC300.

I don’t understand.

  1. There is no input to the AC300’s other than PV. Are you saying that both AC300’s need to be charged at the same input voltage from the same PV?
  2. The output voltage is the same 120V/60Hz.
  3. The UPS mode is Standard UPS on both.

Is there a better source of guidance for the split-phase?

I continue to get multiple errors on the Slave AC300, which prevents the AC Output from staying in

Also, for some reason, I am restricted from posting images of my system

This is very troubling, as the AC300 seems to not be performing properly or as advertised.


  1. Make sure both sides of the communication line must be tightened.
  2. Then confirm that the machine type of AC300s is set to “split phase”. One is “master” and the other is “slave” (see below)
  3. Restart two AC300s to test.

Confirmed one Master and one Slave.
Cables are inserted and tightened

@ProfGrizzlyJon Please disconnect the split-phase charging cable and split-phase output cable, turn off the AC, connect only the communication line, and try restarting the two machines. If the error is still reported after restarting, you can only try to change the communication cable.

@ProfGrizzlyJon Hi, could you please share some updates?