EG4 6000XP Parallel Inconsistent Charge/Discharge with DIY Battery

[Joq]

I have two EG4 6000XP inverters in parallel, each with its own solar array connected. The battery bank is DIY LiFePO4 with BMS that cannot communicate with the inverters. Both inverters always display exactly the same battery voltage (e.g., 55.8V).
Battery is fully charged
Sun is strong, plenty of solar power available
Battery sharing is enabled
Both inverters have their own solar input

Issue:

The master (left) inverter works normally: it supplies loads directly from solar and gently continues to charge the battery.
The slave (right) inverter, even though it also has solar input, reduces its solar output and instead draws power from the battery to supply its loads.
So, the master inverter is both supplying the loads and charging the battery from solar, while the slave inverter “prefers” to use battery power, not its own solar—even when solar is available.
Is this normal? Is this because the battery’s BMS cannot communicate with the inverters? Is there any way to make both inverters use solar to supply their own loads when the battery is already full?
Thank you!

 

[timselectric]

This is normal.
When connected in parallel, they function as a single larger unit.
And if one MPPT is capable of satisfying everything, it will let the others idle.
It can also swing to the other MPPT, or use both, sometimes. If it's trying to mitigate temperature differences in the two units.

 

[TM48]

The battery bank is DIY LiFePO4

What is the exact configuration of the battery? How many cells and total amps hours?

 

[Joq]

This is normal.
When connected in parallel, they function as a single larger unit.
And if one MPPT is capable of satisfying everything, it will let the others idle.
It can also swing to the other MPPT, or use both, sometimes. If it's trying to mitigate temperature differences in the two units.

Thanks for your reply. Today I tested this EG4 6000XP inverter as a standalone unit (no parallel connection). When the battery reaches full charge, it stops supplying the load from solar and switches to battery power. Once the battery voltage drops slightly, it goes back to using solar to recharge the battery and supply the load.
I suspect this issue might be related to residual battery communication settings stored from previously using EG4 smart batteries. Now I'm using an open loop battery. Performing a factory reset did not clear these communication settings.
My other EG4 6000XP inverter, always connected to open loop batteries, doesn't have this issue whether used alone or in parallel.

 

[Joq]

What is the exact configuration of the battery? How many cells and total amps hours?

The battery bank is made up of 16 cells in series , each cell is 3.2V 320ah LiFePO₄

 

[timselectric]

Thanks for your reply. Today I tested this EG4 6000XP inverter as a standalone unit (no parallel connection). When the battery reaches full charge, it stops supplying the load from solar and switches to battery power. Once the battery voltage drops slightly, it goes back to using solar to recharge the battery and supply the load.
I suspect this issue might be related to residual battery communication settings stored from previously using EG4 smart batteries. Now I'm using an open loop battery. Performing a factory reset did not clear these communication settings.
My other EG4 6000XP inverter, always connected to open loop batteries, doesn't have this issue whether used alone or in parallel.

I'm guessing that your bulk and float charge settings are to close to each other.
Set them to 0.5v apart.

 

[Joq]

I'm guessing that your bulk and float charge settings are to close to each other.
Set them to 0.5v apart.

charge is 56.4v float is 54v However, my other 6000XP inverter (with exactly the same settings and firmware) works perfectly fine it does not stop using solar to supply the load or start discharging the battery once the batteries are full.

 

[timselectric]

charge is 56.4v float is 54v However, my other 6000XP inverter (with exactly the same settings and firmware) works perfectly fine it does not stop using solar to supply the load or start discharging the battery once the batteries are full.

It could be a difference in resistance, in the parallel wiring.
Are all of the parallel connections the same size and length?
(Battery to inverters and AC wiring)

 

[Joq]

It could be a difference in resistance, in the parallel wiring.
Are all of the parallel connections the same size and length?
(Battery to inverters and AC wiring)

I sincerely appreciate your assistance.

Both inverters are connected using the same 1/0 gauge wires with the same length. Right now, each inverter is running independently they are not paralleled. The issue only occurs on this unit. The other one works perfectly.
I’m planning to contact EG4 technical support on Monday to see if it’s possible to delete the previous records from when the inverter was connected to an EG4 battery.


Maybe clearing that data could help fix the issue.

 

[TM48]

1/0 cable is under sized for this application. Also put the inverters back in parallel mode. Do you have both shielded parallel cables installed? Are the parallel switches up on both inverters?