Hi all,

I have an Axpert Max 7.2kW with 3x Pylontech US2000C connected in parallel via RS485.

Current settings:

• Param 01 (output source priority): SBU

• Param 05 (battery type): PYL

• Param 12 (back to grid voltage): 48V

• Param 13 (back to battery voltage): 49V (lowered from 51V as a possible fix, no change)

• Param 29: 45V (locked, cannot be changed in PYL mode)

• Firmware U1: 69.01 / U2: 112.19

Every evening when solar drops to zero, the inverter switches to grid and stays there all night. The batteries are sitting at ~49.8V with all SOC LEDs fully lit on every module and no fault codes on the inverter. During the day the batteries charge fine from PV and reach around 53V. After sunset they settle at ~49.8-49.9V, which is above param 13, but the inverter never switches back to battery and ignores them completely until solar comes back in the morning.

I'm wondering if this could be a communication issue between the Pylontech BMS and the inverter in PYL mode, where the BMS might be sending some kind of signal that keeps the inverter on grid even though the batteries are ready. I'm planning to test with RS485 disconnected and param 05 set to USE to see if anything changes. Has anyone tried this as a workaround, or does anyone have a better idea of what might be going on?

Thanks

On 2026/05/01 at 6:44 AM, EmilBenvenuto said:

Firmware U1: 69.01

That's quite old. The latest for your model that I know of is 69.70, available in the post linked below, which is in a thread discussing a problem similar to yours.