Instinct

I have a Axpert 5kv 48v inverter set up with 3strings of 405w PV panels connected in parallel(74v). System worked fine with 100ah  4,8kw lithium ion battery for a long time. Added same make 7800kw 150ah battery in parallel. System is running fine during day with sunshine but when no PV available unit switches over to utility (+-20sec ). After a while unit kicks back to battery? Settings as follows:

1.SbU

2.30A

3.APL

4.SdS

5.Use

6.LfE

7.trd

9.50hz

11.30A

12.49v

13.50v

16.OSO

18.default

19.default

20.default

22.default

23.byE

25.default

26.52,5v

27.51.8

29.47,6v

31.Sbe

Please could any body assist with the setup?? Tried various settings with no positive results. Need inverter to switch over to utility with no PV(after dark)

Regards

Instinct