DIY lifepo4 battery voltage issue

[Flytsetse]

Hi all. A beginner here. I have a couple 200Ah lifepo4 battery with 150A daly BMS(not smart) with 16S CALB cells each bank paralleled which made a 400Ah. I have two Growatt SPF 5000 ES hooked in parallel with 10 x bifacial 525w Jinko solar panels. My usage is around 5000-6000w on day time for the backup so my solar panels can never fulfill the load requirement in the rainy or cloudy days. After 6pm the load is like 700-800w until 9am next morning.
My inverter setting are solar and utility priority output and battery as backup (SUB priority), max charging 60A and max AC Charging 15A for each inverter, CV charging 57V and float to 54 volts. As I read on and research, I now changed to USE2 mode, CV to 55.2V(3.45) and float 53.6V(3.35V). The batteries are on standby mode constantly and hovers around 52.7-52.6 volt immediately after C.V charging which mostly happens after evening when solar is cut off.
Issue 1> The battery will steadily drop to 51.75V only when the inverter detects 75% to 50% SOC and charge when solar is cut off. My battery is in constant back up mode without any load since only solar and utility supplying the load. I can't help but notice everyone saying battery voltage should be around 53.6V(3.35). I never saw the batteries stabilize around these voltages highest I see after CV is 53.4 volts which lasts only like 5-10 minutes then immediately goes down to 52+V. Even when the inverter turned off the battery voltage is around 52.6-52.5V at the terminals with the battery breaker off. Is there anything wrong with my batteries?
Issue 2 > There is only 100-75-50-25% for SOC in inverter since I don't have protocol connection between BMS and inverters. If the inverter does not determine SOC of 75% it will not go to charge mode no matter it is like 51.8 volt or something.
Thanks in advance. Any help is much appreciated. Cheers! :D

 

[BentleyJ]

Fully charged LFP cells settle down to about 53.6V after the charger is turned off and there is only stand-by load to keep the inverter electronics operating. Have you verified the voltage readings using a good multimeter? If those are the values being shown by the inverter display, first step is to double check the readings.

 

[Flytsetse]

Fully charged LFP cells settle down to about 53.6V after the charger is turned off and there is only stand-by load to keep the inverter electronics operating. Have you verified the voltage readings using a good multimeter? If those are the values being shown by the inverter display, first step is to double check the readings.

Thanks for the input. I have checked the battery terminals with a multimeter I check with a Uni T 210E DC Clamp meter if it helps :D

 

[RV10flyer]

Fyi with two SolArk12K...My 10 batteries paralleled into 134kWh bank started at 53.6 yesterday evening. At 7 AM, my 20.6kW pv is waking up with 150W output. My house is consuming 2400W with coffee brewing. My battery is at 52.5V and approx 60% cap.

I would recommend at least another 400 aH more battery capacity. Of course always more PV.

 

[Flytsetse]

Fyi with two SolArk12K...My 10 batteries paralleled into 134kWh bank started at 53.6 yesterday evening. At 7 AM, my 20.6kW pv is waking up with 150W output. My house is consuming 2400W with coffee brewing. My battery is at 52.5V and approx 60% cap.

I would recommend at least another 400 aH more battery capacity. Of course always more PV.

It is nice to know even 134KWh parallel battery setup drop from 53.6V to 5.25V under 2400w load. I never plan to charge the battery on solar which is why it is only used as a backup power and expected to be fully charged whenever electric cut happens. I'd love to add more solar but I have space issues on a rented property ?. The problem is my battery setup will not stand 5000w for more than 1 hr since LVC is 48V and the voltage drop pretty fast since my resting is like 52V-51V ?. I expect it to last at least 2hr with 19KW for 5KW power draw which is only like 10KWh from my perspective?. But since lifepo4 is flat curve I will never know unless I make a capacity test on fixed load. But being the setup from a business which only rest a day per week I don't have much chance to test it fully ?. I was hoping may be experts and enthusiasts here can spot the issue without trouble. ?.