I have a issue with my 5kw sunsynk system with 2 sunsynk 5kw batteries in parallel. The system was installed in december and i had no issues. About a month ago i saw that the SOC was only going to 93% and not the normal 99/100%. I had the installer come out and they charged the batteries individually so they are balanced and the SOC went to 100% but over the weekend i saw that the batteries lights are not equal (1st time seeing it since they came out as my installation is in the garage). All the lights on one battery will show its full while the other battery might have 3 lights when for example the SOC is on 60%. The lights used to be equal when they are full or discharged. Yesterday i just checked the wiring and found the communication wire was on the RS485 port and not the CAN port. I moved this and i was able to see on the inverter LiBMS page the battery temperature etc again. they moved the wire when they came out a few weeks back because i used to see the battery temperature on the LiBMS page . Today it only charged until 93% even when there is still enough PV to charge it. I even tried using grid power to charge the batteries. Anybody had a similar issue.?

The system was always working 100% and nothing changed since then (no new electrical devices/ installations). The max load we normally draw is 1400 if the pool pump is on during the day if there is enough PV. Other than that we run about 350-450watts.

Also there is no battery or inverter errors. The batteries still last the same as the beginning. The lowest the batteries normally will go is about 60%-55% over the course of the nights.

I also checked the settings on the inverter and its all still the same as I took pictures off all the pages when they installed it.

Try what @TaliaB suggested here.

Worth a try.

Communication from inverter to the battery must be CAN, then battery to another battery RS485.

If the batteries are not allowed to drop to the 30%, they seem to develop a resistance to charging up to 99/100%, try discharging the batteries to around 30% a few times, it should help.