I did say that the SOC should be accurate but in actual fact it isn’t really. Once the battery has settled from charging or discharging then you will get a more accurate reading. Don’t be too worried about SOC as your BMS will handle everything.
An example of this is yesterday I was testing my air con in my caravan and run the battery down to 89% within a short time with no load it had risen to 91%. I then connected some portable solar panels and took it up to 100% but at the end the SOC was reading 13.8v @ 100%. Within a short time SOC had dropped to 13.6v and still showed 100%. Just too a quick check in replying to you and SOC is now showing 13.3v @ 100%.
So charge your batteries up to full, let them settle for a while, then set the SOC.
I’m in Port Stephens NSW.
Tim