Hi Shavermcspud I have the same 200amp V3.0 BMSs with the Victron system and had the same experience as you regarding the SoC calculation, I luckily also had a Lynx Shunt which I have been using to manage the SoC accurately, I completed the update on both BMS's yesterday and 100% charged the battery last night and I now have the Lynx shunt and the Seplos BMS SoC tracking consistently. The resolution of the Seplos is still pants as 0.8amps in a two battery system means I miss anything that's 1.6amps and below on either side but it is significantly better than it was prior to the upgrade. My BMS's are now showing FW version 0.7 compared to the 0.5 I was on prior.
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THis is the last 7 days side by side of Lynx shunt vs Seplos, scales are different, but today they are tracking correctly but previously the seplos BMS never went much below 60% that is until I got a low voltage alarm and it dropped straight down to 5% SoC, I will continue to monitor but based on this morning I am pleasantly surprised that they are showing the same data.