I accidentally captured the BMS 'doing its thing'. As battery management gets asked about a lot, on the Facebook at least, I thought I would share my charts (below).
Min SoC is set to 20%, and force charge from solar (only) is set from 1530-0800 to prevent the battery being flat all the time (I don't have a cheap tariff, this will be fixed soon).
Lots of really interesting things to note (for me at least) - for starters, the weak/non-existent relationship between voltage and SoC.
From the charts it appears that the BMS made several attempts to stabilise the measured SoC at 20% (-ve amps = charging, +ve amps = supplying power). It failed to get the SoC to stabilise so then it juiced the battery to a measured 60%. It's nominally a 17kWh system so it seems to be using a very low charge rate (4A@380V ~ 1.5kW or ~10%C). Battery temperature was dropping throughout from 12 to 9.8 degrees C. Normally, a "force charge from grid" uses between 2 and 5kW dependant on SoC (5kW inverter).