Trying to monitor my battery capacity

Hi all

we live in the (not so sunny just now ...) UK in a house with a 4 kW PV array, a Solax SK SU3700 inverter and 2 * 4.7 kWh Pylontech Extra 2000 batteries.  The PV array was installed in 2010 and the inverter & batteries in 2015 by the previous owner using a company that has now stopped trading.  I have managed to access the generation data online from the inverter (though this took 18 months of to and fro with Solax), which is good news, but still can't get any of the battery data.  The only indication of battery charge is on the LED read out on the inverter - there is nothing in the data published by the inverter to its status webpage.  I found a mention of MultiSIBControl on this forum so  tried connecting RJ-11-DB-9/DB-9-USB cables from the RS-232 port on the inverter to a Win 7 laptop running MultiSIBcontrol but get this message on the monitoring screen "Pylon stack 1 stopped" - if I set Stack 1 to "not available"then I get a "Pylon connected 0x" message but no data is transferred.  I have tried switching the USB port on the laptop, switching the RS-232 port on the batteries and using Stack 1 instead of Stack 2 but have so far not been able to check battery level. I checked the cable using Termie but couldn't get anything that looked like useable data from the batteries despite changing the baud rate (9600 and 115200 bps) and various other parameters, so not sure if it is the cable that is the issue or I just haven't found the right settings.  Also not sure if MultiSIBControl works with my Pylontech batteries.

I would just like to be able to download the hourly charge status of the inverter so that I can start trying to work out how to optimise our electricity.  Would appreciate your help - thanks!