In my off-grid solar system I am using 12V lead-carbon batteries capable of surviving 4000 cycles when discharged up to 50%. Capacity is 200Amp-Hours (100 Hour discharge) per battery.
There is no BMS or coulomb counting. I simply configure charging voltage (absorption 14.1V, float 13.6V) and cut-off voltage to limit discharging. The latter is the question: how do I find out the voltage at 50% discharge?
Here are some specs which I reckon should be useful to answer the question but I am not sure how to read them:
(one battery apparently consists of 6 cells in serial).