Battery's Remaining Charge vs Terminal Voltage

The chart you have is for a static state with no load. Which covers most lead acid batteries. The chart you wish to have is one that is under load. It maybe available from the OEM of the battery. But there is no general chart. As each battery model would be different. Changes to the surface area of the plates in the different models. The amount of electrolyte in each would make a general chart impossible.

You are looking for a lead acid battery discharge curve vs. load. If you Google on those words you will find that, as OZZB pointed out, there is no one curve available because it depends upon too many variables. Only the battery manufacturer and your own records can provide some guidance since it is dependent upon things like battery design, age, number of charge/discharge cycles, rate of charge/discharge, even the robustness of the intercell connections.

You can start creating your own charts by recording the all the data available to you on a regular schedule, but if you want an immediate reading on the "health" of your battery get a precision hydrometer and record the specific gravity of the electrolyte of each cell and compare with the appropriate curve from the manufacturer or the above Google search.

If you want to learn more about your own battery bank you can turn off your charger, get a load bank, and chart your parameters in real time, just don't drive the batteries over the knee of the curve or you could permanently damage them unless they're built for deep discharge duty (most aren't). Also be mindful that there will be a decent amount of hydrogen generated under heavy load conditions so make sure the room is well ventilated and you don't cause any sparks with your test leads. Appropriate PPE (Personnel Protective Equipment) is also mandatory.

<...to manage the load at UPS...>

Logic conundrum: an UPS is intended to support all downstream loads attached to it. Were there to be some discretion as to which loads are to be supported, the ones that are not will have no need of connection to an UPS!

The statement about managing the load is nonsense.

I think it's one of those cultural differences. We tend to think of a UPS as a source of continuous power in the event of a grid failure, whereas I suspect that OP relies on the UPS as his primary source of power and wants to implement some form of load management based upon how much is charge is left in his batteries.

How did you measure the state of charge,include a column for specific gravity.

Hello PWSlack

Actually we have energy crises and due to this reason, some time we face power breakdown problem which has been forced us to install lights in department (140 X 130meters) with UPS back up. We check and if power doesn't restore and battery voltage drops, we switch off some lamps.

The facility already exists in the form of proprietary luminaires that have battery storage, which turns on the light when the mains input power fails. The ones in sight here do not have any form of load management or battery charge level assessment.

The big unknown, always, is the question of for how long the power outage will last, and what the facility will do while the power is off.

If the lighting is essential to run the facility, then managing the battery charge level by switching lams off seems from here to be the ar$e-about-face way of doing things. After all, why have the lights been provided at the numbers and intensities required while the power is on (rhetorical question - NNTR)?