A Flooded Lead-Acid Store for a Small Workshop: Electrode Mass, Acid Volume, Gassing Heat and Sulphation-Limited Life for Six Usable Kilowatt-Hours

This paper sizes a flooded lead-acid storage system for a small workshop requiring backup supply through a working day. The duty calls for 6 usable electrical kilowatt-hours delivered at a rated power of 3 kilowatts. Working from a stated specific energy of 35 watt-hours per kilogram, an energy density of 70 watt-hours per litre, a usable depth-of-discharge fraction of 0.5, and a round-trip efficiency of 80 percent, the calculation gives a gross stored energy of 12 kilowatt-hours, an active-store mass of 343 kilograms, a complete system mass of 429 kilograms, and a complete system volume of 214 litres (0.214 cubic metres). Full discharge at rated power lasts 2 hours, and a full recharge takes 8.94 hours at the stated charge power. Losses amount to 2.68 kilowatt-hours per complete cycle, appearing as heat at average rates of 0.15 kilowatts during charging and 0.671 kilowatts during discharge. Standing loss is 0.3 percent of the stored energy per day. Life is limited by the cycle limit, giving 1.2e+03 effective full cycles, about 4 years at the assumed cycling rate, and a lifetime delivered throughput of 7.2 megawatt-hours. All values are computed from the stated assumptions; the system is a design study and has not been built or measured. Status: SIMULATED, NOT MEASURED.