Before connecting the battery, calculate the charge voltage according to the number of cells in series, and then set the desired voltage and current limit. To charge a 12-volt lead acid battery (six cells) to a voltage limit of 2.40V, set the voltage to 14.40V (6 x 2.40). Select the charge current according to battery size. For lead acid, this is between 10 and 30 percent of the rated capacity. A 10Ah battery at 30 percent charges at about 3A; the percentage can be lower. An 80Ah starter battery may charge at 8A. (A 10 percent charge rate is equal to 0.1C.)
Observe the battery temperature, voltage and current during charge. Charge only at ambient temperatures in a well-ventilated room. Once the battery is fully charged and the current has dropped to 3 percent of the rated Ah, the charge is completed. Disconnect the charge. Also disconnect the charge after 16–24 hours if the current has bottomed out and cannot go lower; high self-discharge (soft electrical short) can prevent the battery from reaching the low saturation level. If you need float charge for operational readiness, lower the charge voltage to about 2.25V/cell.
You can also use the power supply to equalize a lead acid battery by setting the charge voltage 10 percent higher than recommended. The time in overcharge is critical and must be carefully observed.
A power supply can also reverse sulfation. Set the charge voltage above the recommended level, adjust the current limiting to the lowest practical value and observe the battery voltage. A totally sulfated lead acid may draw very little current at first and as the sulfation layer dissolves, the current will gradually increase. Elevating the temperature and placing the battery on an ultrasound vibrator may also help in the process. If the battery does not accept a charge after 24 hours, restoration is unlikely.