With reference to a bank of emergency lead acid batteries:

The specific gravity (SG) of a fully charged lead-acid cell is typically about 1.28-1.30 (at the reference temperature, usually 15-27 C). An SG of 1.11 indicates that the cells are substantially discharged (a discharged cell has an SG of about 1.10-1.15). At 16 C (near the reference temperature), the SG reading of 1.11 confirms that the cells are in a low state of charge (approximately 20-30% charged, or nearly discharged). This is an unsatisfactory condition for an emergency battery bank, which must be kept fully charged and ready. The low SG indicates that the cells have been discharged (e.g. by a load, a fault, or insufficient charging) and need recharging; the battery bank is not in a satisfactory state of readiness. The cells should be recharged and the SG checked again; if the SG does not recover, the cells may be sulphated or defective and need replacement.

• Isolate the battery bank from the load (or ensure the charging is controlled) and follow the manufacturer's instructions and the safe working procedures (batteries produce hydrogen - ventilate, no naked flames/sparks, use insulated tools, wear eye protection).
• Check the charging system: verify the charger is operating correctly and the charging voltage/current is appropriate.
• Check each section/cell: measure the specific gravity of each cell (with a hydrometer) and the cell voltage (with a voltmeter); record the readings.
• Compare the readings with the fully-charged value (SG ~1.28-1.30, cell voltage ~2.1-2.2 V) and identify any cells that are low or defective.
• Check the electrolyte level in each cell and top up with distilled water if low (do not overfill).
• Check the terminals for corrosion, tightness and cleanliness.
• Recharge the battery bank (or the affected section) at the correct rate until the SG and voltage are restored; monitor the charging.
• After charging, re-check the SG and voltage of each cell; a cell that does not recover may be sulphated/defective and should be replaced.
• Test the battery bank under load (e.g. the emergency load test) to confirm it can supply the required current for the required period.
• Record the readings and the condition of the battery bank in the log.

• Keep the battery bank fully charged (the charger is kept on, and the battery is maintained at the float/boost charge).
• Check the specific gravity and voltage of the cells periodically (e.g. weekly/monthly) and record the readings.
• Check and top up the electrolyte level with distilled water (do not overfill; keep the plates covered).
• Keep the terminals clean, tight and protected (apply petroleum jelly/anti-corrosion compound).
• Keep the battery room/compartment clean, dry, well-ventilated (to disperse hydrogen) and free from naked flames/sparks; ensure the ventilation is adequate.
• Check the charging system and the changeover to the emergency supply.
• Carry out a load test periodically (e.g. the emergency load test) to confirm the battery can supply the required load for the required period.
• Check the battery for signs of damage, leakage, sulphation or corrosion, and replace defective cells.
• Record all maintenance and tests in the log.