Many health care facilities are making the switch from wet lead-acid or “flooded” emergency generator batteries to sealed or “maintenance-free” batteries. While sealed batteries come with a major perk of saving some time and hassle related to inspections, testing and maintenance (not to mention eliminating the risk of spillage or exposure to harmful chemicals), there are still inspections that must be conducted to measure the condition of the battery life. 

Regardless of whether your batteries are flooded lead-acid, sealed lead-acid or nickel cadmium, you are required to test for either electrolyte levels or battery voltage weekly. The 2010 version of the National Fire Protection Association’s NFPA 110, Standard for Emergency and Standby Power Systems, states that “storage batteries, including electrolyte levels or battery voltage, used in connection with systems shall be inspected weekly and maintained in full compliance with manufacturer’s specification” (section 8.3.7).

However, monthly inspections may differ depending on your battery type. The next section of NFPA 110-2010 states, “maintenance of lead-acid batteries shall include the monthly testing and recording of electrolyte specific gravity. Battery conductance testing shall be permitted in lieu of the testing of specific gravity when applicable or warranted” (section 

Using a hydrometer, a specific gravity test will compare the ratio of the weight of a solution versus the weight of an equal volume of water to determine the solution’s density. A low-density reading shows that the battery has lost some of its electrolyte solution and must be replenished. 

Sealed lead-acid batteries eliminate the ability and need to perform specific gravity tests; however, the requirement to test the battery’s state of charge still applies even if you are unable to perform a specific gravity test. Determining how much charge the battery has left is accomplished by measuring the conductance of the battery, or the ability of a battery to conduct current. This will likely require purchasing a special device designed for conductance testing. Knowing the conductance measurement of your battery is helpful to predict when the battery is approaching its end of life.