Generator Battery Conductance Test
by Brad Keyes, CHSP, on Mar 5, 2019 12:00:26 AM
As you may be aware, you are now permitted to have maintenance free batteries to start your generators. Previous to the adoption of the 2012 edition of the Life Safety Code, the editions of NFPA 110 that had been adopted did not recognize sealed lead acid batteries for use to start the generators. Many AHJs did not accept the maintenance free batteries and made the healthcare facilities remove them.
But that is in the past. According to the edition of NFPA 110 that is now adopted (2010 edition), section 188.8.131.52 says maintenance of lead-acid batteries shall include the monthly testing and recording of electrolyte specific gravity. However, battery conductance testing shall be permitted in lieu of the testing of specific gravity when applicable or warranted. When you have maintenance free batteries you cannot get to the electrolyte to conduct the specific gravity test, so you perform the conductance test.
Electrical conductance in a battery is measured by siemens (symbolized S) and is the Standard International (SI) unit of electrical conductance. The electrical conductivity units are siemens per metre, S⋅m-1. The siemens also used to be referred to as a mho - this is the reciprocal of an ohm, and this is inferred by spelling ohm backwards. Conductance is the reciprocal of resistance and one siemens is equal to the reciprocal of one ohm.
Surveyors are now citing healthcare organizations when you fail to perform the conductance test when you cannot perform the specific gravity test on the electrolyte. You will need to have a special meter (like the one in the picture) that measures siemens (or mhos) and the common volt meter is not capable of performing this test.
Make sure you record this reading on a monthly basis.