Battery Discharge test
The values for discharge time and end point voltage should be selected from the battery manufacturer's published ratings and the values used for the acceptance test should be approximately the same as that of the intended application. The discharge rate should be at a constant current or constant power load equal to the selected manufacturer's rating of the battery. The charging method used as the basis for the published data is an important factor. For a stationary float application, data based on prolonged constant potential charging should be used. If constant current charging has been used to establish the published data, appropriate float charging correction factors should be obtained from the manufacturer. Note that the test discharge current is equal to the rated discharge current divided by the temperature correction factor for the initial electrolyte temperature. Set up a load and the necessary instrumentation to maintain the test discharge rate determined in above. Disconnect the charging source, connect the load to the battery, start the timing, and continue to maintain the selected discharge rate. If the charging source cannot be disconnected, the current being drawn by the load has to be increased to compensate for the current being supplied by the charging source to the battery. Read and record the individual cell voltages and the battery terminal voltage. The readings should be taken while the load is applied at the beginning and after the test and at specified intervals. There should be a minimum of three sets of readings. Individual cell voltage readings should be taken between respective posts of like polarity of adjacent cells so as to include the voltage drop of the inter-cell connectors. Maintain the discharge rate and record the elapsed time at the point when the battery terminal voltage decreases to a value equal to the minimum average voltage per cell as specified by the design of the installation times and the number of cells.