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ELECTRIC VEHICLE BATTERY CAPACITY
BATTERY CAPACITY TESTS The capacity tests specified in the ANSI IEEE 450 standard are categorized into four tests, • • • •
Battery Battery Battery Battery
pack acceptance test pack performance test pack service test variable power test
The battery acceptance test is used to determine if the battery bank meets its purchase specification or the manufacturer’s specification. This test is performed at the manufacturing facility or upon installation of the battery. The battery performance test is performed periodically to measure the battery pack capability, including operation, age, deterioration, and environment. This test can be performed at any time during the entire life of the battery. The battery service capacity test determines whether or not the battery system, as per manufacturer specifications, will meet the battery pack requirements during load and duty cycling. This test is not designed to effectively predict battery life or replacement, rather it is performed as part of the preoperational or periodic DC system check. Before a battery pack undergoes an acceptance or performance test, a complete preventative maintenance inspection should be scheduled. The inspection of the battery pack should include measuring and recording the battery terminal resistance of all the connections in the pack. Resistance tests should be performed on the battery pack. The battery pack should be placed on a float charge for three days and not more than seven days prior to performing a capacity test to ensure that the battery pack is at a 100% SOC. On the contrary, service tests are performed on the battery in an “as is” condition and do not require pretest conditions. For service capacity tests, the rated discharge current and the testing period should ideally match the duty cycle of the system. This means that the user should be prepared to manually or preprogram the test equipment to change the current discharge levels at specified time periods as required by the duty cycle. For the acceptance and the performance capacity tests, a rated discharge current and the testing period are selected from the battery manufacturer’s cell performance data sheet based on the battery model type, amp-hour rating, the load unit’s current rating, and the final end voltage per cell. Typically, the voltage for a VRLA cell as selected to be 1.75 V
