Battery Load Testing

Frequency of Load Testing

To determine the frequency of Load Testing, several questions should be asked… How critical is the battery system? What does it support? Is the system subject to NERC requirements. Does my insurance provider require testing? One of these questions will provide you with an answer. IEEE standards also provide guidelines for frequency and methods of testing.

Aside from that, a relatively new flooded cell system with healthy Preventive Maintenance indicators, a testing frequency of 3 to 5 years may be appropriate. If a battery system is approaching its end of life and PM indicators are less consistent, performing more frequent load tests would be appropriate. Annual load tests are also appropriate for any VRLA (sealed or valve-regulated) battery systems 2 years old or older due to its inherently less predictable nature. Depending on the application, requirements such as NERC may dictate the frequency of load testing.

It is true that load testing does consume an incremental portion of the battery’s life. Its usefulness for identifying problems and ensuring reliability, however, far outweighs this slight degradation if done correctly. All battery discharges, regardless of duration, are cumulative in the life of a battery. The incremental degradation as a result of load testing and its associated cost do not compare to the cost of complete system failure.


Scope of Load Testing

During the test the battery system will be disconnected from the system. Monitoring leads will be attached to each battery post in the segment being tested, as well as to the main battery connection cables. This enables the technician to monitor both system and individual battery voltages during the test. Note – if you must maintain battery back-up during the test, we can provide a temporary battery system for this purpose.

Please note that a Pre-Inspection and Preventive Maintenance Service, including connection impedance measurements, will precede the load test. This will avoid potential problems that could lead to safety or performance issues during the test.

All load tests are performed in accordance with applicable IEEE standards.


Recommended Parameters

The parameters at which the test is performed, as well as its duration, depends on several factors. One scenario would be to test at your actual load plus 20%, for the required duration needed to support the load. Alternately, the battery can be tested at its full load rating until it reaches its low voltage cutoff point, with is typically 1.67 to 1.75 Volts per Cell.


Conclusions Drawn

During the load test, the technician will monitor the overall system, individual cell voltages, and watch for rapid drops in voltage. Not only does the test identify problem cells, it also illustrates how your battery will actually perform when called upon.

Periodic Preventive Maintenance checks are also important to identify more obvious problems or trends that can predict problems. They are no substitute, however, for the true performance indication of a load test.


No battery system is too small or too large. We have access to many types and sizes of load banks that will accommodate your battery system.