With uncertainty in grid power supply, Batteries have become an important element of electrical systems today.
A greater dependence on computers, especially in business and commerce means the performance of batteries is critical to business continuity. However, most electrical professionals often complain about batteries not meeting the promised life and frequently failing to deliver performance when it is needed the most.
A simple but systematic testing routine of batteries will help in early detection of problems before they affect performance.
Battery maintenance approach
Just like a human body, periodic checks are also required on batteries to understand its health so that remedial action can be taken before any permanent damage is done. We discuss below a set of some basic checks that should be conducted to ultimately derive best performance from batteries.
Visual Inspection
Simple visual inspection of batteries is important. Look for cracks, leaks or signs of corrosion. It helps to prevent water accumulating near battery storage area and to keep the surroundings clean.
Frequency of check: Fortnightly
Operator skill level: Basic
Voltage tests
Float voltage is a good measure of battery life. Float voltage is the constant voltage that is applied continuously to a voltaic cell to maintain the cell in a fully charged condition. The appropriate float voltage varies significantly with the chemistry and construction of the battery, and ambient temperature.
A low float voltage is an indication of undercharging. The cells will not supply to full capacity when required. Low float voltage may be caused due to sulfation. If battery tests for high float voltage, there is a possibility of overcharging. Overcharging increases the temperature and can also lead to pre-mature acid corrosion.
Frequency of check: Monthly
Operator skill level: Moderate
Current Tests
Float charging current is the DC current flowing in battery when the battery, charger and load are connected in parallel. High float current could often be read as a sign of thermal runway in future.
High float currents could be caused by short circuit or even a high float voltage. Ripple current could be caused due to faults in charging circuit often related to diode or a rectifier. Higher ripple current can also cause heating of batteries.
Frequency of check: Quarterly
Operator skill level: Moderate
Temperature
Battery temperature is an easy measure of overall health. Higher temperatures reduce the life of battery and can damage the battery permanently in the long run. Higher temperature is just an indication of a problem and other tests are required to understand the root cause.
Frequency of check: Fortnightly
Operator skill level: Low
Specific Gravity
Specific gravity is a key parameter in battery operation. It is defined as ratio of weight of solution to the weight of equal volume of water at a particular temperature. However, specific gravity does not indicate the capacity of the battery.
Specific gravity decreases close to that of water during discharge and is at it’s highest in case of full charge. A comparison of changes in voltage and specific gravity during charging and discharge indicate the performance of the battery. However, methods to measure the same may not be practical in normal operating conditions.
Frequency of check: Quarterly
Operator skill level: Moderate
Impedance and Conductance Testing
Impedance increases with age of the battery, while conductance decreases. The test method involves applying a small AC voltage “E” of known frequency and amplitude across the cell and measuring the in phase AC current “I” that flows in response to it.
Parameters like Impedance that change with age of battery are a good measurement of State of Health (SOH) of the battery. Impedance and conductance testing are reliable, safe, accurate, fast and they don’t affect the battery performance.
They can be carried out while the battery is in use or they can be used to continuously monitor the battery performance, avoiding the need for load testing or discharge testing. Full load cycle testing carried out once every year will yield accurate information and provide an excellent baseline for impedance testing.
Frequency of check: Quarterly
Operator skill level: High
We hope these techniques take you a step closer towards achiveing the best performance from batteries and help you to ensure business continuity.
