Reliable battery performance depends on adequate maintenance.
If you depend on stationary batteries for uninterrupted power to critical processes, you can't ignore battery maintenance. But what does adequate maintenance entail? Before we look at how best to maintain batteries, let's address a popular myth.
In an attempt to solve maintenance problems with flooded cells, manufacturers developed the valve-regulated lead acid (VRLA) battery, a gel-filled construction designed to reduce gassing and electrolyte loss. It has its advantages, but being maintenance-free isn't among them. In fact, VRLAs do lose electrolytes (check your car battery), emit gas, and require ventilation.
According to Glen Alber, co-founder of AlbérPower, “a VRLA has a lower life span and a higher total cost of ownership (TCO) than a properly maintained flooded battery. The VRLA requires more maintenance than a flooded battery — but it typically gets no maintenance and lasts a fraction of its advertised life.”
Even a maintenance-free battery requires maintenance performed “outside the jar.” Posts, cell interconnectors, and load connections need routine inspection and elbow grease. Proper maintenance requires inspection, cleaning, monitoring, manual testing, load testing, and record keeping.
You should inspect batteries under normal float conditions. Flooded cells have translucent or transparent jars, so you can easily see the electrolyte level. Your inspection should also go beyond site checks to include the following:
Inspect the positive plates. Located in the center of the jar, these are usually the first to wear out. They should be dark brown or black. Sparkle is evidence of sulphation or undercharge. Look for cracks, breaks, and pieces hanging on the side, evidence indicating you'll probably need to replace that cell and possibly others.
Inspect the negative plates. These are thinner than the positive plates and sit toward the outside of the jar. These should have a clean lead color from top to bottom. Pink discoloration indicates copper contamination.
Look at the sediment. This will give you a general idea of what the battery has been doing over the past year or more. If you have piles of gray material under the negative plates accompanied by sparse black sediment, check your float voltage — you're probably undercharging. Excess black sediment under the positive plates with little negative sediment indicates you either have an overcharge or excess temperature. If excess sediment covers the bottom of the jar, the battery has cycled heavily or operated at high temperature.
What to look for outside the jar:
Evidence of electrolyte leakage — usually a crusty trail or accumulation.
Signs of corrosion on the terminal connections, intercell connections, and racks.
Before cleaning, note the condition of posts and connectors. Except for a light coating of grease, these should look new. Consider these colors:
Black. This is lead peroxide, indicating an acid leak around the positive post.
Green. This is corroded copper, indicating connectors need cleaning and close inspection — they may no longer be serviceable.
White. This is lead hydrate, indicating a leak around the negative post.
You can wipe the jars clean any time, but cleaning connectors and posts requires opening the battery circuit. If you take the battery out of service without a parallel system, your UPS will not respond to a power loss, so coordinate with your operations department. If you follow these directions, your cleaning should last five years:
Wipe the grease off the posts and connectors, then neutralize them with baking soda and water.
Clean with a scouring pad or brass brush until you see clean lead. Cleaning too vigorously or with a wire brush will remove too much lead.
Degrease the bolts, washer, and nuts. Neutralize with baking soda and water. Replace corroded hardware. Replace lockwashers, regardless of condition. Use only lead-plated or 316-stainless steel bolts, washers, and nuts.
Regrease posts and contact areas of connectors with a light layer of antioxidant grease approved for battery use.
Install washers with the sharp side facing away from the connector. If possible, install lockwashers on the nut side, not the bolt side.
Retorque connections to manufacturer's specifications. Turn the nut, not the bolt, if possible.
Check post-to-post resistance with a micro-ohmmeter. If resistance is high, check the torque — overtorquing degrades the connection. If the torque is correct but the value is high, disassemble and inspect contact surfaces for proper polishing.
Years of field data show monitoring each cell's internal resistance is a reliable way of indicating the health of a battery. This monitoring won't tell you what's wrong, but it will tell you something is about to go wrong. Then it's time for manual testing.
Manual testing has special requirements for safety, training, and equipment. Most battery installations undergo inadequate or even “negative” maintenance — the latter because an untrained person reduced battery life by improper procedure.
Keep a schedule. Each month, measure float voltage (at battery terminals) and charger output (voltage and current). Every quarter, check the float voltage of every cell and the electrolyte temperature of every sixth cell, and record the negative post temperature of VRLAs. Measure intercell resistance and internal cell resistance annually.
Many manufacturers discourage specific gravity measurements because results are so often misleading. A reliable “low invasion” indicator of battery health is internal cell resistance. But, like all other tests but one, it's an inferential test. The only way to know a battery's condition is by performing a load test — which you don't want to do often.
Each battery has its own performance time curve. Load testing shows you how well your battery matches its particular curve. The load test measures the capacity of a battery and its individual cells. The standard threshold for passing this test is 80% of rated capacity. To load test, place a known load on that battery and measure the voltage after a given time. To maximize the effect of a load test, have a thermographer scan the battery before, during, and after the test.
Beware: This is an expensive test. Each time you conduct it, you'll have to take the battery out of service, stealing life from it in the process. For most battery installations, a good monitoring system lets you get by with an annual load test.
The results of inferential testing and maintenance inspections are snapshots in time. To make them meaningful, you must compare data over time. Paper-based logs give you a decent forensic analysis tool for explaining why an outage occurred. Software allows you to quickly plot trend data and spot potential problems. By correcting problems early, you can prevent an outage. Any computerized maintenance management system (CMMS) on the market allows you to do predictive trending. Many battery owners find specialized battery instrumentation better suited to the kind of tracking and analysis they need.
Batteries strike a delicate balance between self-destruction and regeneration. If you monitor their health and take timely corrective action, you'll increase the life of your batteries and save money you would have spent on new ones. However, the real value of proper battery maintenance comes when primary power fails and your healthy batteries keep critical systems running.