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16.3 Battery Analyzers for Critical Missions
Occasionally, a customer will call Cadex because their battery analyzer appears faulty. The complaint: the battery no longer indicates correct capacity readings. In most cases, the customer has just purchased new batteries. When testing these new packs, the capacities read 50 to 70 percent. The customer assumes that, “Naturally, if two or more of these brand new batteries show low readings, it can only be the analyzer’s fault.”
Battery analyzers play a critical role in identifying non-performing batteries, new or old. Conventional wisdom says that a new battery always performs flawlessly. Yet many users realize that a fresh battery may not always meet the manufacturer's specifications. Weak batteries can be identified and primed. If the capacity does not improve, the packs can often be returned to the vendor for warranty replacement. Whole batches of new batteries have been sent back because of unacceptable performance. Had these batteries been released without prior inspection, the whole system would have been jeopardized, resulting in unpredictable performance and frequent down time.
In addition to getting new batteries field-ready, battery analyzers perform the important function of weeding out the deadwood in a battery fleet. Weak batteries can often hide among their peers. However, when the system is put to the test in an emergency, these non-performers become a real nuisance.
Organizations tend to postpone battery maintenance until a crisis situation develops. One fire brigade using two-way radios experienced chronic communication problems, especially during emergency calls which lasted longer than two hours. Although their radios functioned in the receive mode, they were not able to transmit and firefighters were left unaware that their calls did not get through.
The fire brigade acquired a Cadex battery analyzer and all batteries were serviced through exercise and recondition methods. Those batteries that did not recover to a preset target capacity were replaced.
Shortly thereafter, the firefighters were summoned to a ten-hour call that demanded heavy radio traffic. To their astonishment, none of the two-way radios failed. The success of this flawless operation was credited to the excellent performance of their batteries. The following day, the Captain of the fire brigade personally contacted the manufacturer of the battery analyzer and enthusiastically endorsed the use of the device.
Batteries placed on prolonged standby commonly fail. Such was the case when a Cadex representative was allowed to view the State Emergency Management Facility of a large US city. In the fortified underground bunker, over one thousand batteries were kept in chargers. The green lights glowed, indicating that the batteries where ready at a moment’s notice. The officer in charge stood tall and confidently said, “We are prepared for any emergency”.
The representative then asked the officer to hand over a battery from the charger to check the state-of-health (SoH). Within seconds, the battery analyzer detected a fail condition. In an effort to make good, the officer grabbed another battery from the charger bank but, it failed too. Subsequent batteries tested also failed.
Scenarios such as these are common but such flaws do not get rectified quickly. Political hurdles and lack of funding are often to blame. In the meantime, all the officer can do is pray that no emergency occurs.
Eventually, a new set of batteries is installed and the system returns to full operational readiness. However, the same scenario will reoccur, unless a program is implemented to exercise the batteries on a regular basis. Advanced battery analyzers, such as the Cadex 7000 Series, apply a conditioning discharge every 30 days to prevent the memory phenomenon on nickel-based batteries.
Figure 16-1: Results of neglecting your battery’s state-of-health.
Maintenance helps keep deadwood out of your arsenal.The military also relies heavily on batteries. Defense organizations take great pride in employing the highest quality and best performing equipment. When it comes to rechargeable batteries, however, there are exceptions. The battery often escapes the scrutiny of a full military inspection and only its visual appearance is checked. Maintenance requirements are frequently ignored. Little effort is made in keeping track of the battery’s state of health, cycle count and age. Eventually, weak batteries get mixed with new ones and the system becomes unreliable. This results in soldiers carrying rocks instead of batteries. A battery analyzer, when used correctly, keeps deadwood out of the arsenal.
The task of keeping a battery fleet at an acceptable capacity level has been simplified with battery analyzers that offer target capacity selection. This novel feature works on the basis that all batteries must pass a user-defined performance test. Batteries that fall short are restored with the recondition cycle. If they fail to recover, the packs are replaced.
The target capacity setting of a battery analyzer can be compared to a student entry-exam for college. Assuming that the passing mark is 80 percent, the students who do not obtain that level are given the opportunity to take a refresher course and are thereafter permitted to rewrite the exam. In our analogy, the refresher course is the recondition cycle that is applied to nickel-based batteries. If the passing mark is set to 90 percent, for example, fewer but higher qualified students are admitted.
A practical target capacity setting for batteries in public safety is 80 percent. Increasing the capacity requirement to 90 percent will provide an extra 10 percentage points of available energy. However, higher settings will yield fewer batteries since more packs will fail as they age.
Many organizations allocate the top performing batteries for critical applications and assign the lower performers for lighter duties. This makes full use of the available resources without affecting reliability.
Some battery analyzers display both the reserve capacity (motor fuel left in the tank before refill) and the full-charge capacity (full tank) of the batteries serviced. The user is then able to calculate how much energy was consumed during the day by subtracting the reserve from the full-charge capacity. To ensure a reasonable safety margin after a routine day, the reserve capacity should be about 20 percent. If less reserve capacity is available, the target capacity should be set higher. By allowing reasonable reserve capacity, unexpected downtime in an emergency or on extra-strenuous field activities can be eliminated.
