Batteries have a mind of their own. They're stubborn and unpredictable behavior has left many battery users in awkward situations. And yet, the battery is our steady travel companion that allows us to carry out our activities disconnected from home and office. In this paper we observe the battery in personal use and fleet applications.
It is interesting to observe that batteries cared for by a single user generally last longer than those operating in an open fleet environment where everyone has access to but no one is accountable for them. A personal user is one who operates a mobile phone, a laptop or a video camera for pleasure or business. He or she will likely follow the recommended guidelines in caring for the battery. When the runtime gets low, the battery gets serviced or is replaced. Critical failures are rare because the owner adjusts to the performance of the battery and lowers the expectation as the battery ages.
The fleet user, on the other hand, has little personal interest in the battery and has no tolerance for a pack that is less than perfect. He simply grabs a battery from the charger and expects it to last through the shift. The battery is returned to the charger at the end of the day, ready for the next person. Regular battery maintenance is minimal and performance often starts to degrade after one year of service.
How can fleet batteries be made to last longer? I examined the US and the Dutch Army, both of which use fleet batteries. The US Army issues batteries with no maintenance program. If the battery fails, another pack is released, no questions asked. Little or no care is given and the failure rate is high.
The Dutch Army, on the other hand, has moved away from the open fleet system by making the soldiers responsible for their batteries. This change was made in an attempt to reduce operational costs and improve reliability. The batteries are issued to the soldiers and become part of their personal belongings. The results are startling. Since adapting this new regime, the failure rate has dropped considerably and the battery performance has increased. Unexpected down time has almost been eliminated.
It should be noted that the Dutch Army uses exclusively nickel-cadmium batteries. Each pack receives periodic maintenance on a battery analyzer (Cadex) to prolong service life. Batteries that do not meet the 80% target capacity setting are reconditioned; those that fall below target are replaced. The US Army, on the other hand, uses nickel-metal-hydride, a battery that has higher energy density but is less durable. The US army is evaluating lithium-ion batteries for the next generation battery.
Batteries get checked when they no longer hold charge or the equipment is sent in for repair. In an effort to improve reliability and cut replacement costs, many organizations have adapted some type of battery maintenance.
A user may feel that his or her battery works adequately during routine days, not knowing that the pack holds only half the capacity. A system must be fit to operate in unforeseen circumstances and emergencies where every watt of battery power is needed. Breakdowns during these critical moments are all too common and weak batteries are often to blame. The loss of adequate battery power is as detrimental as any other malfunction in the system.
I have recorded a number of stories in which lack of battery maintenance was evident:
Fire brigade - A fire brigade had chronic communication problems with two-way radios. The problems were most acute during call-outs lasting two hours and longer. Although their radios functioned on receive, the transmissions broke up and the calls did not get through.
The fire brigade acquired a battery analyzer (Cadex) and all batteries were serviced through exercise and recondition methods. Batteries that did not recover to a set 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 radios failed. The success of this operation was credited to the good 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.
Emergency response - A Cadex representative was allowed to view the State Emergency Management Facility of a large US city. In the fortified underground bunker, 1400 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 erect and confidently said, "We are prepared for any emergency".
The representative then asked the officer to hand over a battery to check the state-of-health. Within seconds, the battery analyzer detected a fail condition. In an effort to make good, the officer grabbed another battery from the charger but it failed too. Subsequent batteries also fell short.
nickel-based batteries placed on prolonged standby become inoperable due to memory in as little a three months. Scenarios such as these are common. Political hurdles and lack of funding often stand in the way of a quick solution. The only thing the officer can do is pray that no emergency will occur.
Army - 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 is frequently ignored and little effort is made in keeping track of the battery's state of health, cycle count and age. In time, the soldiers begin carrying rocks instead of batteries.
Figure 1: Results of battery neglect.
The soldiers begin carrying rocks instead of batteries. Maintenance helps to keep deadwood out of military arsenal.
Batteries fooled the British Army during the Falkland War in 1982. The army assumed that a battery would always follow the rigid military specifications, even after long neglect. Not so. When the order was given to launch the portable missiles, nothing happened and the missiles did not fly that day. The batteries were dead.
Government services - An organization continually experienced failures with nickel-cadmium batteries. Although the batteries performed at 100% when new, the capacity dropped to 20% and lower in only one year. We discovered that their two-way radios were under-utilized; yet the batteries received a full recharge after each short field use.
After replacing the batteries, we advised the organization to exercise the batteries once per month through a full discharge. The first exercise occurred only after four month of service. Here is what we found:
The capacity on half of the batteries had dropped to 70-75%. With exercise and recondition (deep cycle), all batteries were fully restored (100%). Had maintenance been omitted for much longer, the probability of a full recovery would have been jeopardized.
Construction - I noticed fewer battery problems on two-way radios with construction workers than security guards. The construction workers often did not bother turning off their two-way radios at the end of the shift. As a result, the nickel-cadmium batteries got their needed exercise and kept performing until they fell apart from old age, often held together with duct tape.
In comparison, the security guards pampered their batteries to death by giving them light duty and plenty of recharge. These batteries still looked new when they had to be discarded after only 12 months of service. Because of the advanced memory, recondition was no longer effective.
Memory only occurs on nickel-based batteries, a phenomenon that can be corrected with periodic discharge cycles.
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