Chapter 11: Maintaining Fleet Batteries
Unlike individual battery users, who come to know their batteries like a good friend, fleet users must share the batteries from a pool of unknown packs. While an individual user can detect even a slight reduction in runtime, fleet operators have no way of knowing the behavior or condition of the battery when pulling it from the charger. They are at the mercy of the battery. It’s almost like playing roulette.
It is recommended that fleet battery users set up a battery maintenance program. Such a plan exercises all batteries on a regular basis, reconditions those that fall below a set target capacity and ‘weeds out’ the deadwood. Usually, batteries get serviced only when they no longer hold a charge or when the equipment is sent in for repair. As a result, battery-operated equipment becomes unreliable and battery-related failures often occur. The loss of adequate battery power is as detrimental as any other malfunction in the system.
Implementing a battery maintenance plan requires an effort by management to schedule the required service for the battery packs. This should become an integral component of an organization’s overall equipment maintenance and repair activities. A properly managed program improves battery performance, enhances reliability and cuts replacement costs.
The maintenance plan should include all rechargeable batteries in use. Large organizations often employ a variety of batteries ranging from wireless communications, to mobile computing, to emergency medical equipment, to video cameras, portable lighting and power tools. The performance of these batteries is critical and there is little room for failure.
Whether the batteries are serviced in-house with their own battery analyzers or sent to an independent firm specializing in that service, sufficient spare batteries are required to replace those packs that have been temporarily removed. When the service is done on location and the batteries can be reinstated within 24 hours, only five spares in a fleet of 100 batteries are required. This calculation is based on servicing five batteries per day in a 20 workday month, which equals100 batteries per month. If the batteries are sent away, five spares are needed for each day the batteries are away. If 100 batteries are absent for one week, for example, 35 spare batteries are needed.
Manufacturers of portable equipment support battery maintenance programs. Not only does such a plan reduce unexpected downtime, a well-performing battery fleet makes the equipment work better. If the recurring problems relating to the battery can be eliminated, less equipment is sent to the service centers. A well-managed battery maintenance program also prolongs battery life, a benefit that looks good for the vendor.
The ‘Green Light’ Lies
When charging a battery, the ready light will eventually illuminate, indicating that the battery is fully charged. The user assumes that the battery has reached its full potential and the battery is taken in confidence.
In no way does the ‘green light’ guarantee sufficient battery capacity or assure good state-of-health (SoH). Similar to a toaster that pops up the bread when brown (or black), the charger fills the battery with energy and ‘pops’ it to ready when full (or warm).
The rechargeable battery is a corrosive device that gradually loses its ability to hold a charge. Many users in an organization are unaware that their fleet batteries barely last a day with no reserve energy to spare. In fact, weak batteries can hide comfortably because little demand is placed on them in a routine day. The situation changes when full performance is required during an emergency. Total collapse of portable systems is common and such breakdowns are frequently related to poor battery performance. Figure 11-1 shows five batteries in various states of degradation. [11.1]
Carrying larger packs or switching to higher energy-dense chemistries does not assure better reliability if the weak batteries are not ‘weeded’ out at the appropriate time. Likewise, the benefit of using ultra-advanced battery systems offers little advantage if packs are allowed to remain in the fleet once their performance has dropped below an acceptable performance level.
Figure 11-2 illustrates four batteries with different ratings and SoH conditions. Batteries B, C and D show reduced performance because of memory problems and other deficiencies. The worst pack is Battery D. Because of its low charge acceptance, this battery might switch to ready after only 14 minutes of charge (assumed time). Ironically, this battery is a likely candidate to be picked when a fresh battery is required in a hurry. Unfortunately, it will last only for a brief moment. Battery A, on the other hand, has the highest capacity and takes the longest to charge. Because the ready light is not yet lit, this battery is least likely picked. [11.2]
The weak batteries are charged quicker and remain on ‘ready’ longer than the strong ones. The bad batteries tend to gravitate to the top. They become a target for the unsuspecting user. In an emergency situation that demands quick charge action, the batteries that show ready may simply be those that are deadwood.
A weak battery can be compared to a fuel tank with an indentation. Refueling this tank is quicker than a normal tank because it holds less fuel. Similar to the ‘green light’ on a charger, the fuel gauge in the vehicle will show full when filled to the brim, but the distance traveled before refueling will be short.
Battery Maintenance, a Function of Quality Control
The reliability of portable equipment relies almost entirely on the performance of the battery. A dependable battery fleet can only be assured if batteries are maintained on a periodic basis.
Battery maintenance also needs proper documentation. One simple method is attaching a color dot, each color indicating the month of service. A different color dot is applied when the battery is re-serviced the following month. A numbering system indicating the month of service also works well.
A better system is attaching a full battery label containing service date and capacity. Like the pending service on a car, the label shows the user when maintenance is due. For critical missions, the user will pick a battery with the highest capacity and the most recent service date. The label ensures a properly serviced replacement pack.
Battery analyzers are available that print a label revealing the organization, group, service date, expiry date (time to service the battery), battery capacity and ID number. The label is generated automatically when the battery is removed from the analyzer. Figure 11-3 illustrates such a label. [11.3]
The battery labeling system is simple to manage. It is self-governing in the sense that the users would only pick a battery that is properly labeled and has recently been serviced. The system does not permit batteries to fall though the cracks and be forgotten. It is in the interest of the user to ensure continued reliability by bringing in batteries with dated labels for service.
Battery Maintenance Made Simple
Several methods are available to maintain a fleet of batteries. A simple, self-governing system is illustrated in Figure 11-4 to Figure 11-6. Only 30 minutes per day should be required for a technician to maintain the system. One or several battery analyzers are needed that are capable of producing battery labels. [11.4] [11.5] [11.6]
When taking a battery from the charger, the user checks the service date on the battery label. If expired, the battery is placed into the box marked: ‘To be serviced’. Periodically, the box is removed and the batteries are serviced and re-certified with a battery analyzer.
After service, the batteries are re-labeled and returned to the charger. Those batteries that fail to meet the target capacity are replaced with new packs. All batteries in the charger are now certified to meet a required performance standard.
Battery maintenance has been simplified with the introduction of battery analyzers that offer a target capacity selection. All batteries must meet a user-defined performance test or target capacity to pass. Nickel-based batteries that fall short of the required capacity are automatically restored with the analyzer’s recondition cycle. Those packs that fail to recover are subsequently replaced with new packs.
Recondition is only effective for nickel-based batteries. It is worth noting that batteries with high self-discharge and/or shorted cells cannot be corrected with recondition; neither can a battery be restored that is worn out or has been damaged through abuse.
Another group of batteries that cannot be deep discharged by recondition are ‘smart’ batteries. This includes any pack that contains a microchip that must be maintained by a continuous voltage supply. Discharging these batteries below a certain voltage point will put the battery to sleep. A recharge often fails to wake up these batteries.
Battery Maintenance as a Business
Some entrepreneurs have come up with the novel idea of providing a service to test and restore rechargeable batteries. They operate in convenient locations such as downtown cores, shopping malls and transportation hubs. Customers bring in their batteries to have them serviced. The packs are tested and reconditioned with automated battery analyzers. A full performance report is issued with each battery serviced, showing service date, performance status and the date for the next service. The suggested fee per battery is $10.00US. Higher prices can be requested on specialty batteries which are expensive to replace.
For organizations using a large number of batteries, a special pick-up and delivery service can be organized to provide scheduled maintenance. This ensures that fleet batteries used by organizations are regularly maintained. Such a service would benefit firms that do not want to bother with battery maintenance or do not have the expertise or resources to perform the task in-house.
Increasingly, dealers who sell mobile phones, laptops and camcorders also provide battery service. This activity increases traffic and helps foster good customer relations. A new battery is sold if the old one does not recover when serviced. By knowing that a battery can be checked and possibly restored, customers may try to salvage their weak batteries before investing in new ones. Some dealers may be reluctant to restore used batteries for fear of reduced battery sales.