Miscellaneous/Ask Isidor.Performance

About theAuthor

Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. He is an award winning author of many articles and books.

Q: Can Battery Neglect reduce performance?

Observing batteries in everyday lives

Batteries have a mind of their own. Their 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.

Figure 1: Results of battery neglect. The soldiers begin carrying rocks instead of batteries. Maintenance helps to keep deadwood out of military arsenal. Ó Cadex Electronics Inc. +

The personal battery user

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 battery user

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 are 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 is exclusively using 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.

What lack of battery maintenance can do

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 as 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.

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. (Refer to “Memory: Myth or fact?” See BD February, 2003, pp 95-10 thru 13.).

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(February 2007) How to increase the runtime of your cell phone

by Isidor Buchmann

As the sponsor of www.BatteryUniversity.com, Cadex Electronics gets many interesting enquiries from battery users. One writes, “Hi, I am looking for an answer to a perplexing question. A co-worker and I have identical cell phones from the same provider. Moving into a new house, she complained of short battery runtime. I told her she was out of her mind, but then I noticed my battery behaving differently when I travel. Is there some mysterious force that’s draining the battery?”

Yes, there is a force that’s draining the battery. An active cell phone is in constant communication with the tower and consumes small bursts of energy once every second or so to check for incoming calls. The transmit power is adjusted to the signal strength. If the cell phone is close to a repeater tower, little energy is needed to communicate. Moving further away or entering an environment with high electrical noise, such as a shopping mall, hospital or factory, more energy will be required. An analogy can be made to sitting in a restaurant. In a quiet establishment the voice can be low, but as the crowd grows, everyone needs to talk louder to be heard.

Living in sight of a tower has advantages and your battery will run longer between charges. In essence, towers are the best friends to cell phone batteries. Even the placement of a cell phone in your house has an effect on runtime. At a recent meeting with a large cellular provider in the UK, a manager said that his son noticed short standby times after moving to his basement bedroom. If possible, leave your cell phone in an upstairs room facing a tower. When traveling by car, don’t place your cell phone on the floor. Instead, raise it closer to window level but avoid direct exposure to the sun, as heat will harm the battery.

The same energy savings apply to TETRA and P25 radio systems, cordless telephones, Wi-Fi and Blue Tooth devices. A wireless headset that is communicating with your cell phone on the belt will provide longer runtimes than placing the handset on the dining table while doing the cooking. The Blue Tooth headset needs to work harder when farther away from the user, although the quality of communication may not be affected.

Allow me to clarify that the energy savings from the placement of a wireless device only apply when it’s in the ON position. When OFF, the residual loads are very low; the battery needs only to supply power for housekeeping functions such as maintaining the clock. Housekeeping and self-discharge consume 5-10% of the available battery energy per month.

During the last few years, standby and talk-times have much improved. The Lithium-ion battery has doubled its energy density since its introduction in the early 1990s. In addition, large energy savings are being achieved in the receiver and demodulator circuits. Figure 1 illustrates the reduction of power consumption in these circuits since 2002. We must keep in mind that this saving only applies to standby and receiving. Transmitting requires about five times the amount of power compared to receiving and demodulation. Modern handsets have also achieved better efficiencies in transmit circuits.

Figure 1: Reduction in power consumption. In addition to higher capacity batteries, cell phone manufacturers have achieved notable power savings in the receiver and demodulator circuits. (Sieber et al., 2004). +

It’s not always the battery’s fault

When the cell phone quits, the battery often gets the blame. The battery is the only user-replaceable part on a cell phone and becomes an easy target. Service personnel often replace the pack without testing, only to have the fault recur.

Moving from nickel-based to Lithium-ion batteries eliminated many problems. Lithium-ion packs are maintenance free and don’t require periodic full discharges to restore capacity; there is no memory effect. Still, customers suspect the batteries as the reason of most problems. As a result, large volumes of good packs are replaced and discarded. This is costing the cell phone industry ten million dollars annually. Cell phone providers say that 90% of returned batteries can easily be serviced.

Technology is now available to rapid-test batteries at store level while the customer waits. If a replacement is needed, an exchange is given from a pool of batteries that had previously been serviced. On-site restorations eliminate courier charges and relieve manufacturers from the burden of handling tons of returned batteries.

Figure 2 illustrates the service flow, starting with the customer bringing in the cell phone, checking the battery and providing a replacement. The replacement pack is taken from a pool that had previously been refurbished on site with a battery analyzer. A recent pilot test by a large service provider using this exchange program worked well and no replacement battery ever came back due to failure.

Figure 2: A cell phone is brought in with a suspect battery. The battery is tested while the customer waits. If in need of service, a refurbished pack is given in return. Servicing batteries at point-of-sales saves the industry millions of dollars and adds to customer satisfaction. +

According to a U.S. cellular provider, a typical store gets an average of ten returned batteries a day. The handling cost is estimated at $15US per pack. This amounts to a daily expense of $150 per store. Realizing this high expense and trying to cut cost, ten stores participated in a one-month experiment that involved examining and servicing incoming batteries using Cadex battery analyzers. During this study period, the stores saved 1981 batteries, resulting in a saving of about $30,000.

Battery rapid-testing

One of the key features of a modern battery analyzer is obtaining accurate test results when rapid-testing a battery. In the past, the battery state-of-health was mostly estimated by measuring internal resistance. As Figure 3 shows, the battery’s ability to hold energy (capacity) may not correspond with resistance. On some Lithium-ion batteries, the capacity can drop to half its original level while maintaining low resistance throughout its cycle life.

Figure 3: Relationship of capacity and resistance as part of cycling and aging. The state-of-health of Lithium-ion cannot be obtained my measuring resistance alone. +

For best results, a battery should be tested under similar conditions as used in the field. QuickSort™ by Cadex achieves this through a technology referred to as electrochemical dynamic response. This method can be compared to a mechanical arm under load. A strong arm remains firm, whereas a weak one bends and becomes sluggish when under load. This response can also be applied to estimating battery state-of-health. QuickSort™ provides a correct prediction 90% of the time over a wide population of Lithium-ion batteries in various state-of-charge conditions.

A relatively high number of batteries fail due to over-discharge. We discovered this while checking 1000 customer-returned packs that had been sent to the Cadex lab for further evaluation. Among these packs, 30% had no voltage reading and appeared dead. This was due to over-discharge. At voltages between 2.5 and 2.8V, the internal safety circuit of a Lithium-ion battery disengages and the battery goes into a sleep mode, making a recharge impossible. The Boost program of the Cadex C7000 Series battery analyzers activates the safety circuit and brings the battery back to life. The restoration is permanent and the pack can be returned to the customers. Figure 4 illustrates this process.

Figure 4: Over-discharged battery receives a “Boost” current to raise the cell voltage into the operational threshold, re-engaging the safety circuits and enabling a charge. +

To prevent a cell phone battery from inadvertently falling asleep, apply a 30-minute charge (or longer) after the “Low Batt” indicator comes on. Do not store the cell phone in a totally discharged condition. Peripheral loads, combined with self-discharge, will further discharge the battery. This can lead to an eventual disconnect in which the battery appears dead as described above.

Besides rapid-test and boost, most battery analyzers also offer full battery service programs that consist of charge and discharge cycles. Such programs provide the most accurate battery assessment and are the recommended methods to prepare replacement batteries for exchange purposes. Figure 5 illustrates the Cadex C7400.

Figure 5: Cadex C7400 battery analyzer provides QuickSort™, Boost and full service programs. The four battery stations accommodate virtually any portable battery. +

Conclusion

Battery rapid-testing at point-of-sale has only become practical with the introduction of advanced battery analyzers. Testing batteries at storefronts improves customer service and enhances customer satisfaction. Organizations using these battery analyzers have reported sharp reductions in service related expenses. Manufacturers support storefront testing and restoration, knowing that such a service will greatly reduce warranty returns and save money. The pay back on such equipment is less than one year.