911 Magazine
July/August 1998
"There’s nothing worse than picking your radio up when you need it and it’s dead," says Dennis Granger, Communications for Grant Park, Illinois Sheriff’s Department and EMT Ambulance. It’s happened to everyone. Fast moment, life-or-death communications. All contact lost, because the radio goes dead, or all you hear is static. How can radios, which are the lifeline of work be so unpredictable? It’s not the radio – it’s the battery, and how you manage it every day of the year that often determines the dependability of the radio.
For most public safety and emergency professionals, operating a "Battery Maintenance Program" is low on the list of priorities in day-to-day operations. Bigger operations employ a Communications Officer to help manage equipment and channels. But taking care of the battery is usually the responsibility of the individual, which isn’t so hard to do once you understand batteries.
There are three types of batteries currently being used for portable communications: Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMH) and Lithium Ion (Li Ion). For years, NiCd has been the workhorse of rechargeables. It gives the best value for the money, costs less and provides more charge/discharge cycles than its counterparts. But it is heavier, and can demonstrate problems such as memory effect, which reduces charge capacity and cycle life. NiMH and Li Ion are lighter and have higher capacity than NiCd, but each chemistry has its own drawbacks: high costs, short cycle life and limited power capabilities. And, NiMH also has a memory effect.
Naturally, given the lower cost and longer life, NiCd is the battery of choice for most public safety operations. When misused, NiCd batteries can create frustration and "burn out" early, causing communications breakdown and frustration. However, when properly handled, NiCd batteries do the job dependably and save money.
When a battery is frequently charged before it is fully discharged, it begins to "remember" the level at which it was last charged, and it begins to think that that is the maximum level of capacity. Gradually, the usable time between charges is reduced, until a battery capable of lasting 12 hours can be reduced to only two or three hours. This is "memory effect," which also reduces the life of the battery. Two-way radio NiCd batteries should last about 500-700 charge/discharge cycles, but that’s not the case in operations where no concern for battery chemistry is applied to daily usage. Memory effect is cumulative, so it builds up over time. Inconsistent battery care will usually result in a degree of memory effect, which cannot be undone, even if methods are improved.
John E. McGuire, Operations Liaison at the Unified Port District in San Diego understands how memory effect can shorten battery life. "Batteries have been a very sore subject around here for a long time," he explains. "Even after we got the OEM upgrade charger, we though we were just out of luck with batteries, and that we would continue to replace them every six months until we got the ACTivators."
"I have to change our batteries about every year because of the memory effect. Batteries aren’t lasting long like they are supposed to, " echoes Dennis Granger of Grant Park, Illinois.
It’s no great secret. The key to battery success lies in the charging. You can use or abuse your battery, but if you charge (and discharge) it properly, it will serve you well for a long, long time. And a maintenance program does not have to be labor intensive or costly. At Gwinnett County Police Department (GA), batteries last up to four years, because officers are trained in proper usage and charging practices.
"Each officer has two batteries and a trickle charger at home," explains Lamar Martin, Radio System Coordinator. "They work six days on and three off. They use one battery one week, another battery the next. At the end of six days, they leave radio on until it runs down to full discharge. Others charge and discharge every day they work. The batteries are lasting a 10-hour shift at a time, and often, into a second shift for a part-time job. I condition the batteries regularly, too. But the act of just ‘killing’ it frequently helps to erase any memory."
There is a variety of equipment on the market for battery maintenance -- chargers, conditioners, analyzers, and a new conditioning charger known as an ACTivator. Chargers replenish the energy storage capacity of the battery. Three main types are available: the constant-current trickle charge (commonly referred to as "roasters and toasters"); the constant high-current fast charger, which is often self-terminating; and the pulse charger, which combines steady positive current with brief negative currents. The ACTivators by Advanced Charger Technology, Inc., (ACT) incorporate Dynamic Electrochemical WaveformTM (DEW). DEW, the newest technology on the market, is generations beyond pulse charging. Using an intelligent microchip that reads the chemistry of the battery, DEW responds with very high positive current charging interspersed with variable and brief (microseconds) deep discharging currents and rest periods, which combine to condition the battery as it charges.
Conditioners "exercise" the battery by discharging it very deeply -- usually to about 1v/cell. This "cleans" the battery and helps undo the damage of memory effect. Analyzers measure the capacity of the battery and sometimes measure changes in capacity. Some analyzers can also determine the cause of a bad battery, i.e. external damage, bad condition or bad cell. Most analyzers discharge the battery fully and then recharge it to measure capacity.
Many people mistakenly think that battery management needs to be a labor-intensive process that can only be done by large operations with communications professionals. Myth. Every single person with a radio can be proactive in making his/her battery last longer – between charges and for cycle life – and the steps are simple.
2) Terminate charging – don’t leave the battery on a trickle or fast-current charger indefinitely. If your charger is not self-terminating, buy an inexpensive outlet timer. If your charger takes eight hours to charge your battery – have the timer stop at eight hours – don’t allow the current to over charge your battery by running all night or weekend.
"It’s great when a charger stops when it’s finished. The ACTivator keeps them from cooking. The guys all leave their batteries in the charger overnight and they’re just cooking slowly the whole time – it’s so bad for the batteries," explains Paul Smith of the San Bernardino County Radio Operations Group. "On the other hand," he adds "they’ll warm your hands on a cold morning!"
Recently, during severe flash-flooding off the cape of South Africa, Mossel-Bay township emergency workers found themselves out of radio communications quickly when constant talk-time wore the batteries down quickly and back-up batteries and chargers failed to return the radios to service in a timely fashion. Thanks to the initiative of Graeme Wells, ACT Pty. Ltd., who drove 3.5 hours to Mossel Bay to help out, ACT’ivators incorporating DEW technology were used to fast charge the batteries and get the radios back into service. Wells’ experience in Mossel Bay and with a similar fire catastrophe weeks before illustrated how maintenance of emergency batteries can take a back-seat to daily operations and result in a natural disaster becoming a communications disaster. Similar concerns have been echoed by fire safety officers in the United States, prompting the introduction of the Maintainor, which maintains back-up batteries to deliver peak performance in emergency situation.
A PRIMER ON CHARGING
The standard OEM or consumer-priced battery charger is a "constant current trickle charger." Trickle chargers operate by delivering a steady, low-level, positive current for as long as it is connected to a power supply. Energy-storing ions are generated at one electrode in a battery cell and must move to the other electrode. If the current is sustained over an extended period of time, the ions concentrate on one side and create polarization, which causes heat generation, inadequate charging capacity, and a shorter life for the battery. Although they are an inexpensive consideration when purchasing a two-way system, they are NOT cost-effective. They can significantly increase the cost of operating and maintaining the system.
These slow, "overnight chargers" charge a battery in approximately ten hours and rely on the user to stop them when the battery has reached its maximum capacity. They are inexpensive and simple to design, but do not optimize the performance of the battery -- in fact, they actually contribute to its premature disposal. The low charge rate allows the chemical reactions to localize on the electrode surface, leading to dendrite growth. There is a high likelihood of overcharging, and, in the case of NiCd and NiMH, if the battery isn’t discharged first, voltage depression, or "memory effect" begins to occur.
Memory effect is often responsible for the early demise of batteries. When NiCd batteries and, to a lesser degree, NiMH batteries are recharged before they are fully discharged, electrodes passivate, decreasing the ability of the cells to accept a charge. When a battery is repeatedly charged without being fully discharged, operating time and performance deteriorate and it appears to die before its time. Most radios will stop operating before the battery can reach a low enough per-cell voltage to recover the voltage depression, so even if a user thinks the battery has been "run down," few batteries actually are fully discharged before they are recharged. This practice and the standard OEM constant-current "drop-in" chargers combine to sabotage NiCd and NiMH battery performance. Radio Maintenance Engineers try to compensate for this problem by periodically discharging, or conditioning, the batteries on special equipment. Conditioning helps, but it is time-consuming, and batteries never recover completely from repeated abuse.
Most OEM-upgrade fast chargers operate by increasing the constant current rate, charging the battery in only two or three hours. They usually have basic circuitry that terminates when the battery is fully charged, or decreases the charge current when the battery reaches a certain voltage, usually about 80%-90% charged. However, charging at a high constant current rate ignores the electrochemical process within the battery, which, over time, causes significant deterioration, similar to, or worse than the trickle charger. The result is reduced capacity with each charge, untimely wear-down and fewer charge/discharge cycles for the battery. Although these one-to-three-hour chargers are significantly faster, they require that the battery remain in the bay for an additional 30-60 minutes after the battery is charged.
Pulse-charging, introduced in the 60s, was the first improvement to the constant current trickle charge. Pulse charging operates on the principal of surging power into the battery in "pulses" of electrical current. One-second pulses of power are interspersed with rest periods, lasting just a fraction of a second. Interrupting the pulse current gives ions a chance to diffuse and distribute more evenly throughout the battery and return to normal levels routinely, thus reducing some of the negative effects of trickle charging. While developed to address the chemical process of batteries, pulse charging still ignores the chemical reaction and physical phenomenon taking place in the battery, and the likelihood of the battery not being fully discharged. It provides short-term fixes, i.e. charged batteries, but the costs are heavy -- shortened battery life and reduced charge capacity, which translates to batteries not lasting a shift between charges, or a year out of the box.
The second generation of pulse charging emerged in the 1970s to counter the problem of recharging batteries that aren’t fully discharged. This method, which is only used in a few high-end chargers, augments the rest period by adding a very short negative discharge pulse (depole pulse) interspersed with the positive charging pulses. The depole pulse is 2.5 times as strong as the charge pulse and is followed by another rest period. For many, this method seemed to solve some of the problems of traditional charging. Batteries return to balance more quickly -- speeding up charging rates to as little as one hour for a 700 mAhr battery -- and improving performance. The shortcoming to this approach is that the ion transport problem gets progressively worse as the battery is charged. The single discharge pulse method can only gain limited information about the state of the battery and the charge current cannot exceed the level which is acceptable at the end of the charge, when conditions are most limiting.
Even the OEM conditioners do not discharge the voltage low enough to recapture all the hidden capacity lost to memory effect. However, a new algorithm [pattern of current], discovered by Yury Podrazhansky and patented by ACT, discharges to the lowest possible level to return hidden memory capacity. Podrazhansky, a Russian immigrant with a background in electrical and radio frequency engineering, was busy searching for a solution to the problems plaguing his rechargeable batteries when he developed ACT’s patented Dynamic Electrochemical WaveformTM (DEW). It is this operating system that sets the ACTivator apart from other chargers.
Podrazhansky, Vice President of Research at Advanced Charger Technology (ACT), discovered that single, high-magnitude negative pulses cause ion transportation problems in the reverse direction, as well as excessive discharge of the battery, which increases charge time.
Podrazhansky also found that applying even shorter, multiple negative pulses with a much higher magnitude eliminates charging problems and actually benefits battery chemistries. The larger magnitude discharge pulses are inherently focused in the area of dendrites and help to remove them. When allowed to build up, dendrites can short-circuit a battery’s electrodes. The brief, high currents rapidly balance the ion concentration and improve the crystalline structure of the electrodes. In NiCd batteries, they momentarily pull the battery voltage down, resulting in the reversal of voltage depression. The improved balancing of ion concentration leads to a highly efficient charge process that enables a much higher charge current, yielding the shortest charge times possible and uniquely conditioning batteries as they are charged, eliminating the need to discharge first. Podrazhansky used patented his discovery and named it Dynamic Electrochemical WaveformTM (DEW) technology -- a charging waveform which intersperses variable length positive charging waves with multiple negative discharge waves.
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