Batteries clean up their act
We've made batteries much more environmentally friendly. Most of the harmful mercury is gone, and recycling programs are in full swing. But there's still much work to be done.
By Dan Strassberg, Senior Technical Editor -- EDN, February 4, 1999
  The batteries in 1999-model portable electronic products and cordless electric appliances are far more environmentally friendly than those that most manufacturers were installing five years ago. The improvements result from battery-industry initiatives, legislative cooperation, and the relentless march of technology. Still, this is no time for complacency. Each year, in the United States and Canada alone, users fail to recycle hundreds of millions of nickel-cadmium (NiCd) batteries that they should—and now easily could—recycle. Meanwhile, some promising new battery chemistries present environmental challenges of their own.Probably the most important improvement in the environmental impact of small batteries has been the move from the NiCd chemistry to nickel metal hydride (NiMH). In a landfill, when an NiCd battery's case ruptures or corrodes, cadmium can leach into the water supply. Cadmium is a toxic heavy metal that can harm people and animals that ingest it. NiMH batteries don't contain cadmium, and, despite some concerns about the toxicity of nickel, the US Environmental Protection Agency (EPA) does not classify NiMH batteries as hazardous.
NiMH batteries have substantially replaced NiCd units in new cellular and cordless telephones, laptop PCs, and related portable electronic products. Indeed, lithium-ion (Li-ion) and even newer lithium-polymer batteries have started to take over these electronic applications from NiMH. To each, its own But the situation differs in other types of equipment. NiMH is just starting to make inroads into cordless power tools and vacuum cleaners, in which NiCd still dominates. Cordless appliances and tools are extremely sensitive to cost and reliability. Operating time between recharges—a key attribute of NiMH and Li-ion—is less important. What's more, NiMH-battery suppliers say that NiMH is now at or approaching cost parity with NiCd if you compare the watt-hours per dollar that cells of a given size supply. When manufacturers first marketed NiMH cells, they offered approximately 60% more storage capacity than same-size NiCds, but NiCd suppliers claim to have narrowed that edge to approximately 15%. Although NiMH has established an enviable reliability record in electronics, some cordless-product manufacturers say that it has yet to establish its reliability in motor-drive applications. These experts assert that reliability in powering electronic devices does not guarantee reliability in power tools. Other manufacturers disagree. They insist that more than enough data exists to demonstrate NiMH's reliability for driving small motors. Nevertheless, battery design involves trade-offs between energy density (usually measured in watt-hours per kilogram) and peak power output. Most NiMH cells are optimized for energy storage. Manufacturers may have to produce different cells for different classes of service, although, so far, manufacturers have largely refrained from taking this step in batteries for handheld products. Portable-appliance motors draw order-of-magnitude-higher average currents than do typical electronic circuits. Cell phones draw a few watts; notebook PCs draw about 20W. Electric drills, on the other hand, can draw 200W peak and 60W average while making holes. Because batteries supply a fairly constant voltage under varying loads, output current varies a little more than linearly with output power. But self-heating is proportional to current squared, so temperatures in batteries for motor-drive applications can rise two orders of magnitude more than those in electronic-device batteries. Moreover, power-tool batteries are subject to more severe shock and vibration than are batteries in electronic products. NiMH for hybrid electric cars Notwithstanding the concern about high currents, several companies have developed and are evaluating large NiMH batteries for use in hybrid electric vehicles (HEVs). A typical HEV uses a small internal-combustion engine to charge a battery that drives an electric motor that propels the vehicle. Aside from chemistry, however, NiMH HEV batteries have little in common with NiMH appliance and cordless-tool batteries. Nevertheless, HEV batteries must supply hundreds of amperes when the vehicle is accelerating and must also accept large currents during dynamic braking. Designers of small batteries that must reliably deliver 10A or thereabouts can learn something from HEV-battery designs. In such areas as uninterruptible power supplies (UPSs), emergency-lighting equipment, and cordless electric lawn mowers, small sealed-lead-acid (SSLA) batteries continue to play important roles. These applications benefit from SSLA's low self-discharge rates and, unlike handheld devices, can usually tolerate SSLA's modest energy density. Proponents of battery recycling are quick to point out that a recycled NiCd battery is friendlier to the environment than a worn-out (spent) NiMH battery in a landfill. Inmetco, the company that recycles NiCd batteries for the Rechargeable-Battery-Recycling Corp (RBRC), uses a recovery process that yields nickel and cadmium of high purity for use in new batteries. RBRC is a nonprofit corporation that the rechargeable-battery industry established in 1994 to manage the North American NiCd-battery recycling program. Inmetco's process even ensures that the plastic parts become raw materials for the manufacture of new plastic products. Virtually nothing harmful finds its way into the water supply. Charge up to recycle RBRC designed the US and Canadian Charge Up to Recycle NiCd-battery-recycling program. More than 200 manufacturers and resellers of NiCd batteries and products that use the batteries support the RBRC. The recycling program began in earnest in late 1996. Today, you can find RBRC recycling containers in more than 20,000 locations throughout the United States and Canada. Most of these locations are retail stores that sell NiCd batteries and products that use the batteries. High-volume public- and private-sector users of NiCd batteries also act as recycling depots. Examples are metropolitan police departments that use large numbers of two-way radios. You can find the location of a recycling depot near you by calling 1-800-822-8837. Estimates of the number of NiCd cells that reach the end of life in any year are inexact, but a reasonable estimate for the United States and Canada is 400 million. Part of the problem with the estimates is that most people don't recycle individual cells; they recycle batteries that contain three to 16 cells. Unless you know the number of cells in each battery, you have a problem with counting cells. Officials at RBRC think that the average is approximately six cells per battery. The corporation estimates that it recycled 100 million of those cells in 1998. The RBRC expects to double the recycled percentage to 50% by 2002 and hopes to recycle 80% of spent NiCd cells in 2005. Achieving the current level of success took some doing. In 1996, after two years of operation, the RBRC had designed a sensible, cost-effective recycling program. Still, the organization found that its implementation efforts were stymied. The culprits weren't greedy corporations or an uncaring public. Instead, the very regulations that the federal government had set up to control toxic-waste hazards were at fault. Even though the batteries posed a hazard only if they weren't recycled, the regulations required recycling companies to treat the devices as hazardous waste. This rule made it economically unfeasible to collect and transport the batteries for recycling. The rule applied throughout the United States except in a handful of states that had passed separate hazardous-waste laws. Yet, because new batteries aren't waste, it was (and is) perfectly legal to ship them in quantities identical to those that were illegal for spent batteries. People who know even a little about NiCd batteries know that, as long as the battery cases remain intact, spent batteries present no greater hazard than do new ones. Moreover, even if the case ruptures, the cause of the most serious hazard is the leaching action of water. That cause does not exist if the batteries stay dry. In addition, neither the federal nor the state regulations applied to private individuals. So, people who removed worn-out NiCd batteries from service had no options except to hoard the useless devices or place them in the household trash. Therefore, regulations that were supposed to protect the public from toxic wastes effectively forced people to dispose of batteries in the way that did the most ecological harm. It's easy to blame an inept government bureaucracy for such senseless rules. However, the real culprits were the private citizens and organizations that pressured government officials into enacting those rules too quickly. A little thought about the categories of hazardous waste could have saved enormous amounts of wheel-spinning—and time. Without those delays, the RBRC program could have begun two years earlier, saving several hundred million NiCd cells from moldering in landfills and potentially polluting the water supply. Putting the situation right required an act of Congress. On May 13, 1996, the Battery Act (technically, the Mercury-Containing and Rechargeable-Battery Management Act of 1996) took effect. A few of the law's major requirements are:
You may ask why there is no program to add a refundable deposit to the price of NiCd batteries. If you even mention deposits to Norm England, president of the Portable Rechargeable-Battery Association (PRBA), you had better be prepared for a fight. England spent 15 years in the plastics industry. He knows all about deposits on bottles and cans. England bristles at the suggestion that battery manufacturers ever even discussed deposits. "Never happened," he snaps. Doing so, he argues, would probably invite federal prosecution of battery manufacturers for collusion to raise prices, a violation of antitrust laws. Moreover, the makers of most small rechargeable batteries have no interest in seeing deposits added to the price of their products. Deposits would just drive customers into the arms of suppliers of primary (that is, nonrechargeable) batteries, of which the most common type is alkaline. Alkaline batteries are quite environmentally friendly, especially now that manufacturers have modified the manufacturing processes to eliminate all but trace amounts of mercury. Still, replacing rechargeable batteries with nonrechargeable ones would not help to improve the environment. In fact, the result would be quite the opposite. If deposits are ever added to the prices of NiCd cells, it will be because of legislation at the state level. But England is confident that states will enact no such legislation. He points out that, since 1988, no state has enacted a "bottle law" requiring deposits on soft-drink and juice containers. He says that, in the states that have them, such laws have a terrible reputation with everyone they affect—bottlers, retailers, and consumers. He also claims that the laws have not reduced the litter that they were enacted to reduce. Getting the lead out Notwithstanding the NiCd-battery industry's opposition to deposits, deposits are a part of a model lead-acid-battery-recycling law that was drafted by Battery Council International (BCI), a lead-acid-battery trade association. BCI favors enactment of state laws that impose a mandatory $10-per-battery deposit. Lead-acid-battery-deposit laws exist in only a dozen states, some of which make the deposits voluntary on the part of the retailer. Moreover, the most common deposit is only $5 per battery. Still, BCI estimates that recycling of lead in batteries approaches 95% in the United States. Meanwhile, England points with pride to the 25% recycling rate that the RBRC's recycling program achieved in just its second full year of operation. He believes that those results demonstrate beyond a doubt that the battery industry's voluntary efforts are far more effective than any deposit program could be. Nevertheless, both the PRBA and the RBRC agree that the RBRC program could be still more effective. Some battery manufacturers suspect that many consumers who bring spent NiCd batteries to a store to be sure of finding exact replacements take home both old and new batteries. This situation is the fault of the store personnel who fail to remind the customer to drop off the old batteries in the RBRC container. According to RBRC Executive Vice President Ralph Millard, the RBRC's battle to get store personnel to remind customers about recycling will never end. Work-force turnover is high in retail businesses, and most store employees face heavy demands. Lithium and underground fires If you think that the only environmental problem with batteries relates to the use of heavy metals in some chemistries, you are incorrect. Although Li-ion batteries are free of heavy metals (lithium has a low atomic number), lithium's high degree of chemical activity can create environmental problems. When exposed to water, which is present in most landfills, the metal can burn, causing underground fires that are difficult to extinguish. Because the newer lithium-polymer chemistry contains more metallic lithium than Li-ion does, lithium-polymer batteries can be more difficult to handle. Recycler Toxco operates a facility for reclaiming the materials in batteries that contain lithium. Lead, a toxic heavy metal, has been a constituent of common rechargeable batteries longer than any other metal. Automotive storage batteries use the lead-acid chemistry. More recently, SSLA batteries have found their way into many common applications, such as UPSs and emergency-lighting systems. Uses of lead in batteries represent a large portion of the total uses of the metal. BCI estimates that 75% of US lead use is for batteries. Five states ban disposal of lead-acid batteries, and 38 have enacted laws governing their recycling. According to BCI, the 1994 recycling rates for lead-acid batteries, which approached 95%, exceeded those for aluminum cans (70%), newspapers (60%), and glass bottles (40%). UPS manufacturer MGE uses sealed-lead-acid batteries in most of its UPSs. The company offers minimal-cost replacement of any UPS whose lead-acid batteries require replacement. Even though the batteries within the units are sealed and present no hazard, most customers don't want to deal with opening the units and replacing the batteries. Barry Eisenberg, product manager for the company, says that most of these customers are afraid of coming into contact with the sulfuric acid in the batteries. "For all practical purposes, that can't happen in a UPS that uses sealed batteries, and that includes essentially all UPSs," says Eisenberg. The quick(silver) and the dead Another toxic heavy metal that once was part of many batteries but has now all but disappeared is mercury. Some small batteries in cameras and hearing aids used small amounts of mercury by design. The United States no longer permits sale of such batteries. Other more common batteries, such as alkaline, the most popular type of nonrechargeable battery, once contained more than trace amounts of mercury. The manufacturers added small amounts of mercury to achieve the desired characteristics. Early in this decade, under pressure from environmentalists, the battery industry re-engineered its manufacturing processes. The result is that the only mercury that remains in alkaline batteries is in the impurities in other materials. The battery characteristics no longer depend on the presence of mercury. The process modifications neither degraded the battery performance nor significantly raised the cost. By law, batteries sold in the United States may no longer contain more than trace amounts of mercury. Charge up to charge up The design of chargers and battery packs has become somewhat more complex as a result of the changes in battery chemistry. The added complexity especially affects products that have used NiCd but now use NiMH, Li-ion, or lithium polymer. First of all, both NiCd and NiMH produce a nominal output voltage of 1.2V per cell, whereas the lithium chemistries produce a nominal 3.6V per cell. Fortunately, to manufacture small rechargeable batteries, manufacturers combine cells that are produced by the hundreds of millions. They place these cells into batteries, or "battery packs," that they produce in much smaller quantities. Often, the "smaller" quantities reach hundreds of thousands or millions, however. To design a new battery pack, you can sometimes change from NiCd to NiMH simply by replacing the NiCd cells with NiMH cells. The result is usually a battery with greater capacity between charges than the original. Greater capacity is almost never a problem, but the NiMH battery's higher cost can be a problem. If a mechanical redesign of the battery pack is feasible, the solution to the cost problem might be to substitute smaller cells, say four-fifths C, or "Sub C," for C. The smaller NiMH cells offer capacity close to that of the larger NiCd cells at a price approaching that of the NiCd cells. An added advantage of a redesign can be reduced sensitivity to voltage depression (see sidebar "Memory effect? No, voltage depression"). A more subtle problem is NiMH cells' greater sensitivity to elevated temperatures. Particularly if the charge regime includes a quick-charge mode, the NiMH charger must usually safeguard against overcharging and battery overtemperature. In most cases, NiCd chargers need no such safeguards. A simple safeguard technique that some manufacturers use is to include a thermistor in the battery pack. The charger monitors the battery temperature via the thermistor (often with simple circuitry) and cuts off charging if the temperature becomes too high. Compatibility and confusion Unless designed to handle both battery types, a charger that monitors the battery temperature in this way most likely works only with NiMH batteries. Older NiCd battery packs don't include the temperature sensor that the charger needs to operate. Thus, chargers designed for the older batteries will be unable to monitor the battery temperature and won't work with NiMH batteries. Industrial customers that add NiMH-powered devices to their tool inventories but that want to delay NiCd replacement until the old batteries wear out need separate NiCd and NiMH chargers. Otherwise, the customer must immediately replace all NiCd batteries or must replace all chargers with new ones that handle both battery types. The charger-design problem can become still more complex if you switch a product from NiCd (or NiMH) to one of the lithium chemistries. Lithium cells have a terminal voltage three times as high as those of NiCd or NiMH cells. If you design a product in expectation of a future change to a lithium chemistry, you might make the nominal battery voltage a multiple of 3.6V. This approach lets you change chemistries by reducing the number of cells by two-thirds or placing groups of the higher voltage lithium cells in parallel. If these approaches don't work, the product—not just the battery pack—probably requires a major redesign. A new technology simplifies charger designs in such situations. "Smart batteries" contain sophisticated ICs that communicate with the charger and, with other advanced ICs in the charger, adapt the charger's characteristics to those of the battery. Incorporating such ICs in the battery pack can make it simpler for one charger to safely charge several types of batteries. The charger and the smart batteries must, of course, be designed to work together. Reference
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 Dan Strassberg, Senior Technical EditorYou can reach Senior Technical Editor Dan Strassberg at 1-617-558-4205, fax 1-617-928-4205, ednstrassberg@cahners.com. |
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The US Battery Act of 1996 helped to overcome obstacles to recycling NiCd batteries. Those roadblocks encouraged users to send the batteries to landfills—the worst possible means of disposal.
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