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Rayovac Corporation-Renewal Rechargeable Alkaline Battery System (Renewal System)

Final Decision to Certify Hazardous Waste Environmental Technology

The California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) has made a final decision to certify the following company’s hazardous waste environmental technology listed below:

Applicant: Rayovac Corporation, PO Box 44960, 601 Rayovac Drive, Madison, WI 53711-2497, a manufacturer of household batteries. Technology: Renewal® rechargeable alkaline battery System (Renewal® System).

Chapter 412, Statutes of 1993, Section 25200.1.5., Health and Safety Code, enacted by Assembly Bill 2060 (AB 2060 by Assemblyman Ted Weggeland) authorizes DTSC to certify the performance of hazardous waste environmental technologies. Only technologies that are determined to not pose a significant potential hazard to the public health and safety or to the environment when used under specified operating conditions and which can be operated without specialized training and with minimal maintenance may be certified. Incineration technologies are explicitly excluded from the certification program.

The purpose of the certification program is to provide an in-depth, independent review of technologies at the manufacturers’ level to facilitate regulatory and end-user acceptance.

DTSC makes no express or implied warranties as to the performance of the manufacturer’s product or equipment. The end-user is solely responsible for complying with the applicable federal, state, and local regulatory requirements. Certification does not limit DTSC’s authority to require additional measures for protection of public health and the environment.

By accepting certification, the manufacturer assumes, for the duration of certification, responsibility for maintaining the quality of the manufactured equipment and materials at a level equal to or better than was provided to obtain certification and agrees to be subject to quality monitoring by DTSC as required by the statute under which certification is granted.

DTSC’s proposed decision to certify was published on January 23, 1998, in the California Regulatory Notice Register 98, Volume No. 4-Z, pp. 190-195. Written comments in relation to the proposed certification received during the public review and comment period have been duly considered in the final certification as presented here. DTSC’s final certification shall become effective on April 6, 1998.

Additional information supporting DTSC’s final decision is available for review at:

California Environmental Protection Agency
Department of Toxic Substances Control
Office of Pollution Prevention and Technology Development
P.O. Box 806
301 Capitol Mall, 1st Floor
Sacramento, California 95812-0806
Attn: Mr. Terry Escarda (916) 322-7287

A description of the technology to be certified, the certification statement and the certification limitations for the technology of the company listed above follows.




Rayovac Renewal® rechargeable alkaline battery System (Renewal® System)

Rayovac Corporation; Madison, Wisconsin


Applicant & Manufacturer:
Rayovac Corporation
P.O. Box 44960
601 Rayovac Drive
Madison, WI 53744-4960

Technology Description

Rayovac has developed and introduced to the market a secondary alkaline battery and recharging system called the Renewal® rechargeable alkaline battery System (Renewal® System). The Renewal® System technology consists of rechargeable alkaline batteries, a charging device/method, and pertinent designer and consumer literature. The batteries and charging device are briefly described below; the associated literature is described in the evaluation report.

Consumer, or household, batteries of nominal 1.5 volts, suitable for powering consumer products such as flashlights, clocks, portable stereos, etc. are generally available in standard sizes AAA, AA, C, and D. Typically, these batteries are dry cell alkaline (e.g., potassium hydroxide electrolyte paste with no free-standing liquid, and zinc and manganese-dioxide (Zn-MnO2 ) electrodes) or nickel-cadmium (NiCd). Alkaline batteries traditionally have been primary (non-rechargeable) whereas NiCds are secondary (rechargeable).

To do this, Rayovac reformulated nonrechargeable alkaline zinc-manganese batteries so that they could be recharged. To be rechargeable, the manganese dioxide electrodes are reversible only if the manganese dioxide cathodes are discharged to the point where the MnO2 is converted to Mn2O3. If discharge occurs beyond that level an irreversible phase change occurs which renders the manganese dioxide electrode nonrechargeable. Rayovac used several approaches to ensure reversilibility, including designing the cell to be anode (zinc) limited, and providing electronic means to prevent overdischarge of the MnO2 electrode in some devices that use Renewal cells.

Rechargeablility was further accomplished by reducing the amount of active ingredients, zinc and manganese dioxide, thereby increasing the internal void space so that hydrogen gas generated during recharging could be contained within the battery, thus preventing rupture and leakage of alkaline electrolyte. Silver was added to act as a catalyst in recombining the hydrogen gas and lead was added to the zinc gelling agent as a metal corrosion inhibitor.

Rechargeable batteries are susceptible to “capacity fade”. Capacity fade refers to the loss of energy capacity each time the battery is charged. Each time the battery is discharged and subsequently recharged, the cell does not regain all of its previous capacity. Eventually the battery’s capacity fades to the point that there is not enough capacity remaining for the cell to be useful, and must be discarded. The amount of capacity needed for the cell to be useful depends on the application of the battery and the user’s preferences. For Renewal® batteries, capacity fade is sensitive to depth of discharge, which is related to discharge rate and cut-off voltage. “Depth of discharge” refers to the amount of energy withdrawn from the cell by converting the MnO2 to Mn2O3. Limiting the depth of discharge will reduce the loss in available capacity, i.e., capacity fade, for each successive discharge cycle.

Depth of discharge can be controlled by setting cut-off voltage. For a specific cut-off voltage, more fade occurs at lower discharge rates because the cut-off voltage is reached later due to less pronounced internal resistance losses, and thus more capacity is removed. Therefore, setting a cut-off voltage higher for low discharge rates will reduce capacity fade. For a specific discharge rate, more capacity fade will occur when the batteries are discharged to a lower cut-off voltage because more capacity is removed from the cell. At higher discharge rates, the internal resistance losses will cause the voltage to drop before all of the available capacity is withdrawn. Internal resistance losses are higher at higher discharge rates because the cells are of the “bobbin” type, as opposed to spiral-wound. This “bobbin” design allows high capacity, but causes higher internal resistance. In either case, not all the removed capacity can be regained because the chemical reactions are not completely reversible, therefore, after a certain number of cycles the batteries will no longer regain useful capacity.

The Rayovac Renewal® System charging device is known as a Power StationTM. The Power StationTM charger comes in two sizes: PS1 for any combination of AA and AAA batteries, and PS2 for any combination of one to eight AA, AAA, C, and D batteries.

The Power StationTM and Renewal® batteries are designed so that only Renewal® batteries can be charged by the Power StationTM without compromising the ability of the Renewal® batteries to be used in electronic devices. This is accomplished by two methods, one for battery sizes C and D, and another for sizes AAA and AA. For example, Renewal® sizes AAA and AA have an exposed metal layer on the top of the cell case whereas conventional alkaline cells have an insulating layer covering this surface. When any AA or AAA size battery other than a Renewal® is placed in the charging unit, the charge contact is blocked by the plastic label overwrap of the cell and no charge current can be applied.

According to Rayovac, Renewal® batteries are designed to be able to be charged only by Rayovac’s charging device and method because, “Methods of charging which have been used in NiCd systems such as continuous trickle-charging or constant-current fast charge are not suitable for use with rechargeable alkaline batteries. The rechargeable alkaline cells are not tolerant of high continuous charge currents, and may be damaged if high current is forced into them after they have reached a partially recharged state.” Products which have Rayovac’s charging methods built in can use other types of batteries, but will only charge Renewal® batteries.

The charging device uses a pulse charge method. Fixed amplitude, variable duty cycle pulses are applied to the battery during charge. The pulses are limited in amplitude by current-limiting resistors. The duty cycle is modulated by a control chip specifically designed for use in the Renewal® Power Stations. The average value of the charging current applied to the batteries is gradually reduced as the open-circuit voltage of the battery increases during the charge. A Light Emitting Diode is activated when the battery is properly placed into the charger; it is deactivated when three consecutive charge pulses are disabled (the battery has stayed above the 1.65 volt reference value for this period of time). Rayovac claims that an advantage to this type of charging device is that there is less likelihood of damage to the battery due to overheating or overcharging.

Basis for Certification

Background information and technical literature in support of the technology as a product substitute for primary alkaline batteries and, in some applications, as an alternative to NiCd batteries, were obtained from a variety of sources, including Rayovac-supplied data and literature; independently generated data; DTSC generated data; consumer response surveys; regulatory experts, and industry; professional associations; publication articles; and a limited number of end-users.

DTSC reviewed scientific literature, including descriptions of battery technologies and applicable patents to determine the scientific basis for the technology. DTSC also reviewed Rayovac design and consumer usage guidance, as well as publications, to determine battery selection criteria and typical applications. Pollution prevention measurement criteria were provided by DTSC pollution prevention experts. American National Standards Institute (ANSI) tests of performance as measured by hours of service were used to generate performance data. Performance data generated by Rayovac and data generated by an independent battery testing firm were evaluated by DTSC as part of the certification. Lawrence Livermore National Laboratory independently reviewed the initial results of the performance tests. DTSC also reviewed and evaluated chemical analyses generated by Rayovac and DTSC Hazardous Materials Laboratory of the Renewal® batteries to determine if the hazard of the combined toxic metals content of the Renewal® batteries was less than, similar to, or greater than that of the nonrechargeable alkaline zinc manganese batteries. The Cal/EPA Office of Environmental Health Hazard Assessment assisted with this evaluation of hazard. Finally, DTSC reviewed other organizations’ evaluations of the Renewal® System and conducted limited surveys of end-users.

DTSC based the Renewal® System’s certification as a pollution prevention technology primarily on the Renewal® System’s ability to prevent the generation of nonrechargeable batteries requiring disposal. Fewer batteries need to be disposed because more hours of service are obtained by recharging the Renewal® batteries. In general, under modified ANSI test procedures which simulated typical consumer applications, after 25 discharge/charge cycles, Renewal® batteries provided total hours of service equal to at least seven nonrechargeable alkaline batteries.

The Evaluation Team found the following:

1. Public health risks resulting from disposal of Rayovac Renewal®, or other batteries, are difficult, if not impossible, to estimate because potential exposures to environmental concentrations of landfilled battery metals are not known.

2. Although Rayovac Renewal® batteries contain greater amounts of lead and silver than Rayovac primary alkaline batteries, the benefits from disposing of significantly fewer primary alkaline batteries outweighs possible increased risks from environmental exposures to lead and silver derived from discarded Renewal® batteries.

3. Pollution can be prevented by reducing the amount of alkaline batteries sent to landfills by repeatedly charging and reusing Renewal® batteries. The amount of pollution prevented depends on many factors such as application, discharge rate, and voltage endpoint.

This certification is strictly limited to the pollution prevention achieved through use of the entire Rayovac Renewal® System as specified in the following certification statement. The Renewal® System includes the batteries, charging unit, and pertinent literature. The charging unit is an integral part of the system. Using other chargers may damage the batteries or lead to early failure, thus their use is excluded from this certification. The following recommended certification statement, specific conditions, and limitations are based on the findings by the Evaluation Team.

Certification Statement

Under the authority of Section 25200.1.5. of the California Health and Safety Code, the Rayovac Renewal® rechargeable alkaline battery System (Renewal® System) is hereby certified as a Pollution Prevention Technology subject to the conditions including the limitations/disclaimer set forth below. The Renewal® System consists of the Renewal® batteries, currently available as 1.5 volt (nominal) in sizes AAA, AA, C, and D; the Power StationTM charging unit, and pertinent technical and consumer literature. The Renewal® System can prevent pollution by reducing the quantity of disposed primary alkaline batteries of the same size in most applications for which the primary alkaline batteries are appropriate. Under standard laboratory test conditions, that simulated typical consumer product applications, after 25 charging cycles to specified voltage cutoff points at specified resistance loads, the Renewal® System’s batteries supplied hours of service equivalent to seven or more primary alkaline batteries of the same size. The actual number of obtainable cumulative hours of service, and the number of recharge cycles necessary to obtain those hours of service, depends on a number of factors, such as depth of discharge, frequency of charging, type of application, and other user practices.

Limitations of Certification

DTSC makes no express or implied warranties as to the performance of the Rayovac Renewal® System. Nor does DTSC warrant that the Renewal® System is free from any defects in workmanship or materials caused by negligence, misuse, accident or other causes.

However, DTSC believes that the Renewal® System can be used in place of primary alkaline batteries in most applications for which primary alkaline batteries of the same size are appropriate. DTSC further believes that potentially significant numbers of primary alkaline batteries can be diverted from disposal by replacing primary alkaline batteries with Renewal® System, based on DTSC’s review of data submitted by Rayovac and other pertinent independent information. However, DTSC notes that only Rayovac-manufactured primary alkaline batteries were reviewed in depth as part of the certification evaluation; the performance and toxicity of other manufacturers’ primary alkaline batteries may be somewhat different than Rayovac’s primary alkaline batteries.

This certification is limited to use of the Renewal® System to replace primary household alkaline batteries. When considering replacing other batteries such as carbon-zinc, mercuric oxide, or nickel-cadmium, a wide range of factors such as application, cut-off or end-point voltage, capacity, rate capability, cycle life, shelf life, self-discharge rate, temperature sensitivity, and cost should be considered.

Specific Conditions

1. Continuous Quality Control/Quality Assurance; Monitoring by DTSC

By accepting this certification the applicant assumes, for the duration of the certification, responsibility for maintaining the quality of the manufactured batteries, charging units, and instruction manuals and other documentation at a level equal to or better than that which was provided to obtain this certification. The applicant also agrees to be subject to quality monitoring by DTSC, as required by the law under which this certification is granted.

2. Modifications and Amendments at the Request of the Applicant

Modifications and amendments to this certification may be requested by the applicant. Until applicable regulations are adopted, such requests will be processed according to the provisions under which this certification was issued; following the adoption of regulations, such requests will be processed as provided for in the regulations.

3. Requirements and Conditions of New Regulations.

This Certification is issued under the authority of the California Environmental Technology Certification Program. As a result, this certification will be subject to the conditions set out in the regulations to be developed, such as the duration of the Certification, the continued monitoring and oversight requirements, and the procedures for certification amendments, including decertification.

4. Certification Reference

The holder of a valid hazardous waste environmental technology certification is authorized to use the certification seal (California Registered Service Mark Number 046720) and shall cite the certification number and date of issuance in conjunction with the certification seal whenever it is used. When providing information on the certification to an interested party, the holder of a hazardous waste environmental technology certification shall at a minimum provide the full text of the final certification decision as published in the California Regulatory Notice Register.

5. Encouraging Proper Disposal

Rayovac, when describing the Renewal® batteries as nonhazardous waste, shall plainly inform consumers that this description applies only to current federal regulations, and that consumers should follow applicable state and local laws, regulations, or programs for proper disposal. In California, participating household hazardous waste collection programs should be used for disposal when appropriate and feasible. Of course, recycling of all spent batteries is encouraged.

Applications of the Renewal® System

Typical consumer applications of household batteries include toys and games, portable audio equipment, cameras, sporting goods equipment, test equipment, personal care products, hearing aids, portable data terminals, sub-notebook computers and personal digital assistants, watches, flashlights, lanterns, and cordless or cellular phones. Sometimes the battery is a built-in part of a consumer product; in those cases the battery may or may not be rechargeable. A portable electric razor is one example of such a product where the built-in battery may be rechargeable.

Choice of battery depends on application; no one battery is the optimum choice for every application. Design and end-user considerations include application, frequency of use, size, weight, energy capacity, maximum continuous and peak rate capability (current), self-discharge rate (storage life), temperature sensitivity, environmental impact, and cost. Household battery users should consult consumer product specifications and battery selection criteria when evaluating what type of battery to choose.

The Rayovac Renewal® System is not appropriate for applications such as high current demand portable electric power tools such as electric drills. Nickel-cadmium batteries are better suited for such applications. NiCd batteries are a good choice for applications requiring high continuous currents (for example, currents above 250 mA when using size AAA, and above 400 mA when using size AA batteries), many cycles, frequent use, and deep discharge. Also, devices such as photoflashes and video camera recorders may require more current than Renewal® batteries can deliver.

In general, nonrechargeable alkaline batteries are good for applications which are single use (e.g., disposable devices), require or desire high capacity (e.g., toys, portable stereos), or long storage life (e.g., emergency lighting and communications). Renewal® batteries are appropriate for applications that need high capacity, low self-discharge characteristics, and rechargeability. Rechargeable alkaline batteries are candidates for applications where nonrechargeable alkaline batteries are appropriate. However, rechargeable alkaline batteries such as the Renewal® System batteries are a better choice if the devices are used frequently, use low to medium currents (150 – 400 mA for size AA), and have cutoff voltages of 0.9V or greater. Cutoff voltages lower than 0.9V may allow deep depth of discharge leading to undesirable fade capacity under conditions of very low current and long time of use.

The Renewal® System is especially well suited for intermittent-discharge applications which may not fully drain the batteries prior to each recharge because they do not experience significant capacity fade under those conditions. When fully drained, Renewal® batteries experience capacity fade — the capacity of the cell will be lower in comparison to the previous cycle. Thus, for example, they are appropriate for applications such as emergency lighting, which may require long storage life then frequent use; palm-held computers, cordless or cellular phones, and electric razors, which may require intermittent use; and portable music devices and toys, which require low to moderate discharge rates and high capacity.

Regulatory Implications

DTSC’s Certification is based on the technology’s performance and by itself does not change the regulatory status of alkaline battery systems; it should, however, facilitate and encourage the acceptance of this technology for pollution prevention purposes. When discarded, both Rayovac primary alkaline and rechargeable zinc-manganese dioxide alkaline batteries are considered hazardous waste in California due to zinc content — discarded Renewal® batteries may also be a hazardous waste in California due to silver content. Other manufacturers’ zinc-manganese dioxide alkaline batteries would also be expected to be hazardous in California due to total zinc content.

Duration of Certification

This certification will remain in effect for three years from the date of issuance, unless it is revoked for cause or unless a duration for certifications different from that specified in this certification is adopted in regulations. If a different duration is specified in regulations, the duration of this certification will be that provided for in the regulations, beginning from the date of the issuance of this certification.