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GR-3150: Lithium Battery Certification Levels Based on Criteria For General Product, Safety, and Performance, Part 1
Oct 1, 2007

by Jude Ken-Kwofie

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Copyright 2007 © Telcordia Technologies, Inc. NEBS is a trademark of Telcordia Technologies, Inc.

Editor’s Note: This is the first article in a two-part series on Telcordia’s new GR-3150-CORE standard, covering generic requirements for lithium batteries used in telecommunications facilities. Part 2 will be published in the November issue of Conformity.

Telecom carriers have relied on the standby and emergency power of conventional batteries to enhance network reliability, sustain communications activity, limit FCC interactions and retain customer satisfaction during AC power interruptions and outages in central office (CO), outside plant (OSP) and customer premises facilities. However, this trend may change with the introduction of rechargeable large format lithium batteries.

The Emergence of Lithium Batteries in the Telecommunications Environment
The decentralization of telecommunications networks placed a large number of remote terminals in the stressful conditions of the OSP. It is well known that telecommunications carriers are concerned with the reliability and performance of presently embedded OSP batteries. The unexpected and untimely burden and expense of field engineers replacing weak or failed batteries is a frustration to many carriers. Carriers introducing broadband services are focused on minimizing costs and desire a truly maintenance-free battery product that can provide remote monitoring, offer the reliability of flooded CO cells, operate in extremely cold and hot environments, and provide great energy density.

As a result, within the last few years, carriers have shown interest in deploying rechargeable, maintenance-free, lithium batteries in their outdoor networks.

The Case for Lithium-Battery Generic Requirements
Researchers have been very interested in the energy-storage traits of lithium batteries. Telcordia researchers, for instance, invented a plastic lithium-ion (PL-iON)¹ technology that superseded today’s commercially available lithium cells. This research and the research of other organizations established that lithium batteries can be a viable standby and emergency power option. The lithium battery’s lightweight, high specific energy, high cell voltage (e.g., up to 5 V), and potential for a wide operational range provided this positive outlook.

Researchers also realized that a greater emphasis would need to be placed on safety. Why? Because of lithium’s high specific energy and potentially violent reaction with air or moisture, researchers understood that lithium batteries, if poorly manufactured or mistreated electrically, mechanically, or thermally, could fail in an unsafe manner. The United Nations lithium battery testing regulations, the recent major recalls of millions of lithium-ion cells, the UPS cargo fire in Philadelphia, and the FAA’s push to regulate the transport of lithium battery packs on airline flights are evidence of the researchers’ concerns.

These recent challenges have not stymied the commercialization of the technology in other industries. Focused discussions, manufacturing refinements, testing and inspection processes, improving engineering of protection devices to lessen the effects of electrical, mechanical, and thermal abuse, and the development of more temperature stable cell materials have all helped to continue the commercialization.

Similar to other industries, the telecommunications battery community also does not want these challenges to impede the use of this technology. Therefore, to address these challenges, a new Generic Requirements document (GR) was deemed necessary. GR-3150, Generic Requirements for Secondary Non-Aqueous Lithium Batteries, was developed by Telcordia and several members of the telecommunications industry, and provides vendor-neutral and industry-approved testing of general product design, safety, and performance requirements.

For telecommunications, industry discussion and consensus prior to full deployment is important because:

Lithium Can React Violently: Lithium is very reactive and will oxidize violently in the presence of air or moisture. GR-3150 requirements were developed to evaluate the integrity of the battery construction and assess the hazard potential of lithium batteries before the decision for full deployment is made.
NEBS™ Testing Is Not Enough: Third-party NEBS testing provides physical protection requirements for all network elements, and helps to identify environmental compatibility problems before production. To receive NEBS compliance, a network element such as a battery must undergo a series of environmental, mechanical, and electrical tests. A battery cannot be deployed in the field without complying with NEBS.

However, NEBS does not validate performance requirements, nor anticipate the possible failure modes and responses of lithium batteries. Complying with NEBS, therefore, does not necessarily mean that a battery will operate and perform as expected over its life. Consensus on the electrical, environmental, mechanical, physical design, battery management system, quality and reliability, documentation, and training requirements beyond NEBS is needed to determine if lithium batteries will perform as expected and will not endanger staff or infrastructure.

Verifying Electronics Reliability: Telcordia SR-332, Reliability Prediction Procedure for Electronic Equipment, stipulates that the electronics used in the network should provide a minimum mean time before failure (MTBF) failure. This metric is especially important for the safety circuits that govern lithium cells. Premature failure of the safety circuitry could result in battery system failure and loss of back-up power. It is the responsibility of carriers to make sure that supplier electronics reliability calculations are correct and provide adequate results. Generally, any additional circuitry decreases system reliability but, in the case of lithium batteries, the safety concerns go beyond the potential reduction in reliability.

Figure 1: Laptop flames at conference

Figure 2: UPS cargo plane on fire due to lithium battery mishap

GR-3150 Meets the Challenge
GR-3150 is the first vendor-neutral and concise GR document that addresses the use of telecom-grade, rechargeable, non-aqueous, large-format lithium batteries. With several funding participants from the battery/telecom industry to lend expertise in its development, Telcordia GR-3150 includes 154 generic² requirements, 7³ conditional requirements, 14⁴ objectives, and no conditional objectives⁵ or conditionals⁶, all grouped into three criteria levels to address product selection. In total, there are 175 requirement objects in GR-3150, categorized according to general product , safety, and performance.

GR-3150-CORE is organized into 6 major sections, 3 appendixes, and an ROI list. Sections 1 through 4 are described in the remainder of this article. Sections 5 (Performance Criteria) and 6 (Service Life Criteria), as well as the appendixes and ROI list, are described in Part 2 of this series, which will be published in the November issue of Conformity.

Section 1, Introduction
This section provides the purpose and scope, lithium battery general product and safety and performance criteria levels, and explanations of the requirements terminology and labeling conventions employed in GR-3150-CORE.

Also included is a section on testing criteria (Section 1.7, “Test Criteria”). The test criteria section presents criteria necessary for testing, evaluating, and qualifying lithium batteries. The criteria cover general test information, sample selection, size, retesting, measuring, data acquisition, reporting of results, root cause analysis, and specifications for pre- and post-test functional verifications.

The complexity of the criteria associated with safe and efficient lithium battery operation in the field requires qualification of the technology to aid manufacturers in their development of battery models, and users in their selection of the product that meets their needs. GR-3150 defines three groups of general product, safety and performance criteria levels to simplify product qualification and selection. These levels are defined as follows:

Level I — Safety and Compatibility compliance provides the basic criteria considered necessary for the introduction of lithium batteries in telecommunication networks. Level I is considered the first phase in the process to achieve full deployment.

Compliant Level I batteries are considered first product versions or prototypes that may not be fully featured and may be flawed. As prototypes, Level I batteries can fail unexpectedly. Thus, Level I batteries are not designed for full operability and are not ready for full deployment. Level I batteries should not be operated in adverse conditions and are suited for highly-controlled laboratory use.

Level II — Safety and Limited Operability compliance provides the assurance that batteries, when deployed in more adverse conditions and less supervised representative telecommunications environments than those specified in Level I, can operate and sustain network activities following misuse, dysfunction, or abuse and, if necessary, fail in a safe manner.

Compliant Level II batteries are also not considered ready for full deployment, but offer improved safety and performance in harsher environmental conditions and less supervised locations than their Level I counterparts.

Level III — Safety and Full Operability compliance provides the assurance that batteries are DC power plant compatible, can operate under a full range of environmental conditions, can sustain network activities following misuse, dysfunction, or abuse and, if necessary, fail in a safe manner. Complaint Level III batteries are considered ready for deployment in the OSP.

Table 1 presents the distribution of general product, safety, and performance requirements grouped within the three level compliance framework.

Criteria	Level I	Level II	Level III
General Product Criteria	Quality - Product Samples Documentation and Training Physical Design Electrical Safety Bonding and Grounding Self-Heating and Surface Temperature Battery Management System Fail-Safe Design Reliability Features Physical Design Manufacturing Status and Alarms Accuracy of Measurements	Reliability Quality - Failure Mode and Effect Analysis	Quality - TL9000, Product Changes Documentation and Training Reliability - Fail Safe Design
Safety	Overcharge External Short Circuit External Reverse Polarity Overdischarge High-String Voltage Conducted/Radiated Emissions Lightning and AC Power Fault Handling Shock - Packaged/ Unpackaged	Simulated Telecom Environmental Cycles Immersion (Flooded Conditions) (CR) Overcharge External Short Circuit External Reverse Polarity Overdischarge Conducted/Radiated Immunity System-Level ESD System-Level EFT (O) Earthquake Transportation Vibration	Fire Propagation and Projectile Hazard Characterization Simulated Brush Fire (CR) Operating Altitude Overcharge External Short Circuit External Reverse Polarity Overdischarge 16-Foot Free-Fall Shock (Unpackaged) Crush Low-Level Vibration Resistance
Performance	Float Voltage Capacity Recharge Time End of Discharge Voltage	Cycling Temperature and Humidity During Transportation and Storage Immersion (Flooded Conditions) (CR) Shelf Life and Charge Retention Particulate Contaminant and Corrosive Gas	Cold Temperature Start (CR) Salt Fog Exposure Extended Outages

Table 1: GR-3150-CORE general product, safety, and performance criteria levels

Section 2, General Product Information
This section provides a description of the lithium battery technology and common issues found when operating the technology.

Lithium batteries are intended for continuous float operation under the range of acceptable environmental conditions, and are designed to provide energy for infrequent discharges of durations ranging from a few minutes to several hours. As mentioned earlier, lithium can become violent when exposed to air or moisture. For this reason, products covered in GR-3150 are comprised of a non-aqueous liquid or polymerized electrolyte. The electrolyte provides conductivity between lithiated positive active material and metallic lithium or lithiated negative active material of a lithium cell. (Lithiation is the process of inserting lithium ions and electrons in the active materials of the lithium battery.)

Also, products covered in GR-3150 are outfitted with a battery management system (BMS). The management system is an intelligent electronics system designed to protect cells by operating them within a predefined voltage, current, and temperature safety parameter. The management system suspends operation and can transmit status and alarm signals to users and support network equipment when an operational parameter is violated.

The BMS consists of multiple levels of protection designed for redundancy. Intelligence must be coupled with the lithium electrochemistry to assist in battery survival and to optimize performance.

Although the inclusion of a BMS increases system complexity, it is considered necessary for the operation of the lithium batteries at this stage in their development. The active management of battery operation is required because of the high reactivity of lithium with air and water, imbalances in charge with component cell(s), and the limited tolerance of cell materials to misuse or abuse. There may be a point in time when lithium batteries can operate safely and efficiently without the management system.

Products covered in GR-3150 can also be shipped as cells or multi-cell modules requiring series connections and external electronic control assembly, as well as batteries shipped fully assembled as 48 V systems.

Anode or Negative Active Material	Electrolyte	Cathode or Positive Active Material
Lithium Metal
Li-metal	Solid Polymer Electrode (SPE)	Intercalation Compounds
Lithium Ion
Carbon (Petroleum or Pitch Coke Graphite) Metal Alloys (e.g. Li-cobalt-tin) Intercalation Compounds (e.g., Lithium Titanate)	Organic Liquid Electrolyte Organic Gelled Liquid or Solid Polymer Electrolyte Inorganic Solid Electrolyte	Lithium-Containing Intercalation Compounds Organic Compounds

Table 2

Figure 3

Section 3, General Product Criteria
This section contains general product criteria covering the areas of lithium battery quality, reliability, documentation and training, environmental, physical design, electrical safety, bonding and grounding, illumination, self-heating, surface temperature, and the BMS, noted in the discussion of Section 2 above.

Section 4, Safety Criteria
This section of GR-3150-CORE provides safety requirements for lithium batteries. The requirements address safety issues regarding overcharge, overdischarge, external short circuit, external reserve polarity, high string voltage, fire propagation and projectiles, simulated brush fire, simulated telecom environmental cycles, operating altitude, electromagnetic compatibility, handling, earthquake, vibration, crushing, and water-immersion events.

A battery’s response to typical electrical, mechanical, and environmental misuse or abuse events can be hazardous to network personnel and infrastructure. In the safety section, potential hazards are associated with battery service are defined. The hazards, in order of decreasing magnitude, are:

Explosion — Forceful fragmentation of battery
Fire — Emission of flames
Venting — Intended release of gas or solid through a designed safety feature
Leaking — Unintended release of gas, liquid, or solid not as a result of venting

These hazards form the basis for the safety pass-fail or acceptance criteria. Explosion and fire hazards are considered catastrophic since they can injure network personnel and destroy network infrastructure. GR-3150-CORE does not consider venting or leaking hazards as safe or permitted during normal operation. However, these hazards are permitted when the battery is intentionally forced to fail.

The goal of the safety testing is to aid to carriers, emergency policy makers, first responders, and manufacturers to understand the hazards associated with battery service. All hazards are considered severe.

In Part 2...
Descriptions of the safety tests will be provided in Part 2 of this series of articles, which will appear in the November issue of Conformity. n

Conventional batteries include:

1.    Lead-acid based batteries

A.    Flooded Rectangular/Round Cells — Carriers, for over 30 years have been satisfied with the reliability of flooded lead acid round 2 V cells, which operate in the climate controlled environment of the Central Office. To match the DC plant voltage of -52.08 V, 24 cells are series connected to form batteries which are placed in parallel with rectifiers for continuous network operation even when commercial AC fails. Batteries are typically sized to provide 210 amperes for 8 hours or 1680 Ahs (ampere hours)s. Cells weigh close to 350 pounds and have an expected life of 15 to 30 years. The emergence of digitial loop carrier technologies, allowed carriers to provide network functionality beyond the confines of the Central Office. With the push for network decentralization in the 80’s, carriers seeked to provide network functionality in the uncontrolled and harsh environmental conditions of remote sites and the outside plants. For this transformation, carriers desired back-up batteries with round cell life, and reduced water loss, maintanance costs, and electrolyte spillage hazard.

B.    Valve-Regulated — The decentralization of the network and the deployment of the Outside Plant (OSP) provided a new market for battery technologies which could operate reliably in partially controlled and uncontrolled enviroments and work with minimal maintanance.In these environments, batteries would have to operate in cold (-40 °C) and warm (50 °C) temperatures. The first battery technology to be introduced into this new application was the Valve Regulated Lead-Acid (VRLA) battery. VRLA batteries typically use fiber separators for absorbed electrolyte and operate at voltages between 2.25 -2.27 at 25 °C. Unlike, round cells, VRLAs electrolyte is starved (The electrolyte is absorbed into the separator material and pores of the plates). To minimize water loss and maintanance, VRLAs use valves to recombine oxygen and hydrogen and maintain operational water levels.

First designs of valve regulated lead-acid (VRLA) batteries were not accomodating. Major concerns with the first designs were with thermal instability, fire resistance, and unrealized service life. In response, Telcordia (Bellcore at the time) helped to gain consensus on the design, performance and safety of VRLA batteries. This industry colloboration led to the publication of Telcordia Special Report, SR-4228, “VRLA Battery String Certification Levels Based on Requirements for Safety and Performance”, December 1996 and the widespread deployment of the technology. (As of 2006, it is estimated that over 15 million VRLA batteries are in service.) VRLA batteries are now the major backup power source for the OSP environment.

2. Nickel based batteries

A. Nickel-Cadmium - Nickel cadmium (NiCds) were introduced to compete against VRLA batteries in the OSP back-up power market. NiCds were designed to address carrier frustration with the shortcomings of VRLAs, - thermal instability, unscheduled maintenance, and unrealized service life. NiCds, which have a nominal voltage of 1.2 V, are flooded with an alkaline electrolyte of potassium hydroxide (KOH) and water . 38 to 40 NiCd cells are typically used to form a battery string that can operate on a typical telecom DC buss of 48 VDC. There has been widespread deployment of NICds, but the technology has not supplanted VRLAs in the OSP.

Note: Similar to lithium batteries, another battery technology - Nickel-Metal Hydride (NiMH) – is geared for stationary power use. NiMH batteries were initially introduced in the electrical vehicle marketplace and in the consumer market. NiMH batteries are electrically similar to nickel cadmium batteries. NiMHs were developed to provide higher energy density than NiCds and are made with environmentally friendly materials. Similar to VRLAs, the NIMH electrolyte is starved and is also sealed to minimize maintenance and issues with leakage.

Jude Ken-Kwofie is a network engineer with Telcordia, and can be reached at
jkenkwof@telcordia.com. To obtain copies of the GR-3150-CORE document, please e-mail document-info@telcordia.com.

Notes

Telcordia sold all rights of the PL-iON technology in 2000.
A requirement, identified by the letter “R”, is a feature or function that, in the view of Telcordia, is necessary for client company product selection.
Conditional requirements, identified by the letters “CR”, are features or functions that, in the view of Telcordia, are necessary in specific applications. Conditional requirements are considered requirements when considered necessary for client company product selection.
In Telcordia’s view, objectives are desirable features or functions, which may be required by carriers. Objectives, flagged as “O”, represent goals to be achieved..
Conditionals objectives are features or functions that, in the view of Telcordia, are desirable in specific applications and may be required by carriers.
In Telcordia’s estimation, conditionals, flagged as “Cn” are circumstances that will cause a conditional requirement or conditional objective to apply.