GB/T 42728-2023 PDF in English
GB/T 42728-2023 (GB/T42728-2023, GBT 42728-2023, GBT42728-2023)
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Guidelines for safety design of lithium ion batteries
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GB/T 42728-2023: PDF in English (GBT 42728-2023) GB/T 42728-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.220.99
CCS K 82
Guidelines for Safety Design of Lithium Ion Batteries
ISSUED ON: AUGUST 6, 2023
IMPLEMENTED ON: MARCH 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 4
1 Scope ... 5
2 Normative References ... 5
3 Terms and Definitions ... 5
4 General Principles of Design ... 7
5 Labeling and Warning Instructions ... 8
5.1 Labeling Requirements and Warning Instructions ... 8
5.2 Durability ... 8
6 Cell ... 8
6.1 Selection of Cells ... 8
6.2 Selection of Battery Capacity ... 8
6.3 Cell Consistency ... 9
6.4 Cell Quantity ... 9
6.5 Cell Assembly Gap ... 9
6.6 Cell Safety ... 9
6.7 Cell Appearance ... 9
7 Protection Circuit ... 9
7.1 Overview ... 9
7.2 Voltage Management ... 10
7.3 Current Management ... 10
7.4 Temperature Management ... 11
7.5 Consistency Management ... 12
7.6 Multi-level Protection ... 12
7.7 Protection Reliability ... 12
7.8 Other Considerations ... 12
8 Components and Materials ... 13
8.1 Installation of Overcharging and Over-discharging Protection Devices ... 13
8.2 Connector / Connecting Piece Connection ... 13
8.3 Terminals and Connection Design ... 14
8.4 Fasteners ... 14
8.5 Temperature Sensor... 14
8.6 Wiring ... 14
8.7 Materials ... 14
9 Safety Thermal Design ... 15
9.1 Thermal Protection Design ... 15
9.2 Location of Cells in the Battery ... 15
9.3 Location of Battery in the Equipment ... 15
10 Fireproof Design ... 16
10.1 Flame Retardancy of Materials ... 16
10.2 Anti-burning Design ... 16
11 Installation ... 16
11.1 Prevention of Mechanical Damage ... 16
11.2 Prevention of Drop Injuries ... 16
11.3 Embedment in Other Equipment ... 16
11.4 Installation Direction ... 16
Bibliography ... 17
Guidelines for Safety Design of Lithium Ion Batteries
1 Scope
This document provides guidance related to the safety characteristics of battery in the design of
lithium ion battery, and suggestions for improving product safety characteristics from the
aspects of cells, protection circuits, materials and components, thermal design, fire protection
and installation, etc.
This document is applicable to the design of lithium ion battery, without distinguishing the
fields of application.
2 Normative References
This document does not have normative references.
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 cell manufacturer
Cell manufacturer refers to the manufacturer of lithium ion cells.
3.2 battery manufacturer
Battery manufacturer refers to the manufacturer that assembles cells into batteries.
NOTE: under certain circumstances, battery manufacturer may also be the cell manufacturer.
3.3 lithium ion cell
Lithium ion cell refers to a device that relies on the movement of lithium ions between the
positive and negative electrodes to realize the mutual conversion between chemical energy and
electrical energy, and it is designed to be rechargeable.
NOTE 1: the device usually includes electrodes, diaphragms, electrolytes, containers and terminals,
etc.
NOTE 2: hereinafter referred to as cell.
3.4 module
Module refers to a configuration with multiple cells connected in series or parallel, with or
without protection devices [for example, fuse protector or positive temperature coefficient
thermistor (PTC)] and monitoring circuits.
[source: IEC 62619:2017, 3.9]
3.5 battery protection circuit module; PCM
battery management unit; BMU
battery management system; BMS
A circuit board, circuit module or electronic system with the core function of controlling the
charging and discharging behavior of the battery to protect battery safety.
NOTE 1: usually in the simple application field of portable products, a separate battery protection
circuit module is used to protect the cells, while in the component module of complex
battery systems, the battery management unit is adopted to manage the cells in the
module; in complex battery systems, for example, new energy vehicle power batteries,
the battery management system is adopted to realize the management and protection of
the cells.
NOTE 2: a complex battery management system may include cell voltage, temperature and current
measurement, energy balance, SOC calculation and display, abnormal alarm, charge and
discharge management, and communication, etc.
3.6 battery
Battery system
Battery system refers to a system consisting of one or multiple cells, modules or battery packs.
It has a battery management system. If overcharge, overcurrent, over-discharge or overheating
occurs, the battery management system will take action.
NOTE 1: if the cell manufacturer and the user reach an agreement, over-discharge cut-off is not
mandatory.
NOTE 2: it may include cooling or heating devices, and some even include charge and discharge
modules and inverter modules.
[source: IEC 62619:2017, 3.11]
3.7 large lithium ion battery
Large lithium ion battery refers to lithium ion battery with a total mass exceeding 12 kg.
[source: UN 38.3 (Sixth revised edition), 2.3]
NOTE: it is referred to as large battery in this document.
a relatively large nominal capacity shall be carefully selected to ensure the safety, and necessary
protection devices shall be equipped.
6.3 Cell Consistency
Before assembly, the consistency of the cells needs to be screened (considering capacity,
internal resistance and voltage, etc.); cells of the same brand, model and specifications should
be used, otherwise, they must satisfy the safety requirements of international standards, national
standards and industry standards related to cell consistency.
6.4 Cell Quantity
In order to reduce safety risks, the maximum quantity of cells connected in series or parallel in
the battery respectively shall not exceed the quantity recommended by the cell manufacturer.
6.5 Cell Assembly Gap
In the structural design of the battery, for cells with square structures and polymer (including
liquid flexible package) structures, sufficient expansion space shall be reserved on the largest
surface of the cells. The reserved expansion space shall be at least greater than the minimum
value recommended by the cell manufacturer.
6.6 Cell Safety
The safety of cells used by the battery manufacturer must satisfy the international standards,
national standards and industry standards related to cells.
6.7 Cell Appearance
Before assembly, check the appearance of the cells. The appearance of the cells shall comply
with the stipulations of the battery manufacturer. The surface shall be clean and without
mechanical damage.
7 Protection Circuit
7.1 Overview
When lithium ion cells encounter abnormal conditions, such as: charging overvoltage,
discharging undervoltage, charging overcurrent, discharging overcurrent and external short-
circuit, etc., or are charged and discharged under extreme environmental conditions, or the
charge and discharge rate exceeds their own capabilities in actual application environments,
safety risks may arise. In the design of batteries, the above-mentioned risks shall be proactively
addressed to protect the safety of the constituent cells.
The modes of dealing with the above-mentioned risks include actively stopping charging and
discharging behavior or controlling charging and discharging behavior within the safety range
specified by the manufacturer.
Priority should be given to the circuit function design to respond to the above-mentioned safety
considerations, that is, to design a protection circuit that can control the charging and
discharging behavior of the battery, for example, adding PCM/BMU/BMS to the battery.
Priority shall be given to design of the above-mentioned protection circuit in the battery. If the
above-mentioned protection circuit is only designed in the system equipment circuit and a
battery without its own protection circuit is used, then, it is not appropriate to design the
system’s battery as a user-replaceable structure.
In order to achieve a complete protection function, considerations may be given to adding
necessary information collection devices to the battery. Necessary communication and control
buses can be added to the connection between the battery and the equipment. In certain
scenarios (for example, on the premise of ensuring personal and property safety), the system
control circuit can respond to the protection strategy.
7.2 Voltage Management
The protection circuit of the battery should have an overvoltage charging protection function,
so as to prevent any cell from being charged to beyond its upper limited charge voltage.
The protection circuit of the battery should have an undervoltage discharging protection
function, so as to prevent any cell from being discharged to below its discharge cut-off voltage.
For a multi-cell lithium ion battery connected in series, even if the total voltage does not exceed
the safety range of the battery, a certain single cell may be overvoltage or undervoltage due to
poor consistency of the constituent cells. Therefore, it is quite necessary for multi-cell battery
connected in series to manage the voltage of each cell or each parallel-connected cell block.
For multi-stage lithium ion battery connected in series, proper balancing design can reduce the
probability of charging overvoltage or discharging undervoltage caused by the inconsistency of
the constituent cells. However, the battery should not rely solely on the circuit balancing
function to prevent the hazard of charging overvoltage or discharging undervoltage.
If the upper limited charge voltage or discharge cut-off voltage of the battery or its constituent
cells is closely related to the ambient temperature, then, in addition to having reliable voltage
protection, it is also advisable to control any constituent cell during charging and discharging
to not exceed its upper limited charge voltage and discharge cut-off voltage at the current
ambient temperature.
For protection circuits designed with measures to protect cells from being charged or discharged
to beyond the safe voltage range, the voltage management requirements can be reduced.
7.3 Current Management
The protection circuit of the battery should have a charging overcurrent protection function, so
as to prevent the charging current of any cell from exceeding its maximum charging current.
The protection circuit of the battery should have a low-temperature protection function, so as
to prevent the battery from being charged below the lower limit of charging temperature of the
constituent cells.
The temperature collection of the battery should cover every constituent cell as much as
possible, and its surface temperature shall be monitored. It is advisable to monitor the surface
temperature of the cell where it is most likely to generate heat. If necessary, it is advisable to
manage the temperature difference between the constituent cell with the highest temperature
and the constituent cell with the lowest temperature in the battery, so as to reduce the possibility
of cell failure or accident.
7.5 Consistency Management
Multi-stage battery connected in series should have a certain cell balancing function.
For large-scale lithium ion batteries, it is advisable to have the function of monitoring the status
information of the constituent cells of the batteries. In addition, the battery should have the
capability of reporting cell status information to the system equipment through the battery
interface.
The system equipment should be able to detect the consistency of the constituent cells of the
battery through communication signals, and promptly notify the user or manufacturer of
unacceptable cell consistency problems.
7.6 Multi-level Protection
It is recommended that the battery adopts a Level-2 or above overcharge protection design, so
as to increase the redundancy of electrical safety protection.
If the battery adopts an integrated circuit device that integrates the charging management circuit
and the protection circuit, in order to prevent the failure of this single integrated circuit device
from causing over-range charging and discharging behavior of the cell, and it is crucial to adopt
a Level-2 or above cell protection design.
7.7 Protection Reliability
The protection circuit of the battery needs to be able to initiate protection actions as expected
throughout the battery’s entire life cycle. For example, key devices that perform the battery
protection function, in addition to being able to initiate overvoltage charging protection as
expected, also need to withstand foreseeable sustained high-voltage inputs. The antistatic
capacity of cell protection devices is also one of the reliability factors that need to be considered.
When designing a battery with a software-controlled protection circuit, it is also advisable to
design a hardware protection circuit as the final safety protection.
7.8 Other Considerations
For the battery of certain equipment, if the charging and discharging loops are directly cut off,
it may cause derivative hazards, and this risk is more unacceptable than the cells being
overcharged or over-discharged. For example, if the cell used in a balance bike is directly cut
off and discharged, the rider may fall and be injured. For this type of battery, it should be
considered to advance the Level-1 protection settings of the battery and equipment to the system
equipment, and leave a certain threshold, so that the system equipment can actively limits
charging and discharging behavior to protect the cell.
For high-voltage batteries with an upper limited charge voltage exceeding 60 V, the protection
against the hazard of electric shock is also a factor that needs to be considered. For lithium ion
batteries, please refer to the requirements related to electric shock safety of information
technology equipment products in GB 4943.1.
NOTE: in the standards on the safety of home appliances, DC voltage exceeding 42.4 V is regarded
as dangerous voltage, which requires electric shock safety-related tests and assessments.
When the upper limited charge voltage of the battery used in portable home appliances
exceeds 42.4 V, the protection against the hazard of electric shock must also be considered.
8 Components and Materials
8.1 Installation of Overcharging and Over-discharging Protection Devices
Overcharging and over-discharging will destroy the cells in the battery, causing potential
dangers, such as: fire, explosion and leakage.
In addition to the protection circuit, its main component is the metal-oxide semiconductor field-
effect transistor (MOSFET). The battery can also be equipped with corresponding protection
devices in the charging and discharging loops, such as: thermostats (interrupt the current),
positive temperature coefficient thermistors (PTCs), as well as thermal fuses, etc. The key
components of safety need to comply with the relevant requirements of battery standards or
component standards.
8.2 Connector / Connecting Piece Connection
When cells are connected in series and parallel, the connecting pieces cannot be directly welded
to the cells through welding with high heat input. For example, soldering can easily cause
overheat of the cells. Although overheating damage is invisible, it will probably trigger leakage,
rupture, fire, or even explosion. In order to avoid overheating damage, it is recommended to
use welding modes with low heat input, such as: ultrasonic welding, resistance welding and
laser welding, to connect the cells. Use the welding modes with low heat input to firmly weld
the cells, so as to prevent insufficient welding and falling off.
For cells connected by nickel strips, the structural design must ensure that the nickel strips do
not come into contact with any other cell nodes that are not connected, or that short circuits will
not be caused by the insulating coat on the cell surface being punctured by the edge burrs of the
nickel strips.
electrolytes, high temperatures, physical shock and other hazards during use. Battery designers
choose materials for wire insulation, cell insulation and battery casing, etc. that can withstand
electrolytes and high temperatures. The resistance and strength shall be adapted to the specific
location and mode of usage. Taking all possible uses into consideration is quite important in
battery design.
8.7.3 Insulation materials
The insulation materials used in the battery (such as: insulation tapes and wire sheaths, etc.)
shall have sufficient insulation properties and corresponding voltage resistance capabilities, and
with good chemical, electrochemical, mechanical and thermal stability within the expected
temperature ranges of storage and usage.
9 Safety Thermal Design
9.1 Thermal Protection Design
The battery can be equipped with structural protection devices and thermal management (for
example, ventilation) to avoid overheating of the cells caused by the working process or the
surrounding environment. Large-capacity battery modules are generally realized through dense
assembly of small cells. Therefore, when using them at high voltage or large capacity, the
specific energy and thermal behavior characteristics of small cells need to be taken into
consideration. The failure of individual units in the battery will affect the operation of the entire
system. Generally, the mode of ventilation cooling or liquid cooling is adopted for the thermal
management of the battery, or phase-change materials can be used. In order to avoid
overcooling of the cells caused by the surrounding environment, the mode of supplementary
heating can be adopted to raise the temperature of the surrounding environment of the cells.
9.2 Location of Cells in the Battery
During the structural design of the battery, components that may generate heat shall be placed
as afar away from the cells as possible, so as to prevent the cells from being affected by high
temperatures; power devices that may easily generate heat in the battery management system
should be placed as far away from the cells as possible in design, so as to prevent the high
temperature of the heating elements from being transmitted to the cells.
9.3 Location of Battery in the Equipment
The location of the battery in the equipment needs to consider the impact of other heat sources
on the cell temperature. A proper thermal diffusion environment is conducive to the mitigation
of temperature rise.
10 Fireproof Design
10.1 Flame Retardancy of Materials
The flame-retardant requirements of the protective circuit board (PCB), casing, wire sheath and
insulation materials used in the battery need to satisfy the requirements of relevant standards.
10.2 Anti-burning Design
Large-scale batteries have the capability of avoiding or delaying system fires in the event of
thermal runaway of the cells and satisfy the requirements of relevant standards.
11 Installation
11.1 Prevention of Mechanical Damage
During the assembly process, take protective measures for the cells to prevent scratches, bumps
and other damage to the cells. During the process of loading the battery into the battery holder,
a sufficient positioning accuracy shall be set to prevent the cells from being squeezed, and the
protective board or terminals from being bent or deformed, etc.; during the assembly process,
prevent screws and other foreign objects from falling into the battery holder.
11.2 Prevention of Drop Injuries
Make sure that the battery is securely installed on the equipment, so as to prevent the battery
from sliding inside the equipment, or even being ejected if the equipment is dropped or subject
to a sudden impact. Necessary cushion pads can be configured to avoid damage to the cells and
battery due to collision.
11.3 Embedment in Other Equipment
If the battery is embedded in other equipment, the battery shall not be designed as a closed
structure, and shall have a pressure relief device.
For applications where water logging may be encountered, the battery must have a
corresponding level of structural waterproof design.
11.4 Installation Direction
Install the cells or battery in accordance with the direction recommended by the cell
manufacturer.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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