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Development of a Proposed Performance Standard for Battery Storage System connected to a Domestic/ Small Commercial Solar PV system

Recommended criteria to select a battery management system (BMS)

Report Number: PP198127-AUME-MS04-TEC-02-R-01-A

Project Partners

Funding Partners

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Revision History:

Disclaimer:The views expressed herein are not necessarily the views of the Australian Government, and the Australian Government does not accept responsibility for any information or advice contained herein.

Recommended Criteria: Battery Management Systems (BMS) of 33Version 1.0

Revision No Date Authored by Reviewed by Approved by DNV GL Approval

IR1 2019-09-10 DNV GL, CSIRO CSIROIR2 2019-11-11 DNV GL, CSIRO CSIROIR3 2019-11-19 DNV GL, CSIRO DNV GL

Recommended criteria to select a battery management system (BMS)

- for PV connected residential/small-scale commercial systems



These recommended criteria for the selection of a battery management system were developed as part of the Proposed Australian Battery Performance Standard project. This project aims to create a performance standard applicable to PV connected residential/small-scale commercial battery energy storage systems within Australia and has been developed by DNV GL, CSIRO, the Smart Energy Council & Deakin University in conjunction with industry involved in renewable energy battery storage equipment.

Disclaimer

<The section will contain a general disclaimer>

Acknowledgements

The project consortium (CSIRO, DNV GL, Smart Energy Council and Deakin University) wishes to acknowledge and thank the Australian Renewable Energy Agency (ARENA) and the Victorian Government for funding this work.

This Project received funding from ARENA as part of ARENA’s Advancing Renewables Program and the Victorian Government through the New Energy Jobs Fund.



Table of contents1 INTRODUCTION..............................................................................................................................1.1 What is the purpose of this document?1.2 Why have these criteria been developed?1.3 Who should use this guide?1.4 Existing related standards

2 SCOPE AND GENERAL....................................................................................................................2.1 Scope2.2 Limitations2.3 Terms and definitions

3 OVERVIEW OF BATTERY MANAGEMENT SYSTEMS........................................................................3.1 BMS vs EMS3.2 Types of BMS3.2.1 Centralised BMS3.2.2 Modular BMS3.2.3 Distributed BMS3.3 Role of the BMS3.3.1 Operational functions3.3.2 Safety functions

4 RECOMMENDED CRITERIA............................................................................................................

5 CHEMISTRY SPECIFIC MONITORING REQUIREMENTS...................................................................

6 PARAMETER TOLERANCES AND ACCURACY LIMITS......................................................................6.1 Practical considerations6.2 Measurement resolution

7 DATA SHEET REQUIREMENTS.......................................................................................................

8 REFERENCES................................................................................................................................

AppendicesNO TABLE OF CONTENTS ENTRIES FOUND.



List of tablesTable 3-1: Overview of the BMS management functions............................................................................14Table 3-2: Overview of BMS operation and safety functionalities...............................................................18Table 5-1: Chemistry specific recommended minimum monitoring requirements.....................................22Table 7-1: Overview of recommended minimum reporting requirements..................................................25

List of figuresFigure 2-1: Example pre-assembled integrated BESSS equipment............................................................11Figure 3-1: BMS hierarchical architecture...................................................................................................14Figure 3-2: Centralised BMS.......................................................................................................................16Figure 3-3: Modular BMS.............................................................................................................................16Figure 3-4: Distributed BMS........................................................................................................................17



Table of abbreviations

Abbreviation MeaningABPS Australian Battery Performance StandardAC Alternating CurrentARENA Australian Renewable Energy AgencyAS Australian Standard BESS Battery Energy Storage SystemBMS Battery Management SystemCEC Clean Energy CouncilCMS Cell Management SystemCSIRO Commonwealth Scientific and Industrial Research OrganisationDC Direct CurrentDELWP Department of Environment, Land, Water and Planning (representing the State of Victoria)DNV GL Det Norske Veritas and Germanischer LloydEMS Energy Management SystemIEC International Electrotechnical CommissionkW KilowattkWh Kilowatt hourMMS Module Management SystemNZS New Zealand StandardOORH Out of Range HighOORL Out of Range LowOV Over VoltagePCE Power Conversion EquipmentPV PhotovoltaicRTC Real-time ClockSoC State of ChargeSoH State of HealthTMS Thermal Management SystemUV Under VoltageVLA Vented Lead AcidVRLA Valve Regulated Lead AcidWh Watt Hour



1 INTRODUCTION

1.1 What is the purpose of this document?The purpose of this document is to describe the minimum set of criteria recommended for battery management systems (BMS) connected to Battery Storage Equipment (BSE) intended for use with domestic and small commercial photovoltaic systems.

This guide endeavours to capture the recommended criteria that a BMS available in the current market should incorporate, but does not intend to provide design advice or practices.

It should be noted that the expected safety features of a BMS are largely addressed in the Best Practice Guide: “Battery Energy Storage Equipment – Electrical Safety Requirements” and AS/NZS 5139- Electrical Installations- Safety of battery systems for use with power conversion equipment. Therefore, in addition to the safety requirements outlined in these documents, this guide intends to complement them by addressing other desirable features such as monitoring, computational, communication, and optimisation functions for battery storage equipment.

1.2 Need for this guideIn a battery application the battery management system plays a critical role in ensuring the battery operates in a safe manner as well as ensuring that the battery also provides the best performance for the desired application. For a large segment of the PV connected domestic market, the Battery Energy Storage System (BESS) comes pre-installed with a manufacturer designed BMS. However, there is provision, in the current market where the BMS can be sourced from a third party:

Custom designed battery systems Australian battery integrators and BESS designers including new business ventures

This battery management system criteria guide is designed to assist with the choice of third party commercially available BMS for integration to PV connected batteries. This guide helps readers identify the ideal technological requirements the BMS should have for system development. Further it serves to assist existing BESS manufacturers to identify the best practices for future product development. This guide also highlights gaps in current BMS reporting which battery users have identified to assist both custom designers, integrators and also current BESS manufacturers to provide the state-of-the art information as requested by current users1.

1.3 Why have these criteria been developed?A BMS is an electronic system that may provide monitoring, computational, communication, protection and optimisation functions to battery storage equipment and ensures safe operation and optimises the battery efficiency and lifetime. The availability of the functions within the BMS is largely determined by the battery chemistry and its manufacturer. There is currently no dedicated standard or a best practice guide that can be used to determine the selection of a battery management system suitable to particular battery storage equipment.

On the other hand, for many interested parties (e.g. installers, utility operators, integrators, retailers, importers), information about the BMS system is typically not clearly visible or readily available. This recommended practice may assist the interested parties in the following ways:

1 Identified through survey of industry and stakeholder participants at the Performance Standard Workshop 3, Engineers Australia, Collins Street, Melbourne, 12 November 2019.



- By highlighting how different battery management systems can be compared on a like-for-like basis

- By defining information that is to be provided by BMS manufacturers to help installers, utilities, etc.

- Standardising the reporting allowing BMS to be benchmarked against others

- Simplifies the process to understand BMS suitability into third party battery storage equipment

- By providing an educational guide to interested parties (such as governments, researchers, etc)

- Allowing manufacturers to demonstrate that their product meets the minimum set of recommended criteria for BMS in terms of safety, performance, etc.

Battery technology is constantly evolving and therefore the possibility exists that new requirements may be demanded by industry or mandated by legislation. In this case, the designers and manufacturers should ensure that any such requirements will be adequately addressed in conjunction with this guide.

Compliance with this guide does not exempt any Supplier (or other stakeholders involved with the supply chain) from meeting their statutory responsibilities under any Australian legislation including Australian Consumer Law.

1.4 Existing related standards, recommended practises & guides

This guide should be used in conjunction with relevant sections of the following standards:

AS/NZS 3000:2018, Electrical installations

AS/NZS 3008.1.1:2017, Electrical installations - Selection of cables | Cables for alternating voltages up to and including 0.6/1 kV - Typical Australian installation conditions

AS/NZS 4777.2:2015 (part 1 and 2), Grid connection of energy systems via inverters Inverter requirements

IEC 61427-2:2015, Secondary cells and batteries for renewable energy storage - General requirements and methods of test - Part 2: On-grid applications

IEC 61508(Part 1-7), Functional safety of electrical/electronic/programmable electronic safety-related systems

AS/NZS 5139, Electrical Installations - Safety of battery systems for use with power conversion equipment

IEC 61508-3, Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 3: Software requirements

IEC 62443-4-1:2018, Security for industrial automation and control systems - Part 4-1: Secure product development lifecycle requirements

DNV GL-RP-0043, Safety, operation and performance of grid-connected energy storage systems

Best Practice Guide for Battery Storage Equipment – Electrical Safety Requirements

Australian Battery Performance Standard | Industry Best Practice Guideline (to be released by June 2020)



2 SCOPE AND GENERAL

2.1 ScopeThis guide provides a set of recommended criteria to determine the suitability of battery management systems that may be used in conjunction with:

- Standalone components, or with

- Battery modules, or

- Pres-assembled battery equipment, or

- Pre-assembled integrated battery energy storage systems (BESS)

The recommended criteria for BMS outlined in this document are intended for systems with a maximum capacity of 100 kW / 200 kWh, intended for use with domestic and small commercial photovoltaic systems.

2.2 LimitationsThis guide does not intend to cover the following aspects of BMS:

• In-depth design details

• Installation requirements

• Recycling

• Handling and transport

• Training requirements

This guide does not replace or override requirements in the Best Practice Guide: Battery Energy Storage Equipment – Electrical Safety Requirements, AS/NZS 5139 Electrical Installations- Safety of battery systems for use with power conversion equipment and other relevant requirements stated in Australian Standards, laws or any regulations.

2.3 Terms and definitions The definitions outlined here have been taken, with permission, from the best practise guide for battery storage equipment, electrical safety requirements [1] and AS/NZS 5139:2019 Electrical installations — Safety of battery systems for use with power conversion equipment [2].

Battery Storage Equipment

For the purpose of this guide, battery storage equipment is pre-packaged, pre-assembled, or factory built equipment that has been designed, manufactured and tested/verified as a stand-alone complete package supplied by the one manufacturer or importer for installation. It may be supplied in several parts for transport and assembled on site, but does not need on-site modification or manufacturing or supply of other parts for that assembly to occur.

Battery storage equipment could be any of the following three types:



i. Battery module

One or more cells linked together. It may also have incorporated electronics for monitoring, charge management and/or protection.

Battery modules are installed within pre-assembled battery system equipment or pre-assembled integrated battery energy storage system equipment or as part of a master/slave configuration of such equipment.

ii. Pre-assembled battery system (BS) equipment

A system comprising one or more cells, modules or battery systems, and auxiliary supporting equipment such as a battery management system and protective devices and any other required components as determined by the equipment manufacturer. It does not include Power Conversion Equipment (PCE). Pre-assembled battery system equipment comes in a dedicated enclosure. The equipment is a complete package for connection to a d.c. bus or d.c. input of PCE.

iii. Pre-assembled integrated battery energy storage system (BESS) equipment

A battery energy storage system manufactured as a complete integrated package comprising of one or more cells, modules or battery system, protection devices, power conversion equipment and any other required components as determined by the equipment manufacturer. Pre-assembled integrated battery energy storage system equipment are supplied in a dedicated enclosure. Integrated battery energy storage system equipment is a complete package that has a.c. output for connection to the electrical installation.


Enclosure

Figure 2-1: Example pre-assembled integrated BESSS equipment


auxiliary equipment/battery equipment

equipment required for supporting different battery technologies and associated battery infrastructure

Battery

Unit consisting of one or more battery cells connected in series, parallel or series parallel arrangement.

Battery management module (BMM)

Distributed battery and battery module devices that feed into the BMS and are generally part of the electronics on an individual cell or module.

Note: If a BMM unit dedicates to a cell level, it will be labelled as a Cell Management System (CMS) and if the unit is dedicated to a module it will labelled as a Module Management System (MMS)

Battery management system (BMS)

An electronic system that monitors and manages a battery or battery system’s electric and thermal states enabling it to operate within the safe operating region of the particular battery. The BMS provides communications between the battery or battery system and other parts of the device (e.g. vents or cooling).

Note: The BMS monitors cells, battery or battery modules to provide protective actions for the battery system in the case of overcharge, overcurrent, over discharge, overheating, overvoltage and other possible hazards that could occur. Additional BMS functions may include active or passive charge management, battery equalization, thermal management, specific messaging or communications regarding charge rates and availability.

battery module

one or more batteries linked together. May also have incorporated electronics for monitoring, charge management and/or protection

battery system

system comprising one or more cells, modules or batteries

Capacity (C)

electric charge which a cell or battery can deliver under specified discharge conditions



Cell

Basic functional unit, consisting of an assembly of electrodes, electrolyte, container, terminals and usually separators, which is a source of electric energy obtained by direct conversion of chemical energy.

charging

operation during which a secondary cell or battery is supplied with electric energy from an external circuit which results in chemical changes within the cell and thus the storage of energy as chemical energy.

competent person

person who has acquired knowledge and skill, through training, qualifications, experience, or a combination of these, and which enables that person to correctly perform the task required.

discharge

operation by which a battery delivers, to an external electric circuit and under specified conditions, electric energy produced in the cells

Isolation devices

Devices used to electrically separate parts, such as a switch disconnector operating in all live conductors to isolate the battery parts from other parts within the equipment.

Interface

Point for connection for communication to other devices/systems. Examples include connection to a computer or communications system, or a digital display on the device.

Manufacturer

The company that is responsible for the design, assembly, testing and claims of compliance of the parts together as the final assembled battery storage equipment is the manufacturer. This may be a different company to the manufacturer(s) of any particular components.

Integrator

A person or an entity which buys separate components and assembles them to make a workable unit. For example, a pre-assembled battery system can be integrated with a third party BMS and PCE.



End user

For the purpose of this guide, an end user is the person/entity who ultimately uses the system

Master/slave configuration

Master/slave configuration with respect to an energy storage system may be of two types:

1. The parts may be supplied separately and assembled together by an installer on site into the one supplied enclosure. An example of this is where there are multiple battery modules that can be added into an enclosure, which already has a pre-assembled integrated battery energy storage system (BESS), to increase capacity of the battery storage equipment and the BESS (master) controls the battery module (slave).

2. The parts may be in separate enclosures. If the master/slave configuration are in separate enclosures then only one device connects directly to the electricity installation, the other parts connect to that device, and there is one device (master) that has control over all the connected devices (slaves). The separate parts would be expected to be physically co-located and these parts connected together in the final configuration must have been tested and assessed as battery storage equipment to this guide. An example of this is where there is a pre-assembled integrated battery storage system equipment (BESS) that can have connected to it a pre-assembled battery system (BS) to increase the overall energy storage of the equipment and the BESS (master) controls the BS (slave). In this situation the combined BESS and BS have been tested by the manufacturer as one battery storage equipment to this guide.

Note: A master/slave configuration is not a collection of separate individual battery storage equipment devices combined together on site (in series, parallel, individually connected to installation wiring or any other combination) and configured to operate in unison, or controlled by a separate energy management system or the like. These situations are an electrical installation of multiple battery energy storage equipment. Each individual battery storage equipment may be within this guide, but the combination is an installation to be designed and installed in accordance with appropriate installation standards.

Power Conversion Equipment (PCE)

An electrical device converting and/or manipulating one kind of electrical power from a voltage or current source into another kind of electrical power with respect to voltage, current and/or frequency. Examples include but are not limited to d.c./a.c. inverters, d.c./d.c. converters, charge controllers.

Protection devices

Device to limit a hazardous situation, such as overcurrent protective devices.

Protective electronic circuit

An electronic circuit that prevents a hazardous situation under abnormal operating conditions, such as overvoltage, but not an electronic circuit that is used purely for functional requirements, such as reporting or logging cell voltage.



risk

possibility that harm (death, injury or illness) might occur when exposed to a hazard.

state of charge (SoC)

charge available in a battery or battery system expressed as a percentage of the rated capacity of the battery or battery system.

state of health (SoH)

ability of a battery system to store and deliver energy compared to its original rated capacity

thermal management system

a system that monitors and manages a battery or battery system’s thermal state enabling it to operate within the safe operating region of the particular battery. A TMS be part of the BMS, can however also be a separate system

thermal runaway

unstable condition arising during constant voltage charge in which the rate of heat dissipation capability, causing a continuous temperature increase with resulting further charge current increase, which can lead to the destruction of the battery.



3 OVERVIEW OF BATTERY MANAGEMENT SYSTEMS

A BMS is equipment that may provide monitoring, computational, communication, protection and optimisation functions to the battery equipment that ensures safe operation and optimises the battery efficiency and lifetime. It may monitor and control battery critical parameters, estimates its state, performs balancing and ensures that batteries are operated in recommended safe conditions. In general, Lithium-ion based battery equipment needs comparatively advanced BMS compared to other chemistries such as lead acid and metal hydride batteries. Each BMS is designed specifically for a particular chemistry type and is not useable for other chemistries. It is strongly recommended for best safety protection and best performance that users confirm the BMS is correct for the specific battery chemistry it will be used in conjunction with. It is also noted that for the specific case of lithium-ion batteries, there are a wide range of chemical materials utilised which can affect both current and voltage ranges and advise that the BMS used is tuned to the specific chemical make up of the lithium ion battery and ensure the setpoint parameters match the electrical properties of the specific chemistry type and do not cause issues such as overcharging or overvoltage conditions.

The possible layers of a battery management system are shown in Figure 3-2, which includes Cell Management Systems (CMS), Module Management Systems (MMS) and BMS. provides an overview of the management functions typically undertaken by a battery management system.

Table 3-1: Overview of the BMS functions2

Function Category Examples

Measurement Operational Measurement of parameters such as: voltage, temperature, 2 NOTE: As stated previously, it is not expected that all functionalities are included within the battery management system. This will be determined depending on many factors such as manufacturer, battery chemistry etc. However, it should be noted that some functionalities of a BMS should be made compulsory as a minimum requirement.


Figure 3-2: Possible BMS hierarchical architecture for Lithium Ion Batteries

External Devices

MMS

CMS

cell

CMS

cell

CMS

cell

BMS

MMS

CMS

cell

CMS

cell

CMS

cell


Function Category Examples

and Safety current

Monitoring Operational and Safety

Monitoring the states of variables such as voltage, temperature, current, State of Charge (SoC), State of Health (SoH) with respect to manufacturer recommended values

Computational Operational and Safety

Computation of variables such as charge current, discharge current, SoC, SoH

Communication

Operational and Safety

Centralised, de-centralised (master-slave control)

Internal: Cell balancing

External: Energy Management System (EMS), Temperature Management System (TMS), Power Conversion Equipment (PCE)

Protection3 Safety Detection of critical states such as under voltage, over-voltage, under temperature, over temperature.

Optimisation Operational Optimisation of the operation of the battery system through cell balancing, optimal operation of TMS, load management

3.1 BMS vs EMSThe state of the energy storage equipment is monitored and controlled by the low-level controls, the battery management system. It may read all relevant data from the energy storage equipment such as voltages, currents and temperatures, etc. Furthermore, it may also ensure that the energy storage equipment is working within its operating range and checks whether the electric power and energy requested are within the operating range of the current system status.

The high-level functional controls are undertaken by the energy management system (EMS) of the energy storage equipment. The EMS is responsible for co-ordinating the operation of the battery equipment through the power converter applicable to the relevant operating schedule e.g. to provide frequency response services. In this regard, the EMS determines when and at what rate the energy storage equipment shall be charged, idle or discharged. Depending on the functionality of the energy storage equipment this can happen locally with minimal response times (milliseconds and below) based on locally measured data (e.g. current, voltage, energy, power, frequency), or within an external energy management system, connected via a digital protocol (DNP3, Modbus, etc.) and maybe with external signals4 (e.g. from utility operator), which leads to slower response times (seconds). When the energy storage equipment is set up for multifunctional performance a combination of local and external high-level controls is possible.

3.2 Types of BMS

3 More specific information is given in AS/NZS 5139 -Electrical installations — Safety of battery systems for use with power conversion equipment (refer to Cl. 6.3.4.5 to 6.3.4.9)

4 E.g. Virtual power plant operation



Battery storage equipment can usually be segmented into several sections, of which a subset the BMS may be able to monitor and control. Residential sized battery packs are typically segmented into modules, which are made up of series-connected battery cells. Each of these layers (cell and module) are able to serve as a platform for the BMS. In addition, the static electrical set-up of these series-parallel combinations of cells can be adaptively changed and therefore, the classification of the battery management system should be reviewed in terms of the architecture and adaptability as well [3].

The BMS may able to measure the condition of the battery via sensors/relays connected to cells and modules. The BMS hierarchical architecture is shown in Figure 3-2. Different battery chemistries can result in variations of the hierarchical architecture of a BMS, however, the functionality of the BMS should satisfy some minimum requirements. Some BMS’s only employ one layer of the hierarchy (e.g. MMS only) as opposed to two-layers, such as an MMS and CMS. This choice is generally driven by economic factors, as installing each cell with a dedicated CMS can be expensive. In addition, a BMS may also be able to communicate with other components such as EMS, TMS, protection systems, etc.

The following discusses the most common architectures that a BMS consists of.

3.2.1 Centralised BMS

A single controller is connected to the battery cells or modules through a multitude of wires. One or more functions included in are provided through a single central controller as shown in Figure 3-3. This arrangement provides the simplest architecture when compared to Modular and Distributed BMS. One of the disadvantages of this arrangement is less flexibility in terms of expandability with further cells or modules.

Figure 3-3: Centralised BMS

3.2.2 Modular BMS

This arrangement consists of a central BMS which is connected to several MMS, in which the latter monitors the cell level and also communicates with the BMS as shown in Figure 3-4. The central BMS will collect the information provided by the MMS and also communicate with external components (e.g. EMS,


External Devices

cellcell

Module 2

cellcellcell

Module 1

cell

Battery Management System


TMS). The MMS may have an integrated cell balancing feature. This architecture provides flexibility in terms of scalability.

Figure 3-4: Modular BMS

3.2.3 Distributed BMS

Each cell is incorporated with a CMS which may able to measure the parameters such as voltage, temperature, and current. In addition, it may also consist of a cell balancing functionality. Each CMS communicates with central BMS via the communication bus interface as shown in Figure 3 4. This is more complex than the modular and centralised BMS architecture, however provides flexibility in terms of scalability.

Figure 3-5: Distributed BMS

NOTE: There may be further architectures in addition to the ones stated in this document, however, they are not detailed here.


MMSMMS

External Devices

cellcell

Module 2

cellcellcell

Module 1

cell


CMSCMSCMSCMSCMSCMS

External Devices

cellcell

Module 2

cellcellcell

Module 1

cell



3.3 Role of the BMS

3.3.1 Operational functionsIn general, a BMS may be equipped with measuring, monitoring, communication and control capabilities. A BMS may measure some parameters of the battery storage equipment such as voltages and temperatures. Less frequently, some advanced BMS’s also measure other variables such as current, and leakage current. With these measurement inputs, a BMS should be able to calculate/estimate the state of charge (SoC), state of health (SoH) and other relevant parameters of cell, module or battery storage equipment. This data can be communicated on two levels; internally among cells and modules (e.g. to manage the cell balancing5) and to external components (e.g. EMS, TMS, etc.) to ensure safe and optimum operation of the battery storage equipment.

Note: The operational functionalities may change depending on various factors such as the battery chemistry and is at the discretion of the manufacturer. For more information refer to Table 3-2.

5 A BMS may use either passive or active cell balancing methods to control the cells to ensure that all cells experience the same charge and discharge rates to optimise the battery capacity.



3.3.2 Safety functions

There are risks associated with the operation of a battery storage equipment due to many factors including the volatile nature of the chemical materials used and the presence of electricity. Good BMS design provides fail-safe protections6 that ensure safe operation of the system.

During operation, depending on the necessity, it is important that the following are monitored and managed accordingly:

Over-current protection

Over/under voltage protection

Overcharge protection

Over-discharge protection

High/low temperature charging limits

High/low voltage charging limits

The values of safe operation are unique to each battery equipment and its chemistry and so there are no uniform temperature and voltage limits across the market. Any fluctuations outside of the safe operating window can result in the BMS using its protection functionality to protect the battery system equipment. It may communicate with protection devices (e.g. isolators) and protective electronic circuits. In addition, a BMS may also use the communication channel to send potentially hazardous fluctuations in operating conditions to the EMS/PCE to then trigger an operational alarm or TMS to vary its operation to mitigate the hazardous situation. The typical BMS operation and safety functionalities are summarised in Table 3-2.

Table 3-2: Overview of Possible BMS monitoring and control functionalities

Item Monitoring ControlVoltage Monitors upper and lower

voltage limits of cells / modules prescribed by the manufacturer.

If the battery energy equipment is outside the operating range, a BMS may:

• Redirect charge if cells are over charged / discharged

• Initiate battery Shutdown / tripping of battery protection device(s)

• Communicate with EMS / PCE to prevent the charge or discharge of the battery beyond the prescribed limits of the manufacturer

• Generate an alarm signal

Refer to Cl. 6.3.4.8 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) for more information.

6 A design feature or practice that in the event of a specific type of failure, inherently responds in a way that will cause no or minimal harm to other equipment, the environment or to people



Item Monitoring ControlTemperature

Monitors upper and lower temperature limits prescribed by the manufacturer

If the battery energy equipment is outside the operating range, a BMS may:

• Initiate battery shutdown / tripping of battery protection device(s)

• Communicate with EMS / PEC / TMS to prevent operating the battery storage equipment beyond the prescribed limits of the manufacturer


Refer to Cl. 6.3.4.5 and Cl. 6.3.4.6 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) for more information.

Current / charge rate

Monitors current limits / charge and discharge limits during operation (generally only over-current is monitored)

In case of an overcurrent7 and over-discharge8, a BMS may:


• Communicate with EMS to prevent operating the battery storage equipment beyond the prescribed limits of the manufacturer


Refer to Cl. 6.3.4.7 and Cl. 6.3.4.9 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) for more information.

Battery capacity, SoC, SoH

BMS may estimate the battery capacity, SoC and SoH and compare the values with manufacturer recommended values

If the battery energy storage equipment is outside the operating range a BMS may:


• Communicate with EMS / PEC/ TMS to prevent operating the battery storage equipment beyond the prescribed limits of the manufacturer


Refer to Cl. 6.3.4.9 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) for more information relevant to SoC.

Cell balancing

Monitors SoH / SoC / voltage of the cells

If the battery storage equipment cells are not balanced, a BMS may utilise either active or passive cell balancing. Transfers (active) or bleeds (passive) charge to cells / modules to ensure battery cells are balanced. This is important to ensure safe operation of the battery and to optimise performance of the system by ensuring that the system performance is not limited by a single or small group of cells.

Impedance / advanced diagnostics

Some BMS may measure impedance or other parameters (such as cell pressure, electrolyte conductivity, flow rates, density of electrolyte, etc.). This may be used as an input variable to calculate SoC, SoH or other critical cell parameters.

N/A

7 E.g. control function loss or shunt calibrator error, etc.8 E.g. control function loss, software error, etc.



3.3.3 Performance functions

The performance of a BESS is inherently linked with the performance and functionality of the BMS. Good BMS design enables battery cells and modules to operate at peak performance and highest longevity. Poorly designed, or poorly programmed BMS systems will significantly affect battery performance.

During operation, depending on the necessity, it is important that the following are monitored and managed accordingly:

Current

Voltage

Temperature

Time

Depth of discharge and SoC

The values of optimum performance are unique to each battery equipment and its chemistry and typically defined by battery cell or module manufacturers. The typical BMS performance functionalities are summarised in Table 3-2.Table 3-3: Overview of Possible BMS monitoring and control functionalities

Item Monitoring ControlVoltage Monitors voltage applied

to cells / modules Measures and monitors applied cell/module voltage with fast response (less then ms) and provides data for BMS calculations

Temperature

Monitors cell/module temperature

Measures and monitors cell or module temperature and provides data for BMS calculations

Time Monitors time provides time data for BMS calculations

Current / charge rate

Monitors current / charge and discharge during operation



Item Monitoring ControlDepth of discharge or SoC

BMS may estimate the battery capacity, SoC and SoH and compare the values with manufacturer recommended values

BMS monitors the depth of discharge and controls cell/module operation within prescribed limits as required by manufacturer

If the battery energy storage equipment is outside the operating range a BMS may:


• Communicate with EMS / PEC/ TMS to prevent operating the battery storage equipment beyond the prescribed limits of the manufacturer


Refer to Cl. 6.3.4.9 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) for more information relevant to SoC.

Cell balancing

Monitors SoH / SoC / voltage of the cells

If the battery storage equipment cells are not balanced, a BMS may utilise either active or passive cell balancing. Transfers (active) or bleeds (passive) charge to cells / modules to ensure battery cells are balanced. This is important to ensure safe operation of the battery and to optimise performance of the system by ensuring that the system performance is not limited by a single or small group of cells.

Impedance / advanced diagnostics

Some BMS may measure impedance or other parameters (such as cell pressure, electrolyte conductivity, flow rates, density of electrolyte, etc.). This may be used as an input variable to calculate SoC, SoH or other critical cell parameters.

N/A



4 RECOMMENDED CRITERIA

The following items represent the recommended requirements a BMS should fulfil, as well as the information that should be provided by manufacturers of BMS. However, it should be noted that some of the functions listed following may not apply to all chemistries, as some battery chemistries do not have severe failure modes related to every parameter listed here.

Refer to Table 5-4 for an overview of battery specific recommended monitoring requirements. Table 3.1 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment) also provides more information on hazard classifications by battery type.

a. Monitoring and Safety

The minimum monitoring and safety requirements of a BMS under normal and fault conditions are covered in clauses 6.3.4.4 to 6.3.4.9 of AS/NZS 5139:2019 (Electrical installations — Safety of battery systems for use with power conversion equipment). These mainly discuss the expected features of a BMS when it operates under abnormal operating conditions such as over voltage, over / under temperature, over current and over discharge conditions.

b. Calculations

It is recommended that a BMS is capable of monitoring and calculating / estimating the following parameters:

i. SoC

ii. SoH

iii. Available capacity

iv. Time remaining to full / empty (100% / 0% SoC)

v. Energy throughput

c. Cell balancing

Cell balancing is critical for some chemistries over the life of the battery to ensure that end-users are able to realise the full value of their system. It also aids in preventing individual cell abuse. Refer to Table 5-4 for chemistry specific recommendations for the cell balancing functionality of BMS.

d. Communication

At a minimum, a BMS must be able to communicate with higher level systems. It is recommended a BMS also include the following capabilities:

i. Exhibit communication protocol flexibility

ii. Report real-time data

iii. Ability to communicate to PCE, EMS, TMS

iv. Ability to communicate with other energy storage equipment

v. Ability to generate, display and communicate fault/alarm messaging



vi. Diagnostic – ability to record the battery life history log9

e. Cyber Security

It is recommended that the design of a BMS include adequate protection measures with respect to cyber security concerns, considering the availability integrity and authenticity and connection type of the system.

f. List of approved cells/modules

The BMS manufacturer should list the approved cells/modules and chemistries that are supported by the BMS

g. Real-time Clock (RTC)

The BMS should be designed to provide fail-safe protections that ensure safe operation of the system. It is recommended the BMS be subjected to a functional safety analysis according to IEC 62619. As a result, the BMS should be evaluated to an appropriate safety integrity level (SIL).

NOTE: it is recommended that manufacturers provide a datasheet as per the requirements set out in section 6 as well as a User Manual with the settings & parameters of the BMS explained to third parties.

The following table provides an overview of the recommended BMS functions that are required with respect to the chemistry type.

Table 5-4: Chemistry specific recommended minimum monitoring requirementsBattery chemistry

Safe

ty a

nd

mon

itor

ing

(Vol

tage

, cu

rren

t,

disc

harg

e ra

te,

tem

pera

tur

e)

Calc

ulat

ion

Cell

bala

ncin

g

Com

mun

ica

tion

Cybe

r Se

curi

ty

List

of

appr

oved

ce

lls

Fail

safe

op

erat

ion

Lead acid Refer to AS/NZS 5139, Electrical installations — Safety of battery systems for use with

power conversion equipment, for further

information.

h h d h h h

Advanced lead acid h h d h h h

Lithium manganese oxide h h h h h hLithium iron phosphate h h h h h d

Lithium supercapacitor h h h h h d

Lithium titanate h h h h h d

Nickel cobalt aluminium h h h h h h

Nickel manganese cobalt h h h h h h

Zinc bromine flow h h na h na d

Notes: h-highly desirable, , d- desirable, o- optional, na- Not applicable

9 It is recommended to have access to at least three months of historical data logging, which may be helpful for system fault diagnostics, performance monitoring, etc.



5 PARAMETER TOLERANCES AND ACCURACY LIMITS

5.1 GeneralThe measurement methods used by the BMS should enable an accurate measurement of the relevant parameters to be made. The measurement accuracies should fulfil the requirements outlined in the following sections.

5.2 Measurement resolutionThese tolerances include all errors associated with the measurements, including accuracies of the measuring instruments, measuring methods and analysis.

5.2.1 Voltage measurementsVoltage measurements should be within ±1% of the specified or actual value to be measured, as per IEC 62133.1 (Secondary cells and batteries containing alkaline or other non-acid electrolytes) and IEC 62281 (Safety of primary and secondary lithium cells and batteries during transport).

For example, a CMS for a 3.7 V lithium based battery should have a minimum accuracy of ±0.037 V, whereas that of a 100 cell string would require a minimum accuracy of ±3.7 V.

5.2.2 Current measurementsCurrent measurements should be within ±1% of the specified or actual value to be measured, as per IEC 62133.1 and IEC 62281.

5.2.3 Impedance measurements…

5.2.4 Temperature measurementsTemperature measurements shall have an absolute accuracy of at least 0.5°C and a tolerance of ±2°C as per AS3731.2 ±1 °C

5.2.5 Time measurementsTime measurements shall have an absolute accuracy of at least 0.1% relative to the specified or actual measurement as per IEC 62281.

For example, a BMS sampling at period of 100 ms should have a time accuracy of 0.1 ms.



6 DATA SHEET REQUIREMENTS Data and specification sheets are the first and often simplest means that customers have to evaluate devices. They allow for an initial quick mean to evaluate a BMS for the intended energy storage applications. The following details represent a basic selection of product information that should be reported as a minimum, but not limited to, for a BMS.

1. Available alarms and signals

2. IP rating

3. BMS Operating temperature range

4. Communications protocols

5. Standards compliance

6. Voltage measurement range

7. Current measurement range

8. Max/min number of cells/modules that can be monitored

9. Approved cells/module and chemistries

10. Measurement accuracies

11. Monitoring parameters (e.g. voltage, current, charge/discharge rates, temperature)

12. Operational Power requirements (voltage, current, power consumption)

13. Physical Dimensions

14. Weight

15. Warranty

16. Chemical hazards associated with battery storage equipment

Table 7-5 provides an example datasheet template for a 3rd party battery management system with examples of the type of information expected to be included.



Table 7-5: BMS data sheet – recommended reporting requirements.10

Declared characteristics

Manufacturer declared values

Battery type BMS is designed for11

e.g. Lead Acid (AGM, GEL), Lithium-Ion, Flow, etc.

Only for lithium ion batteries

state actual materials in battery: cathode (positive) chemical material (e.g. lithium nickel manganese cobalt), anode (negative) chemical material (e.g. graphite) and electrolyte (solid, liquid or polymer)

Approved cells and modules

List of manufacturer approved cells and modules (if available)

Allowable number of minimum and maximum cells/modules

Minimum Maximum

Battery charging regimes

e.g. Float charge, trickle charge, bulk, absorption, constant current constant voltage, constant voltage etc.

Nominal voltage Nominal system voltage for which the BMS is designed for

Voltage operating window

Minimum to maximum useable voltage operating range

Allowable Charge/discharge rates

Minimum to maximum useable charge and discharge rates

Operating temperature range

Operating temperature grade12 of the BMS

Configuration e.g. Centralised, distributed or modular

Monitoring parameters

Voltage

Current Temperature

Capacity Power SoH SoC Other

10 This report format is a guide only. However, it is recommended that BMS manufacturers report the requested information in a clear and concise manner to interested parties11 If the BMS is applicable to multiple chemistries, please use one data sheet for each chemistry12 Grades are defined as: commercial: 0 °C to 45 °C, industrial: −20 °C to 85 °C, automotive: −40 °C to 125 °C, extended: −40 °C to 125 °C and military: −55 °C to 125 °C





Measurement accuracyAlarms and signals e.g. over-voltage, under-voltage, over-temperature, under temperature, low liquid density, loss of communication, etc.

Communication Protocols

e.g. Modbus, TCP, SNMP, HTTP, RS485, CAN

Communication interfaces

e.g. PCE, EMS, Thermal control etc.

Cell balancing If available (e.g. Active or passive)

IP Rating e.g. IP64

Protection mechanisms

e.g. Over-voltage, over-discharge, cell over heating

Connection to Peripheral Devices

e.g. EMS, Thermal management, Inverter

Mode of Operation e.g. Initialisation modeConfigurable modeNormal operation modeDegrade modeShutdown modeMaintenance/Test mode

Power Supply e.g. This should be a voltage range, 9-24V DC

Warranty Period e.g. two years after installation





WeightDimensions e.g. WxHxL

User Manual with settings

e.g. included (check box option)

Historic data logging capability

e.g. yes/no (check box option) with time (e.g. 3 months)

MTBF and MTTRe.g. values for mean time between failures and mean time between repairs.

Certifications e.g. IEC 61580, IEC 61851, IEC 61427-2, IEC 61850, IEC 60950

Hazardous materials information

e.g. flammable, toxic, etc.

NOTE: some of the above reporting elements are optional.



7 REFERENCES[1] Ai Group, CESA, CEC, CSIRO, SEC, “Best Practice Guide: Battery Storage Equipment | Electrical Safety

Requirements, Version 1.0,” 06 July 2018.[2] Standards Australia, “AS/NZS 5139:2019 - Electrical installations — Safety of battery systems for use

with power conversion equipment,” 20019.[3] A. Steinhorst, Z. Shao, S. Chakraborty, M. Kauer, S. Li, M. Lukasiewycz, S. Narayanaswamy, M. Usman

Rafique, Q. Wang, “Distributed Reconfigurable Battery System Management Architectures,” in 2016 21st Asia and South Pacific Design Automation Conference (ASP-DAC),, Macau, 2016.



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