Powering Up

Understanding traction batteries: technology and standards

Sushovan Bej, Technical Expert, NDC Transport Initiative for Asia (NDC TIA) – India Component, GIZ India
Bhagyasree, Junior Technical Expert, NDC TIA – India Component, GIZ India

The automotive sector is experiencing a profound change with a remarkable growth in the e-mobility market. The aim to attain energy security, reduce dependency on international markets for oil and the urgent need to prohibit carbon emission from the transportation sector is promoting a rapid shift towards electrified mobility. Considering the current momentum in the mobility sector, the deployment of efficient battery technologies is essential. Batteries are one of the key components of an electric vehicle (EV) which acts as a powerhouse for the vehicle. Among the current available battery chemistries, lithium-ion batteries (LiB) are the most adopted traction battery due to its remarkable energy and power density. The shift towards EVs would be incomplete without a clear technical understanding of the chemistry and the supporting standards in the battery ecosystem. The standards act as a guiding principle for the key players including the manufacturers, distributers, technicians, operators, fire and safety regulators, environmental regulators, and recyclers.  This article focuses on the key characteristics of a traction battery, status quo of battery chemistries for traction application and the standards related to Li-ion batteries that could be adopted by the key players in the ecosystem.

Key characteristics of traction batteries

Batteries are used in an EV to power the electric motor. These batteries are rechargeable in nature and are expected to be deep cycle batteries and are designed to give power over longer periods of charging and discharging cycles. The key characteristics that a traction battery should exhibit are high energy density, high power density and high crate capability. These batteries need to be proficient to withstand the regular deep discharge cycles (80% Depth of Discharge). It should be capable to deliver full power output even during deep discharge to ensure long range operation. Typically, traction batteries need to have a high cycle life and lifetime which will depend on the discharge rate as well. Lower discharge rates signify lesser number of charging discharging cycles and ultimately higher cycle life. EVs are expected to serve in a varied range of geographic conditions. The operating temperature range of traction batteries should endure with the wide temperature changes.

Comparative analysis of key battery chemistries

The lower cost and the tolerance to overcharging capability of Lead Acid batteries dominates its use in the 2W and 3W segments. The chief limiting factors of the Lead Acid Batteries are its poor cycle life and high weight. To address these issues, while still reaping the benefits of the traditional lead acid batteries, a new generation of batteries were developed known as the advanced lead acid batteries.

Lower specific energy and the higher charging time requirement of lead acid batteries paved way for deployment of lithium-ion batteries (LiBs) in most of the traction application. The key characteristics of LiBs are high energy density, high power density, high cycle life and tolence to memory effect. Based on the cathode material, Li-ion batteries can be further classified as Lithium Iron Phosphate (LFP), Lithium Nickel Manganese Cobalt Oxide (NMC), Lithium Cobalt Oxide (LCO), Lithium Nickel Cobalt Aluminium Oxide (NCA), Lithium Manganese Oxide (LMO) and Lithium Titanate (LTO). At certain level of voltage and temperature, Li-ion battery electrolyte can become volatile causing certain safety and other related issues which drives the need for research and development to address such concerns. The table below concludes the high-level benchmarking of the variants of LiBs based on selected performance parameters:

Table 1: Comparison table for variants of LiBs based on selected performance parameters

Parameters LFP NMC LCO NCA LMO LTO
Operating voltage range 2.5-3.65V/cell 3.0-4.2V/cell 3.0-4.2V/cell 3.0-4.2V/cell 3.0-4.2V/cell 2.5-3.65V/cell
Energy Density (Wh/kg) 90-120 150-220 150-200 200-260 100-150 70-80
Typical C-rate (Charge) 1C 0.7-1C 0.7-1C 0.7-1C(3C max) 0.7-1C(3C max) 0.7-1C(5C max)
Crate (Discharge) 1C;25C possible 1C;2C possible 1C 1C IC;10C possible IC;10C possible
Cycle life 1000-2000 cycles 1000-2000 cycles 500-1000 cycles 500 cycles 300-700 cycles 3000-7000 cycles
Cost (Approx) 580$/kWh 420$/kWh NA 150$/kWh NA
Thermal runaway limits 270 ֯C 210 ֯C 150 ֯C 150 ֯C 250 ֯C NA
EV compatibility High (e-4W) High(e-4W) Low High (e-2W, ,4W) High Low`

Source: (PushEVs), (InsideEVs) , (Battery University-Comparison Table of Secondary Batteries), (Logan Goldie-Scot)

Future chemistries like metal-air, solid state batteries, high temperature batteries for e-mobility possess promising performance as well as safety features. However, for such technologies to be commercialised, adequate research is required to address the various shortcomings perceived in full scale commercialisation. The table below illustrates a high-level benchmarking of the mentioned technologies based on selected performance parameters:

Table 2: Comparison table of secondary battery technologies

 

Source: (Battery University-Comparison Table of Secondary Batteries)

Overview of LiB standards

Global standards

Standards provide the fundamental building blocks for product development, makes it easier to understand, compare competing products and urges products to adopt a safer operating environment. Notably, safety and testing, quality, reliability, and environmental compliance all come under the supervision of standards globally. The integrity of standards is maintained by standards and testing organisations across the world such as IEC, ISO, CENELEC, BIS, QC/T, UN to name a few. Battery standards have been instrumental in the development of various battery technologies around the world. These standards provide much needed reference points and guidance for R&D, safety, performance, testing of various battery chemistries. With the increasing adoption of EV envisaged across the world, the need for harmonised acceptance of standards is necessary to keep the EV revolution on track as more and more advanced battery technologies with higher performance characteristics enter the market.

The battery standards can be generally categorised into four different sections such as general standards, performance and lifecycle standards, safety assessment standards and recycling standards. Apart from the fundamental categorisation, the transportation standards serves for deployment of a proper guidelines/ regulations for transportation and shipping of batteries.

The table below concludes the global standards for Li-ion chemistry. International bodies such as IEC (International Electrotechnical Commission), ISO (International Organization for Standardization), CENELEC (European Committee for Electrotechnical Standardization), QC/T (Chinese standards), UN are the major bodies to disseminate the mentioned standards.

Table 3: Global standards for LiB chemistry

Type of standard Available standards Description
General IEC 62902:2019, ISO/IEC PAS 16898:2012, ISO 18300:2016, UL 2271, J2289, J3124, QC/T 1023- 2015, QC/T 743-2006, QC/T 840-2010, QC/T 989- 2014, IS 16827: 2018 Specifies methods for the clear identification of secondary cells, batteries, battery modules and monoblocs according to their chemistry, The standard specifies the requirements, testing methods, inspection rules, symbols, package, transport and storage of Li-ion battery used in electric vehicles, Specifies the general requirements, safety requirements, mechanical strength, appearance and dimension, environmental resistance requirements of cell assembly
Performance and lifecycle standards IEC 62660-1:2018, ISO 12405-4:2018, EN IEC 62660-1:2019, J2288, J2758, J1634, IS 16893: Part 1: 2018 Specifies test procedures for the basic characteristics of performance, reliability and electrical functionality for the battery packs and systems for either high-power or high-energy application. Typical applications include hybrid electric vehicles (HEV), FCV (Fuel cell vehicle), BEV (battery electric vehicles), plug-in hybrid electric vehicles (PHEVs)
Safety Standards IEC 62485-3:2014, IEC 62485-6:2021, IEC TR 62660-4: 2017, IEC 62281:2019+AMD1:2021, ISO 18243:2017, EN 50604-1:2016/A1:2021, EN 62485-3:2014, EN IEC 62485-6:2021, IEC 62660- 3:2021, J2289, J2929, QC/T 989-2014, AIS 048, IS 16894: Part 3: 2018, IS 16893: Part 3: 2018 It provides requirements on safety aspects associated with the installation, use, inspection, maintenance, and disposal of traction batteries
Recycling standards EN 61429:1 996, IEC 61429:1 995, J3071, J2984 Identification of Transportation Battery Systems for Recycling Recommended Practice. The chemistry identification system is intended to support the proper and efficient recycling of rechargeable battery systems used in transportation applications
Transportation Standards QC/T 989- 2014, J2950, IEC 62281:2 019+AM D1:2021 Recommended Practices for Shipping Transport and Handling of Automotive-Type Battery System – Lithium Ion The standard aids in the identification, handling, and shipping of lithium batteries to and from specified locations.

Source: (Ruiz and Persio), (International Standards and Testing Applicable to Batteries)

Indian standards

The Indian standards related to traction batteries are dispersed by ARAI (Automotive Research Association of India) and BIS (Bureau of Indian Standards). Many of the Indian standards developed refers to the international standards from IEC and ISO. The table below concludes the Indian standards for LiB chemistry.

Table 4: Indian standards for LiB chemistry

Type of standard Standards Organisation Description
General standard IS 16827: 2018 BIS The standard is identical to ISO/IEC PAS 16898: 2012. It provides the dimensions and designation of secondary lithium-ion cells for integration into battery pack and systems used in electrically propelled road vehicles
Performance and life cycle standard IS 16893: Part 1: 2018 BIS The standard is identical to IEC 62660-1: 2010. It specifies performance and life testing of secondary lithium-ion cells used for propulsion of electric vehicles.
Safety standards AIS 048 ARAI The standard specifies electrical tests such as short circuit test and overcharging test.
IS 16894: Part 3: 2018 BIS The standard is identical to IEC 62485-3:2014. It provides requirements on safety aspects associated with the installation, use, inspection, maintenance, and disposal of batteries
IS 16893: Part 3: 2018 BIS The standard is identical to IEC 62660-3: 2016. This document intends to determine the basic safety performance of cells used in a battery pack and system under intended use and reasonably foreseeable misuse or incident, during the normal operation of the EV.

 

Source:  (Bureau of Indian Standards), (AIS-048)

Information related to standards applicable for communication between the battery, and the various components of the EV and EVSE (Electric Vehicle Supply Equipment) can be found in second article which is part of this series, named Crucial Communication.

Conclusion

Rapid improvements in battery technologies are crucial in achieving the required pace of transition to cleaner mobility. The high energy density, specific energy, and cycle life of the LiBs makes these batteries outperform other available battery chemistries. With the increasing adoption of EV across the globe, the need of harmonised standards is essential to evaluate the performance, safety, and other characteristics of the emerging battery technologies.

India aims to reach its target of installing 500 GW of non-fossil fuel electricity generation capacity and reaching 30 per cent sales share of EVs by 2030 (COP 26: India Commitments). The total growth in the LiBs could grow to between 105 and 263 GWh annually by 2030 depending on the aggressiveness of the uptake of EVs and battery energy storage (RMI 2022). Thus, development of a proper framework for end-of-life management of these LiBs is crucial.

This article is sixth in the series that elaborates on the available traction battery technologies and the related standards. The next article in this series would discuss the status quo of the recycling ecosystem of these battery technologies.

References

AIS-048. “Battery Operated Vehicles – Safety Requirements of Traction Batteries .” 2009.

Battery University-Comparison Table of Secondary Batteries. n.d. <https://batteryuniversity.com/article/bu-107-comparison-table-of-secondary-batteries>.

Bureau of Indian Standards. “IS 16893 : PART 3 : 2018.” 2018.

COP 26: India Commitments. COP26: India Commits to 500GW of Renewables by 2030, Net Zero by 2070,” PV-Tech, November 2021. n.d. <www.pv-tech.org/cop26-india-commits-to-500gw-of-renewables-by-2030-net-zero-by-2070/. >.

InsideEVs. “Compare Electric Cars: EV Range, Specs, Pricing & More.” n.d. InsideEVs.

International Standards and Testing Applicable to Batteries. Electropedia. n.d. <https://www.mpoweruk.com/standards.htm#lithium>.

Logan Goldie-Scot. “A Behind the Scenes Take on Lithium-ion Battery Prices.” 2019.

PushEVs. Comparison of different EV batteries in 2020. 2020. <https://pushevs.com/2020/04/04/comparison-of-different-ev-batteries-in-2020/>.

RMI. “Towards a Sustainable Battery Manufacturing Industry.” 2022.

Ruiz, V and Di Persio. “Ruiz V., Standards for the performance and durability assessment of electric vehicle batteries -Possible performance criteria for an Ecodesign Regulation.” JRC Technical Reports (2018).

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