Battery Safety Centre | WMG, University of Warwick
Battery Safety Centre
What is the Battery Safety Centre?
The Battery Safety Centre is a critical component of WMG’s Energy Innovation Centre that focusses on enabling the design and manufacture of safer batteries.
It comprises seven test chambers that allow for the the destructive testing of cells and battery modules in a safe and repeatable environment. These chambers are fire and pressure tight compartments to contain flames, hazardous gasses and projectiles. The gasses and smoke from any fires are safely extracted and scrubbed before release to the environment.
This facility allows our researchers and partners to fully explore what happens to batteries when they experience conditions beyond their safe limits, which may be electrical abuse, over-heating or physical damage. The test chambers are designed to be flexible so that we can fit them with a wide range of sensing equipment and data logging, enabling us to better understand these fast and destructive events in great detail.
Society’s progress towards greater cross-sector electrification has been very rapid and this continues to gather pace. This already includes energy storage, electric vehicles and personal mobility devices as well the ubiquitous smartphones and laptops. Potentially, batteries and electric motors will replace internal combustion engines in most applications, such as light aircraft and urban air mobility, construction and agricultural equipment.
The drive towards ever greater energy density has meant that modern battery chemistries and formats are potentially volatile and sensitive to external conditions. Although these have a better safety record than internal combustion engines, modern safety expectations mean that a very high level of safety verification is needed.
The Battery Safety Centre provides the necessary facilities and skilled engineers for research in this field and makes this service available for industry. Our industrial partners can access our equipment and deep expertise on a unique, flexible basis. This is a valuable resource for the research and development of new battery designs.
Cell characterisation
Different cell chemistries and form factors behave very differently under abuse conditions. Knowing this behaviour is critically important in selecting the best cell for a particular application. These tests will provide data on failure mode, cell and gas temperature, pressure and emitted gas species.
Calorimetry
Our EV ARC+ calorimeter is used for “heat-wait-seek” experiments as well as heat capacity and heat release experiments. This test will determine the onset temperature for thermal runaway. This information is critical for safe pack design and for aligned modelling work.
The calorimetry may also be done in a sealed pressure chamber within the ARC which allows measuring the volume of gas released to undertake species identification of the released gas.
Gas measurement
An important facet of battery safety is the toxicity of smoke and gasses released from thermal runaway events. We use both mass spectrometry and FTIR techniques to identify and quantify gas species, either as part of a calorimetry test or as a sampled gas stream from thermal events in the abuse chamber.
Cell-to-cell Propagation
If it is possible to reliably limit a thermal runaway event to a single cell within a module or pack, then that device is inherently safer. Many of our partners wish to carry out precise and scientific small-scale tests on designs, often incorporating anti-propagation materials, to develop a more robust design before proceeding to certification testing.
Side wall rupture (SWR)
SWR is a rare but extremely hazardous failure mode for certain cell formats in which a cell splits, and a jet of hot flame and ejecta impinges on neighbouring cells to cause almost instant propagation. WMG has developed test methodologies to cause this failure mode in a highly repeatable way. This enables our partners to develop solutions to overcome this failure mode within an efficient test programme and with a high degree of confidence.
Tear down and forensics
Industry has a high level of demand for safe and scientific tear down of faulty or suspect cells, modules and packs to provide evidence of root cause. This work must be carried out by specialist staff within abuse chambers to ensure safety and that crucial evidence is well documented. We have access to glove boxes for cell level tear down, CT scanning and state-of-the-art microscopy.
New Method Development
Fundamental to the research undertaken by the Battery Safety Centre is the creation of new experimental methods to continually improve the reliability and robustness of battery abuse experiments, while concurrently reducing cost and their environmental impact. Our work includes a focus on in-cell metrology, repeatable methods of failure initialisation and an increasing transition towards virtual methods of safety evaluation.
Training and skills development
The Battery Safety Centre provides unique training through the WMG Skills Centre to support the dissemination of best practice throughout industry and academia via a suite of specialised, hands-on, courses.
Automotive
We have many long-term partnerships within the automotive industry and have been involved in the electrification of this industry from the beginning. As the number of hybrid and electric vehicles rose sharply, the issue of Safety became a serious concern. The field of safety testing was rather immature at that time and WMG contributed heavily to the development of test methodologies for data-rich and deterministic testing. Our partners benefited from this with a much greater understanding of the initiation and behaviour of thermal runaway events. This has enabled the design and successful certification of automotive battery packs that are now in market leading vehicles in volume production.
Aerospace
The electrification of aerospace is in its early days and safety is even more crucial in mid-air. WMG has worked with the leading UK-based companies working in this field, for example Rolls-Royce’s “Spirit Of Innovation” world record holding design. Recent work has used our Side Wall Rupture test method to develop a robust design that will resist this failure mode with minimal impact on overall system weight. This allows the design of packs that have the ability to limit thermal runaway to a single cell, making them inherently safer.
Personal Mobility
An emerging safety concern in electrification is the fast-growing personal mobility market. These devices are often brought into the home for storage and charging. Some imported products are known to be of low quality, which is often exacerbated by the use of third-party charging equipment or after-market modification. WMG was commissioned by the UK Office Product Safety and Safety (OPSS) to undertake independent research into product safety risks associated with lithium-ion batteries, chargers and conversion kits when used with e-bikes and e-scooters.
Facilities and Equipment
The WMG Battery Safety Centre is the academic centre with the most capable, battery abuse chambers in the UK. Unlike most other facilities the test work is carried out in an enclosed environment and all emissions are scrubbed before release to the environment, significantly reducing the environmental impact of testing when compared to “open-air” tests. This makes the test work more controlled, repeatable and sustainable.
Our chambers are equipped to measure temperature, blast over-pressure, identify and quantify smoke and gasses released and capture high quality video, including high speed and thermal imaging. As part of the wider WMG and University of Warwick we have access to a diverse range of equipment and expertise that is not generally available in industry, e.g. extensive cell characterisation, forensic and imaging provision.
We work closely with our colleagues to provide access to all the facilities of the Energy Innovation Centre, including in-cell instrumentation, fault diagnostics, Battery Management Systems, structural testing and much more.
Our particular focus is in developing precise and repeatable test methods and equipment to improve the rigor and efficiency of this emerging scientific field. This includes novel methods such as using a laser to trigger thermal runaway and in-cell measurement of temperature and pressure. Our partners come to us to understand the causes of thermal runaway and precise information of the extreme and fast-developing conditions that ensue. This enables them to design safe solutions to the problem with fewer tests and greater confidence.
SafeBatt - Science of Battery Safety
AEROspace BATtery design space evaluation and safety verification (AEROBAT)
OPSS - Personal light electric vehicle (PLEV) battery safety research
Dr Simon Jones
Chief Engineer, Energy Innovation Centre
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Marek Smalera
Lead Engineer Battery Safety
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Elliot Read
Lead Engineer (Cell Safety)
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