The impact of battery testing in achieving vision zero objectives

This article originally appeared in the July'22 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

In the last few months, a new factor has started to have a major influence, as rising fuel prices have further encouraged the transition away from ICE dominance. By Arturo Vargas, Chief Solutions Marketing Manager, National Instruments (NI).

Global EV sales more than doubled between 2020 and 2021, reaching a 6.75 million by the end of that year (according to figures from EV Volumes). With sales now getting close to one million/ month, BloombergNEF expects that there will be a total of 26 million plug-in EVs on our roads before the start of 2023.

EV manufacturers, and the tier 1 technology partners that supply them, are looking to develop exciting new battery concepts that will give them a competitive edge - since it is mainly via the battery that EV differentiation will be realised.

They are, unfortunately, under enormous pressure to achieve that goal within the briefest possible timeframe, so that they are not too late to market. Achieving sustainable scalability that does not compromise on safety is the key to this.

The evolving EV landscape

Although in the past the battery aspect of EV manufacturers’ vehicles would be offloaded to their chosen battery supplier, everyone no longer favours this practice.

Seeing how unquestionably important superior battery design can be to the success of an EV model, many manufacturers are looking to tighten up their supply chain. They are bringing battery development work and even battery production in house (or in some cases collaborating with battery suppliers on joint ventures in this area).

In order that production volumes can be increased, to keep up with the unprecedented EV demand now starting to be experienced, battery testing needs to be carried out at a faster pace and test capabilities expanded substantially. The cost of test also needs to be reduced, to make operations more economical. 

Therefore these companies must own their test strategy and overcome the problems that are inherent to fast growth such as sustainability as operations scale up and coordination of work as organisations increase in size.

The dynamics affecting EV battery design

EV batteries’ form factors will become ever more constrained, with a greater number of cells being squeezed into a given volume. This will place battery cells under even greater stresses than before and thereby increase the safety risks involved.

The transition from 400V to 800V based EV powertrains will enable faster charging, which will be appealing to car buyers. In addition, it can bring increased efficiency levels (extending EV range) and reduce heat generation that will impact the thermal management needed.

If they are to prove the validity of their latest battery designs, engineering staff must have a better understanding of what is going on within the battery cells. They need to be able to determine the places at which unacceptable stresses might be happening or find where production/assembly-based defects are situated. 

Among the various safety-oriented issues that engineers have to address are:

• The temperature dependency of battery performance - which if not attended to will, at a certain point, can result in thermal runaway occurring
• The high-power hazard of not only the batteries, but the equipment used to test them (e.g. battery cyclers)
• Mechanical tests need to be done on battery cells, modules, and packs to characterize behaviour under stress, vibration, etc.
• Electrical performance testing, like open circuit voltage (OCV) and AC internal resistance (AC-IR)

Avoiding a short circuit or thermal runaway is paramount. As well as the hefty costs that having to recall a model will cause, EV manufacturers cannot put their brand reputation in jeopardy through incidents of this kind. That is why more sophisticated battery testing will be an essential part of the vision towards zero emissions and zero automotive-related fatalities.

Taking EV batteries into other dimensions

Because of the energy storage capacity that EV batteries provide, there is the prospect of them not just being used for transportation purposes. Bi-directional operation will mean that they may also serve as an energy storage reserve within the home.

Here they could enable peak shaving - so that electricity might be drawn from the grid at off-peak times, when tariffs are low, then utilised at times when tariffs are higher (thus reducing utility bills and saving money).

Another possibility is to leverage such storage for grid frequency stabilisation - helping prevent power outages when demands on the grid are at their highest.

Employing EV batteries in this way within domestic environments will mean that safety is even more critical, so to make certain that such functions do not cause fire hazards.

Implementing better test solutions

Engineers clearly need detailed information on the batteries they are developing, as they continue to push the performance envelope. 

Measurements must be captured at high speed across a large number of different channels and over long test runs. Through the data collected, it will be possible to identify problems, and then work out what the appropriate action will be to resolve them.

This might be to alter the production/assembly process to eliminate regularly occurring faults. It could also be to tune the battery management system (BMS), to compensate for any underlying nuances within the battery design.

The long test times that have to be undertaken mean that multiple battery pack DUTs must be running in parallel. In many cases, this will be across several different test sites within a global organisation, each of which might be using different items of test hardware.

Often manufacturers will rely on proprietary data platforms at the backend to deal with the large datasets, enabling issues to be uncovered quicker.

With the test criteria constantly evolving - reliance on a closed, vendor-dependent approach for testing can prove problematic and costly.

It is also very difficult to scale such arrangements, and this will limit EV manufacturers’ ability to handle the future workload volumes that they are going to face. 

In contrast to this, the NI Battery Test System (BTS) offers an open platform-based system that is flexible enough to adapt to changing test requirements and has complete scalability. Through its use, a more than 40% reduction in the engineering time needed for acquiring, manipulating, and analysing data can be realised - meaning that new batteries are introduced after a far shorter development period.

This software-connected and data-centric system enables integration of all the different hardware elements that constitute the test set-up.

These include the battery cycler and power electronic circuitry (for charging/discharging the battery DUT), the environmental chamber (for keeping the battery DUT within the stipulated ambient conditions), the data acquisition hardware, and the data/system management equipment (for accessing the measurement data and analysing the results).

The modular nature of the I/Os of the NI BTS means that extra measurement channel capacity can be added, as test volumes are ramped up, without significant increases in either cost or complexity.

This provides battery suppliers and EV manufacturers with the ability to scale their test activities, so various different test procedures can be running simultaneously on a large number of batteries situated at different sites.

The I/O flexibility also gives the assurance that equipment from numerous third-party vendors can be used in the test system. The upshot of this is that any outlay already made on such equipment (which will generally come at a high price tag) is not wasted.

To further facilitate battery testing tasks, NI has just introduced its latest version of the BTS. 

Innovations within this version include a specific workflow via which engineers can request a test, and define the particular parameters involved.

By automating the process, and leveraging a shared database, the test lab manager has all the information needed to define exactly the test procedure for it to be executed correctly. They can assign responsibility to technicians and operators to change the configuration as required.

In addition to this, through the recent acquisitions of Heinzinger, NH Research, and Kratzer Automation, NI now has the necessary power electronics expertise to offer a complete testing portfolio to customers. This has extended the scope of the company’s test capabilities even further, making the company a one-stop-shop for EV battery testing.

Conclusion

The battery suppliers serving the EV sector and the vehicle manufacturers themselves need to keep progressing battery designs if they are to stay ahead of the competition. Implementing expansive, highly automated, software-connected test systems will allow them to conduct detailed and accurate battery testing at higher throughputs.

Test procedures are completed rapidly and with greater cost-effectiveness, which will bring tangible commercial benefits.