AUTOMOTIVE TESTING: BATTERIES


❱❱ Millbrook has invested heavily in its battery testing facilities to meet increasing demand, below; crash testing of electric vehicles includes an assessment of post-crash hazards, bottom


Facility charges up for surge in battery testing


Jonathan Newell talks to Millbrook to see how its battery testing facility evaluates modules through to complete assemblies across a range of tests for performance and crashworthiness


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n October 2019, automotive engineering and testing organisation, Millbrook opened its automotive battery test facility. The 12 battery cycling climatic chambers and


supporting infrastructure represents the biggest private investment in independent testing in the UK so far. According to chief engineer Peter Miller,


battery technology is evolving at a staggering rate as the industry seeks to make electric vehicles universally accepted as an alternative to the internal combustion engine. “We pride ourselves on our in-depth knowledge of battery technology and our ability to provide testing which helps developers better understand, anticipate and ultimately eliminate failure in future models,” he says.


TEST CAPABILITIES Millbrook’s customers can assess the performance of battery cells, modules and packs, determine pack performance during a crash and subject batteries to a range of environmental conditions. They benefit from 48V hybrid test cell capability, full EV durability testing and electric machine and inverter testing. The facilities are suitable for a range of tests on the latest powertrains including mild hybrids (MHEV), plug-in hybrids (PHEV), battery electric (BEV) and fuel cell vehicles (FCV). The battery


test chambers can cycle complete automotive battery packs up to 1,100V and 750kW in temperatures from -40°C to +90°C, including simulation of rapid temperature changes.


RELIABILITY TESTING Important factors that consumers consider before making the switch to electric cars are range and reliability. Vehicle OEMs are keen to understand battery equipment life cycles and how they can extend existing warranty lengths to attract more buyers. The life testing facility at Millbrook offers


insight into expected reliability through accelerated life testing. According to Miller, it takes 12 months to measure a 10-year life and it isn’t possible to accelerate beyond this without over-stressing or over-heating the parts under test. “With batteries, the margins are quite small so stressing them too much changes the characteristics to a point where the test becomes invalid.”


The industry is taking a cautious


approach until more data is available and is in a constant process of learning from test and field data to refine future products. Miller says the cooling systems and


electronics are already established technologies and so reliability and longevity are predictable. The chemistry is the part that’s new and needs testing fully. When asked what factor most influences


reliability, Miller explains that temperature beats current. “Temperature control is crucial because for every 10°C increase, the life expectancy can be halved,” he says.


RESEARCH WORK Millbrook also has a group of independent researchers focused on in-house testing of battery safety and abuse. This contributes to the general body of knowledge on the subject. Such research covers altitude, thermal, short-circuit and over-charge testing as well as crush, over discharge and fire resistance testing. A big plus for Millbrook is that it can


also perform crash testing on electric vehicles, as some crash test facilities are unable to carry out such evaluations because of the post crash hazards of EVs. Overall, with its latest addition to the


testing facilities, Millbrook can offer the complete range of evaluations needed for battery and hybrid vehicles, including cell, module, powertrain and crash testing. For the future, as demand starts to


ramp up, Millbrook will be ready. “Both Millbrook and the industry in general is investing heavily now and expects to continue to do so in the future,” concludes Miller. T&TH


February 2020 /// Testing & Test Houses /// 29


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