Why battery health management is crucial to electric vehicle values

As electric vehicles enter the used market, pressure is growing on manufacturers and sellers to provide detailed information on their battery health so that purchasers know what they're buying. Factors affecting it include unit age, high temperatures, operating at high and low states of charge, and high electric current and usage (energy cycles). Variations in battery chemistry, thermal management and buffer limits (the cap a manufacturer places on the top and bottom ends of a battery's charging range) also affect battery health. Market analyst Autovista Group recently published a report outlining how, without information on these factors, residual value data on electric cars will become harder to calculate with certainty. Published in partnership with battery analytics specialist Twaice, it said that how an electric car is charged and driven over the first eight to 10 years of its life has a major impact on its driving range and suggested that a battery health report could add £400 to the value of a three-year-old C-segment electric vehicle. A spokesperson for Twaice said: “Many people underestimate the impact of battery treatment. At the three-year point with 28,000 miles on the clock, a battery that has been poorly treated will perform worse on a promised range by about 5%. This gap will only increase because battery quality, once lost, cannot be recovered.” Derren Martin, director of valuations at CAP HPI, said battery health will become an issue for car buyers: “If your neighbour buys an identical car to you but the battery health and range of your car is 10% less, you would want to have paid less for it.” He claimed, however, that vehicle manufacturers are reluctant to share battery health data: “It’s not something that most OEMs are happy to provide. There is a suggestion that we might need legislation to be passed to ensure that data is shared." Sara Ridley, engineering and quality director at Autocraft Solutions Group, a battery manufacturing and repair company, said pressure for battery data to be made more available is growing. "Monitoring battery health is becoming important," she said. "Owners will need to be able to have either permanent diagnostics fitted to their vehicle or be able to go to a dealer to have a device fitted that will monitor their battery's performance, with the data analysed at the next visit." At the recent Cenex LCV exhibition, representatives of Silver Power Systems, a specialist in battery monitoring and analytics, presented its latest battery monitoring system. Aimed at smaller manufacturers looking to incorporate it at the vehicle production stage, and fleet and commercial vehicle operators wanting their own aftermarket battery health records, it tracks battery degradation using a range of measures and real-time and historical data that can be presented in the form of a battery passport. "The passport is a record of the battery's behaviour and condition and a vehicle with one has more value than one without," said Liam Mifsud, program manager at SPS. "Until now, operators have been focused on getting electric vehicles onto their fleets but now they're getting their heads around battery degradation. Having a clear picture of battery health will be key to the efficient operation of these new vehicles and help provide an accurate understanding of their market value." SPS's system records, tracks and monitors battery data, including charge and discharge cycles, internal and external battery temperatures and the location of charge events. The effects of rapid charging on battery health are monitored, too. Based on the data, the system can also predict future performance and the battery's end of life, information that, as more used vehicle batteries are repurposed for energy storage elsewhere, is becoming valuable. One of SPS's key findings is that battery health can vary widely across vehicle fleets and even outwardly similar vehicles. "Judging an electric vehicle on simply its age, condition and mileage is no longer sufficient," said Pete Bishop, founder and chief technology officer at SPS. "Across even a single fleet, variations in battery health can be up to 10%. Considering that in most commercial applications, 80% battery capacity is deemed to be end of life in operational terms, 10% represents half a vehicle's life." Mifsud said that SPS is seeing end of life reached at around eight years for most electric vehicles but earlier for heavily used commercial ones. However, he added that 'end of life' is open to interpretation: "Someone operating a specialist vehicle will probably keep it for longer and not regard 80% as end of life. If they don't drive far, a private vehicle owner may also be happy with that capacity. However, we've noticed that when a battery gets to 70%, it degrades more rapidly." Whatever the figure, knowing the ones that give the fullest picture of a battery's current and future health is becoming essential. SPS's battery passport The electric vehicle battery data analytics system presented by Silver Power Systems at the Cenex LCV exhibition in September helps commercial vehicle operators maximise vehicle performance and residual value. It does so by monitoring a battery's past and present health, as well as predicting its future behaviour. Data direct from the vehicle is analysed to determine the battery's state of health, a condition that can have a bearing not only on a vehicle's operability but also its total cost of ownership. To date, SPS has accumulated over two million kilometres of vehicle usage data and found a 5-10% variability in battery health. The work has also revealed that battery chemical age does not correspond to vehicle age. SPS's battery passport gives users a summary of a battery's condition and behaviour across a range of measures including range, energy throughput, temperature, voltage, current and charge history. It also expresses the battery's state of health in age terms, comparing it against a fleet average so that, for example, a battery might be found to have a 92% SoH (state of health) compared with the figure it should be reporting for its age of 97%. "Our purpose is to capture, present and analyse battery data in actionable ways," said Liam Mifsud, program manager at SPS.