17/07/2010 - How to extend a lithium EV battery life?
How to extend a lithium EV battery life
Experts from A123 Systems, Nissan and the online resource Battery University are providing advice on how to prolong the battery life of lithium-based batteries for your future electric vehicle.
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The technology platform earth2tech spoke with battery maker A123 Systems about the lifecycle of li-ion batteries and how to extend the battery life. A123 Systems will supply the upcoming Fisker Karma and the electric Fiat 500 with its battery packs. A123 system experts, as well as Nissan representatives and feedback from users at BatteryUniversity.com pointed into the same direction. The two main areas to extend the life of a li-ion battery that can be influenced by the EV driver are the charging behaviour and the temperature:
Lower state of charge
Li-ion batteries prefer a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, one advice could be to charge the battery more often and keep the battery at a 40% charge level when not using the car for a longer period.
However, according to earth2tech, A123′s VP of marketing and communications, Andy Chu, believes that in most cases drivers will not need to “concern themselves regarding the best state of charge in which to leave their battery.” But Chu did comment that keeping a battery fully charged for an extended period of time would have “a somewhat shorter life than batteries that are held at a lower state of charge.”
One solution to this problem is that some electric vehicles manufacturers will generally have batteries limited from discharging below about 50 percent.
Li-ion likes smooth and frequent charging
The ideal for a li-ion battery would be to charge it every day a little bit as the li-ion batteries generally last longer when they are charged and discharged more shallowly, rather than fully from 100 percent charge to zero.
Also the rate of charging, meaning how quick you charge a battery could affect the capacity of the battery. Asked about DC fast charging, Mark Perry, Nissan's director of product planning for the Nissan Leaf replied: “If fast charging is the primary way that a Leaf owner recharges, then the gradual capacity loss is about 10 percent more than 220-volt charging. In other words, it will bring the capacity loss closer to 70 percent after 10 years.”
Generally speaking, batteries live longer if treated in a gentle manner. High charge voltages, excessive charge rate and extreme load conditions will have a negative effect and shorten the battery life.
Cool but not too cool
The speed by which lithium-ion ages is not only governed by the state-of-charge but also by temperature. High charge levels and elevated temperatures hasten permanent capacity loss. So keep the lithium-ion battery cool.
“One simple thing that a driver can do,” said Chu, “is to park the vehicle in the shade,” as sunlight increases the cabin temperature in the vehicle and over time the repeated exposure to high temperatures will shrink the battery’s lifespan. However, while moderately cool temperatures can help to extend battery life, true cold can reduce the range of the electric vehicle.
Improvements in chemistry are permanently increasing the storage performance of lithium-ion batteries, however, there is room for improvement for a future that drives electric.
