When Nissan launched the LEAF electric car back in 2011, it came with the ability to recharge its 24 kilowatt-hour lithium-ion battery pack from empty to 80- percent full in around 30 minutes using a dedicated CHAdeMO DC quick charging station. At the time, rapid charging was marketed as a way for LEAF owners to quickly extend the range of their car beyond its EPA-approved 73 miles of range, but owners were also strongly warned in the LEAF owners’ manual that continual rapid charging — especially multiple times a day — would have a negative effect on battery pack life.
Since then, despite Nissan’s own assertions that rapid charging wasn’t as bad for a LEAF’s battery pack as it once thought it was, the general consensus remains that rapid charging isn’t great for your car’s battery pack.
But now a new study from Stanford University and the Stanford Institute for Material Sciences has come to the conclusion that rapid charging really won’t do as much harm to your electric car battery pack as the electric automotive industry once thought. What’s more, the study suggests that quickly discharging your car’s battery pack might actually be good for it.
As Green Car Congress (via) GreenCarReports details, the researchers built and tested a selection of coin-cell battery packs and charged them with different amounts of current for differing periods of time, before disassembling the battery packs and then examining them under magnification and x-ray radiation to see how they were responding at a molecular level.
The goal: to examine how the nanoparticles in the lithium-ion phosphate cathode used in each battery behaved during charge and discharge cycles, and to see if current flow had any impact on battery life. By understanding more clearly how battery cathodes expand and contract as they absorb and release ions, the researchers had hoped to develop more robust cell design and also change the way battery packs are charged to promote longer cell life.
In theory, the more ions absorbed during a charge cycle and released during a discharge cycle by the cathode, the longer the battery will last, but the researchers found that only a small amount of the nanoparticles were absorbing and releasing ions during testing, regardless of how quickly the battery was charged. In other words, rapid charging or slow charging, the battery absorbed ions at the same rate, quite different to what had been originally thought.
While the rate of charge didn’t seem to affect battery performance or life however, the researchers noted that discharge speed was more important to long-life than charging.
In fact, comparing a one-hour discharge cycle to a six-minute discharge, the researchers found that there was a much more homogenous discharge rate across the cathode at higher currents than lower ones. In turn, that suggests that higher discharge rates might actually be better for an electric car battery pack.
The challenge now, is trying to put that discovery into practice in electric car battery packs and other consumer electronics devices. While the researchers have shown that quicker discharge rates seem to promote longer battery life, the definition of quick isn’t clear from the summary we’ve seen.
What we can tell you however, is that it’s good to have another study proving that rapid charging won’t destroy your car’s battery pack — and perhaps driving at 70 mph and recharging more regularly might actually help your battery pack live a long and healthy life.
It also opens up the possibility of a world where faster rapid charging technology means we’ll have to wait just a few minutes rather than half an hour to refill our car’s battery pack — something that perhaps Tesla has already hinted at with its continuing attempt to bring down the time it takes us to refill our electric car’s battery pack.
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