Electric vehicle batteries before and after fast-charging in testing. Source: University of California, RiversideRecharging stations for electric vehicles (EVs) are increasing in number all over the world in step with an increase in EVs. But these fast charging stations may cause EV batteries to crack, leak and lose storage capacity after just a handful of charges.
The new research, which comes from the University of California, Riverside, shows that fast-charging subjects car batteries to high temperatures and high resistance causing the damage. The researchers have also developed a method for charging at lower temperatures with less risk of catastrophic damage and loss of storage capacity.
Researchers charged a set of discharged Panasonic NCR 18650B cylindrical lithium-ion batteries inside a Tesla vehicle using fast-charging found along freeways and other locations. They also applied a new fast-charging algorithm based on the battery’s internal resistance, which interferes with the flow of electrons. They found that the internal resistance of automotive batteries fluctuates according to temperature, charge state, battery age and other factors. The higher the resistance the more problems that can be found during charging.
For the first 13 charging cycles, battery storage for both charging techniques remained the same, but after 40 charging cycles the industry fast-charging technique caused capacity to fade much faster, only keeping 60% of their storage capacity. However, batteries charged using the new method retained more than 80% capacity after the 40th cycle.
At 80%, rechargeable lithium-ion batteries have reached the end of their use life for most purposes. After just 25 fast-charging cycles, EV batteries were found to have reached this point.
“Industrial fast-charging affects the lifespan of lithium-ion batteries adversely because of the increase in the internal resistance of the batteries, which in turn results in heat generation,” said Tanner Zerrin, doctoral student at the University of California, Riverside.
After 60 charging cycles using the fast-charging method, the EV battery cases cracked, exposing the electrodes and electrolyte to air and increasing the risk of fire or explosion. Fast-charging at high temperatures of 140° F accelerated both the damage and the risk, researchers said.
Researchers have applied for a patent on the adaptive internal resistance fast-charging algorithm that could eventually be licensed by battery and car manufacturers. Meanwhile, the team recommends minimizing the use of commercial fast chargers, recharging before the battery is completely drained and preventing overcharging.
The full research can be found in the journal Energy Storage.
