SwRI Develops New Model Controller to Improve Charging in EV

SwRI is solving fast charging issues with internal research funds to decrease the time taken by EV to recharge. 

FREMONT, CA : Engineers at Southwest Research Institute are solving fast charging problems with internal research funds to minimize the time it takes to recharge electric vehicles (EVs).

As electric vehicles become more mainstream, customers expect a smooth transition to battery-driven platforms, with the same acceleration, efficiency, and comfort as vehicles powered by fossil fuels. Manufacturers have delivered for most of the part, but the technology still lacks some regions, like battery recharge. While it takes just a few minutes to fill a gas tank before getting back on the road, it takes hours for an electric vehicle (EV) to do the same.

To significantly speed up charging, fast charging transforms AC power found in homes to the DC power necessary by batteries inside the charging station. The speed brings new difficulties.

Fast recharging boosts lithium-ion transfer within a battery pack. At these high rates, ions will accumulate on the surface of the battery's anode and deposit metallic lithium through a procedure known as lithium plating, reducing battery performance and, if left unattended, can cause the battery to short circuit and fail.

"The electrochemistry that causes lithium plating is complex and not completely understood," said Dr Bapiraju Surampudi, a staff engineer in SwRI's Powertrain Engineering Division. "ur physics-based model allows us to detect, in real time, the occurrence of lithium plating so we can adjust the charging rate to prevent battery damage while also allowing for shorter charging times."

SwRI created and calibrated a linearized battery model for a 57 Ah nickel manganese cobalt (NMC) cell that accurately predicted when lithium plating would occur. The model measures various battery inner states using differential equations involving no external instrumentation or resources. Other cutting-edge methods for detecting lithium plating are non-real-time and require a disruptive physical examination of the cell.

"The SwRI charge controller showed several improvements compared to the two baseline profiles, including a significant decrease in capacity fade, a 35 percent reduction in battery charge time and an average charge efficiency of 89 percent," Surampudi said. "While pleased with these results, we believe there are additional improvements to be made."