Fast Charging of 3000- and 3500-mAh Lithium-Ion Batteries Using a Sinusoidal Ripple Current Method

Author(s):

Richard L. Thomas Jr.

Abstract:

The U.S. Army is interested in fast charging the most energy-dense lithium-ion batteries (LIBs) currently available—i.e., 18650 size with an Ampere hour (Ah) rating between 3.0 and 3.5 Ah. The common charging method currently used is a constant current–constant voltage (CC-CV) method that is very effective for nominal charging and usually takes about 1.5 h or more to achieve a 100% charge. When CC CV charging is used for faster charging of LIBs (i.e., at twice the standard charging rate), studies and common understanding suggest it can reduce battery lifespan. Specifically, some sources indicate that when a battery’s State of Health (SOH) is down to 80%, using fast charging can cause significant life-cycle reduction, with some studies suggesting a reduction of approximately 75%. In this report, the CC-CV charging method will be compared with the sinusoidal ripple current average constant voltage method. To evaluate this method the rate of charge will be three times the nominal charging rate for the LIBs under test, which equates to 3 C for 3000-mAh LIBs and 1.5 C for 3300- and 3500-mAh LIBs.