Lithium ion battery performance and charge control

This paper presents the initial results from testing of SONY US18650B Li-ion cells from 0 to 40°C. Charge rates from C/10 to C/1.4 and discharge rates of C/2.4 to C/0.8 have been studied, which covers 24% to 70% depth-of-discharge (DOD) in simulated low Earth orbit (LEO). When cells are rated at the capacity delivered to 3.00 V at the C/2 rate, following a C/10 charge to 4.07 V at 20°C, the specific energy of the cells is 70 Wh/kg. This specific energy is significantly higher than the specific energy of Ni-H₂ cells. The preferred operating temperature range for these cells is 10 to 30°C. Constant current charging to a battery voltage was effective, and this method of charge control may be adequate for short life missions with eight series cell batteries. For longer life missions, it will probably be desirable to supplement available current limited, constant potential battery charging with small electronic circuits to assure no cell exceeds the charge voltage maximum