BATTERY RECHARGING SYSTEM WITH STATE OF CHARGE DETECTION THAT INITIALLY DETECTS WHETHER A BATTERY TO BE CHARGED IS ALREADY AT OR NEAR FULL CHARGE TO PREVENT OVERCHARGING
 Inventor: Daniele C. Brotto, Baltimore, Md.
 Assignee: Black & Decker Inc., Newark, Del.
 Appl. No.: 203,541
 Filed: Feb. 28,1994
 Int CI.6 H01M 10/44
 U.S. CI 320/21; 320/31; 320/39
 Field of Search 320/20, 21, 22,
320/23, 24, 31, 32, 39, 40, 43, 44, 45
 References Cited
U.S. PATENT DOCUMENTS 4,388,582 6/1983 Saaretal 320/20
Primary Examiner—-Edward Tso
Attorney, Agent, or Firm—Harness, Dickey & Pierce, P.L.C.
A state of charge test is first performed on the battery by applying a current pulse and then observing the voltage decay characteristics which result Batteries which are initially nearly fully charged exhibit a larger voltage decay than batteries which are not as fully charged. The result of this initial state of charge test is used to determine how to best terminate battery charging. In this way battery overcharging is prevented regardless of the initial state of charge of the battery.
47 Claims, 3 Drawing Sheets