Apparatus and method for charging and testing batteries

A method for charging a rechargeable battery which comprises the steps of:

• (a) measuring the open circuit voltage of said battery and estimating the number of cells possible for the measured open circuit voltage;
• (b) supplying a controllably varying charging current or voltage to the battery for a predetermined period of time and testing said battery for the evolution of gas;
• (c) charging said battery automatically at any charge voltage until the battery charge voltage equals the estimated number of cells of the battery multiplied by a predetermined voltage which is characteristic of the battery;
• (d) repeating steps (a), (b) and (c) until step (b) indicates the evolution of gas;
• (e) determining the current and voltage at which the said battery evolves gas in the increasing current direction ("Igas-up") or in the increasing voltage direction ("Vgas-up"), and the current and voltage at which the battery stops evolving gas in the decreasing current direction ("Igas-down") and in the decreasing voltage direction ("Vgas-down");
• (f) determing the true number of cells in the said battery from Vgas-up and/or Vgas-down;
• (g) charging the said battery automatically at any charge rate until the battery voltage equals the true number of cells multiplied by a predetermined voltage which is characteristic of the battery;
• (h) charging the said battery at a constant voltage equal to voltage in step (g) until the charge current decreases to a predetermined low value;
• (i) charging the said battery with a predetermined constant current at any voltage for a predetermined period of time;
• and
• (j) repeating steps (b), (e), and (i) until step (b) indicates the evolution of gas and step (e) indicates that Igas-down reaches a predetermined lower limit which is characteristic of the desired state of charge of the battery.