Back-up battery management apparatus and method for charging and testing battery cells in a string of battery cells

An apparatus for selectively charging and testing battery cells in a serial string of battery cells and employed as part of a back-up power supply to a primary power source that supplies power to a main bus connected to a load, the apparatus comprising:

• a regulator configured to receive charging power from an external power supply via a charging power bus, and supply and regulate charging power to the string of battery cells;
• a variable impedance;
• a first controllable switch electrically connected in parallel with the variable impedance, wherein the parallel combination of the variable impedance and the first controllable switch is connected in series between the load bus and the corresponding string of battery cells;
• and
• a controller configured to selectively control the variable impedance and the first controllable switch, wherein the controller is configured to detect when a voltage of the main bus is falling and subsequently initiate operation of the variable impedance and the first controllable switch simultaneously, wherein the variable impedance is operated for a predetermined time period.

A method for selectively charging and testing battery cells in one or more strings of battery cells electrically connected to one another within each string and employed as a back-up power supply for a primary power source, the one or more strings of battery cells selectively connectable to a load bus supplied by the primary power source in order to deliver power in the event of a failure of the primary power source, the method comprising:

• providing a charging power and discharging voltage using a first power supply in a main control module;
• and
• selectively isolating the one or more strings of battery cells from the load bus using a combination of a controllable impedance and a first controllable switch both controlled by a first controller located within a corresponding battery string module connected to a respective string of battery cells of the one or more strings of battery cells;
• selectively receiving charging power at each of the battery string modules from the first power supply via the charging power bus;
• supplying and regulating charging power to the respective string of battery cells with each of the battery string modules;
• detecting when a voltage of the load bus is falling using the first controller;
• and
• initiating operation of the controllable impedance and the first controllable switch simultaneously, wherein the controllable impedance is operated for a predetermined time period.