Abstract: A method for testing safety circuitry in rechargeable battery packs is provided herein by which the operation and integrity of circuits associated with rechargeable cells may be verified. A controller 103 senses current flow during cell 108 charge or discharge. The controller 103 then activates the safety circuitry and once again senses current to ensure high circuit impedance. If a fault is detected, the controller 103 notifies the user or host device. The controller 103 then decides if the fault warrants isolating the cell 108 from the terminals of the battery pack 111, 112. If such action is warranted, the controller 103 clears the current carrying path 104, 105, creating a fail condition that does not endanger the user or associated equipment.

Abstract: A battery pack (100) includes a battery cell (102), a power switch (104), a regulator circuit (106), control circuit (108), electronic drive switch (112), and a mechanical driver switch (116). The battery pack is placed in the hibernate mode by sending a hibernate message to the control circuit from an external device (134). The control circuit removes a control signal from the electronic driver switch, causing the power switch to open, removing power from the regulator circuit and all attached circuitry, including the control circuit. No current flows from the battery cell past the opened power switch, and the battery pack is then in the hibernate mode. To wake up the battery pack, the mechanical driver switch is actuated by a user, causing the power switch to close, allowing current and voltage from the battery cell to power up the regulator circuit, which in turn powers up the control circuit. The control circuit applies a control signal to the electronic driver switch to hold the power switch closed.

Abstract: A battery pack (62) comprises cells (74), and is charged by a charger (64) providing a current level. The charger (64) is a typical nickel-cadmium battery charger providing a first charge current level in excess of an optimum charge current level. The battery pack (62) further comprises a thermal sensing element (76) and an overcurrent charge protection circuit having an overcurrent switch (78), current sense circuit (80), comparator circuit (82), and temperature signal switch (84). If the current level through the cells (74) exceeds the optimum charge current level, the current sense circuit (80) provides a signal to comparator circuit (82) which actuates the temperature signal switch (84), simulating a hot battery pack. The charger (64) then switches to a second charge current level which does not exceed the optimum charge current level.

Abstract: A battery pack (10) has a memory (26) for storing a password. Upon connecting to a host device (12), or similar load, the battery waits for a data word to be communicated from the host device over a communications channel (22). If an incorrect data word is received a predetermined number of time, or if an initial power time period, as defined by a timer (30), is reached, a switch (16) is opened, thereby disconnecting the battery cell or cells (14) from the load.