A battery protection circuit is provided that includes a safety circuit and an
overpower circuit. The safety circuit monitors the voltage and current of at least
one rechargeable cell within the battery pack, and disconnects the cell(s) from
the external terminals of the battery pack when either the voltage becomes too
high or low, or when excessive current is being drawn from the battery pack. The
overpower circuit monitors the power being delivered to or sourced from the battery
pack to the load. The overpower circuit actuates when the power exceeds a predetermined
threshold, thereby simulating an overcurrent condition in the safety circuit. The
overcurrent condition causes a disconnect means, like a transistor, to open, thereby
disconnecting the cell(s) from the external terminals. The battery protection circuit
then latches in this disconnected state until a load is removed from the terminals
of the battery pack.
