Patent ID: 7508171
Filing Date: 2009-03-24
Classification: B25F,B60L,H01M,H02J,Y02E,Y02T

Abstract:
1. A battery pack configured to power a cordless power tool and including a plurality of serially-connected battery cells, the battery pack including a protection arrangement adapted to limit or interrupt current in the battery pack upon a fault condition that is sensed in the battery pack; and at least one protection circuit monitoring pack voltage for a potential over-discharge fault condition in the pack and adapted to perform an automatic shutdown of current flow in the pack if the monitored voltage reaches a given dynamic voltage threshold, wherein the dynamic voltage threshold is varied by subtracting a proportion of instant discharge current from an absolute threshold level to compensate for impedance of the battery pack and to avoid a spurious automatic shutdown of current flow, if monitored voltage momentarily drops below the threshold.