Patent ID: 7679873
Filing Date: 2010-03-16
Classification: H02H

Abstract:
1. A method of preventing deep discharge of the battery pack ( 1 ) with series-connected cell groups ( 2 a , 2 b ) by polarity reversal of an individual weakest cell ( 3 ), comprising a difference measurement step ( 8 ) which is repeated over time for detecting an event (Θ) indicative of a probable reversal of polarity and in which a change over time of a voltage difference between two cell groups ( 2 a , 2 b ) having identical numbers of cells is checked to determine if the change in the voltage difference has exceeded an amount corresponding to a difference threshold value (S D ) that reliably distinguishes a fast polarity reversal of an individual weakest cell ( 3 ) in exactly one cell group ( 2 a , 2 b ) from a slow fluctuation of a voltage difference between two cell groups ( 2 a , 2 b ) during an ordinary discharge characteristic curve without polarity reversal of an individual weakest cell ( 3 ).