Apparatus for improving cell balancing and cell failure detection

Abstract

Disclosed are systems and methods for improved cell-balancing circuits, back-up failure detection circuits and alarm extension for cells and modules of an energy storage system. One aspect of the invention comprises an energy storage device cell balancing apparatus. The apparatus comprises a first and a second dissipative component connected in series. The first dissipative component and the second dissipative component are coupled to an energy storage cell. The second dissipative component monitors a voltage of the energy storage cell and, if the voltage is at or above a reference voltage, the second dissipative component conducts a discharging current through the first and second dissipative components. The first dissipative component maintains a voltage drop across the first dissipative component that is proportional to the voltage of the energy storage cell. The second dissipative component maintains a constant voltage drop across the second dissipative component when conducting the discharging current.

What is claimed is: 
     
         1 . An alarm detection apparatus for an energy storage device comprising:
 a rectifier comprising an anode and a cathode, wherein the cathode of the rectifier is configured to be connected to a positive terminal of an energy storage module; and   a current source connected to the anode of the rectifier and configured to generate a constant current in response to anode voltages outside a minimum voltage and a maximum voltage.   
     
     
         2 . The apparatus of  claim 1 , further comprising an isolation device configured to generate an electrically isolated signal to an external circuit based on the constant current. 
     
     
         3 . The apparatus of  claim 1 , wherein the rectifier comprises a rectifier bridge configured to enable the current source to generate the constant current in response to a positive or negative voltage at the energy storage module. 
     
     
         4 . The apparatus of  claim 1 , further comprising:
 a transistor; and   a capacitor;   wherein the transistor is configured to turn on in response to the constant current;   wherein the capacitor is configured to generate an alarm in response to the constant current, wherein the transistor is configured to charge the capacitor, and wherein the capacitor is configured to continue generating the alarm when the constant current is no longer present.