System and method for measuring series-connected cell voltages using a flying capacitor with self calibration

Abstract

System and method for measuring series-connected cell voltages using a flying capacitor with self-calibration. In at least one embodiment of a system of the present disclosure, the system comprises a capacitor, a switch, an amplifier, an analog-to-digital converter, and a precision voltage device. In an exemplary method of the present disclosure, the method comprises the steps of charging a capacitor, obtaining a charge voltage reading, discharging the capacitor for a known duration, obtaining a discharge voltage reading, and signaling a malfunction of the discharge voltage reading is greater than a predetermined voltage level.

1 . A system for measuring voltage of individual cells in a plurality of cells connected in series, said system comprising:
 a capacitor for storing a charge of at least one of the cells, said capacitor including terminals;   at least one switch electrically connected to said capacitor for selectively connecting at least one of the cells to said capacitor;   an amplifier including inputs electrically connected to said terminals of said capacitor and an output;   an analog-to-digital converter (ADC) electrically connectable to said output of said amplifier for converting an amplified analog voltage supplied by said amplifier into digital voltage data; and   at least one precision voltage reference (PVR) device for providing a known reference voltage.   
   
   
       2 . The system of  claim 1 , wherein said at least one PVR device is electrically connectable to said ADC such that the known reference voltage is provided to said ADC. 
   
   
       3 . The system of  claim 1 , further comprising a multiplexer having a first multiplexer input, a second multiplexer input, and a multiplexer output electrically connected either of said first multiplexer input or said second multiplexer input to said multiplexer output, wherein said first multiplexer input is electrically connected to said amplifier, said second multiplexer input is electrically connected to said PVR device, and said multiplexer output is electrically connected to said ADC. 
   
   
       4 . The system of  claim 3 , further comprising a controller in communication with said ADC for receiving the digital voltage data from said ADC. 
   
   
       5 . The system of  claim 4 , wherein said controller is in communication with said multiplexer for controlling which of said multiplexer inputs of said multiplexer are electrically connected to said multiplexer output. 
   
   
       6 . The system of  claim 1 , wherein said at least one PVR device is electrically connectable to said capacitor such that the known reference voltage is provided to said capacitor. 
   
   
       7 . The system of  claim 6 , wherein said at least one PVR device is further defined as a first PVR device and a second PVR device. 
   
   
       8 . The system of  claim 1 , further comprising:
 a plurality of cell switches for electrical connection to a plurality of cells, wherein each cell switch includes a first side and a second side, wherein said first side of each cell switch is electrically connectable to a positive terminal of one of the cells;   a first bus electrically connected to said second side of alternate cell switches; and   a second bus electrically connected to said second side of each cell switch not connected to said first bus.   
   
   
       9 . The system of  claim 8 , wherein the at least one PVR device comprises a first PVR device and a second PVR device, wherein the first PVR device is electrically connectable to the first bus, and wherein the second PVR device is electrically connectable to the second bus. 
   
   
       10 . A system for measuring voltage of individual cells in a plurality of cells connected in series, the system comprising:
 a capacitor having terminals;   at least one switch electrically connected to the capacitor;   an amplifier having inputs and an output, the inputs electrically connected to the terminals of the capacitor;   an analog-to-digital converter (ADC) electrically connected to the output of the amplifier; and   at least one precision voltage reference (PVR) device electrically connectable to the ADC.   
   
   
       11 . The system of  claim 10 , wherein the at least one switch selectively connects at least one of a plurality of cells to the capacitor. 
   
   
       12 . The system of  claim 10 , wherein the PVR device provides a known reference voltage to the ADC when the PVR device is electrically connected to the ADC. 
   
   
       13 . The system of  claim 10 , further comprising:
 a plurality of cell switches for electrical connection to a plurality of cells, wherein each cell switch includes a first side and a second side, wherein said first side of each cell switch electrically connectable to a positive terminal of one of the cells;   a first bus electrically connected to said second side of alternate cell switches; and   a second bus electrically connected to said second side of each cell switch not connected to said first bus.   
   
   
       14 . The system of  claim 13 , wherein the at least one PVR device comprises a first PVR device and a second PVR device, wherein the first PVR device is electrically connectable to the first bus, and wherein the second PVR device is electrically connectable to the second bus. 
   
   
       15 . The system of  claim 10 , further comprising a controller in communication with said ADC for receiving the data from said ADC. 
   
   
       16 . A system for measuring voltage of individual cells in a plurality of cells connected in series, the system comprising:
 a capacitor having terminals;   at least one switch electrically connected to the capacitor;   an amplifier having inputs and an output, the inputs electrically connected to the terminals of the capacitor;   an analog-to-digital converter (ADC) electrically connected to the output of the amplifier;   at least one precision voltage reference (PVR) device electrically connectable to the ADC; and   a multiplexer having a first multiplexer input, a second multiplexer input, and a multiplexer output electrically connected either of said first multiplexer input or said second multiplexer input to said multiplexer output, wherein said first multiplexer input is electrically connected to said amplifier, said second multiplexer input is electrically connected to said PVR device, and said multiplexer output is electrically connected to said ADC.   
   
   
       17 . A system for measuring voltage of individual cells in a plurality of cells connected in series, the system comprising:
 a capacitor having terminals;   at least one switch electrically connected to the capacitor;   an amplifier having inputs and an output, the inputs electrically connected to the terminals of the capacitor;   an analog-to-digital converter (ADC) electrically connected to the output of the amplifier;   at least one precision voltage reference (PVR) device electrically connectable to the ADC;   a plurality of cell switches for electrical connection to a plurality of cells, wherein each cell switch includes a first side and a second side, wherein said first side of each cell switch electrically connectable to a positive terminal of one of the cells;   a first bus electrically connected to said second side of alternate cell switches; and   a second bus electrically connected to said second side of each cell switch not connected to said first bus.   
   
   
       18 . A method for measuring voltage of individual cells in a plurality of cells connected in series, the method comprising the steps of:
 charging a capacitor electrically connected to at least one cell for a first charge duration;   obtaining a charge voltage reading from the capacitor;   discharging the capacitor for a first discharge duration;   obtaining a discharge voltage reading from the capacitor; and   signaling a malfunction if the discharge voltage reading is greater than a predetermined voltage level.   
   
   
       19 . The method of  claim 18 , wherein the step of signaling a malfunction further comprises the step of comparing the discharge voltage reading to the predetermined voltage level. 
   
   
       20 . The method of  claim 18 , wherein the step of charging a capacitor further comprises the step of electrically disconnecting the capacitor from the at least one cell after the first charge duration. 
   
   
       21 . The method of  claim 18 , wherein the step of discharging the capacitor is performed by electrically connecting one or more terminals of the capacitor to a ground. 
   
   
       22 . The method of  claim 18 , wherein the steps of measuring capacitor voltage are performed by amplifying the capacitor voltage, converting the amplified capacitor voltage to a digital voltage signal, and reading the digital voltage signal using a controller.