Battery sensing method and apparatus
A method and apparatus is provided the battery sensor for a large-scale battery system. More specifically, the present disclosure relates to the architecture and measurement scheme for a high-accuracy battery voltage sensor based on a calibration scheme. The present disclosure also related to the architecture and measurement method for a cell-level current sensor to effectively and reliably manage a battery pack.
1. A sensing system for a battery pack which includes a multiplicity of battery cells, comprising:
a multiplicity of single cell sensing modules (SCSM), each SCSM respectively configured to facilitate both a current measurement and a voltage measurement exclusively with respect to one of the multiplicity of battery cells in the battery pack;
each SCSM comprising
an analog switching multiplex;
an analog-to-digital converter (ADC);
a signal conditioner which conditions an input signal received at the analog switching multiplex and communicates the input signal after conditioning to the ADC;
a reference voltage generator which generates a plurality of reference voltages; and
a calibration engine which is configured to use the plurality reference voltages to improve a measurement accuracy with respect to the input signal;
wherein each SCSM is configured to facilitate the current measurement of a particular battery cell by determining a voltage drop between first and second locations spaced apart a predetermined distance along an output terminal of the battery cell.
2. The sensing system according to claim 1 , wherein the calibration engine is configured to determine a drift error.
3. The sensing system according to claim 2 , wherein the reference voltage generator generates top and bottom reference voltages which define the full-scale input range for the ADC.
4. The sensing system according to claim 3 , wherein the top and bottom reference voltages are applied to inputs of the signal conditioner in a calibration condition to generate an output calibration voltage, and the calibration engine is configured to determine the drift error value by calculating a difference between a predetermined reference value and a measured value output of the ADC in the calibration condition.
5. The sensing system according to claim 4 , wherein the signal conditioner includes a voltage divider and the calibration engine is configured to automatically use the drift error value to adjust the voltage divider.
6. The sensing system according to claim 5 , wherein the calibration engine is configured to automatically adjust the top reference voltage and the bottom reference voltage based on the drift error value which has been determined.
7. The sensing system according to claim 1 , wherein the analog switching multiplex is configured to select when in a sensing mode one or more of a plurality of the input signals from the particular battery cell and wherein the input signals is selected from the group consisting of a voltage sense signal and a current sense signal.
8. The sensing system according to claim 7 , wherein the analog switching multiplex is further configured to select as the input signal a temperature sensor signal associated with the particular battery cell.
9. The sensing system according to claim 1 , wherein the SCSM is configured to measure the voltage drop as caused by an inherent resistance of a portion of the output terminal.
10. The sensing system according to claim 9 , wherein the signal conditioner includes two voltage conditioners which respectively independently condition an input voltage potential at each of the first and second locations.
11. The sensing system according to claim 10 , further comprising a master controller which receives from each of the SCSM a value which specifies the voltage drop for each of the battery cells.
12. The sensing system according to claim 11 , wherein the master controller is configured to calculate a shunt resistance value associated with each single battery cell using the value which specifies the voltage for each battery cell and based on a total battery pack current measured at a time when the battery pack is first assembled.
13. The sensing system according to claim 12 , wherein the master controller is configured to determine an individual battery cell current for each of the battery cells by using the shunt resistance value and the voltage drop for each battery cell as measured at each of the SCSM.
14. The sensing system according to claim 13 , wherein the master controller automatically determines a condition of each battery cell based on the battery cell current for each battery.
15. The sensing system according to claim 12 , wherein the total battery pack current is determined using a Hall-effect sensor at a battery pack output terminal.
16. A sensing system for a battery pack which includes a multiplicity of battery cells, comprising:
a multiplicity of single cell sensing modules (SCSM), each SCSM respectively configured to facilitate both a current measurement and a voltage measurement exclusively with respect to one of the multiplicity of battery cells in the battery pack;
each SCSM comprising a calibration engine configured to reduce measurement errors; and
wherein each SCSM is configured to facilitate the current measurement of a particular battery cell by determining a voltage drop between first and second locations spaced apart a predetermined distance along an output terminal of the battery cell.
17. A method for determining battery cell current and battery cell voltage for a multiplicity of battery cells associated with a battery pack, comprising:
providing a multiplicity of single cell sensing modules (SCSM) respectively for monitoring a multiplicity of battery cells in the battery pack;
exclusively using each of the multiplicity of SCSM to respectively facilitate both a current measurement and a voltage measurement for a corresponding one the multiplicity of battery cells;
for each of the battery cells, facilitating the current measurement by precisely determining a voltage drop between first and second locations spaced apart a predetermined distance along an output terminal of the battery cell.
18. The method according to claim 17 , further comprising performing at least one calibration operation to facilitate the precise determination of the voltage drop.
19. The method according to claim 17 , further comprising determining for each battery cell a resistance value associated with the electrical path between the first and second locations.
20. The method according to claim 19 , further comprising determining the resistance value for each cell at a time when the battery pack is first assembled.
21. The method according to claim 19 , further comprising using the resistance value which has been determined for each battery cell, and the voltage drop which is measured during a battery management session, to calculate the battery cell current.
22. A sensing system for a battery pack which includes a multiplicity of battery cells, comprising:
a multiplicity of single cell sensing modules (SCSM) respectively provided for the multiplicity of battery cells, each SCSM in communication with a master control module;
each SCSM respectively configured to facilitate both a voltage measurement and a current measurement exclusively with respect to one battery cell of the multiplicity of battery cells in the battery pack; and
a data transceiver to facilitate communications with the master control module;
wherein each SCSM is configured to facilitate the current measurement of a particular battery cell by determining a voltage drop between first and second locations spaced apart a predetermined distance along an output terminal of the battery cell.