Battery management system with temperature sensing and charge management for individual series-connected battery cells

• US 10,396,570 B2
• Filed: 01/07/2013
• Issued: 08/27/2019
• Est. Priority Date: 11/10/2006
• Status: Active Grant

• Current Assignee: Lithium Balance A/S (Sensata Technologies Holding Plc)
• Original Assignee: Lithium Balance A/S (Sensata Technologies Holding Plc)
• Inventors: Loncarevic, Ivan
• Primary Examiner(s): Isla, Richard
• Assistant Examiner(s): Sharief, Mohammed J
• Application Number:
  US13/735,946
• Publication Number:
  US 20130207613A1
• Time in Patent Office: 2,423 Days
• Field of Search: 320134
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits

Abstract

A method and apparatus are disclosed for a Battery Management System (BMS) for the controlling of the charging and discharging of a plurality of battery cells (12). Each battery cell has an associated plurality of control circuits (32, 36) which monitor and control the charging of individual battery cells. These units are controlled by a central microcontroller (14) which shunts current around the battery cell if fully charged and stops discharge if a battery cell is fully discharged in order to prevent damage to the other cells.

Claims

1. A modular battery management system for controlling and monitoring a plurality of battery cells connected in series in a battery connected to a load, the system comprising:

a central controlling microcontroller;

a plurality of cell balancing means and a plurality of slave sensing means, each of the cell balancing means and each of the slave sensing means being in communication with the central controlling microcontroller and operatively connected to an associated one of the battery cells in the plurality of battery cells; and

a plurality of temperature sensors operable to monitor the temperature of each of the plurality of cell balancing means and each of the plurality of slave sensing means to determine if an excessive temperature has been reached;

wherein the cell balancing means and the slave sensing means connected to each associated one of the plurality of battery cells are operable;

(a) to measure a charging state of the associated one of the plurality of battery cells;

(b) when a maximum charging state is reached in at least one of the associated battery cells, to establish a shunt across the at least one of the associated battery cells that has reached the maximum charging state, thereby allowing a continued charging of the remaining battery cells in the plurality of battery cells;

(c) when the shunt is established, to communicate to the central controlling microcontroller a message representing that the maximum charging state has been reached in the at least one of the associated battery cells in which the maximum charging state has been reached;

(d) during discharging of the battery, to inform the central controlling microcontroller when a non-zero minimum voltage has been reached in the associated one of the battery cells so as to cause the central controlling microcontroller to disconnect all the cells in the plurality of cells from the load in order to prevent further discharging of the associated one of the battery cells in which the non-zero minimum voltage has been reached to a cell-ruining voltage below the non-zero minimum voltage; and

(e) shut down charging of the battery when the excessive temperature is reached;

wherein each of said cell balancing means is configured to establish the shunt in response to a signal from the slave sensing means when the respective slave sensing means has measured a maximum voltage across the at least one of the associated battery cells that has reached the maximum charging state; and

wherein each of the plurality of slave sensing means is further operatively connected to the central controlling microcontroller via a common data bus, whereby a continuous charging of the remaining battery cells is controlled by the central controlling microcontroller.

2. The modular battery management system according to claim 1, wherein the common data bus is separated from the central controlling microcontroller by an isolation stage and a coupling stage.

3. The modular battery management system according to claim 1, wherein each of the plurality of temperature sensors is further operable to measure the temperature of an associated one of the battery cells, each of the plurality of temperature sensors being operatively connected to a respective slave sensing means, wherein the respective slave sensing means is configured for reducing a charging current to the associated one of the battery cells in response to the measured temperature of the associated one of the battery cells.

4. The modular battery management system according to claim 1, further comprising a microcontroller temperature sensor operable to monitor the temperature of the central controlling microcontroller, thereby allowing the central controlling microcontroller to shut down charging or discharging of the plurality of battery cells when an excessive temperature is reached.

5. The modular battery management system according to claim 1, further comprising means for shutting down charging and discharging of the plurality of battery cells controlled by the central controlling microcontroller in the case of an overload or a short circuit of the battery.

6. The modular battery management system according to claim 1, further comprising current monitoring means, including a shunt resistor in series with the plurality of battery cells, for monitoring current through the plurality of battery cells.

7. The modular battery management system according to claim 1, further comprising a fuse for protection in case of an overload or a short circuit of the battery.

8. The modular battery management system according to claim 1, further comprising a power supply unit operable to supply power to the central controlling microcontroller.

9. The modular battery management system according to claim 1, further comprising a fuel gauge operable to monitor a charge capacity of the battery.

10. The modular battery management system according to claim 1, wherein each of the plurality of cells has a positive terminal and a negative terminal, and where the shunt is established by connecting the positive terminal to the negative terminal through a power resistor and a fast-switching transistor.

11. The modular battery management system according to claim 10, wherein pulse-width modulation is used to provide adjustable current through the power resistor.

12. The modular battery management system according to claim 1, wherein the battery is a lithium-ion battery.

13. The modular battery management system according to claim 1, wherein the minimum voltage is 2.8V.

14. A method for controlling and monitoring a plurality of individual battery cells connected in series in a battery connected to a load, each of the individual battery cells having a positive terminal and a negative terminal, each of the individual battery cells being operatively connected to an associated one of a plurality of slave sensing means, the method comprising:

(a) during charging of the battery;

(i) measuring a voltage across each individual cell by the associated one of the plurality of slave sensing means;

(ii) shunting any individual cell in which the voltage measured by the associated one of the plurality of slave sensing means has reached a maximum voltage, the shunting being performed by shorting the positive and negative terminals of the individual cell through a resistor and a switching transistor, thereby bypassing the individual cell in which the maximum voltage has been reached to allow continued charging of the remaining battery cells in the plurality of individual battery cells;

(iii) sensing the temperature of each of the plurality of the slave sensing means; and

(iv) shutting down the charging of the battery when the temperature of any of the slave sensing means exceeds a predetermined temperature;

(b) during discharging of the battery;

measuring the voltage across each individual cell by the associated one of the slave sensing means until the measured voltage reaches a non-zero minimum voltage in one or more individual cells, at which time all of the plurality of individual cells in the battery are removed from the load to prevent the one or more cells in which the measured voltage has reached the non-zero minimum voltage from further discharging to a cell-ruining voltage below the non-zero minimum voltage;

(c) wherein the shunting of each of the individual cells during charging is controlled by the associated one of the plurality of slave sensing means, wherein continued charging of the remaining cells in the battery is controlled by a central controlling microcontroller, which is operatively connected to each of the plurality of slave sensing means via a common data bus, and wherein removal of all the plurality of individual cells in the battery from the load during discharging is performed by the central controlling microcontroller.

15. The method according to claim 14, further comprising:

(d) measuring the temperature of one or more individual cells; and

(e) reducing charging current to any of the individual cells for which a measured temperature exceeds a predetermined maximum temperature.

16. The method according to claim 14, where the charging and the discharging of the individual cells is interrupted in case of an overload or a short circuit of the battery.

17. The method according to claim 14, further comprising the step of separating the common data bus from the central controlling microcontroller by an isolation stage and a coupling stage in order to prevent the central controlling microcontroller from being affected by high voltages.

18. The method according to claim 14, further comprising the steps of:

(d) monitoring the temperature of the central controlling microcontroller, and

(e) shutting down the charging or discharging if the temperature of the central controlling microcontroller reaches a predetermined temperature.

19. The method of claim 14, wherein the battery is a lithium-ion battery.

20. The method according to claim 14, wherein the minimum voltage is 2.8V.