Self discharge of batteries at high temperatures

• US 6,025,699 A
• Filed: 12/12/1997
• Issued: 02/15/2000
• Est. Priority Date: 12/12/1997
• Status: Expired due to Term

• Current Assignee: Dell USA LP (Dell Technologies Inc.)
• Original Assignee: Dell USA LP (Dell Technologies Inc.)
• Inventors: Cummings, John A.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): SHIN, KYUNG E
• Application Number:
  US08/989,605
• Time in Patent Office: 795 Days
• Field of Search: 320/150-154, 320/132-136, 320/112, 320/113, 320/128, 320/127, 429/7, 429/62, 429/90-93
• US Class Current: 320/136
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0036 using connection detecting circuits H02J7/0034 takes precedence

Abstract

A rechargeable battery pack that includes a temperature monitoring circuit a rechargeable battery, and a discharge circuit, advantageously provides a battery pack which senses when the battery pack is exposed to a harmful temperature and cause the discharge circuit to discharge electricity stored in the battery until the battery'"'"'s charge level is reduced to a safe level for the particular temperature. The rechargeable battery has a positive terminal and a negative terminal. The discharge circuit is coupled to the rechargeable battery. A controller is coupled to the discharge circuit. The temperature monitoring circuit is coupled to the controller and measures a temperature of the battery, providing a temperature indication to the controller. The controller causes the discharge circuit to discharge electricity from the battery based upon the temperature indication.

Claims

1. A rechargeable battery pack comprising:

a rechargeable battery having a positive terminal and a negative terminal;

a discharge circuit coupled to the rechargeable battery;

a controller coupled to the discharge circuit;

a voltage measuring circuit coupled to the battery, the voltage measuring circuit determining the voltage across the battery and supplying a voltage indication to the controller;

a current measuring circuit coupled to the battery, the current measuring circuit determining the current provided by the battery and supplying a current indication to the controller; and

a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of the battery and providing a temperature indication to the controller, the controller using the voltage indication, the current indication, and the temperature indication to determine a battery charge level, and, for a particular temperature, the controller causing the discharge circuit to discharge electricity from the battery until the battery charge level is reduced to a safe battery charge level.

2. The battery pack of claim 1 wherein the discharge circuit is coupled in parallel with the rechargeable battery.

3. The battery pack of claim 1 wherein the discharge circuit includes a resistor and a transistor coupled in series, the transistor being controlled by the controller.

4. The battery pack of claim 1 wherein the discharge circuit includes a variable resistance field effect transistor.

7. The battery pack of claim 1 further comprising a bus interface coupled to the controller.

8. The battery pack of claim 7 wherein the bus interface is a system management bus interface.

9. The battery pack of claim 1 wherein the rechargeable battery uses a battery chemistry selected from nickel cadmium, nickel-metal hydride, lithium ion, and lithium-polymer chemistries.

10. The battery pack of claim 1 wherein the controller is an integrated circuit selected from the group consisting of microcontrollers, microprocessors, application specific integrated circuits (ASICs), and embedded processors.

5. A rechargeable battery pack comprising:

a rechargeable battery having a positive terminal and a negative terminal;

a discharge circuit coupled to the rechargeable battery;

a controller coupled to the discharge circuit; and

a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit including;

a temperature sensor, the temperature sensor producing an analog temperature signal;

an analog-to-digital converter coupled to the temperature sensor, the converter converting the analog temperature signal to a digital temperature value;

a memory device;

a comparator coupled to the converter and the memory device, the comparator including an output terminal, the comparator providing an output signal on the output terminal based on a comparison of the digital temperature value to a threshold temperature value stored in the memory device; and

an interface coupled to the converter and the memory device, the interface allowing communication between the temperature monitoring circuit and the controller;

wherein the temperature monitoring circuit is capable of measuring a temperature of the battery and providing a temperature indication to the controller, the controller causing the discharge circuit to discharge the battery based upon the indication.

6. The battery pack of claim 5 wherein the temperature sensor is a silicon bandgap temperature sensor.

11. A rechargeable battery pack comprising:

a rechargeable battery having a positive terminal and a negative terminal;

a discharge circuit coupled to the rechargeable battery;

a controller coupled to the discharge circuit; and

a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of the battery and providing a plurality of temperature indications to the controller including a temperature warning signal and a temperature value signal, the controller causing the discharge circuit to discharge the battery based upon at least one of the indications.

12. A battery powered computer system comprising:

a host device; and

a rechargeable battery pack coupled to the host device, the battery pack capable of providing power to the host device, the battery pack including;

a rechargeable battery having a positive terminal and a negative terminal;

a discharge circuit coupled to the rechargeable battery;

a controller coupled to the discharge circuit;

a voltage measuring circuit coupled to the battery, the voltage measuring circuit determining the voltage across the battery and supplying a voltage indication to the controller;

a current measuring circuit coupled to the battery, the current measuring circuit determining the current provided by the battery and supplying a current indication to the controller; and

a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of the battery and providing a temperature indication to the controller, the controller using the voltage indication, the current indication, and the temperature indication to determine a battery charge level, and, for a particular temperature, the controller causing the discharge circuit to discharge electricity from the battery until the battery charge level is reduced to a safe battery charge level.

13. The battery powered computer system of claim 12 wherein the host device includes a processor and a memory coupled to the processor, and wherein the processor and the memory are powered by the rechargeable battery pack.

14. The battery powered computer system of claim 12 wherein the discharge circuit is coupled in parallel with the rechargeable battery.

15. The battery powered computer system of claim 12 wherein the discharge circuit includes a resistor and a transistor coupled in series, the transistor being controlled by the controller.

16. The battery powered computer system of claim 12 further comprising a communications bus, the host device being coupled to the communications bus, the battery pack including a bus interface coupled to the controller and to the communications bus.

17. The battery powered computer system of claim 12 wherein the rechargeable battery uses a battery chemistry selected from nickel cadmium, nickel-metal hydride, lithium ion, and lithium-polymer chemistries.

18. The battery powered computer system of claim 12 wherein the controller is an integrated circuit selected from the group consisting of microcontrollers, microprocessors, application specific integrated circuits (ASICs), and embedded processors.

19. A method of protecting a rechargeable battery comprising:

providing a rechargeable battery pack including a rechargeable battery, a temperature monitoring circuit, a discharge circuit, and a controller;

measuring a temperature of the rechargeable battery with the temperature monitoring circuit;

comparing the measured temperature with a threshold temperature to obtain a comparison result;

measuring a battery charge level of the rechargeable battery; and

discharging, based upon the comparison result and the measured battery charge level, the rechargeable battery with the discharge circuit until the battery charge level is reduced to a safe battery charge level.

20. The method of claim 19 wherein the comparing step is performed by the temperature monitoring circuit.

21. The method of claim 19 wherein the comparing step is performed by the controller.

22. The method of claim 19 wherein the rechargeable battery pack includes a voltage monitoring circuit and a current monitoring circuit, the method further comprising:

measuring a voltage of the battery;

measuring a current of the battery; and

using the measured temperature, voltage, and current to determine the battery charge level.

23. An apparatus for protecting a rechargeable battery comprising:

a discharge circuit, the discharge circuit capable of being coupled to a rechargeable battery;

a controller coupled to the discharge circuit, the controller being capable of receiving a voltage indication from the of rechargeable battery and a current indication from the rechargeable battery; and

a temperature monitoring circuit coupled to the controller, the temperature monitoring circuit being capable of measuring a temperature of a rechargeable battery and providing a temperature indication to the controller, the controller using the voltage indication, the current indication, and the temperature indication to determine a battery charge level, and, for a particular temperature, the controller causing the discharge circuit to discharge electricity from the battery until the battery charge level is reduced to a safe battery charge level.

24. The apparatus of claim 23 wherein the discharge circuit is coupled in parallel with the rechargeable battery.

25. The apparatus of claim 23 wherein the discharge circuit includes a resistor and a transistor coupled in series, the transistor controlled by the controller.

26. The apparatus of claim 23 further comprising a bus interface coupled to the controller.