CELL VOLTAGE SENSING FOR RECHARGEABLE BATTERY PACKS

• US 20160093921A1
• Filed: 07/20/2015
• Published: 03/31/2016
• Est. Priority Date: 09/25/2014
• Status: Abandoned Application

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Manthiri, Soundararajan, Kadirvel, Karthik, Reddiconto, Salvatore, Tan, Liquan
• Application Number:
  US14/804,121
• Publication Number:
  US 20160093921A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 2010/4271 Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
• CPC Class Codes: H01M 2200/00 Safety devices for primary or secondary batteries
• CPC Class Codes: H01M 50/574 Devices or arrangements for the interruption of current
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery system has positive and negative pack terminals, and positive and negative sense terminals. An electrochemical cell assembly has positive and negative cell terminals. An electrically conductive power path has a positive leg that connects the positive cell terminal to the positive pack terminal, and a negative leg that connects the negative cell terminal to the negative pack terminal. A power switch circuit is connected in the power path. An electrically conductive sense path separate from the power path has a positive leg that connects the positive cell terminal to the positive sense terminal, and a negative leg that connects to the negative sense terminal. A sense switch circuit is connected in the sense path. Other embodiments are also described and claimed.

Claims

1. A battery system comprising:

a positive pack terminal and a negative pack terminal;

a positive sense terminal and a negative sense terminal;

an electrochemical cell assembly having a positive cell terminal and a negative cell terminal;

an electrically conductive power path having a positive leg that connects the positive cell terminal to the positive pack terminal, and a negative leg that connects the negative cell terminal to the negative pack terminal;

a power switch circuit connected in the power path;

an electrically conductive sense path, separate from the power path, having a positive leg that connects the positive cell terminal to the positive sense terminal, and a negative leg that connects the negative cell terminal to the negative sense terminal; and

a sense switch circuit connected in the sense path.

2. The battery system of claim 1 wherein the electrochemical cell assembly is one of (i) a single cell having one or more sub-cells connected in parallel, or (ii) multiple cells connected in series.

3. The battery system of claim 1 wherein the sense switch circuit is connected between the positive cell terminal and the positive sense terminal.

4. The battery system of claim 1 wherein the sense switch circuit is connected between the negative cell terminal and the negative sense terminal.

5. The battery system of claim 1 further comprising a discrete resistor connected in series with the sense path.

6. The battery system of claim 1 wherein there are no active devices in the sense path, between the cell terminals and the sense terminals, except for one or more transistor based switches.

7. The battery system of claim 1 further comprising a protection control circuit that is powered by the cell assembly and connected to the power switch circuit, wherein the protection control circuit signals the power switch circuit into an open circuit state in response to detecting a fault condition.

8. The battery system of claim 7 wherein the fault condition is one of a) an overvoltage state, b) an undervoltage state, or c) an overcurrent state.

9. The battery system of claim 7 wherein the protection control circuit is connected to the sense switch circuit and signals the sense switch circuit into an open circuit state in response to detecting the fault condition.

10. The battery system of claim 9 wherein the same control signal from the protection control circuit is used to signal both the power switch circuit and the sense switch circuit into the open circuit state in response to detecting the fault condition.

11. The battery system of claim 1 wherein the sense switch circuit is connected in the negative leg of the sense path.

12. The battery system of claim 7 wherein the protection control circuit, the power switch circuit, and the sense switch circuit are all packaged within a battery pack housing, and the pack terminals and sense terminals are individually accessible from outside of the housing.

13. The battery system of claim 12 further comprising a pack connector system, wherein the pack terminals and sense terminals are individual contacts of the pack connector system.

14. The battery system of claim 1 further comprising:

a voltage sensing circuit connected to the sense terminals; and

a charging circuit connected to the pack terminals, wherein the charging circuit increases, reduces and cuts off current in the power path during a charging cycle of the cell in accordance with voltage as measured by the voltage sensing circuit through the sense terminals.

15. A battery system comprising:

a positive pack terminal and a negative pack terminal;

a positive sense terminal and a negative sense terminal;

an electrochemical cell assembly having a positive cell terminal and a negative cell terminal;

an electrically conductive power path that connects the positive and negative cell terminals to the positive and negative pack terminals, respectively;

a switch circuit connected in the power path; and

a voltage sensing circuit having first and second input nodes connected to the positive and negative cell terminals, respectively, and first and second output nodes connected to the positive and negative sense terminals, respectively.

16. The battery system of claim 15 wherein the cell assembly, the switch circuit, and the voltage sensing circuit are all packaged within a battery pack housing, and the pack terminals and sense terminals are individually accessible from outside the housing.

17. The battery system of claim 16 further comprising a pack connector system, wherein the pack terminals and sense terminals are individual contacts of the pack connector system.

18. The battery system of claim 15 wherein the voltage sensing circuit comprises a voltage divider circuit connected to the first and second input nodes, and an amplifier whose input is connected to an output of the voltage divider circuit, and wherein a control signal activates the voltage sensing circuit to sense voltage of the cell.

19. The battery system of claim 18 further comprising:

a protection control circuit that is powered by the cell assembly and is connected to the switch circuit, wherein the protection control circuit signals the switch circuit into an open circuit state in response to detecting a fault condition.

20. The battery system of claim 19 wherein the fault condition is one of a) an overvoltage state, b) an undervoltage state, or c) an overcurrent state.

21. The battery system of claim 19 wherein the control signal that activates the voltage sensing circuit is produced by the protection control circuit.

22. The battery system of claim 15 further comprising:

a charging circuit having a pair of voltage sense inputs connected to the sense terminals, and a pair of power nodes connected to the pack terminals, respectively, wherein the charging circuit increases, reduces and cuts off current in the power path during a charging cycle of the cell assembly in accordance with voltage obtained through the sense terminals.

23. A battery system comprising:

a single cell battery pack having,

a positive pack terminal and a negative pack terminal;

a positive sense terminal and a negative sense terminal;

an electrochemical cell having a positive cell terminal and a negative cell terminal;

an electrically conductive power path having a positive leg that connects the positive cell terminal to the positive pack terminal, and a negative leg that connects the negative cell terminal to the negative pack terminal; and

an electrically conductive sense path, separate from the power path, having a positive leg that connects the positive cell terminal to the positive sense terminal, and a negative leg that connects the negative cell terminal to the negative sense terminal.

24. The battery system of claim 23 further comprising:

a power switch circuit connected in the power path; and

a sense switch circuit connected in the sense path.

25. A method for charging a battery, comprising:

sensing pack voltage of a battery through a pair of sense terminals, which are separate from a pair of power terminals of the battery;

monitoring the sensed pack voltage during battery charging, while a charging current is delivered to the power terminals, by comparing the sensed pack voltage to a predetermined cutoff voltage representing a fully charged state for the battery; and

cutting off the charging current in response to the comparison indicating that a fully charged state is reached.

26. The method of claim 25 further comprising performing analog signal conditioning or conversion to digital format or both, upon the sensed pack voltage.