Method and system for monitoring battery stacks

• US 20070182377A1
• Filed: 12/29/2006
• Published: 08/09/2007
• Est. Priority Date: 12/29/2005
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Vandensande, Geert
• Granted Patent: US 7,638,979 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• 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

Abstract

A monitoring system (14, 24, 34, 50) monitors voltage of a stack of batteries (10, 20, 30.) Each battery has a plurality of cells (13). A monitoring unit (14, 24, 34) is associated with each battery and measures voltage across a selected cell. A first monitoring unit and a second monitoring unit measure the same cell, e.g. cell Cn,1 of battery 10. The first and second measurements are used to calculate a correction factor which can be used to correct a set of measurements made by one of the monitoring units (14, 24). The monitoring units (14, 24, 34) are arranged in a chain, with adjacent units in the chain being connected by a communication interface in which data is transmitted as signalling voltage levels between interface units. The interface units (16, 25) of a pair of monitoring units (14, 24) use the same signalling voltage levels.

Claims

1. A monitoring system for monitoring voltages in a stack of batteries, each battery comprising a plurality of cells, the monitoring system comprising:

a plurality of monitoring units, a monitoring unit being associated with each battery and being operable to measure voltage across one or more selected cells,

first monitoring unit of the plurality of monitoring units being for measurement of a cell, or group of cells, of one battery to provide a first voltage measurement;

a second monitoring unit of the plurality of monitoring units, arranged to measure the same cell, or group of cells, of the same battery to provide a second voltage measurement; and

,

means to calculate, based on the first and second measurements, a correction factor which is useable to correct a set of measurements made by one of the first and second monitoring units.

2. The monitoring system according to claim 1 wherein the first monitoring unit is arranged to measure voltage across a cell, or group of cells, of the battery with which it is associated.

3. The monitoring system according to claim 1 wherein the first and second monitoring units are associated with adjacent batteries in the stack of batteries.

4. The monitoring system according to claim 3 wherein the monitoring unit associated with each battery comprises an input stage having a set of input lines which connect to terminals of the cells in the battery, and the input stage further comprises as an additional selectable input line which connects to a terminal of a cell in an adjacent battery.

5. The monitoring system according to claim 4 wherein each monitoring unit is arranged to sample a voltage across a cell, or group of cells, using a sampling capacitor, and wherein each monitoring unit is provided as an integrated circuit and the sampling capacitor is external to the integrated circuit.

6. The monitoring system according to claim 1, wherein each monitoring unit comprises an analog-to-digital converter having a local voltage reference source.

7. The monitoring system according to claim 1 further comprising a central controller and wherein the central controller is arranged to receive the voltage measurements and to calculate the correction factor.

8. The monitoring system according to claim 7 wherein the monitoring units are arranged in a chain, and wherein only the monitoring units at each end of the chain have a signalling connection to the central controller.

9. A method of monitoring voltages of a stack of batteries, each battery comprising a plurality of cells and having a plurality of monitoring units each associated with a battery, the method comprising:

measuring a cell, or group of cells with a first monitoring unit, of one battery to provide a first voltage measurement;

measuring the same cell, or group of cells of the same battery with a second monitoring unit to provide a second voltage measurement; and

,

calculating a correction factor useable to correct a set of measurements made by one of the monitoring units based on the first and second measurements.

10. The method according to claim 9 wherein the first and second monitoring units are associated with adjacent batteries in the stack of batteries.

11. The method according to claim 9 further sampling a voltage across a cell, or group of cells, using a sampling capacitor.

12. The method according to claim 9 further comprising analog-to-digital conversion of a voltage measurement using a local voltage reference source.

13. The method of claim 9 further comprising receiving the voltage measurements at a central controller and calculating the correction factor in the central controller.

14. A controller for use as part of a monitoring system for monitoring voltage in a stack of batteries, each battery comprising a plurality of cells, the monitoring system comprising monitoring units each associated with a battery and being operable to measure voltage across one or more selected cells, and wherein the controller comprises an interface to receive measurements from the monitoring units and control logic comprising:

means to receive a first voltage measurement from a first of the monitoring units of a cell, or group of cells, of one battery;

means to receive a second voltage measurement from a second of the monitoring units of the cell, or group of cells, of the same battery; and

,

means to calculate a correction factor which can be used to correct a set of measurements made by one of the monitoring units based on the first and second voltage measurements.

15. A monitoring unit for use as part of a monitoring system for monitoring voltage in a stack of batteries, each battery comprising a plurality of cells, wherein the monitoring unit is associated with a battery and comprises an input stage having a set of selectable input lines which connect to terminals of the cells of the battery, the input stage further comprising an additional selectable input line which connects to a terminal of a cell in an adjacent battery and wherein the monitoring unit is operable to measure voltage across a selected cell, or group of cells, of the battery, or of the cell, or group of cells, of the adjacent battery by selection of the input lines.

16. A monitoring system for monitoring voltage in a plurality of batteries, each battery having a monitoring unit associated therewith and being operable to measure voltage across the battery, or one or more cells within the battery,

wherein the monitoring units are arranged in a chain, with adjacent monitoring units in the chain being connected by a communication interface in which data is transmitted as signalling voltage levels between interface units, and

the interface units of a pair of monitoring units use the same signalling voltage levels.

17. The monitoring system according to claim 16 wherein interface units of a pair of monitoring units are both connected to the terminals of one cell, or a group of cells, in one of the pair of batteries associated with the monitoring units.

18. The monitoring system according to claim 17 wherein interface units of a pair of monitoring units are both connected to a common terminal of the batteries and also receive a regulated supply from an output terminal of one of the batteries.