Patent Description:
Battery management systems can be implemented in a variety of applications, such to monitor and control battery cells for a variety of applications. Control functions, battery health, and battery temperature may be monitored and used for managing individual batteries and battery packs. For instance, battery cells may be monitored for voltage and other performance, and managed accordingly (e.g., such as by balancing charge across multiple batteries that provide a combined source of stored energy).

Battery management systems often use an integrated circuit (IC) controller to measure and balance cell voltages. For instance, serval cells may be monitored in serial, and in accordance with battery cell voltage ranges. However, such monitoring and balancing can be difficult to implement for various types of batteries. As new and different technologies evolve, battery management systems may not be capable of carrying out such functions.

United states patent number <CIT>, discloses a battery cell voltage monitor and method, making differential voltage measurements when one or both measurement points are at voltages that exceed those allowed by a typical differential amplifier, for monitoring individual cell voltages of a number of theories-connected cells that make up a rechargeable battery in which some cell voltages must be measured in the presence of a high common mode voltage.

United States patent number <CIT> discloses a cell voltage detecting device for combination the battery. The cell voltage detector determines the voltage of each unit cell, group by group, based on a difference between the divided potential and the reference potential.

Various example embodiments are directed to issues such as those addressed above and/or others which may become apparent from the following disclosure concerning battery monitoring and/or balancing.

In certain example embodiments, aspects of the present disclosure involve monitoring battery voltage levels that may be greater than a specified voltage measuring range. Such approaches may involve, for example, utilizing switching circuitry to monitor different components of a battery output level and combining the measurements to provide an indication of overall battery level. Such approaches may further involve utilizing switching circuitry that may also be used for balancing the level of various battery cells within an apparatus, and/or using such switching circuitry to mitigate leakage when measurements are not being taken. These and other aspects may involve monitoring and/or balancing of automotive type battery packs, or other types of battery packs used in industrial, home and other settings.

The present invention defines an apparatus as defined by the independent apparatus claim <NUM>.

The present invention defines a method as defined by the independent method claim <NUM>. Further embodiments of the invention are provided in the dependent claims.

On the contrary, the intention is to cover all modifications, and alternatives falling within the scope of the invention, the invention is solely defined by the appended claims.

Aspects of the present disclosure are believed to be applicable to a variety of different types of apparatuses, systems and methods involving batteries and monitoring thereof, such as may be applicable to electric vehicles, hybrid electric vehicles, uninterruptible power supply (UPS) systems, premises-based energy storage systems (e.g., homes, businesses), large-scale energy storage systems for community and/or manufacturing use, in so-called green energy systems such as solar, wind and wave systems, tools, appliances, and in various industrial applications. Various aspects of the present disclosure are directed to using a battery controller circuit to monitor cell voltages that are higher than a specified voltage range otherwise directly measurable by the controller. Two (or more) measurements, such as may be provided by differential channels, are used to monitor a battery cell voltage higher than the specified channel voltage range. The respective measurements collectively provide a value corresponding to an actual voltage of the battery cell. This can be achieved with limited leakage.

In certain implementations, aspects of the present disclosure have been shown to be beneficial when used in the context of monitoring battery voltage levels in battery packs, and balancing the voltage in those packs. Such implementations may be useful for automotive applications in which the battery voltage range exceeds a nominal voltage range otherwise operable for such monitoring and balancing. This involves providing partial battery voltage levels at one or more nodes that, when added, provide an indication of an actual voltage level of the battery. While not necessarily so limited, various aspects may be appreciated through the following discussion of non-limiting examples which use exemplary contexts.

In the following description, various specific details are set forth to describe specific examples presented herein. It should be apparent to one skilled in the art, however, that one or more other examples and/or variations of these examples may be practiced without all the specific details given below. In other instances, well known features have not been described in detail so as not to obscure the description of the examples herein. For ease of illustration, the same or similar reference numerals may be used in different diagrams to refer to the same elements or additional instances of the same element. Also, although aspects and features may in some cases be described in individual figures, it will be appreciated that features from one figure or embodiment can be combined with features of another figure or embodiment even though the combination is not explicitly shown or explicitly described as a combination. The scope of the invention is however solely defined by the appended claims.

Embodiments as characterized herein may be implemented in accordance with a variety of different types of batteries and battery systems. For instance, one or more aspects of the disclosure may be implemented with battery cell controllers MC33771 and MC33772 (NXP Semiconductors, Eindhoven, The Netherlands); LTC6801- LTC6804, LTC6811, and LTC6813 (Linear Technology, Milpitas, California); BQ76PL536, BQ76PL455, and EMB1432Q (Texas Instruments, Dallas, Texas); MAX17830 and MAX17843 (Maxim, San Jose, California); ISL9208, ISL78600, and ISL94212 (Intersil, Milpitas, California); and ATA6870 (Atmel, San Jose, California/Microchip Technology of Chandler, Arizona). One or more such battery management systems (BMS) may use an integrated circuit (IC) controller to measure the cells voltages, which may also be balanced. In various applications, such ICs monitor serval cells in serial (e.g., <NUM> and <NUM>), with a maximum cell voltage per channel specified. Total cell voltage for cells exceeding a specified battery level (e.g., two or more times such a level) are measured by measuring and combining portions of the total battery level. For instance, an IC battery controller can use two channels to measure respective portions of a higher cell voltage. The two channel measurements can be added digitally to retrieve the cell voltage. This architecture can be used several times on a battery pack monitoring interface, to effectively upgrade an "N" cell battery controller with a "U" Volts/cells maximum measurement into an N/<NUM> cells battery controller with 2xU Volts/cells maximum. Some margin may be added on expected range due to IC clamp diode leakage when cell voltage is close to maximum ratings. This upgrade may be useful for new battery technologies such as solid-state (e.g., to measure 8V voltages with circuitry otherwise limited to 5V measurements).

Respective battery cell measurements may be obtained in a variety of manners. In some embodiments, an intermediate cell terminal is polarized in a manner that facilitates measurement of a partial voltage range of a cell while mitigating additional leakage in the circuit. This is done by using a resistor bridge turned ON for measurement and otherwise OFF, using a cell balancing (CB) switch system. Hence, additional leakage is added only during cell measurement, during which the leakage may be generally negligible in front of IC consumption during measurements, and removed by turning the CB switch OFF for sleep mode. Where one cell balancing switch circuit/system is used per measurement channel, the switch for one of the channels can be used to turn the polarization of the intermediate cell terminal ON and OFF, and the switch for the other of the channels can be used (in conjunction with the first switch) for cell balancing purposes. The resistor bridge can be sized to have an equivalent filtering and a good start-up time at the intermediate cell terminal, and also an acceptable leakage across the cell.

As may be implemented in accordance with the invention, an apparatus includes switch circuitry configured to be selectively activated for passing current, a monitoring circuit, and a voltage-measurement circuit, each of which are operable with a plurality of battery cells (e.g., a battery pack or assembly) having an actual voltage-sourcing level that is at or above a specified battery-level. The monitoring circuit is responsive to activation of the switching circuitry to distribute energy corresponding to an actual voltage-sourcing level of a particular one of the plurality of battery cells to a voltage node. Activation in this regard may, for example, involve coupling the monitoring circuit to one or both terminals of the particular battery cell. The voltage-measurement circuit then provides an indication of the actual voltage-sourcing level across the particular battery cell by ascertaining voltage differentials between the voltage node and respective voltage nodes/terminals of the particular battery cell. The ascertained voltage differentials are each less than the actual voltage-sourcing level, yet when combined provide an indication of the entire voltage-sourcing level.

Such an approach may, for example, be useful in ascertaining the actual voltage-sourcing level of a battery using two or more measurements obtained via the voltage-measurement circuit, which otherwise is incapable of directly measuring the entire voltage-sourcing level. This may be useful to permit utilization of components in high voltage applications involving voltages larger than the components are designed for. For instance, certain analog-to-digital converters (ADCs) operate with a maximum voltage range for use in battery applications involving a relatively low (e.g., 5V) voltage-sourcing level. In battery packs having relatively high voltage battery cells (e.g., 7V, 8V or higher), this approach can facilitate measurement of a total voltage of the battery cells. Further, this can be done in battery packs using the same switching circuitry for cell balancing and while limiting current leakage. Various such aspects are discussed further below.

The monitoring circuit may distribute the energy in a variety of manners. In some embodiments, bridging circuitry is used to provide a voltage level at the voltage node that is a fraction of the voltage level provided by the particular battery cell. The switch circuitry operates with the bridging circuitry by, in response to being activated, connecting a high voltage node of the particular battery cell to the bridging circuitry, therein providing the voltage at the voltage node. When the switching circuitry is de-activated, current leakage is mitigated by effectively disconnecting the bridging circuitry from the particular battery cell.

Bridging circuitry as noted above may utilize resistor circuitry that, when coupled to one or both terminals of a particular battery cell, provides an intermediate voltage level on an intermediate terminal. In a particular embodiment, the bridging circuitry includes a first resistor connected in a circuit path extending from the switch circuitry to the voltage node, and a second resistor in series with the first resistor and connected in a circuit path extending between the voltage node and a reference or ground node.

The monitoring circuitry may be implemented in a variety of manners, to suit particular embodiments. In some embodiments, the monitoring circuit distributes the energy corresponding to the actual voltage-sourcing level of one of the plurality of battery cells to the voltage node by providing a voltage level that is between a high voltage level and a low voltage level of the particular battery cell. To facilitate this approach, the monitoring circuit may utilize resistors to provide the voltage level that is between the high voltage level and the low voltage level of the particular battery cell. In certain embodiments, the monitoring circuit includes resistors configured to provide a filtering constant at the voltage node that matches filtering at the respective voltage nodes of the particular battery cell.

For multiple cell monitoring, the switch circuitry and monitoring circuit may be couple to each of the plurality of battery cells for determining a voltage differential across each cell. In some embodiments, additional ones of the switch circuitry and the monitoring circuit are utilized for other ones of the plurality of battery cells, in which the monitoring circuits are connected to one another to balance voltage levels between the respective battery cells. In such applications, the voltage-measurement circuit may utilize ascertained voltage differentials for all cells. In certain balancing embodiments, the switch circuitry balances voltage differentials across respective ones of the battery cells by connecting the particular battery cell to another one of the plurality of battery cells.

The voltage-measurement circuit may be implemented in a variety of manners. In the invention, the voltage-measurement circuit combines the ascertained voltage differentials to provide an actual voltage differential across the battery cell that exceeds a maximum voltage differential measurable by the voltage-measurement circuit. For certain applications, the voltage-measurement circuit may ascertain voltage differentials sequentially, and thereafter add the ascertained voltage differentials to provide an actual voltage differential across the particular battery cell. This approach may be further carried out with multiple battery cells. Further, the voltage-measurement circuit can be operated by power provided at or below a maximum operating-voltage level that is less than the actual voltage-sourcing level. In such applications, the monitoring circuit may operate at the actual voltage-sourcing level (e.g., while the voltage-measurement circuit operates at a lower voltage level), and provide the voltage differentials to the voltage-measurement circuit at or below the maximum operating-voltage level.

In accordance with the invention, a plurality of battery cells having an actual voltage-sourcing level that is at or above a specified battery-output level are operated as follows. Switch circuitry is selectively activated for passing current, and in response to activation of the switching circuitry, a monitoring circuit distributes energy to a voltage node, in which the distributed energy corresponds to an actual voltage-sourcing level of a particular one of the plurality of battery cells. A voltage-measurement circuit provides an indication of the actual voltage-sourcing level across the particular battery cell by ascertaining voltage differentials between the voltage node and respective voltage nodes of the particular battery cell. The ascertained voltage differentials are less than the specified battery-output level, facilitating measurement of a lower voltage. Further, the ascertained voltage differentials are combined to provide an actual voltage differential across the battery cell that exceeds a maximum voltage differential measurable by the voltage-measurement circuit. Further, the switch circuitry may be used to balance voltage differentials across respective ones of the battery cells by connecting the particular battery cell to another one of the plurality of battery cells.

Distributing the energy in this regard involves providing a voltage level that is between a high voltage level and a low voltage level of the particular battery cell. In certain embodiments, bridging circuitry is used to provide a voltage level at the voltage node that is a fraction of a voltage level provided by the particular battery cell. The switches are selectively activated to connect a high voltage node of the particular battery cell to the bridging circuitry, therein providing the voltage at the voltage node, and for mitigating current leakage by disconnecting the bridging circuitry from the particular battery cell. Distributing energy in this regard may involve using resistors to provide a filtering constant at the voltage node that matches filtering at the respective voltage nodes of the particular battery cell.

Turning now to the figures, <FIG> illustrates an apparatus <NUM> for ascertaining battery level, in accordance with the present disclosure. The apparatus <NUM> includes a monitoring/measuring circuit <NUM> for monitoring one or more battery cells, with battery cells <NUM> and <NUM>-N shown by way of example. A bridge circuit <NUM> and switch circuit <NUM> operate to, when the switch circuit is active for coupling the bridge circuit between low and high voltage terminals <NUM> and <NUM> of battery <NUM>, provide an intermediate voltage level at intermediate cell terminal <NUM>. The switch circuit <NUM> may, for example, be integrated within the monitoring/measuring circuit <NUM> as shown in dashed lines. The monitoring/measuring circuit <NUM> then uses this intermediate voltage level for ascertaining respective partial voltage differentials between the battery's low (<NUM>) terminal and the intermediate cell terminal <NUM>, and between the intermediate cell terminal <NUM> and the battery's high voltage terminal <NUM>.

In some instances, the monitoring/measuring circuit <NUM> includes an adder circuit <NUM> that adds the partial voltage differentials to provide a total voltage differential across the low and high voltage terminals <NUM> and <NUM>. This may be carried out using, for example, circuitry operable over a limited voltage range that is less than the total voltage differential.

The monitoring/measuring circuit <NUM> may be implemented in a variety of manners. In some instances, the monitoring/measuring circuit <NUM> includes a further switch <NUM>, which operates with switch <NUM> for balancing between respective battery cells. For instance, where similar bridge/switch circuitry is implemented with battery cell <NUM> (coupled via dashed line as shown), the respective cell voltages can be balanced accordingly.

<FIG> illustrates another apparatus <NUM> for ascertaining battery level, in accordance with the present disclosure. The apparatus <NUM> includes a battery cell controller (circuitry) <NUM> and various connecting circuits for ascertaining the level of batter cell <NUM> and further operable with one or more additional battery cells <NUM>-N for cell balancing. The battery cell controller includes switch <NUM> coupled to nodes CB2 (<NUM>) and CB2_1C (<NUM>), and switch <NUM> coupled to nodes CB1 (<NUM>) and <NUM> as well. A resistor bridge <NUM> is coupled between node <NUM> and a reference/ground node, and when coupled to node <NUM> via switch <NUM> or to node <NUM> via switch <NUM>, provides an intermediate cell voltage CT1 (<NUM>). A measurement circuit <NUM> (e.g., including an analog-to-digital converter (ADC)) ascertains voltage differentials between node <NUM> and <NUM>, and between node <NUM> and <NUM>. These differentials can then be added to ascertain the total battery voltage level of cell <NUM>, or other ones of cells <NUM>-N when connected similarly. For instance, where the measurement circuit <NUM> is configured to measure a maximum voltage differential of 5V and the battery cell <NUM> operates at 7V, providing the intermediate node <NUM> facilitates measuring partial voltages of the total battery cell voltage, which can be added and used accordingly. Further, both switches <NUM> and <NUM> may be utilized concurrently to provide a measurement of the respective voltage differentials.

Switches <NUM> and <NUM> may also be used to facilitate cell balancing when activated. Specifically, with switches <NUM> and <NUM> closed, a current path is provided from the high voltage node CELL1P of the battery <NUM> to node <NUM>, through switch <NUM> and switch <NUM>, and to node <NUM> and the low voltage node CELL1M of the battery. A balancing resistor Rbal may further be used at node <NUM> in this regard to facilitate balancing. A further balancing resistor Rbal may be used at node <NUM> (CB3) when additional battery cells are coupled as shown.

The circuitry shown and/or various additional circuitry can be configured and utilized to facilitate measurement and control, to suit particular applications. For example, the Rin resistors used in the bridge circuit <NUM> can be sized to have an equivalent impedance at the input of the measurement circuity <NUM>. Filtering circuitry may also be utilized, such as resistors Rlpf1 and Rlpf2 with a node therebetween coupled to reference/ground via capacitor Clpf, and sized accordingly. For instance, if Rlpf1 is 3kOhm and Rlpf2 is 2kOhm, Rin can be sized at twice the combined amount at <NUM> kOhm (<NUM> x (<NUM> + <NUM>)), to provide a similar bandwidth and a similar filter output impedance. Mirrored capacitors Cin can also be coupled as shown to nodes <NUM>, <NUM> and <NUM>, and to further battery cells if applicable.

Accordingly, two channels may be used to measure a single battery cell <NUM>, utilizing an intermediate cell terminal CT1 relative to a high voltage terminal (CT2) and reference voltage (CTREF). The intermediate cell terminal CT1 is polarized at the middle cell voltage with a resistor bridge made by Rin resistors. Further, the bridge leakage on the battery cell <NUM> can be removed when measurement of the cell is not needed, by turning he switch <NUM> (and/or <NUM>) OFF. When the measurement is OFF, the circuit leakage is generally negligible and depends on the switches and cell terminal channel leakages. Further, this configuration can be utilized on respective channels of a plurality of battery cells in a pack, for instance resulting in transformation of a <NUM> cell battery controller with a 5V/cell voltage range capability into a <NUM> channel battery controller with 10V/cell voltage range capability. Some margin may be added on the range (e.g., because of clamp diodes, additional leakage may be added from <NUM> to 10V).

<FIG> illustrates a plot of filtering with and without a bridge, as may be implemented in accordance with the present disclosure. The vertical axis shows resistance (kOhms) and the horizontal axis shows frequency. Plot <NUM> shows an example filtering output without a bridge, and plot <NUM> shows performance with a bridge (e.g., <NUM> of <FIG>).

<FIG> illustrates plots of terminal rise time for different types of filters, as may be implemented in accordance with the present disclosure. Referring to <FIG> by way of example, sizing of the resistors Rin in the bridge <NUM> may provide a trade-off between measurement turn ON time and cell leakage during measurement. The plots in <FIG> represent 7V battery cell measurements. Plot <NUM> depicts voltage at a high voltage cell node, and plots <NUM>-<NUM> depict rise time of a corresponding intermediate cell terminal using bridge resistors (Rin) of 1kOhm, 10kOhm, 100kOhm and <NUM> MOhm, respectively (e.g., implemented with the circuit shown in <FIG>, with Cin = 47nF).

As discussed herein, leakage from a bridge can be mitigated by turning the bridge off when not being used for measuring. The following chart depicts exemplary leakage at various battery cell levels with respective bridge resistor sizes, as may be utilized with <FIG>.

Terms to exemplify orientation, such as upper/lower, left/right, top/bottom and above/below, may be used herein to refer to relative positions of elements as shown in the figures. It should be understood that the terminology is used for notational convenience only and that in actual use the disclosed structures may be oriented different from the orientation shown in the figures. Thus, the terms should not be construed in a limiting manner.

Claim 1:
A battery-monitoring apparatus for monitoring a plurality of battery cells each having an actual voltage-sourcing level that is at or above a specified output-level corresponding to a maximum voltage differential measurable by a channel of a multichannel battery controller, the apparatus comprising:
the multichannel battery controller;
an intermediate cell terminal operational as a voltage node;
switching circuitry (<NUM>) configured and arranged to be selectively activated for passing current;
a bridging circuit (<NUM>) configured and arranged to, in response to activation of the switching circuitry, pass current to distribute energy from a particular one of the plurality of battery cells to the voltage node, such that the voltage at the voltage node is intermediate a voltage at a high-voltage terminal and a voltage at a low-voltage terminal of the particular battery cell; and
a voltage-measurement circuit (<NUM>); the voltage-measurement circuit being configured and arranged to provide an indication of the actual voltage-sourcing level across the particular battery cell by ascertaining, in respective first and second channels of the multichannel battery controller, voltage differentials between the voltage node and respective voltage nodes of the particular battery cell, the ascertained voltage differentials being less than the specified output-level, and to combine the ascertained voltage differentials by adding them to provide an indication of the actual voltage-sourcing level of the particular battery cell.