Patent Application
20230085882
Some systems include multiple battery modules, Each battery module includes multiple battery cells connected in series. The battery modules may be connected in series to form a stack of batteries. A busbar may be used to connect one battery module to another. Electric vehicles (EVs) may include multiple battery modules connected in series to provide, for example, a 400V or 800V voltage source.
Battery monitors (e.g., integrated circuits) are used to measure the voltage of individual battery cells in battery modules during charging or discharging of the battery modules. The charge or discharge current also flows through the busbar and results in a voltage drop across the busbar itself. For some battery monitors, the busbar voltage may be included in series with the voltage of the first battery cell in a battery module that is connected to the busbar. Some battery modules may include a voltage measuring channel that is dedicated to measuring the voltage across the busbar. Such battery monitors then may subtract the busbar voltage from the voltage measured for the first cell in the module (which also includes the busbar voltage) to obtain the voltage of the first cell.
In one example, a system includes a first multiplexer and a second multiplexer. The first multiplexer has a first multiplexer input, a second multiplexer input, and a first multiplexer output. The second multiplexer has a third multiplexer input, a fourth multiplexer input, and a second multiplexer output. A first analog-to-digital converter (ADC) has a first ADC input and a second ADC input. The first ADC input is coupled to the first multiplexer output. A second ADC has a third ADC input and a fourth ADC input. The third ADC input is coupled to the second multiplexer output. A first measurement channel pin is coupled to the first multiplexer input and to the third ADC input. A busbar pin is coupled to the second multiplexer input and the third multiplexer input.
The same reference number or other type of designator is used in the drawings for the same or similar (either by function and/or structure) features.
In one or more embodiments, one or more battery monitors may be used to measure voltages of battery cells within battery modules. A battery module may include multiple battery cells with each battery cell being monitored individually by a battery monitor. Battery modules may be connected in series via busbars. In a technical environment, any two battery modules may be connected by a busbar. In accordance with one or more embodiments, a voltage value of a battery cell adjacent to the busbar may be monitored individually without being affected by the voltage of the busbar. In these embodiments, the voltage of the busbar is bypassed while obtaining the voltages of the battery cells connected next to the busbar in series. The voltage of each battery cell may be determined using measurement channels that measure the voltage of a next battery cell with respect to the voltage of a previous battery cell connected in series. To avoid measurement and subtraction of the voltage generated by the small resistance of the busbar, the measurement channel configured to receive the voltage of a battery cell adjacent to the busbar receives the voltage of the battery cell with respect to a voltage of the busbar provided via a single connection (e.g., input) pin. The single connection pin is different from the measurement channels given that it is only connected to multiplexers. The measurement channels need at least two pins, and additional front end analog components and materials to regulate voltage collected by the at least two pins. The voltage of any adjacent battery cell to the busbar may be determined based on a difference between the voltage at the battery cell and the voltage at the busbar. As a result, battery monitors monitoring the voltages of individual battery cells may include a number of channels that is equal to a number of battery cells in a monitoring system (a channel dedicated to just measuring the busbar voltage is not needed).
In some embodiments, the described battery monitor may be used in technical environments in which at least two battery modules are connected via a busbar. Examples of technical environments include battery monitoring applications, battery management systems (BMS), electric vehicles (EVs), and hybrid vehicles (HVs). These technical environments may include battery modules configured to supply power to one or more systems. For example, in an EV, the battery modules may be configured to provide power to all systems and electronic devices of the EV. Multiple battery modules may be connected in series via busbars to provide a voltage of, for example, 400 Volts (V), 800V, etc.
The number of cells in a given module may vary from, for example, 2 cells in series to over 100 cells in series. In some embodiments, multiple battery monitors may be used to monitor the individual cells of all of the battery modules in the series stack of modules. A given battery monitor may individually monitor battery cells in adjacent battery modules connected via a busbar. In some embodiments, the battery monitor may monitor the individual battery cells to which it is connected without using software to subtract the voltage of the busbar from voltage measured for a battery cell that also includes the busbar voltage. The voltage at each battery cell may be measured using respective dedicated measurement channels within the battery module while bypassing the voltage of the busbar.
In the example of
Current and temperature measurements of the battery modules 180 may be obtained using sensors 160 connected in parallel with a shunt resistor 165 that is in turn connected in series with the battery modules 180 after the last battery module of the series stack of battery modules. The sensors 160 may include multiple electronic components (capacitors, resistors, transistors, and the like) arranged to perform the functions of an ADC, current sensing, and temperature sensing. In some embodiments, the sensors 160 may be configured to perform voltage measurements of the shunt resistor 165, convert the voltage using a dedicated ADC, and calculate a corresponding current through the shunt resistor 165. The sensors 160 may be configured to obtain temperature measurements using a Negative Temperature Coefficient (NTC) resistor/thermostat, or one or more thermistors to measure the temperature at the shunt resistor 165 based on the current values obtained.
The system 100 includes a safety box 115 that operates as a high-speed overcurrent protection device for power forwarded from an on-board charger 120 to charge the battery modules 180 or from the battery modules 180 to power a load such as an electric motor 105. The safety box 115 may include a combination of solid-state switches or fuses that trip (e.g., turn OFF or open) responsive to an overcurrent in the line to/from the battery modules.
The battery modules 180 store electrical energy to power the electric motor 205 and/or other electronics. A power inverter 110 converts the DC voltage from the battery modules 180 to a time varying voltage (e.g., sinusoidal voltage/current) to drive the electric motor 105. In the context of an EV, the electronics may be automotive devices or systems such as the heating, ventilation, and air conditioning (HVAC) system (not shown), window control operations (not shown), etc. In an EV, the electric motor 105 may cause the vehicle to move forward or in reverse.
Referring still to
An on-board battery 135 coupled with a DC/DC converter 140 provides additional power to the controller 130. The on-board battery 135 may produce a substantially smaller voltage (12V) than the series combination of battery modules (e.g., 400V). This additional power may be redundant power to maintain the controller 130 powered at a constant voltage while the system 100 transitions in and out of charging operations.
As indicated by arrows 210A and 210B, a current flow in the battery stack may occur in either direction in accordance with a charging operation or a discharging operation, respectively. During the charging operation, voltage is accumulated by the on-board charger 120, and current flows from the anode (positive terminal) to the cathode (negative terminal) of each cell (represented by arrow 210A pointing to the left). During the discharging operation, voltage is supplied by the battery stack to a load (e.g., the electric motor) and current flows from the cathode to the anode of each cell (represented by arrow 210B).
The battery monitor 240 includes multiple inputs (labeled as “VC”) connected to the nodes between battery cells. For example, inputs of VC measurement channels 250A and 250B are connected to the negative and positive terminals, respectively of battery cell 325A. The VC inputs correspond to measurement channels 250A, 250B, and 250C (collectively, measurement channels 250) connected to each battery cell in the battery modules 220. Input 280 is labeled “BB” and is connected to one end of the busbar 230 as shown. The VC measurement channels 250 receive the voltage corresponding to a respective battery cell 225, and BB input 280 receives the voltage corresponding to one end of the busbar 230. In this example, the measurement channel 250A is connected to the cathode of battery cell 225B in battery module 220A, which is the anode of a previous battery cell 225A. The measurement channel 250B is connected to the anode of the battery cell 225B. The BB input 280 is connected to one end of the busbar 230 that coincides with the cathode of a battery cell 225C in battery module 220B. The measurement channel 250C is connected to the anode of the battery cell 225C.
The battery monitor 240 is configured to determine voltage drops between consecutive measurement channels 250 and/or between a measurement channel and the BB input 280. In accordance with some embodiments, measurements of the voltage difference across the busbar 190 itself may be avoided while the voltages of individual the battery cells 225 are obtained. As described herein, the battery cells 225 may be located in battery modules 220 connected to one another using busbars. In the example of
In the example shown in
Each multiplexer 370 includes two voltage inputs and a selection input. Either of the two voltage inputs can be coupled to the output as specified by the logic state of a selection signal (SELO, SELS1, and SEL2 provided to multiplexers 370A, 370B, and 370C, respectively). The SELECT signal may be provided by, for example, the controller 130 described in
In the example of
In
A ground connection is connected to the VC ground terminal 340E via the capacitor CF. The VC ground terminal 340E is not directly connected to the ground connection. Instead, the VC ground terminal 340E is connected to the ground connection through a differential filter incorporated via the capacitor CF.
In the aforementioned connections, the ADC 360A produces a digital output value that is proportional to the voltage drop between the anode of the battery cell 305A and the anode of the battery cell 305B. This digital output value is provided to the controller 130 and is interpreted by the controller 130 as a voltage of the battery cell 305A. The ADC 360B converts a voltage drop between the anode of the battery cell 305B and the one end of the busbar 310. This digital output value is provided to the controller 130 and is interpreted by the controller 130 as a voltage of the battery cell 305B. The ADC 360C converts a voltage drop between the anode of the battery cell 305C and the anode of the battery cell 305D. This digital output value is provided to the controller 130 and is interpreted by the controller 130 as a voltage of the battery cell 305C. The ADC 360D converts a voltage drop between the anode and the cathode of the battery cell 305D. The cathode of the battery cell 305D is also the VC ground terminal 340E. This digital output value is provided to the controller 130 and is interpreted by the controller 130 as a voltage of the battery cell 305D.
In one or more embodiments, the aforementioned voltages (e.g., their digital equivalent values) are obtained without requiring software intervention to subtract the voltage across the busbar 310. The multiplexers 370 may be individually configured to select a path that excludes the busbar 310 between any two battery modules when measuring a voltage in a battery cell. For example, based on the application, two consecutive battery modules (interconnected by a busbar) may be unevenly matched to the number of measurement channels available in the battery module. In this case, the BB input 350 may be configured to connect to the busbar between any two measurement channels. In this example, the voltage of the busbar is not measured and digitized as long as a corresponding multiplexer is selected for an ADC conversion. In
In one or more embodiments, no external components, monitor channel waiting, or software complexity are needed to measure the individual voltages across battery cells. The battery monitors described herein may be configured by selecting a busbar bypass option and obtaining the voltages of the individual battery cells without measuring the voltage drop across the busbar. The flexible coupling of the busbar at any of multiple locations in a battery module allows for a variety of module cell counts to be measured.
At 410, a battery module obtains, via a first measurement channel, a first voltage measurement value for a battery cell. At this point, the battery module may receive a first voltage reference value at one of the ADCs via a corresponding measurement channel. In the example of
At 420, the battery module obtains, via a dedicated busbar input pin, a second voltage measurement value for a busbar. The battery module may receive a second voltage reference value at the same ADC where the first voltage reference value was received. Following the example in
At 430, a first converter receives a voltage value across the first battery cell based on a voltage difference between the first voltage measurement value and the second voltage measurement value. As described above, the ADC receives the first voltage measurement value and the second voltage measurement value as different inputs on the positive terminal and the negative terminal, respectively. At this point, the ADC 360B receives a voltage value that is equal to the difference between the first voltage measurement value and the second voltage measurement value.
At 440, the first converter converts the voltage value across the first battery cell. At this stage, the voltage value across the battery cell is converted from an analog type to a digital type. Upon receiving the voltage, the ADC 360B converts the voltage received from the previous step.
At 450, the first converter provides the converted voltage value to a processor. The processor may be the controller 130 described in reference to
The flowchart ends at 460, the processor identifies the converted voltage value as a first voltage cell value corresponding to the first battery cell. In this step, the processor determines that the converted voltage value is an individual voltage value of the battery cell. In this case, despite the battery cell being adjacent to the busbar, the busbar voltage is not measured or received by any of the ADCs. Instead, the voltage of the busbar is avoided to only measure the voltage across the battery cell.
In this description, the term “couple” may cover connections, communications, or signal paths that enable a functional relationship consistent with this description. For example, if device A generates a signal to control device B to perform an action: (a) in a first example, device A is coupled to device B by direct connection; or (b) in another example, device A is coupled to device B through intervening component C if intervening component C does not alter the functional relationship between device A and device B, such that device B is controlled by device A via the control signal generated by device A.
A device that is “configured to” perform a task or function may be configured (e.g., programmed and/or hardwired) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or reconfigurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construction and/or layout of hardware components and interconnections of the device, or a combination thereof.
As used herein, the terms “terminal”, “node”, “interconnection”, “pin” and “lead” are used interchangeably. Unless specifically stated to the contrary, these terms are generally used to mean an interconnection between or a terminus of a device element, a circuit element, an integrated circuit, a device or other electronics or semiconductor component.
Circuits described herein are reconfigurable to include additional or different components to provide functionality at least partially similar to functionality available prior to the component replacement. Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in series and/or parallel to provide an amount of impedance represented by the resistor shown. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two nodes as the single resistor or capacitor.
Uses of the phrase “ground” in the foregoing description include a chassis ground, an Earth ground, a floating ground, a virtual ground, a digital ground, a common ground, and/or any other form of ground connection applicable to, or suitable for, the teachings of this description. In this description, unless otherwise stated, “about,” “approximately” or “substantially” preceding a parameter means being within +/−10 percent of that parameter.
Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.
This application claims priority to U.S. Provisional Application No. 63/246,398, filed Sep. 21, 2021, which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63246398 | Sep 2021 | US |
