JPH07226233A - Method and equipment for monitoring battery capacitance and doing charging - Google Patents

Abstract

PURPOSE: To provide a method and device for judging a charged state of a battery in a battery pack and for executing charge. CONSTITUTION: In a method and device for judging a charged state of a battery in a battery pack and for executing charge, data of battery charge and temperature stored in a memory in the battery pack are transferred to a controller. The controller calculates a remaining capacity and selects an appropriate charge profile based on the data from the memory and the calculated remaining capacity. The above-mentioned device is equipped with a battery pack which surrounds a memory unit, a temperature monitor, and a current sensor. Data from the memory unit, the temperature monitor, and the current sensor are inputted to the controller. The controller is a microprocessor, an EEROM, or an element having a similar capability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for determining the state of charge of a battery and charging the battery in a battery pack. More particularly, the present invention determines the state of charge of a battery and based on the determined state of charge, stored battery parameters, electrical and thermal response, and temperature and charge progress, the appropriate battery. The present invention relates to a device that determines and executes a charging cycle.

[0002]

BACKGROUND OF THE INVENTION Many portable devices use a rechargeable battery as a power source where no external power source is available. If the external power source is available for some time, it is effective to recharge the battery pack to accumulate additional charge during the time when the external power source is unavailable.

Because the use of portable devices is limited while the battery is being recharged, the remaining battery capacity of the battery is monitored and the battery is effectively and quickly recharged and when it should be recharged. The focus is on developing charging technology that informs users of Many of these technologies use "smart" battery charging cycles that adjust charging parameters to respond to the characteristics of the battery. Such techniques typically require data associated with the battery being charged in order to optimize charging performance. For example, data regarding battery charge progress, maximum battery capacity, battery makeup and temperature progress can be used to assess the state of charge of the battery and form an appropriate charge cycle. Also, the charging current,
Active information related to charging temperature and battery voltage can be used to more accurately assess the state of charge and improve the speed and efficiency of the battery charging cycle.

A fixed charge cycle can be used if each of the above parameters is known or fixed. However, if these parameters change, it is effective to adapt the charging cycle appropriately.

Since the battery life and charging capacity are not infinite, it is often necessary and effective to replace a given battery with a different battery. In such a case, some or all of the known or measured parameters of the battery may change. The fixed charge cycle adapted to the original battery may not be appropriate for the replacement battery.

[0006]

In order to apply new batteries having different characteristics, it is often necessary to perform battery evaluations to measure or estimate battery parameters. If this evaluation is to be carried out actively by the device, the time and energy expended during the determination of the new parameters causes some delay and inaccuracy. This limits the speed and effectiveness of the adaptive charging cycle.

Another approach is to establish a fixed charge cycle for all batteries, but such techniques have limitations. Because different battery types,
This hinders optimization of the charging cycle with respect to temperature and charging level.

[0008]

SUMMARY OF THE INVENTION The present invention is primarily directed to an apparatus for determining the state of charge of a battery pack, determining its parameters, and controlling charging accordingly in a battery energizer having a rechargeable battery. And method. A memory element for storing charging and temperature data and battery characteristics is incorporated in the battery pack, and a built-in "fuel gauge" is provided in the battery pack. The battery pack also includes a temperature sensor.
Batteries used in such packs include, for example, nickel cadmium or nickel metal halide batteries. The preferred embodiment of the device of the present invention also includes a backup battery. This device incorporates a controller such as a microprocessor to evaluate the parameters of the battery pack based on active measurements and stored data. The controller also regulates and provides a charging current to the rechargeable battery pack in response to the charging progress and parameters of the battery pack by providing an input to the adjustable charging power supply. The device of the present invention also includes an indicator or gauge that allows the user to determine the remaining battery capacity. The output of this fuel gauge is visible or audible.

The method according to the invention uses a computer controller to obtain the desired result. The computer controller accesses the memory contained within the battery pack to determine the characteristics of the battery. The controller also uses the data from the A / D converter in connection with the battery voltage and temperature monitors to determine the charge and operating conditions of the battery.

Alternatively, E including a look-up table
A simple element such as an EROM could be used instead of the computer controller.

The device of the present invention also has an audible output and expansion capability for connecting auxiliary devices. Audible output is achieved through the use of speaker elements.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram illustrating a preferred embodiment of device 10 in an environment controlled by microprocessor-based controller 15. When the external power supply is available, the device 10 operates using the electric power sent from the main power supply unit 12 to the input terminals 11A and 11B. The main power supply unit 12 is externally energized by the AC line power represented by the power supply cord 13, for example.
The main power supply unit 12 is a known power supply unit such as a commercial power supply that uses a switching regulator to generate a regulated voltage for the system. Alternative power sources are known and can be used without departing from the scope of the invention.

Further, in the preferred embodiment, an external power supply sensor 30 is connected between the input terminals 11A and 11B, the output terminal 31 of which is electrically connected to the input terminal 34 of the controller 15. The power supply sensor 30 is a known circuit such as a series resistance circuit forming a voltage divider.
The power sensor 30 detects the presence of an external power source in the controller 15
Instruct to.

The device of FIG. 1 further comprises a rechargeable battery pack 38. This battery pack 38
Uses a commercially available rechargeable battery 39 such as a nickel cadmium or nickel metal halide battery.

Conventional comparator 16 in battery pack 38
Is a dead battery output terminal 18A and a low battery output terminal 18 when the voltage measured between the pack output terminals 20 and 21 of the battery pack 38 falls below a specified level.
B and used to generate a battery level indicator signal at the battery alarm terminal 18C. The comparator 16 may be in the main power supply unit 12 or may be separately incorporated in the device.

Dead battery output terminal 18 of comparator 16
A, low battery output terminal 18B and battery alarm terminal 1
The signal from 8C is input to the controller 15.

A current sensing resistor 32 having a current sensing output terminal 32A is connected in series between the pack output terminal 21 and the reference potential. The current sense output terminal 32A provides an indication of charging current as described below. The current sensor 32 of the preferred embodiment is a sense resistor 32, although alternatives will be apparent to those skilled in the art.

The rechargeable pack 38 also includes a temperature sensor 41 and a temperature output terminal 40. As shown in FIG. 1, the temperature sensor 41 of the rechargeable battery pack 38 includes a thermistor 41 that makes thermal contact with the battery 39.
Is. The thermistor 41 has an impedance proportional to the temperature of the battery pack. Thermistor 41
Is biased by the bias resistor 37. The voltage across the thermistor 41 changes as its resistance changes. This provides a voltage as an input to controller 15 as described below. The controller 15 can determine the temperature change of the battery pack by comparing the voltage across the thermistor 41 with the output voltage from the ambient temperature monitor 57. The ambient temperature monitor is a temperature sensor 41.
It has the same structure as. The battery pack 38 can have a range of power storage capacity, battery type and temperature sensing capabilities.

In the preferred embodiment, memory 42 is incorporated into rechargeable battery pack 38 to provide the memory function of the battery pack. Second memory 44
Is also housed in the battery pack. In the presently preferred embodiment of the device of the present invention, a three terminal 256 bit serial interface ROM / RAM chip 43 is used for both memory 42 and second memory 44. Chip 43 is a 32-bit factory programmed ROM
As a memory 42, and a 224 bit CMO
The S static RAM is included as the second memory 44. Other types of battery pack memories will be apparent to those skilled in the art.

Memory 42 contains factory-programmed information about the battery, including battery type, capacity, and charge control parameters. The second memory 44 is
Programmed during operation to indicate charging progress and current status. Therefore, the second memory 44 constitutes a state-of-the-art monitor for the remaining charge of the battery. The battery pack 38 has a memory output terminal 46, a second memory output terminal 48 for transmitting data to the data input of the controller 15, and a memory input terminal 45 for receiving data from the controller 15. .

Output terminal 20, current sensing output terminal 32A,
The analog data from the ambient temperature monitor 57 and the temperature sensing terminal 40 is converted into digital data via the A / D converter 17 and sent to the controller 15. It provides controller 15 with output voltage, charging current, and battery and ambient temperature measurements.

The controller 15 is the A / D converter 17
It is an advantage of the device that the data from can be used to calculate the slope of the battery discharge curve. From this curve, the controller 15 can estimate the remaining battery capacity. The controller 15 uses conventional algorithmic calculations to make this estimation, although other techniques such as lookup tables may be used. When using look-up table technology, an EEROM controller can be used in place of the microprocessor-based controller 15 to evaluate the remaining battery capacity of the battery and select the appropriate charging cycle.

In the preferred embodiment, the remaining battery capacity determined is used to construct a "fuel gauge" for the user. That is, the estimated remaining battery capacity of the battery is provided to the operator on the visual display 59 under the control of the controller 15. The visible display 59 is a visible display 59.
May be part of a conventional cathode ray tube display. Other displays, such as graphic displays in a linear array of LCDs or LEDs, will be apparent to those skilled in the art.

The charging current is controlled by a charging control circuit 35, which is composed of a D / A converter 52, a reference amplifier 54, and a pass transistor circuit. The pass transistor circuit includes a pass transistor 56 and a bias resistor. It is composed of 58. The input of the D / A converter 52 is connected to the output bus 49 of the controller 15. D
The output of the A / A converter 52 is input to the reference amplifier 54, the other input is connected to the current sensing resistor terminal 32A, and its output is connected to the pass transistor circuit. Pass transistor 56 has its emitter connected to input terminal 11A and its collector connected to provide current to rechargeable battery pack 38.

The device has a battery discharge capability incorporated as a transistor 50, whose gate 51A is driven by the discharge output 55 of the controller 15. The transistor 50 has its drain 51B connected to the reference potential and its source 51C electrically connected to the output terminal 20 via the source resistor 53. Discharge transistor 50
When the gate voltage is supplied to the transistor 50,
Provides a current path to the reference potential. Since the resistance to the current is only given by the source resistance 53, the device can exhibit a rapid discharge capability if a low resistance value is selected for the source resistance 53.

Battery discharge capability is effective when a charge cycle using battery discharge is desired. Such cycles are well known and are useful for batteries having "memory" characteristics such as nickel cadmium batteries. For example, battery “burping” technology requires battery discharge capability.

The calculated estimate of battery capacity and the measured parameters are used to update the data in the second memory 44. When each estimate of remaining battery capacity is determined and parameters are measured,
They are compared with the stored values. When the estimated value or parameter changes from the last recorded value, a new value is written to the second memory 44 of the battery pack 38 via the data return line 45, thus leaving the fuel gauge to maintain its current value. Update the estimated battery capacity of.

In addition to active updating and visual display of estimated battery capacity, the preferred embodiment uses hardware measurements to indicate a low battery level similar to a low fuel alarm in a vehicle fuel gauge. This is the comparator 16
Done by Three voltage thresholds are set using the comparator 16 which compares the battery voltage with the selected threshold value. The first threshold occurs at a specified non-critical low battery level, which is typically about 10% remaining capacity. When the battery voltage is below the non-critical undervoltage threshold,
Comparator 16 produces a signal at battery alarm terminal 18C for input to the controller. The second threshold is the critical low voltage level that typically occurs at about 1% remaining capacity. At this critical low voltage level, the comparator 16 produces a signal at the low battery output terminal 18B for input to the controller. The third threshold is the dead battery threshold, which occurs at or near 0%. At voltages below the dead battery threshold, the comparator 16 produces a signal at the dead battery terminal 18A for input to the controller. When a signal is generated at the dead battery terminal 18A, as described below, the second memory 4
4. The system is switched off, except that 4 is powered.

In the preferred embodiment, the backup battery 36 in the battery pack 38 provides backup power to the second memory 44 when the power from the charging power source or the battery in the battery pack is shut off. This backup battery prevents the data in the second memory 44 from being lost when the rechargeable battery runs out. Backup battery 36 is a commercially available rechargeable battery such as a lithium battery.
The backup battery 36 is recharged from the charging device or from the rechargeable battery 39 in the battery pack 38 during normal operation. Alternatively,
An EEROM may be used as the second memory 44, and in this case, the lithium battery 36 is unnecessary.

The preferred embodiment also includes an audible output 22 for producing audible feedback to the user as a low battery capacity audible alert. The audible output 22 produces a desired analog signal using a D / A converter under the control of the controller and drives an output speaker 23 as described below. Alternatively, a speaker 23 may be driven with a signal generator programmed for the desired duty cycle and frequency.

The measured battery parameters are also output from the controller to an output device such as a gauge type indicator, a display on a view screen or a printer.

The implementation of the charging method according to the present invention will be described below. The normal charging cycle is the external power sensor 30
When it detects an external power source and sends a signal to the controller or when the device 10 is activated as described above. First, controller 15 tests whether the pack is rechargeable by reading factory programmed parameters from memory 42. If the battery of the battery pack 38 is rechargeable, the controller reads the state of charge from the second memory 44 and determines if recharging is desired. Alternatively, in an interactive system, the unit may display the remaining capacity to the user and ask the user if they would like to recharge.

When it is determined to be recharged, the controller 15 initiates the charge cycle by selecting an initial charge rate and then sends an appropriate digital signal from the charge output bus 49 to the D / A converter 52 to charge. A signal is transmitted to the control circuit 35. The digital signal is converted into an analog signal and input to the reference amplifier 54. The output of amplifier 54 drives pass transistor 56 to turn it on, allowing current to flow through battery pack 38. The current flowing through the pass transistor 56 increases, increasing the current into the rechargeable battery pack 38. Then, a current flows through the current sensing resistor 32,
The voltage at the current sensing output terminal 32A is increased. this is,
Increasing the voltage at the positive input of the reference amplifier 54,
This voltage is fed to the inverting input of the reference amplifier 54, D /
The output voltage of the A converter is reached. At this point, the charging current becomes stable. When the battery is recharged, the state of charge data in the second memory 44 is updated and the visible gauge indicates to the user the gradually increasing remaining battery capacity.

Alternatively, the controller 15 may, if appropriate, before starting the charging cycle, for example,
Before charging a nickel-cadmium battery with a lower capacity than usual due to the "memory effect", the transistor 50
Thus, the battery 39 can be completely discharged.

Next, the controller monitors the voltage of the pack with the digital data from the A / D converter 33. The charging rate is set in the charging rate parameter based on the data read from the memory 42. The controller also periodically monitors ambient temperature, pack temperature, and pack voltage by selecting the appropriate channel for the A / D converter. The charging cycle is selected in response to standard monitoring data.

A typical charging cycle is as follows. If the measurement indicates a fully charged battery response, the charge rate is set to trickle charge. Typically this is
It occurs when the battery voltage rises, peaks and falls above the specified limit for the battery pack (typically 10 MV / cell). The full charge state can be represented by setting the charge state bit of the second memory 44 to full charge.

When the temperature of the battery pack rises rapidly and exceeds the specified limit, the charging rate is set to trickle charge. Typical values are 5 ° C to 10 ° C above constant or non-falling ambient temperature. In this case, the charge status bit is set to full charge.

The charging rate is also set to trickle charge if the charging time exceeds the specified limit for the pack. When the charge time exceeds the specified time, the charge status bit is set to full charge.

Charging is disabled if the battery temperature is outside the limits set for the pack. The status bit indicating excess temperature is stored in the second memory 44.
Set at.

Charging is also disabled if the specified voltage limit for the pack is exceeded. A status bit indicating excess voltage is set in the second memory 44.

In devices with a real-time clock associated with the controller, a watchdog timer is used to prevent overcharging. The controller 15
Monitors the total charge time and disables charge if the watchdog timer expires. A status bit indicating the expiration of the timer is set in the second memory 44. At the completion of the charging cycle, the data in the second memory 44 is updated and the visual indication of the remaining state of charge is updated to reflect the increased remaining battery capacity.

The battery pack is designed so that the on / off switch must be in the off position before it can be removed. This allows sufficient time for the static memory to systematically transition to energize the lithium battery 34 and prevent data damage.

While particular embodiments of the present invention have been described in detail above, it will be apparent that various changes may be made without departing from the spirit and scope of the invention. Accordingly, the invention is to be limited only by the claims that follow.

[Brief description of drawings]

FIG. 1 is a block diagram showing a preferred embodiment of the apparatus of the present invention.

[Explanation of symbols]

 10 Device 12 Main Power Supply Unit 13 Power Cord 15 Controller 16 Comparator 30 Power Supply Sensor 35 Charging Control Circuit 38 Rechargeable Battery Pack 39 Rechargeable Battery 41 Temperature Sensor 42 Memory 44 Second Memory 50 Transistor 56 Pass Transistor 57 Ambient temperature monitor 59 Visible display

Claims (17)

[Claims] 1. A method of determining the remaining battery capacity of a battery in a battery pack, wherein information about the battery is stored in a memory within the battery pack, the information from the memory is retrieved by an electronic controller, and the selected operating parameter is selected. Is monitored by the electronic controller, and the remaining battery capacity is determined by the electronic controller from the retrieved information and the monitored operating parameters. 2. The method of claim 1, wherein the controller is a microprocessor and the step of determining the remaining battery capacity comprises calculating the state of charge with the microprocessor. 3. The controller is an integrated memory,
The method of claim 1, wherein the step of determining the remaining battery capacity comprises retrieving an estimate of the remaining battery capacity from a look-up table in the integrated memory. 4. The method of claim 1, wherein the selected operating parameter comprises at least one of the group of ambient temperature, battery temperature, output voltage and charging current. 5. The method of claim 1, wherein the controller is a microprocessor and the step of determining the remaining battery capacity comprises calculating the remaining battery capacity with the microprocessor. 6. The method of claim 1, wherein the retrieved information about the battery includes battery capacity when fully charged and charge control parameters. 7. Adaptively determining a recharge cycle in response to the determined battery capacity and retrieved information,
The method of claim 1, further comprising the step of controllably supplying a battery charge current to the battery in response to the determined recharge cycle. 8. The step of monitoring operating parameters comprises:
8. The method of claim 7, including monitoring battery voltage and charging current to generate electrical data. 9. The method of claim 8, further comprising displaying the determined remaining battery capacity for a user to view. 10. The method of claim 9, wherein the displaying step includes displaying the determined remaining battery capacity on a view screen. 11. The method further comprising the steps of monitoring the temperature of the battery to generate battery temperature data, inputting the battery temperature data to a controller, and adjusting the charging current in response to the battery temperature data. 7. The method according to 7. 12. A housing, a rechargeable battery in the housing, a battery pack memory in the housing for storing information about the rechargeable battery, and the rechargeable battery. A battery pack comprising a plurality of connected battery terminals and a memory unit output terminal connected to the battery pack memory. 13. The battery pack of claim 12, further comprising a second battery pack memory within the housing, the second battery pack memory being programmable. 14. The second battery pack memory comprises:
14. The battery pack according to claim 13, wherein the battery pack is programmed with data regarding the state of charge of the rechargeable battery. 15. The battery pack of claim 14, further comprising a second battery within the housing, the battery being electrically connected to the battery pack memory to provide backup power to the battery pack memory. . 16. The battery pack according to claim 12, further comprising a battery temperature monitor in the housing, and a temperature output terminal connected to the battery temperature monitor. 17. A device for monitoring and recharging a battery pack, the monitoring and recharging device comprising a controller having a data input terminal, a voltage input terminal, and a charging current output terminal. The data input terminal of the controller is electrically connected to the output terminal of the memory unit, and further has a battery voltage monitor having a voltage monitor output terminal electrically connected to the voltage input terminal of the controller; and charging the controller. A charging current adjusting circuit having an input electrically connected to a current output terminal.
The battery pack described in 2.