JP2001511639A - Method and apparatus for charging a rechargeable battery - Google Patents

Abstract

(57) Abstract A method and apparatus for charging a battery is provided. During charging of the battery, a rate of change of the battery temperature is determined for at least a portion of the charging process. A reference value is determined based on the obtained value of the battery temperature change rate, and the determined value of the battery temperature change rate is compared with the reference value, whereby the end of the charging process is controlled based on the comparison. . The reference value may be determined as a minimum value of the obtained value of the battery temperature change rate, and the end of the charging process may be started when the battery temperature change rate exceeds the reference value by a predetermined amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

TECHNICAL FIELD The present invention relates to a method and an apparatus for charging a rechargeable battery. In particular, the present invention relates to control for ending the charging process.

(Background) Generally, NiCD (nickel cadmium), NiMH (nickel metal
When charging a rechargeable battery or a secondary battery such as a hydride, it is known to perform a high-speed charging process of supplying a relatively high constant current to the battery until a certain event occurs. A common way to detect this event is to measure the increase in battery temperature as a function of time to detect when the rate of change of battery temperature (ΔT / Δt) reaches a preset high limit. For example,
See U.S. Patent No. 3,852,652, U.S. Patent No. 5,329,219 and U.S. Patent No. 5,550,453.

However, a common drawback of the above-described known charging process is that a predetermined reference value is specified as a value at which the measured rate of change in battery temperature reaches the end of the charging process. In order to obtain an optimal charging process, such a reference value must be selected as a function of the battery technology, the battery manufacturer, the number of cells in the battery and the battery cell size. Furthermore, its optimal reference value is
Varies as a function of battery application and aging. Therefore, using a fixed reference value throughout the life of the battery will result in undercharging of the battery leading to a reduction in the capacity of the battery and overcharging of the battery leading to a reduction in the life of the battery. Therefore, there is a need for a battery charging method and apparatus in which the charging reference value is determined during the charging process as a function of the measured battery temperature change rate.

Another drawback of known charging processes in which the value of the characteristic charging parameter indicating the end of the rapid charging phase is monitored to detect certain events is that the peak value of the battery parameter appears during the initial charging phase. is there. In order to prevent the charging process from being terminated prematurely due to such a rise in the characteristic parameter, measurement of the characteristic parameter in the initial charging stage should be avoided, and a fully charged battery should be detected and already fully charged. There is a need for a battery charging method and apparatus that can avoid overcharging the battery.

(Summary of the Invention) In the present invention, the end of the charging process is controlled in an optimal manner by using a reference value determined during the charging process based on the determined value of the rate of change in battery temperature. Provides a way in which changes in the reference value are considered, for example, as a function of battery life.

According to a first aspect of the present invention, this includes connecting a power source to a battery terminal to supply a charging current to the battery, and providing a value of the battery temperature change rate during at least a portion of the battery charging process. Is determined, a reference value is determined and stored based on the obtained value of the battery temperature change rate, the value of the battery temperature change rate is compared with the stored reference value or its function, and the charging process is performed based on the comparison. Is achieved by a method for charging a rechargeable battery comprising the step of controlling the termination of the rechargeable battery.

When monitoring battery temperature during the charging process, the temperature increases as the battery approaches a fully charged state. Therefore, it is preferable to use a threshold value for the battery temperature change rate, and to end the charging process based on such a threshold value. In order to make this threshold adaptable, it is preferable to determine the threshold based on the determined reference value. Therefore, for example, the end of the charging process may be started when the determined value of the battery temperature change rate exceeds the stored reference value by a predetermined amount.

To avoid overcharging the battery, it is important to use the smallest possible value as the termination threshold, and the determined and stored reference value is the obtained value of the battery temperature change rate. It is preferred to represent the minimum. In such a case, the threshold can be calculated by adding a predetermined maximum allowable change in the rate of change of the battery temperature to the obtained reference value. Such a predetermined maximum allowable change is:
It is in the range of 0.25 to 2 ° C / min, preferably about 0.5 ° C / min. However, the optimum value varies with different battery capacities and battery technologies.

[0009] In order to control the end of the charging process, the power supplied to the battery needs to be reduced. Here, it is preferable that the end of the charging process includes a step of reducing the charging current. This reduction may be abrupt by turning off the power, but the end of the charging process comprises a final charging period during which the battery is charged at a lower current until the charging process stops at the end. It may be.

Here, the final charging period may be determined as a function of the total charging time that has elapsed at the time when the end of the charging process starts. For example, the length of the final charging period may be in the range of 5% to 50% of the total charging time elapsed at the beginning of the charging process, and may be preferably about 25%. However, the final charging period need not be a function of the charging time, but may be a predetermined period.

In order to reduce the charging power supplied to the battery during the final charging period, the charging process is controlled to reduce the battery terminal voltage by at least a predetermined amount at the beginning of the final charging period to avoid overcharging. You may. For example, the battery terminal voltage may be reduced by at least 100 mV, preferably at least 200 mV at the beginning of the last charging period, so that the battery terminal voltage preferably does not increase during this last period. However, the battery terminal voltage may also be reduced as a function of the number of cells in the battery. Such a reduction is a factor of 10 per cell.
It is in the range of １００100 mV, preferably in the range of 20-70 mV per cell, more preferably about 40 mV per cell.

The charging power may be reduced by controlling the charging process so as not to increase the battery terminal voltage during the final charging period, for example, by maintaining the voltage constant during the final charging period. .

When charging the battery, the predetermined rate of change of the battery temperature during the rise of the charging process may change as a function of the initial battery temperature. Thus, for a battery that is stored at a low temperature but is charged at a high temperature, a high value of the battery temperature change rate is seen during the start of the charging process until the battery reaches ambient temperature. Therefore, it is an object to avoid the effects of such an initial high rate of battery temperature change.

Therefore, the charge process termination control is performed after a predetermined time has elapsed or after the value of the specific start-up charge parameter measured at the first stage of the charge process reaches the preset value. Preferably, it is based on the value of the battery temperature change rate determined. In a preferred embodiment, the particular rising charge parameter is the battery terminal voltage, which terminal voltage may be measured as an open circuit voltage.

When the charging process is stopped, the battery capacity may have been reduced due to battery self-discharge. Such self-discharges may vary due to battery and technology differences. However, when self-discharge is a problem, it is preferable that the state of charge of the battery be held after the end of the charging process by a pulsating minute current or a low holding current.

According to a first aspect of the present invention, a battery terminal is connected to a power supply that supplies a charging current to a battery having a battery terminal voltage and a temperature, and at least a part of a battery charging process is performed. Means for measuring the rate of change of the battery temperature during the period; means for determining and storing the charge reference value based on the measured value of the rate of change of the battery temperature; and storing the measured value of the rate of change of the battery temperature or the reference value or A rechargeable battery charger is provided, comprising: means for comparing with a function; and means for controlling termination of the charging process in accordance with the comparison.

It is preferable that the termination control means starts the termination of the charging process when the determined value of the battery temperature change rate reaches a threshold value exceeding the storage reference value by a predetermined amount. In such a case, the comparing means may determine such a threshold value by adding a preset maximum allowable change of the battery temperature change rate to the obtained reference value. Good.

As already mentioned, it is important to be able to determine the minimum possible threshold end value. Therefore, it is preferable that the means for determining and storing the reference value determine and store the minimum value of the obtained value of the rate of change in battery temperature.

In order to terminate the charging process, it is preferable that the termination control means reduces the charging current during the termination process. The ending means may be adapted to determine a final charging period, wherein the ending means is adapted to determine the final charging period as a function of the total charging time that has elapsed at the beginning of the charging process. preferable.

In a preferred embodiment, the termination control means is configured to reduce the battery terminal voltage by at least a predetermined amount during the final charging period to avoid overcharging. The termination control means preferably performs such a reduction at the beginning of the final charging period.

According to one embodiment of the device of the present invention, the device comprises means for measuring a specific start-up charging parameter, and the termination control means comprises: After the value of the specific rising charge parameter measured during the step reaches a predetermined value, the end of the charging process is controlled based on the determined value of the rate of change in battery temperature. preferable.

The specific rising charge parameter may be a battery terminal voltage, and it is preferable that the means for measuring the rising charge parameter measures the battery terminal voltage as an open circuit voltage.

When self-discharge of the battery becomes a problem, the device preferably further comprises means for maintaining the state of charge of the battery after the end of the charging process. Such a maintenance means may supply a pulsating microcurrent or a low maintenance current.

According to a second aspect of the present invention, a power supply is connected to the battery terminal to supply a charging current to the battery, and a value of the first characteristic charging parameter is determined during at least a part of the charging process. The end of the charging process is determined based on the value of the first characteristic charging parameter determined after the second characteristic charging parameter measured in the initial stage of the charging process reaches a predetermined value or after a predetermined criterion is satisfied. A method is provided for charging a rechargeable battery with a controlling step.

Here, the first characteristic charging parameter is a charging process such as a battery terminal voltage, a charging current, a change rate of these parameters, or a combination of these parameters, and / or a combination of these change rates. Any battery parameters suitable for control may be used. Preferably, the first characteristic charging parameter is a battery temperature change rate calculated from a measured value of the battery temperature.

Similarly, the second characteristic charging parameter may be selected from any of the first characteristic charging parameters as long as it is not the same as the parameter selected as the first characteristic parameter. However, the second characteristic charging parameter is preferably the battery voltage.

To end the charging process, the obtained value of the first parameter is compared with a stored reference value or a function thereof, and the end of the charging process is preferably based on the comparison. Preferably, the end of the charging process is started when the measured value of the first charging parameter reaches a threshold value that is a function of the stored reference value. Therefore, for example, the end of the charging process
It starts when the obtained value of the first characteristic charging parameter exceeds the stored reference value by a predetermined amount.

In a preferred embodiment, the stored reference value is determined during the charging process based on the obtained value of the first parameter. The reference value may be determined as the maximum value of the obtained values, but it is preferable that the reference value represents the minimum value of the obtained first parameter values.

When terminating the charging process, preferably the termination comprises a final charging period, the length of the final charging period being a function of the total charging time elapsed at the beginning of the charging process. Is preferably determined as Further, the charging process preferably includes a step of reducing the charging current or a step of charging with the reduced current during the final charging period.

According to a second aspect of the present invention, means for connecting a terminal of a battery having a battery terminal voltage and temperature to a power supply to supply a charging current to the battery, and charging a value of the first characteristic charging parameter An apparatus for charging a rechargeable battery is provided, comprising: means for determining during a portion of the process, means for determining a second characteristic charging parameter at an early stage of the charging process, and means for controlling termination of the charging process. You. Here, the termination control means controls the termination process based on the value of the first characteristic charging parameter determined after the second characteristic charging parameter reaches a predetermined value or satisfies a predetermined criterion. It has become.

In a preferred embodiment, the means for determining the first characteristic parameter is adapted to determine a rate of change of the battery temperature, and the means for determining the second characteristic parameter is adapted to determine the battery temperature. Is preferred. Preferably, the voltage is determined as an open circuit voltage.

In order to end the charging process, the apparatus according to the second aspect of the present invention includes means for storing a reference value, and means for comparing the determined value of the first parameter with the stored reference value or its function, Preferably, the termination control means terminates the charging process based on the comparison. The apparatus may further comprise means for determining a reference value, wherein the reference value determining means determines the reference value during the charging process based on the obtained value of the first characteristic charging parameter. preferable.

In a preferred embodiment, the reference value determining means determines a minimum value of the obtained first parameter value. However, the reference value determining means also
The maximum value of the obtained first parameter value may be determined.

With respect to the termination of the charging process, the termination control means starts the termination of the charging process when the determined value of the first characteristic charging parameter exceeds the stored reference value by a predetermined amount. Is preferred.

In order to end the charging process, the end control means determines a final charging period, and the final charging period is preferably determined as a function of the total charging time elapsed at the time when the end of the charging process starts. . In such a final charging period, the termination control means preferably reduces the charging current. However, the termination control means may also be configured to terminate the charging process suddenly without a final charging period.

If self-discharge of the battery is deemed to be a problem, the device according to the second aspect of the invention further comprises means for maintaining the battery in a charged state after completion of the charging process. Such a maintenance means supplies a pulsating microcurrent or a low maintenance current.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic operating principle of the battery charger according to the present invention is shown in FIG. FIG. 1 shows a battery pack 10, which is charged by a battery charger 20. The battery pack 10 includes a number of individual battery cells 10 connected in series, a battery temperature detecting thermistor 12 (NTC thermistor), a battery type resistor 13, and battery pack output terminals 14,1.
5, 16, 17 are provided. The battery output voltage is output between terminals 14 and 17, and the charging current supplied to the battery is detected by a detection resistor 23 connected between battery terminal 17 and ground. Thermistor 12 has a current supplied through pull-up resistor 21 to sense battery temperature and provide an associated output at terminal 16. Type resistor 13 has a current supplied through pull-up resistor 22 and provides a voltage at terminal 15 associated with the battery type.

The battery charger 20 includes a power supply 24, a microcontroller 25, and a signal adjustment circuit 26. Power supply 24 is preferably a switch mode power supply,
It has a power supply input 27, preferably receiving a DC voltage in the range of 12-15V. The power supply has an output terminal 28, which outputs charging power, preferably via a switch 29. The charging output 28 of the power supply 24 is controlled by the control output 30 of the microcontroller 25. When the power supply 24 is a switch mode power supply, the control output 30 is preferably a PWM (pulse width modulation) signal, which signal is converted to a variable analog voltage by a filter and used to control the power supply 24. P
When using the WM control signal 30, the microcontroller 25 controls the power output to the battery 10 and the terminal 28 by controlling the on / off period of the PWM signal.

The signal adjusting circuit 26 converts a voltage input signal representing the battery terminal voltage, the battery type, the battery temperature and the charging voltage into an appropriate voltage as an input signal for the analog / digital, A / D converter input 32 of the microcontroller 25. Convert to output signal. Preferably, the current sensing resistor 23 has a very low value, on the order of 0.1Ω, and the adjustment circuit 26 includes an operational amplifier to output a suitable output. The power supply voltage for the microcontroller 25 is preferably 5 volts, and since the battery terminal voltage may exceed 5 volts, the regulation circuit may include a voltage divider to output an appropriate output signal for the battery terminal voltage. Good.

Preferably, the microcontroller 25 has a switch control output 31 for turning the switch 29 on and off. The switch 29 is turned off for a short time during the charging process in order to measure the open-circuit voltage of the battery, thereby removing a voltage drop due to internal resistance loss when measuring the battery terminal voltage.

Microcontroller 25, for example COP 8 manufactured by National Semiconductor
The ACC is programmed to perform battery charging according to the present invention.
Accordingly, the microcontroller 25 controls the power output from the power supply 24 to the battery 10 based on the input signal from the adjustment circuit 26. The input signal is based on the battery type and battery charging parameters, that is, the battery terminal voltage, the battery temperature, and the charging And current.

Next, a method for performing this will be described with reference to FIGS. Referring to FIG. 2, there is shown a flow diagram starting from an initial step 40 and proceeding to a processing step 41. Step 40 is to connect the battery pack 10 to the charger 2
0 and initializing the microcontroller 25. During the initialization process 40, the microcontroller 25 reads the battery type voltage value, which is used as a reference value to address certain battery specific charging parameters stored in the microcontroller 25.

These predetermined parameters are a maximum charging current Imax; an initial value of an end time End_Time which defines a safety time for stopping the charging process when a new value is not determined and stored during the charging process period; A maximum value ΔT / Δt_add of the rate of change of the battery temperature which defines the maximum allowable value of the rate of change of the battery temperature in comparison with a predetermined minimum value Min_ΔT / Δt of the rate of change of the battery temperature which is determined as a variable value. Initial value of Min_ΔT / Δt that is preferably set; Initial voltage limit value VoltLimit that defines the minimum value that the measured battery voltage reaches before updating the initial value of predetermined Min_ΔT / Δt; Represents the initial period TimeLimit that defines the period that ends before the initial value is updated. Specific values of End_Time, Min_ΔT / Δt, and ΔT / Δt_add are given based on the description of FIGS.

Here, the value of VoltLimit is usually 1.4 V per battery cell, and TimeLim
The value of it is typically 5 minutes for NiCD or NiMH batteries. TimeLimi
If the measured battery voltage reaches VoltLimit before the end of t, the update of the initial value of Min_ΔT / Δt starts when VoltLimit is reached, otherwise Min_ΔT
The update of the predetermined initial value of T / Δt starts when the TimeLimit period ends.

After the initial setting in step 40, the charging process starts in processing step 41.
Here, the charging process is controlled based on the measured values of the open battery voltage Vopen, the charging current Char, and the battery temperature Tbat. The value of the battery temperature change rate ΔT / Δt is calculated from the value of Tbat. In the first stage of the charging process, it is preferable to increase the charging current Ichar until a predetermined Imax is reached. When Imax is reached, a second charging phase is entered, in which the output of the power supply is controlled to charge with a constant charging current,
That is, the output of the power supply is preferably controlled so that Ichar approaches Imax. In a preferred embodiment, the value of Imax is chosen in the range of 0.5-1.5 A for NiCD or NiMH batteries.

In decision step 42, it is determined whether the charging time has reached the stored value of TimeLimit and whether ΔT / Δt is smaller than the stored value of Min_ΔT / Δt. If so, in step 43, the stored value of Min_ΔT / Δt is replaced with the measured value of ΔT / Δt, and the process then proceeds to decision step 44. If the request is not satisfied in step 42, the process proceeds directly to decision step 44, where it is determined whether the measured open circuit voltage Vopen has reached the stored value VoltLimit. If not, the process proceeds to decision step 49, where it is determined whether the charging time has reached the stored value of End_Time.

If the charging time has not reached End_Time, the process returns to processing step 41, where charging is further performed. If the End_Time has been reached, the normal charging process is stopped, and in process step 50, the charging current is reduced to a low maintenance current or a small charging current, and the charged state of the battery is maintained.

The maintenance or micro charge current is preferably set in the range of 0.05 to 0.1 C, where 1 C is equal to the charge current used to fully charge the battery in one hour. .

It should be noted that proceeding from steps 44 to 49 and 50 is not a normal charging process route. However, if the battery being charged is defective or the battery terminals are poorly connected, this will result in the measured battery voltage not reaching the stored VoltLimit value within the initial safety value of End_Time. Therefore, the charger automatically ends the charging process at the end of the initial End_Time period.

If the measured battery voltage reaches VoltLimit in step 44, processing proceeds to decision step 45, where it is determined whether the measured value of ΔT / Δt is less than the stored value of Min_ΔT / Δt. . If so, in step 46, the stored value of Min_ΔT / Δt is replaced with the measured value of ΔT / Δt, and the process proceeds to decision step 4.
Proceed to 7. If the request in step 45 is not satisfied, the process proceeds directly to decision step 47, where the measured value of ΔT / Δt determines the current stored minimum value as ΔT / Δt
Is determined to be greater than a value added to the predetermined maximum allowable value of the change in, that is, whether the measured value of ΔT / Δt has reached Min_ΔT / Δt plus ΔT / Δt_add.

If the answer to the determination in step 47 is negative, the charging process has not yet reached the normal stage of termination, so the process proceeds to determination step 49, from which the charging process proceeds as described above. Stop.

If the answer in decision step 47 is affirmative, the process proceeds to processing step 4
Proceed to 8 where the maximum allowable battery voltage MaxVolt is defined as f1 (Voltage). When step 48 is reached, the charging process enters a third stage where the remainder of the charging process is controlled so that the measured battery voltage does not exceed MaxVolt. M
The value of axVolt is not a preset value but a function of the measured battery voltage V (ΔT / Δt) when ΔT / Δt reaches Min_ΔT / Δt plus ΔT / Δt_add. In a preferred embodiment, f1 (Voltage) is defined as (k1 × V (ΔT / Δt) −k2), where the constant k1 is set to 1 and k2 is 0-100 mV per battery cell. And preferably about 40 mV. Therefore, for a four-cell battery, the value of MaxVolt is preferably set to V (ΔT / Δt) -160 mV.

For NiMH batteries, it is preferable to make such a reduction in battery voltage to avoid overheating of the battery. This is because such overheating damages the battery and shortens the life of the battery. The constant k2 may be set to zero, which may be useful, for example, for NiCd batteries. However, for NiCd batteries, k2 is preferably in the range of 50 mV.

In processing step 48, at the time t (ΔT / Δt) when ΔT / Δt reaches Min_ΔT / Δt plus ΔT / Δt_add, the storage initial value of End_Time is the total charging time f2 (
Time) is replaced by a new End_Time value that is a function of Time). In a preferred embodiment, En
The new value of d_Time is defined as (k3 × t (ΔT / Δt) + k4), where the constant k3 may be set to about 1.25 and k4 may be set to zero.
However, k3 can be selected from the range of 1-2, and k4 may represent a fixed time in the range of 0-20 minutes.

In process step 48, the method of ending the charging process is determined, ie, the final charging period and the maximum battery voltage are determined. It should be noted that in a preferred embodiment, the measured battery temperature is compensated for variations due to changes in battery temperature. By using the maximum allowable voltage, the charging current during the final charging period will be reduced.

The end of the charging process is indicated by a loop including a processing step 51 and a determination step 52. After the determination of the MaxVolt and the new End_Time value, the charging process continues as described above until the total charging time reaches the stored value of End_Time in step 52, at which point the charging process stops, and in step 50 the charging current is stopped. Decreases to a low maintenance current or a small charging current to maintain the state of charge of the battery. The variables, predetermined constants and functions of the preferred embodiment described above are shown in Table I.

[0057]

[Table 1]

For the process of FIG. 2, the measured battery voltage is preferably the open battery voltage Vopen. This is shown in Table I, where f1 (Voltage) is given as F1 (Vopen). However, it should be understood that the principles of the present invention are also applicable when the measured battery terminal voltage is the terminal voltage during charging.

Referring to FIG. 3, there is shown a charging curve of the charging process controlled as described above according to the flowchart of FIG. The battery of FIG. 3 is fully discharged before the charging process begins, and the battery is charged at room temperature with an initial battery temperature of about 23 ° C. In FIG. 3, the thick solid line represents the measured open battery voltage, the dashed line represents the measured charging current, and the thin solid line represents the measured battery temperature.

The battery of FIG. 3 is a 1600 mAh NiMH battery with 6 cells. Imax is set to 900 mA, the initial value of Min_ΔT / Δt is set to a high value of 10 ° C./min, thereby disabling the effect of the temperature change rate during the rising period of the charging process, and the value of ΔT / Δt_add is set to 0. It was set to 0.5 ° C./min, the value of TimeLimit was set to 5 minutes, and the value of VoltLimit was set to 8.25V. The MaxVolt function is set to V (ΔT / Δt) −240 mV, and the End_Time function is 1.25 × t (
ΔT / Δt).

It should be mentioned here that the optimal value of ΔT / Δt_add varies as a function of battery capacity and maximum charging current. Therefore, the value of ΔT / Δt_add should be large for both small nominal battery capacity and high charging current. Measuring the relative change in ΔT / Δt at 0.5 ° C./min requires measuring the battery temperature change with relatively high resolution. In a preferred embodiment, the temperature is measured using a 10-bit A / D converter and the resolution of ΔT is about 0.1 ° C.

When compared to the stored value of VoltLimit, the measured open circuit voltage Vopen is preferably compensated for fluctuations due to battery temperature changes. Such compensation is Vo
When comparing pen to VoltLimit, it may be 20 mV / ° C subtracted from the measured value of Vopen for temperatures below 35 ° C.

As can be seen from FIG. 3, the first stage of charging is rather short, and the charging current is short and Imax
Reach During the second stage of charging, the current is controlled to maintain approximately Imax,
During the third stage of charging corresponding to the final charging period, the charging current decreases.

In FIG. 3, the value of TimeLimit is smaller than the time for the compensated Vopen to reach VoltLimit. Thus, when TimeLimit is reached, the new value of Min_ΔT / Δt is stored by steps 42 and 43. However, in the preferred embodiment, the new value of Min_ΔT / Δt is not used at all to control the end of the charging process until VoltLimit is reached by step 44.

FIG. 4 shows the charging curve corresponding to FIG. 3 for another example, that of a 1600 mAh NiMH battery with 6 cells. The preset charging parameters and functions are equivalent to those of the charging process of FIG. The battery of FIG.
The battery of FIG. 4 was started at a high pre-charging temperature of about 27 ° C., although the battery of FIG.

Therefore, in the charging curve of FIG. 4, the temperature change rate ΔT / Δt is smaller than the curve of FIG. Therefore, it is necessary that the final value of ΔT / Δt is smaller in the charging process of FIG. 4 than in the charging process of FIG. 3 in order to avoid overcharging.

This problem is solved by the method of the present invention. The determined and stored value of Min_ΔT / Δt is smaller for the hot battery of FIG. 4 than for the cold battery of FIG. 3, so the resulting maximum allowable value of ΔT / Δt, namely Min_
ΔT / Δt + ΔT / Δt_add is smaller in FIG. 4 than in FIG.

For a battery that has a lower initial temperature than the battery of FIG. 3, but is charged at the same ambient temperature, the value of ΔT / Δt will be higher in the early stages of charging and will equal the desired final value of ΔT / Δt. Can be seen. Therefore, the charging process should be controlled not to end based on the initial high value of ΔT / Δt. This is TimeLimi
It may be done in a simple way by setting t to a high value, for example 15 minutes.

However, this may cause overcharging when charging an almost fully charged battery. This problem is solved by the charging method of the present invention.
If the battery is almost fully charged, the battery voltage will reach a high value such as VoltLimit in a relatively short time, and for an empty battery the battery voltage will rise very slowly.

This is shown in FIG. 5, which shows the charging curve for the battery of FIG. 3 when the battery holds 90% of the battery capacity at the start of the charging process.
Here, the battery voltage reaches VoltLimit within 4 minutes from the start of the charging process as compared to 35 minutes of the fully discharged battery in FIG. Thus, when the value of ΔT / Δt is used to control the end of the charging process, using the parameter VoltLimit provides a charging solution that avoids overcharging of a nearly fully charged battery.

FIG. 6 also shows the charging process of the battery of FIG. Here, the battery holds 50% of its charging capacity at the start of the charging process. However, the initial battery temperature is very low, about -7C, while the charging ambient temperature is high, about 35C. Here, the battery temperature is 5 ° C. from the time when the normal charging process is started.
Until it reaches a low maintenance current. As can be seen from FIG. 6, if TimeLimit is set to 5 minutes, normal charging starts at Time equal to 9 minutes and correspondingly reaches TimeLimit at Time equal to 14 minutes.

Due to the temperature compensation and the low battery temperature, the measured value of Vopen will be the corresponding VoltLim
You need to reach a relatively high value before reaching the it value. Therefore, in FIG.
pen has a value of about 8.45V at a Time equal to 27 minutes, the battery temperature is about 25 ° C, resulting in a voltage compensation of 200mV corresponding to Vopen meeting the criteria of VoltLimit at a Time equal to 27 minutes. (VoltLimit + 200mV = Vopen).

Therefore, for the processing of FIG. 6, the value of Min_ΔT / Δt is not updated until Time is equal to 14 minutes, but only the reference value stored after Time is equal to 27 minutes is Used for termination processing. Since the value of ΔT / Δt decreases through the charging process until it reaches a nearly fully charged state, a new reference value is stored until this nearly fully charged state. Therefore, the value of ΔT / Δt does not need to reach a very high value to start the termination process, thereby avoiding overcharging of the battery.

What has been described with reference to this embodiment shows how the reference values determined and stored during the charging process are used for the rate of change of the battery temperature. The obtained reference value is used in determining a control threshold value for terminating the charging process, whereby this embodiment of the invention performs adaptive battery charging. This allows this embodiment to account for changes and differences in the threshold of the rate of change in battery temperature due to aging and creating tolerances. In addition, this embodiment can account for variations in threshold due to differences in ambient temperature.

The above embodiment for the charging process also provides a solution that accounts for the difference in the initial battery temperature, thereby avoiding the charging process ending prematurely due to a high rate of initial temperature change.

It should be understood that the above embodiments of the invention are not only useful for single type batteries, such as NiMH (nickel metal hydride) batteries, but also for example NiCd (nickel cadmium). ) And other types of rechargeable batteries such as lithium batteries.

The foregoing description of the preferred embodiment of the invention has been presented for the purposes of illustration and description. It is obvious to those skilled in the art that the present invention is not limited to the disclosed form, and that many modifications are possible based on the present invention. All such variations using the basic principles disclosed and claimed herein,
It is within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The operation of the present invention, together with further objects and advantages thereof, will best be understood by reference to the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram of a battery charging device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 shows a charging process according to the present invention.

FIG. 4 illustrates a charging process for a battery similar to the process of FIG. 3 but having a high initial temperature.

5 shows the charging curve of the battery of FIG. 3 when the battery retains 90% of its capacity at the start of the charging process.

FIG. 6 illustrates a charging process according to the present invention for a low initial battery temperature and a high ambient charging temperature.

[Procedure amendment]

[Submission Date] January 20, 2000 (2000.1.20)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims310. The method of claim 1, wherein the ending of the charging process comprises a step of reducing the charging current. Or 2 The method described in.

4. A method according to any one of claims 1 to 3 in which the charging process ends comprises a final charging period.

5. The method according to claim 4 , wherein the final charging period is determined as a function of the total charging time required up to the point in time when the end of the charging process starts.

6. The method according to claim 4 , wherein the last charging period has a preset period.

The length of 7. The final charging period is in the 5-50% range of the total charge time has elapsed at the time when the end of the charging process begins, the method according to claim 5 preferably from about 25% .

Claims8The charging process is performed at the beginning of the final charging period to avoid overcharging.
Controlling the battery terminal voltage to be reduced by at least a predetermined amount. 4-7 The method according to any one of the preceding claims.

9. The battery terminal voltage is at least 100mV at the beginning of the final charging period, preferably at least 200mV decreases, the battery terminal voltage,
9. The method according to claim 8 , wherein said method preferably does not increase during said last period.

10. The end control of the charging process is performed after a predetermined time has elapsed or after a value of a specific rising charge parameter measured at an initial stage of the charging process reaches a predetermined value. the method according to any one of claims 1 to 9 based on the value of the battery temperature change rate determined.

11. The method of claim 10 rising charging parameters specific is the battery terminal voltage.

12. The method according to any one of claims 8-11 for the battery terminal voltage is measured as the open-circuit voltage.

13. The charging state of the battery, the method according to any one of claims 1 to 12, which is maintained by the micro current to pulsating after the charging process ends.

14. A means for connecting a battery terminal to a power supply for supplying a charging current to a battery having a battery terminal voltage and a temperature, and a means for measuring a rate of change of the battery temperature during at least a part of the battery charging process. Means for determining the minimum value of the obtained value of the rate of change of the battery temperature and storing the determined minimum value as a charge reference value; and storing the measured value of the rate of change of the battery temperature as a reference value or a function thereof. An apparatus for charging a rechargeable battery, comprising: means for comparing; and means for controlling termination of the charging process in accordance with the comparison.

15. Exit control means, Apparatus according to claim 14, measured or determined values of the battery temperature change rate so as to initiate the termination of the charging process at the time of exceeding the stored reference value by a predetermined amount.

Apparatus according to claim 16] termination control means, any one of claims 14 or 15 so as to reduce the charging current to the processing period ends.

17. The termination control means for determining a final charging period, wherein the final charging period is determined as a function of the total charging time that has elapsed at the time when the end of the charging process is started . 16 apparatus according to any one of.

18. Exit control means, Apparatus according to claim 17 which is adapted reduce at least a predetermined amount battery terminal voltage to the initial final charging period to avoid overcharging.

19. further comprising means for measuring the specific rising charging parameters, termination control means, or after a predetermined time has elapsed, or characteristic that is measured during the first stage of charging process of rising charging parameters The device according to any one of claims 14 to 18 , wherein the end of the charging process is controlled based on the determined value of the battery temperature change rate after the value reaches a predetermined value.

20. The apparatus according to claim 19 , wherein the specific rising charge parameter is a battery terminal voltage.

21. Apparatus according to claim 19 or claim 20 , wherein the means for measuring a rising charge parameter measures the battery terminal voltage as an open circuit voltage.

22. Connect the power to the battery terminals to supply a charging current to the battery, determining the value of the battery temperature change rate calculated from the measured value of the battery temperature during at least part of the charging process, the charging Recharging comprising the step of controlling the end of the charging process based on the value of the battery temperature change rate determined after the battery voltage in the initial stage of the process reaches a predetermined value or meets a predetermined criterion. Possible battery charging method.

23. The method of claim 22 , wherein the obtained value of the battery temperature change rate is compared to a stored reference value, and termination of the charging process is based on the comparison.

24. The storage reference value A method according to claim 23 which is determined during the charging process based on the value obtained with the battery temperature change rate.

25. The method of claim 24 , wherein the reference value represents a minimum of the obtained value of the rate of change in battery temperature .

End of 26. charging process, any one of claims 23 to 25 which begins when the set value of the battery temperature change rate exceeds a stored reference value by a predetermined amount 1
The method described in one.

27. The method according to any one of claims 2 2-26 of the charging process ends comprises a step of reducing the charging current.

28. The method of claim 22 to 27 in which the charging process ends comprises a final charging period.

29. The final charging period The method of claim 28 which is determined as a function of the total charge time has elapsed at the time when the end of the charging process begins.

30. A means for connecting a terminal of a battery having a battery terminal voltage and a temperature to a power supply to supply a charging current to the battery, and a means for determining a value of a change rate of the battery temperature during a part of the charging process. Means for determining the battery voltage at an early stage of the charging process, and the charging process based on the value of the battery temperature change rate determined after the battery voltage reaches a predetermined value or meets a predetermined criterion. Rechargeable battery charger comprising means for controlling termination.

Means for storing a 31. reference values, and means for comparing the determined value of the battery temperature change rate and stored reference values, so end control means finishes the charging process based on the comparison 31. The device of claim 30 , wherein the device comprises:

32. The system further comprising means for determining a reference value, wherein the reference value determining means determines the reference value during the charging process based on the obtained value of the rate of change in battery temperature. The device according to 31 .

33. reference values A device according to claim 32 which is determined as the minimum value of the obtained values of the battery temperature change rate.

34. The end control means according to claim 31 , wherein the end of the charging process is started when the determined value of the battery temperature change rate exceeds the stored reference value by a predetermined amount. An apparatus according to one.

35. A termination control means, Apparatus according to any one of claims 30 to 34 adapted to reduce the charging current during the processing of termination.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP , KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (71) Applicant Ordrupvej 101,3. Sal, DK-2920 Charlottenlund d Denmark (72) Inventor Ostergold, Kim Denmark-2720 Van Rose, Denmark, Bellahowy 115,1. Monkey (72) Inventors Andersen, Kim, Artur, Stouk Denmark, Dk-2990 Nyvo, Broleswey 62

Claims (41)

[Claims] A power supply is connected to a battery terminal to supply a charging current to the battery, a value of the battery temperature change rate is determined during at least a part of the battery charging process, and the battery temperature change rate is obtained. Determining and storing a reference value based on the value; comparing the value of the rate of change of the battery temperature with the stored reference value or a function thereof; and controlling termination of the charging process based on the comparison. How to charge the battery. 2. The method according to claim 1, wherein the charging process is terminated when the determined value of the rate of change in battery temperature exceeds a stored reference value by a predetermined amount. 3. The method according to claim 1, wherein the determined and stored reference value represents a minimum of the obtained value of the rate of change of the temperature of the battery. 4. The method according to claim 1, wherein the end of the charging process comprises a step of decreasing the charging current.
4. The method according to any one of items 1 to 3. 5. The method according to claim 1, wherein the end of the charging process comprises a final charging period. 6. The method of claim 5, wherein the final charging period is determined as a function of the total charging time required at the beginning of the charging process. 7. The method of claim 5, wherein the last charging period has a preset period. 8. The method of claim 6, wherein the length of the final charging period is in the range of 5 to 50% of the total charging time elapsed at the beginning of the end of the charging process, preferably about 25%. . 9. The method according to claim 5, wherein the charging process is controlled so as to reduce the battery terminal voltage by at least a predetermined amount in order to avoid overcharging at the beginning of the final charging period. . 10. The method according to claim 9, wherein the battery terminal voltage decreases by at least 100 mV, preferably at least 200 mV at the beginning of the last charging period, and the battery terminal voltage preferably does not increase during this last period. 11. The termination control of the charging process is performed after a lapse of a preset time or after a value of a specific rising charge parameter measured in an initial stage of the charging process reaches a preset value. The method according to any of the preceding claims, based on the value of the rate of change of the battery temperature determined. 12. The method according to claim 11, wherein the specific rising charge parameter is a battery terminal voltage. 13. The battery terminal voltage is measured as an open circuit voltage.
13. The method according to any one of items 12 to 12. 14. The method according to claim 1, wherein the state of charge of the battery is maintained by a pulsating microcurrent after the end of the charging process. 15. A means for connecting a battery terminal to a power supply for supplying a charging current to a battery having a battery terminal voltage and a temperature, and a means for measuring a rate of change of a battery temperature during at least a part of a battery charging process. Means for determining and storing a charge reference value based on the measured value of the rate of change of the battery temperature; means for comparing the measured value of the rate of change of the battery temperature with the stored reference value or a function thereof; A charging device for controlling the end of the charging process. 16. The apparatus according to claim 15, wherein the termination control means starts the termination of the charging process when the measured or determined value of the battery temperature change rate exceeds the stored reference value by a predetermined amount. 17. The apparatus according to claim 15, wherein the means for determining and storing the reference value determines and stores a minimum value of the obtained values of the rate of change in battery temperature. 18. The apparatus according to claim 15, wherein the termination control means reduces the charging current during the termination processing period. 19. The termination control means is adapted to determine a final charging period, wherein the final charging period is determined as a function of a total charging time that has elapsed at the time when the end of the charging process is started. Apparatus according to any one of the preceding claims. 20. The apparatus according to claim 19, wherein the termination control means reduces the battery terminal voltage by at least a predetermined amount at the beginning of a final charging period to avoid overcharging. 21. Means for measuring a specific rising charge parameter, wherein the termination control means includes a value of the specific rising charge parameter measured after a predetermined time has elapsed or during an early stage of the charging process. The device according to any one of claims 15 to 20, wherein after the time when the value reaches a predetermined value, the end of the charging process is controlled based on the value of the battery temperature change rate determined. 22. The apparatus according to claim 21, wherein the specific rising charge parameter is a battery terminal voltage. 23. Apparatus according to claim 21 or claim 22, wherein the means for measuring a rising charge parameter is adapted to measure the battery terminal voltage as an open circuit voltage. 24. Connecting a power source to a battery terminal to supply a charging current to the battery, determining a value of a first characteristic charging parameter during at least a part of the charging process, and measuring the value in an initial stage of the charging process Rechargeable comprising the step of controlling the end of the charging process based on the value of the first characteristic charging parameter determined after the second characteristic charging parameter reaches a predetermined value or meets a predetermined criterion How to charge the battery. 25. The method of claim 24, wherein the first characteristic charging parameter is a rate of change in battery temperature calculated from a measured value of the battery temperature. 26. The battery of claim 2, wherein the second characteristic charging parameter is a battery voltage.
26. The method according to 4 or 25. 27. The method according to claim 24, wherein the obtained value of the first characteristic charging parameter is compared with a stored reference value, and the termination of the charging process is based on the comparison. 28. The method of claim 27, wherein the stored reference value is determined during a charging process based on the obtained value of the first characteristic charging parameter. 29. The method of claim 28, wherein the reference value represents a minimum of the obtained first characteristic charging parameter value. 30. The method according to claim 27, wherein the end of the charging process is started when a preset value of the first characteristic charging parameter exceeds a stored reference value by a predetermined amount. . 31. The method of claim 2, further comprising the step of terminating the charging process reducing the charging current.
31. The method according to any one of 4 to 30. 32. The end of the charging process comprises a final charging period.
The method described in. 33. The method of claim 32, wherein the final charging period is determined as a function of a total charging time that has elapsed at a time when the end of the charging process has begun. 34. A means for connecting a terminal of a battery having a battery terminal voltage and a temperature to a power supply to supply a charging current to the battery, and a means for determining a value of a first characteristic charging parameter during a part of the charging process. Means for determining a second characteristic charging parameter at an early stage of the charging process; and a first characteristic charging parameter determined after the second characteristic charging parameter reaches a predetermined value or satisfies a predetermined criterion. Means for controlling the end of the charging process based on the value. 35. The apparatus of claim 34, wherein the first characteristic charging parameter is a rate of change of a battery temperature. 36. The battery of claim 3, wherein the second characteristic charging parameter is a battery voltage.
36. The device according to 4 or 35. 37. The apparatus further comprising: means for storing a reference value; and means for comparing the determined value of the first characteristic charging parameter with the stored reference value, wherein the termination control means terminates the charging process based on the comparison. Apparatus according to any one of claims 34 to 36, wherein the apparatus comprises: 38. The apparatus of claim 38, further comprising means for determining a reference value, wherein the reference value determining means determines the reference value during the charging process based on the obtained value of the first characteristic charging parameter. Item 38. The apparatus according to Item 37. 39. The apparatus of claim 38, wherein the reference value is determined as a minimum of the first characteristic charging parameter value. 40. The end control means according to claim 37, wherein the end of the charging process is started when the determined value of the first characteristic charging parameter exceeds the stored reference value by a predetermined amount. An apparatus according to any one of the preceding claims. 41. Apparatus according to any one of claims 34 to 40, wherein the termination control means is adapted to reduce the charging current during termination processing.