JP2000134706A - Detection of battery remaining amount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve forecasting the accuracy of remaining amount battery by forecasting battery remaining based on release voltage corresponding to a battery voltage sampled at a prescribed timing. SOLUTION: A battery 10 is newly connected to a heavy current electrical load 17, and an MPU 15 is reset. Initialization is made, and their initial values are set to various types of counters. A battery voltage VBATT of the battery 10 is sampled by a DC/DC converter 12 and an A/D converter 13 converts it into voltage data DBATT and loaded in the MPU 15 to forecast the initial battery remaining, based on the loaded voltage data DBATT. The remaining battery amount can always be forecast based on the release voltage, regardless of the sampling timing of the battery voltage VBATT of the battery 10. Thus the forecasting accuracy of the remaining amount of the battery is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a remaining amount of a battery based on a terminal voltage of the battery.
The present invention relates to a battery remaining amount detection method capable of accurately detecting the remaining amount of a battery.

[0002]

2. Description of the Related Art In recent years, vehicles using a battery as a power source (hereinafter, referred to as electric vehicles), such as electric vehicles and hybrid vehicles, have attracted attention from the viewpoint of consideration for the environment and effective use of resources. In such an electric vehicle, since the travelable distance depends on the remaining amount of the battery, accurate measurement of the remaining amount is required.

A system for monitoring the remaining amount of a battery is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 10-13898. As described, a method of detecting a remaining amount based on a voltage difference between when a load is applied and when no load is applied has been proposed.

[0004]

The method of estimating the remaining amount of the battery based on the battery voltage is performed after the battery is fully left without any load and the terminal voltage converges to the open-circuit voltage. Thus, the remaining amount can be accurately predicted. However, since the voltage gradually recovers and converges to the open voltage after use of the battery, the battery voltage immediately after use is lower than the open voltage. Therefore, when the remaining amount is predicted based on the battery voltage immediately after use, the predicted remaining amount is lower than the actual amount.

Conversely, after charging is completed, the voltage gradually decreases and converges to the open voltage, so that the battery voltage immediately after charging exceeds the open voltage. Therefore, if the remaining amount is predicted based on the battery voltage immediately after charging, the prediction result will be higher than the actual remaining amount.

As described above, when trying to predict the remaining amount based on the battery voltage, the prediction result changes depending on the sampling timing of the battery voltage, and there is a problem that it is difficult to accurately detect the remaining amount.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to make it possible to accurately predict the remaining amount of a battery voltage based on a terminal voltage regardless of the sampling timing.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a battery remaining amount monitoring device for periodically measuring the remaining amount of a battery mounted on a vehicle. The relationship between the battery voltage and the battery open voltage after the battery is sufficiently left is determined in advance, and the remaining amount of the battery is predicted based on the open voltage corresponding to the battery voltage sampled at the predetermined timing.

According to the above configuration, the remaining amount can always be predicted based on the open circuit voltage regardless of the sampling timing of the battery voltage, so that the accuracy of the remaining amount prediction is improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a main part of a battery remaining amount display device 100 to which the present invention is applied.

The battery 10 has a capacity of 22 to
Generates a voltage of 28V. The power supply circuit 11 includes the battery 1
The terminal voltage VBATT of 0 is converted to a logic voltage V of about 5 V and supplied to the power supply terminal of the MPU 15. The DC / DC conversion circuit 12 converts the range of 22 to 28 V of the battery voltage VBATT to 0 to 5 V. The A / D converter 13 is a DC / D converter.
The output voltage of the C conversion circuit 12 is converted from 0 to 5 V to digital data DBATT of 0 to 255 and supplied to the data input terminal of the MPU 15.

The main power switch 20 opens and closes a connection between the battery 10 and a large current electric load 17 such as a drive motor. The SW input circuit 14 converts the battery voltage VBATT into a logic voltage and supplies the logic voltage to the MPU 15. MPU15
Is based on the logic voltage.
The open / closed state of 0 is determined.

The charger 18 is connected to the charging terminal 100a of the remaining amount display device 100, performs constant current charging until the battery voltage VBATT reaches a predetermined voltage, and then switches to constant voltage charging. The remaining amount indicator 16 is, for example, five LEDs
Each of the display elements is turned on when the LED drive signals D0 and P1 to P4 output from the MPU 15 are at "L" level.

FIGS. 2 to 6 are flow charts showing the operation of the above-described battery remaining amount display device 100, mainly the operation of the MPU 15, wherein the battery 10 is newly connected and the MP
When U15 is reset, the main flow of FIG. 2 starts.

In FIG. 2, in step S1, an initial process is executed, and initial values are set in various counters described later. In step S2, the battery voltage VBATT
Is sampled by the DC / DC converter 12 and the A / D converter 13 and is converted into voltage data DBATT.
The data is read by the PU 15. In step S3, the “initial remaining amount” of the battery is predicted based on the voltage data DBATT.

The "initial remaining amount" in the present embodiment is the remaining amount of the battery which has been sufficiently left unloaded, and its terminal voltage VBATT, that is, the open voltage, and the battery which has been sufficiently left unloaded. It is predicted based on the data table specific to the battery.

In the present embodiment, as will be described in detail later, the "charging" predicted based on the terminal voltage VBATT after the end of charging, which is higher than the open-circuit voltage when the device is sufficiently left without any load, is described. The "remaining remaining amount" is defined based on the terminal voltage VBATT after use, which is lower than the open-circuit voltage, and the remaining amount is defined based on the terminal voltage VBATT. A unique data table for prediction is provided.

FIG. 7 is a diagram showing an example of a data table for estimating the initial remaining amount based on the voltage data DBATT. For example, when the battery voltage VBATT is 24.2 to 24.
In the range of 6 V, the voltage data DBATT is 131 to 14
6, the remaining amount level G is predicted to be “2”.
The remaining amount level G indicates the number of times that the LED of the remaining amount indicator 16 is turned on from the empty EMP side.

In step S4, a monitoring timer is referred to.
When the monitoring period comes, the process proceeds to step S5 and subsequent steps. In this embodiment, the monitoring cycle is set to 50 ms.

In step S5, the state of the main power switch 20 is read. In step S6, it is determined whether a 200 ms timer for periodically sampling the battery voltage VBATT has timed out. 200m
If the s timer has timed out, in step S7, a sampling process of the battery voltage VBATT and a remaining amount prediction process are executed. The predicted remaining amount is displayed on the remaining amount indicator 16 by the LED display process in step S8.

Next, the sampling process / remaining amount prediction process in step S7 will be described in detail with reference to the flowcharts of FIGS.

In step S701, step S5
Reference is made to the open / closed state of the main power switch 20 taken in at step (c). When the main power switch 20 is open, that is, when the main power is off, in step S702, a charging flag Fcharge indicating whether or not the battery 10 is being charged by the charger 18 is referred to. Flag Fch
If arge is "0", that is, if charging is not being performed, step S
At 703, the sampling flag Fsample is referred to. If the sampling flag Fsample is "0", that is, if sampling is not being performed, the process proceeds to step S704.

In step S704, it is determined whether the 5-minute timer has timed out. If the 5-minute timer has timed out, the process proceeds to step S705 and the subsequent steps to execute sampling of the battery voltage VBATT. If it is determined in step S701 that the main power switch 20 is closed, or if it is determined in step S702 that charging is in progress, the processing always proceeds to step S705 and subsequent steps regardless of the 5-minute timer.

As described above, in the present embodiment, the main power switch 20 is closed, in other words, when the large current electric load 17 is connected to the battery 10 and the remaining amount should be frequently detected, or When charging by the charger 18 and it is not necessary to be aware of an increase in power consumption due to sampling of the battery voltage, the remaining amount detection is performed for 200 ms.
When the main power switch 20 is open, in other words, when the large current electric load 17 is not connected to the battery 10 and the change in the remaining amount is slight,
The remaining amount detection is performed in a 5-minute cycle. As a result,
It is possible to achieve both accurate detection of the remaining amount and reduction of power consumption.

As described above, when the process shifts to the sampling process at a period of 200 ms or a period of 5 minutes, at step S705, the sampling flag Fsample is set to "1".
Is set. In step S706, the number of samplings n (initial value “0”) is incremented by “1”. In step S707, the battery voltage VBATT is sampled by the A / D converter 13, and the voltage data DBATT is used as the current voltage data D (n) in the MPU1.
5 is stored. In step S708, it is determined whether or not the number of samplings n is “6”. When six voltage data D (1) to D (6) are stored in a 200 ms cycle, in step S709, the number of samplings is determined. n
And the sampling flag Fsample is reset.

In step S710, an average value Dave of four voltage data obtained by removing the maximum value and the minimum value from the six voltage data D (1) to D (6) is calculated. In step S711, the previous temporary remaining amount DS-1 is updated to the current temporary remaining amount DS, and the current average value Dave is newly registered as the current temporary remaining amount DS.

In step S720 of FIG. 4, the voltage data DBATT sampled in step S707 is compared with the charge determination reference value Dref1. Charge judgment reference value D
ref1 is a threshold value for determining whether or not the battery 10 is being charged. In the present embodiment, ref1 is set to 27.8V.

As shown in FIG. 13, constant-current charging starts at time t0, and voltage data D at time t1.
If BATT exceeds the charge determination reference value Dref1, it is determined that the battery 10 is being charged by the charger 18, and the process proceeds to step S
Proceeding to 722, the charging flag Fcharge is set to "1". Thereafter, constant current charging by the charger 18 proceeds,
At time t2, when the voltage data DBATT reaches the reference value Dref2, the charging method by the charger 18 switches from constant current charging to constant voltage charging.

Thereafter, at time t3, the charger 18 stops charging, and at time t4, the voltage data DBATT changes to the charge determination reference value D
ref1, and when this is detected in step S720, in step S721, the charging flag Fcharge
Is referred to. Immediately after the charging is stopped, the charging flag Fcharge remains "1", and the process proceeds to step S723. In step S723, the current temporary remaining amount DS and the previous temporary remaining amount DS-1
At time t5, when the difference between the two falls within the reference range and the voltage drop after charging substantially stops, in step S724, based on the current provisional remaining amount DS, the "remaining charge after charging" of the battery is performed. Is expected.

FIG. 8 shows an example of a data table for estimating the remaining charge after charging based on the current provisional remaining amount DS. For example, when the battery voltage VBATT is 24.2 to 24.6.
V, the current provisional remaining amount DS is 131-146.
And the remaining level G is predicted to be “1”.

In step S725, the charging flag Fcharge, a ten-time counter and a temporary remaining amount counter described later are all reset. In addition, step S721 is performed.
If the charging flag Fcharge has not been set in step, the process proceeds to step S730 in FIG.

In step S730, the current provisional remaining amount DS
Is compared with the previous provisional remaining amount DS-1. When the difference between the two falls within the reference range Dref and the voltage recovery after using the battery is settled, the counter (initial value "0") is counted ten times in step S732. It is incremented by "1". In step S733, the count value of the ten-time counter becomes “1”.
It is determined whether the count value is “0” or not, and when the count value reaches “10”, the counter is reset ten times in step S734.In step S735, the “use of the battery” is performed based on the current temporary remaining amount DS. The remaining amount is predicted.

FIG. 9 is a diagram showing an example of a data table for estimating the used remaining amount based on the current temporary remaining amount DS. For example, when the battery voltage VBATT is 24.2 to 24.6 V
, The current provisional remaining amount DS indicates a range of 131 to 146, and the provisional remaining amount level G is predicted to be “3”.

In step S736, the temporary remaining level G is stored in the storage area defined by the count value of the temporary remaining counter.
Is stored. In step S737, it is determined whether or not the count value of the temporary remaining amount counter is "6". When the count value becomes "6" and six temporary remaining amount levels G are stored, in step S738. The temporary remaining amount counter is reset. In step S739, four average values Gave excluding the maximum value and the minimum value of the six provisional remaining levels G are calculated.

In step S740, the currently displayed remaining amount level G is compared with the average value Gave of the temporary remaining amount. If the temporary remaining average value Gave is smaller than the currently displayed remaining amount level G, In step S741, the current remaining level G is updated to the temporary remaining average value Gave.

As described above, in the present embodiment, when the remaining amount is predicted based on the terminal voltage VBATT of the battery, the prediction result is obtained even if the same terminal voltage is detected in accordance with the sampling timing of the terminal voltage VBATT. Are different.

That is, after the battery is fully left without any load, for example, after a new battery is connected, the terminal voltage converges to the open-circuit voltage. To represent. However, FIG.
As shown in (2), after the battery is used, the voltage gradually recovers and converges to the open voltage Vopen, so that the terminal voltage VBATT immediately after use is lower than the open voltage Vopen. Therefore, when the remaining amount is predicted based on the terminal voltage VBATT immediately after use,
The predicted remaining amount is lower than the actual amount.

Conversely, as shown in FIG. 11, after the end of charging, the voltage gradually decreases and converges to the open voltage Vopen.
More than open. Therefore, the terminal voltage VBATT immediately after charging
When the remaining amount is predicted based on the remaining amount, the prediction result becomes higher than the actual remaining amount.

Therefore, in this embodiment, as shown in FIGS. 7 to 9 and in comparison with FIG.
For the same terminal voltage VBATT, the relationship between the terminal voltage VBATT and the remaining amount is set for each sampling timing of the terminal voltage VBATT so that the remaining amount after charging is predicted to be lower than after use. As a result, the remaining amount of the battery can be accurately predicted regardless of the sampling timing of the terminal voltage VBATT.

More specifically, the data tables of FIGS. 8 and 9 are determined as follows. That is, in this embodiment, at each sampling timing,
The relationship between the battery voltage VBATT and the open voltage Vopen at the time when the rate of change of the battery voltage becomes equal to or less than a predetermined value is experimentally obtained in advance. Further, the relationship between the battery voltage VBATT and the remaining amount at each timing is converted into a data table by experimentally obtaining the relationship between the open-circuit voltage Vopen and the remaining amount.

For example, comparing FIGS. 7 and 8, FIG.
Is equal to the open voltage Vopen, the open voltage Vopen of 24.2 to 24.6 V corresponds to the remaining level G of “2”. On the other hand, when the condition of step S723 is satisfied after the battery is charged and the rate of change of the battery voltage becomes equal to or less than the predetermined value, even if the battery voltage at that time is 24.7 to 25.1 V, finally It is predicted to converge to 24.2 to 24.6 V, and the remaining amount level G becomes “2” similarly.

Similarly, comparing FIG. 7 with FIG. 9, if the condition of step S730 is satisfied ten times after the battery is used and the rate of change of the battery voltage falls, the battery voltage at that time becomes 23.7-24. Even if the voltage is 1 V, it is predicted that the voltage will eventually converge to 24.2 to 24.6 V, and the remaining level G will be “2”.

Since the battery voltage VBATT rises with temperature, it is desirable to add the battery temperature as a parameter so that the higher the temperature, the lower the remaining level G for the same battery voltage. For example, assuming that the example of FIG. 7 is related to 25 ° C., at 25 ° C., when the terminal voltage is 24.2 to 24.6 V, the remaining level G is “2”.
At 30 ° C., the terminal voltage was 24.7 to 2
At the time of 5.1 V, the remaining level G is set to "2".

FIG. 6 is a flowchart of the LED display process in step S8. In step S801, the open / closed state of the main power switch 20 captured in step S5 is referred to. If the main power switch 20 is open, in step S802, all the LEDs are turned off. If the main power switch 20 is closed, it is determined in step S803 whether or not charging is being performed. If charging is in progress, all LEDs are determined in step SS804.
Flashes.

If it is not charging, the remaining level G is referred to in step S807, and the remaining level G is set to "0".
If so, in step S808, only the LED 5 blinks. If the remaining level G is other than “0”, in steps S809, S811, S813, and S815, it is referred to which of the remaining levels G is 1 to 5, respectively, and steps S810, S812, S814, and S81 are performed.
6, in S817, the number of LEs corresponding to the remaining level G
D is turned on.

[0046]

According to the present invention, the following effects are achieved. (1) According to the first aspect of the invention, the remaining amount can always be predicted based on the open-circuit voltage regardless of the sampling timing of the battery voltage, so that the accuracy of the remaining amount prediction is improved. (2) According to the second aspect of the invention, the remaining amount can be accurately obtained regardless of the temperature of the battery. (3) According to the third aspect of the invention, it is possible to predict the remaining amount of the battery based on the open voltage after charging the battery and after using the battery, as in the case where the battery is newly connected. Therefore, the prediction accuracy is improved. (4) According to the invention of claim 4, when the elapsed time after using the battery becomes longer and the terminal voltage approaches the open-circuit voltage, the terminal voltage is regarded as the open-circuit voltage in the same manner as after newly connecting the battery. Since the remaining amount is predicted, the prediction accuracy is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a battery remaining amount display device to which the present invention is applied.

FIG. 2 is a flowchart showing an operation of the embodiment.

FIG. 3 is a flowchart showing an operation of the embodiment.

FIG. 4 is a flowchart showing an operation of the embodiment.

FIG. 5 is a flowchart showing an operation of the embodiment.

FIG. 6 is a flowchart showing an operation of the embodiment.

FIG. 7 is an example of a data table for estimating an initial remaining amount.

FIG. 8 is an example of a data table for estimating the remaining capacity after charging.

FIG. 9 is an example of a data table for estimating the remaining amount after use.

FIG. 10 is a diagram showing a relationship between a terminal voltage and a lapse of time after use of a battery.

FIG. 11 is a diagram illustrating a relationship between a terminal voltage after battery charging and a lapse of time.

FIG. 12 is a diagram showing a relative relationship between the data tables shown in FIGS. 7, 8, and 9;

FIG. 13 is a diagram showing a change in terminal voltage during battery charging.

[Description of Signs] 10 ... Battery, 11 ... Power supply circuit, 12 ... DC / DC conversion circuit, 13 ... A / D converter, 14 ... SW input circuit, 1
5: MPU, 16: remaining amount indicator, 17: high current electric load, 20: main power switch, 100: battery remaining amount display device

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshihiro Iijima 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 2G016 CA03 CB11 CB12 CB31 CC06 CC13 CC16 CC24 CC27 CE02 5H115 PC06 PG04 PI16 PI29 PO02 PV02 QN03 TI02 TI05 TO05 TO13 TU17 UB01 UB05

Claims (5)

[Claims] 1. A method for detecting the remaining amount of a battery mounted on a vehicle, the method comprising: determining a correspondence between a battery voltage at a predetermined timing and a battery open voltage after the battery is left unattended. And determining a remaining battery level based on an open-circuit voltage corresponding to the battery voltage sampled at the predetermined timing. 2. The method according to claim 1, wherein the open-circuit voltage is determined as a function of temperature. 3. The predetermined sampling timing,
The method according to claim 1, wherein at least one of after newly connecting the battery, after charging the battery, and after using the battery, the correspondence between the battery voltage and the open-circuit voltage is determined for each timing. 2. The method for detecting a remaining amount of a battery according to claim 1. 4. If the present remaining amount predicted by the battery voltage sampled after using the battery is larger than the previous predicted result, the previous predicted result is output as the current remaining amount. Item 6. The method for detecting the remaining amount of a battery according to Item 1. 5. The battery voltage at the timing after the use of the battery is represented by a sampling result when the fluctuation range of the sampling result after using the battery falls within a predetermined range, and the fluctuation range of the sampling result is within a predetermined range. If the elapsed time until the battery life exceeds a predetermined time, the prediction of the remaining amount based on the battery voltage sampled at the timing after the use of the battery is performed with the battery voltage sampled at the timing after the new connection of the battery. The method according to claim 3, wherein the method is performed based on a relationship with an open circuit voltage.