JP2005094974A - Charging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging apparatus capable of staring appropriate charging, without being affected by the level of the circumferential temperature of a secondary battery. <P>SOLUTION: This charging apparatus is 10 for charging a battery pack 11. The temperature Ts of a battery cell 13 is detected, and charging the battery pack 11 is started when a change rate C in lowering the temperature Ts becomes at or lower than the preset change rate Cs which is preset, in advance. Therefore, it is not necessary to wait for a long time, even when the circumferential temperature of the battery pack 11 is relatively high, and efficiently charge, when the circumferential temperature of the battery pack 11 is relatively low. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a charging device that controls charging of a secondary battery based on the temperature of the secondary battery.

  2. Description of the Related Art Conventionally, a charging device including a temperature sensor that detects the temperature of a secondary battery is known. The secondary battery exhibits a maximum voltage value in a fully charged state. Since the maximum voltage value varies depending on the environmental temperature of the secondary battery, the charging device detects the environmental temperature of the secondary battery with the temperature sensor and reaches the maximum voltage value corresponding to the environmental temperature. Thus, the fully charged state of the secondary battery can be known, and charging is terminated (see, for example, Patent Document 1).

  By the way, when the secondary battery is discharged during use, the temperature rises as shown by the characteristic lines G1 and G2 in the graph of FIG. 5, and when the discharge is stopped, the temperature of the secondary battery becomes It decreases with time and approaches the environmental temperature of the secondary battery. Characteristic line G1 shows the relationship between time and temperature change when the environmental temperature of the secondary battery is high, and characteristic line G2 shows that when the environmental temperature is low. If the secondary battery (for example, a nickel metal hydride secondary battery) is charged immediately after discharging, when the temperature of the secondary battery is high, charging efficiency is poor and the secondary battery is deteriorated.

For this reason, a charging device has been proposed in which charging is performed after the temperature of the secondary battery that has risen due to discharge falls below a preset temperature.
JP 2003-47165 A (page 1-10, FIG. 1)

  However, since the set temperature is fixedly set to a certain value, it is affected by the environmental temperature where the charging device is placed. That is, when the environmental temperature of the secondary battery is high, the temperature of the secondary battery requires a long time until the temperature becomes equal to or lower than the set temperature. In order to improve charging efficiency, the charging device charges the secondary battery. You have to wait a long time before starting. In addition, when the environmental temperature of the secondary battery is low, the charging device is configured to operate at the set temperature even though the set temperature can be lowered so as to further improve the charging efficiency of the secondary battery. The next battery starts to be charged.

  Accordingly, an object of the present invention is to provide a charging device capable of starting appropriate charging without being affected by the environmental temperature of the secondary battery.

  In order to solve the above-described problems, the present invention basically uses a temperature change rate that is hardly affected by the environmental temperature. That is, the invention of the present application is a charging device for charging a secondary battery, when the temperature of the secondary battery is detected and the rate of change when the temperature decreases is below a preset rate of change. The charging of the secondary battery is started.

  The charging device according to the present invention detects the temperature of the secondary battery, and starts charging the secondary battery when the rate of change in temperature falls below a preset change rate. Accordingly, it is not necessary to wait for a long time even when the environmental temperature of the secondary battery is relatively high, and charging can be performed efficiently when the environmental temperature of the secondary battery is relatively low.

  The present invention will be described in detail with reference to the embodiments shown in FIGS.

  As shown in FIG. 1, the charging device 10 includes a charging stand 12 for charging a rechargeable battery pack 11.

  The battery pack 11 includes a battery cell 13 made of a secondary battery and a battery case 15 that houses the battery cell 13 via a buffer material 14 as is well known in the art. The battery case 15 is formed with a plug 17 having a connector pin 16 electrically connected to the charging stand 12 at the lower end thereof. The battery case 15 is provided with a temperature sensor 18 that detects the temperature of the battery cell 13. For example, a thermistor is used as the temperature sensor 18.

  By connecting the plug 17 to the charging stand 12, the battery cell 13 and the temperature sensor 18 are electrically connected to the charging control circuit of the board described later of the charging stand 12 through each connector pin 16 of the plug 17.

  The charging stand 12 has a case 19. A substrate 21 having a charge control circuit 20 connected to a power source (not shown) is disposed in the case 19. The case 19 is provided with a display unit 22 for displaying the state of charge of the battery cell 13 and the like, and an insertion port 23 for receiving the plug 17 is formed. The insertion port 23 is provided with a connector 24 that fits with the plug 17, and the connector 24 is formed with a contact 25 that is electrically connected to the connector pin 16 of the plug 17 during the fitting. The charging control circuit 20 is electrically connected to the contact point 25 of the connector 24 and the display unit 22 via the base 21.

  As is well known in the art, during charging, the battery pack 11 is inserted into the insertion port 23 so that the plug 17 of the battery pack is aligned with the connector 24 of the charging stand 12, and is electrically connected to the charging control circuit 20. Connected. The plug 17 is fitted to the connector 24 to fix the battery pack 11 to the charging stand 12. The charge control circuit 20 starts charging the battery cell 13 provided in the battery pack 11 when a condition described later is satisfied. Information on the state of charge of the battery cell 13 is displayed on the display unit 22, and the user of the charging device 10 can know the state of charge of the battery cell 13.

  FIG. 2 is a block diagram schematically showing the configuration of the electric circuit in the present embodiment.

  As shown in FIG. 2, the charging control circuit 20 includes an arithmetic control circuit 26 and a memory 27. The arithmetic control circuit 26 is connected to a memory 27, a temperature sensor 18 that detects the temperature of the battery cell 13, and a charging circuit 28 that charges the battery cell 13.

  The temperature sensor 18 outputs an electrical signal corresponding to the temperature Ts of the battery cell 13 to the arithmetic control circuit 26 as a detection signal.

  The memory 27 stores information about the first limit temperature Tu, the set change rate Cs, the second limit temperature Tm, and the like.

  The first limit temperature Tu is effective in charging the battery cell 13 when the temperature Ts of the battery cell 13 is lower than the first limit temperature, and greatly affects the deterioration of the battery cell 13 during charging. There is no limit temperature. In this embodiment, for example, the temperature is set to 30 ° C.

  The setting change rate Cs is a threshold value of the change rate C indicating a change due to a decrease in the temperature Ts of the battery cell 13 with respect to time. Here, the graph which shows the characteristic of the temperature Ts of the battery cell 13 is demonstrated. In the graph shown in FIG. 3, the horizontal axis represents time, and the vertical axis represents temperature. T1 indicated on the temperature axis indicates a relatively low environmental temperature, and T2 indicates a higher environmental temperature. A characteristic line Ts1 and a characteristic line Ts2 shown in the graph of FIG. 3 both indicate temperature characteristics with respect to time of the temperature Ts of the battery cell 13. A characteristic line Ts1 indicates the temperature characteristic of the battery cell 13 from the start of discharge until the battery pack 11 stops discharging at the environmental temperature T1 until the start of charging. The characteristic line Ts2 indicates that the battery pack 11 is below the environmental temperature T2. Similar temperature characteristics in some cases are shown. The temperature Ts of the battery cell 13 rapidly increases when discharge is started as indicated by the characteristic lines Ts1 and Ts2, and slowly decreases along gentle curves when the discharge is stopped. The change rate C of the temperature Ts of the battery cell 13 in the characteristic line Ts1 from time t1 to t2 at this time can be expressed by the following equation (1).

C = (ab) / (t1-t2) (1)
As indicated by the characteristic lines Ts1 and Ts2 of the temperature Ts of the battery cell 13, the temperature Ts starts to increase from the start of discharge, and the increased temperature Ts decreases from the time when the discharge is stopped, and as time approaches the environmental temperatures T1 and T2, The width of temperature decrease is reduced. That is, the rate of change C when the temperature Ts of the battery cell 13 decreases gradually decreases, and this rate of change C approaches zero. Further, as shown in FIG. 3, the characteristic line Ts1 and the characteristic line Ts2 discharged for the same time transition in the same change mode with respect to time even though the environmental temperature is different.

  The set change rate Cs, which is a threshold value when the temperature Ts of the battery cell 13 is decreased, is defined by using this characteristic to define the threshold value of the change rate C, regardless of the environmental temperature of the battery pack 11. This is for obtaining the temperature Ts of the battery cell 13 that has a substantially constant temperature difference as seen from the environmental temperature. As a result, the temperature Ts of the battery cell 13 having a substantially constant temperature difference as seen from the environmental temperature of the battery pack 11 can be obtained without detecting the environmental temperature of the battery pack 11.

  Considering the charging efficiency and the influence of deterioration on the battery cell 13 due to charging, it is desirable that the temperature Ts of the battery cell 13 is relatively low when charging the battery cell 13, and the temperature Ts of the battery cell 13 is the environmental temperature. Can drop. However, it takes a long time for the temperature Ts of the battery cell 13 to decrease to the ambient temperature as indicated by the characteristic lines Ts1 and Ts2. Therefore, when charging of the battery cell 13 is started when the temperature Ts of the battery cell 13 has a substantially constant temperature difference as seen from the environmental temperature of the battery pack 11, the battery pack 11 is kept at the environmental temperature without waiting for a long time. The battery cell 13 can be charged with relatively high charging efficiency and little influence of deterioration on the battery cell 13 due to charging.

In this embodiment, the set change rate Cs, which is a threshold value when the temperature Ts of the battery cell 13 decreases, is set to 0.2, for example, and the change rate C is a value of the following equation (2).
0 ≧ C ≧ −0.2 (℃ / 5min) (2)
That is, charging of the battery cell 13 is started when the decrease value of the temperature of the battery cell 13 is 0.2 or less in 5 minutes or when the decrease value is 0 (the temperature Ts of the battery cell 13 does not change).

  The second limit temperature Tm is a temperature at which if the battery cell 13 is charged when the temperature Ts of the battery cell 13 is higher than the second limit temperature, the charging efficiency is low and the influence on the deterioration of the battery cell 13 is large. In this embodiment, it is set to 45 ° C., for example.

  Refer to FIG. 2 again. The arithmetic control circuit 26 detects the temperature Ts of the battery cell 13 from the detection signal output from the temperature sensor 18 and compares it with information stored in the memory 27 as necessary. The calculation control circuit 26 outputs a signal to the charging circuit 28 to instruct the start of charging of the battery cell 13 when a certain condition is satisfied as a result of the comparison calculation.

  When the charging circuit 28 receives a signal for instructing the start of charging from the arithmetic control circuit 26, the charging circuit 28 starts charging the battery cell 13.

  Next, a process until charging in the charging control circuit 20 is started will be described with reference to a flowchart of FIG.

The arithmetic control circuit 26 detects the temperature Ts of the battery cell 13 based on a signal sent from the temperature sensor 18 provided in the battery pack 11. (Step S1)
The arithmetic control circuit 26 compares the temperature Ts of the battery cell 13 with the first limit temperature Tu stored in advance in the memory 27. (Step S2)
When the temperature Ts of the battery cell 13 is equal to or lower than the first limit temperature Tu, the battery cell 13 can be charged efficiently and can be charged without affecting the deterioration of the battery cell 13, so that the battery cell 13 can be charged immediately. Since this is possible, the process proceeds to step S5 for starting charging. When the temperature Ts of the battery cell 13 is higher than the first limit temperature Tu, the process proceeds to step S3 for determining the rate of change C in order to further increase the charging efficiency and reduce the influence on the deterioration of the battery cell 13 due to charging. .

When the temperature Ts of the battery cell 13 is higher than the first limit temperature Tu, the arithmetic and control circuit 26 obtains the rate of change C of the temperature Ts of the battery cell 13 every predetermined time and is preset and stored in the memory 27. Compare with the set change rate Cs. (Step S3)
When the rate of change C due to the decrease in the temperature Ts of the battery cell 13 is equal to or less than the set rate of change Cs, the charging efficiency is relatively high at the environmental temperature of the battery pack 11, and the influence of deterioration on the battery cell 13 due to charging is small. Therefore, the battery cell 13 can be charged. If the arithmetic control circuit 26 determines that the rate of change C is equal to or less than the set rate of change Cs, then the process proceeds to step S4 for comparison with the second limit temperature Tm.

  On the other hand, when the rate of change C of the temperature Ts of the battery cell 13 is larger than the set rate of change Cs, there is a problem with the charging efficiency and the effect on the deterioration of the battery cell 13 due to charging, so the process returns to step S1, The same operation is repeated until the change rate C due to the decrease in the temperature Ts becomes equal to or lower than the set change rate Cs or the temperature Ts of the battery cell 13 becomes equal to or lower than the first limit temperature Tu.

When the rate of change C due to the decrease in the temperature Ts of the battery cell 13 is equal to or less than the set rate of change Cs, the arithmetic control circuit 26 calculates the temperature Ts of the battery cell 13 and the second limit temperature Tm stored in the memory 27 in advance. Compare (Step S4)
If the temperature Ts of the battery cell 13 is lower than the second limit temperature Tm, there is no problem with the charging efficiency and the effect on the deterioration of the battery cell 13 due to the charging, so the process proceeds to step S5 for starting charging. If the temperature Ts of the battery cell 13 is higher than the second limit temperature Tm, charging the battery cell 13 lowers the charging efficiency and greatly affects the deterioration of the battery cell 13, so the process returns to step S <b> 1. The same operation is repeated until the temperature Ts becomes lower than the second limit temperature Tm.

Therefore, when the criteria of the first limit temperature Tu, the set change rate Cs, and the second limit temperature Tm are satisfied, the arithmetic control circuit 26 determines that the charging start condition of the battery cell 13 is satisfied, and the battery cell 13 A signal indicating the start of charging is output to the charging circuit 28. As a result, the charging circuit 28 starts charging the battery cell 13. (Step S5)
In the charging device 10 according to the present invention, the temperature Ts of the battery cell 13 of the battery pack 11 does not affect the deterioration of the battery cell 13 even when the battery cell 13 is charged, and the first limit is high. When the temperature is equal to or lower than Tu, in this embodiment, for example, charging is immediately started when the temperature is 30 ° C. or lower.

  Further, when the temperature Ts of the battery cell 13 is equal to or higher than the second limit temperature Tm at which charging the battery cell 13 has a great influence on the deterioration of the battery cell and the charging efficiency is deteriorated, for example, 45 in this embodiment. When the temperature is higher than or equal to ° C., charging is not started, and the start of charging is waited until the temperature Ts of the battery cell 13 reaches the second limit temperature Tm or lower (45 ° C. or lower).

  When the temperature Ts of the battery cell 13 of the battery pack 11 is between the first limit temperature Tu and the second limit temperature Tm, in this embodiment, for example, in the range of 30 ° C. to 45 ° C. Charging is started at a change rate C of the temperature Ts of the battery cell 13 with respect to a certain time. Charging is started when the rate of change C due to the decrease in the temperature Ts of the battery cell 13 is equal to or less than the set rate of change Cs, in this example, for example, 0> C ≧ −0.2 (° C./5 min). For this reason, charging is started at the temperature Ts of the battery cell 13 that has a substantially constant temperature difference as seen from the environmental temperature of the battery cell 13 regardless of the environmental temperature of the battery cell 13.

  Thereby, in the battery cell 13 used for the same discharge time, charge can be started when substantially the same time has elapsed from the stop of discharge regardless of the environmental temperature of the battery cell 13. Furthermore, since charging of the battery cell 13 is started at a temperature that is a substantially constant temperature difference when viewed from the environmental temperature of the battery pack 11, the charging efficiency is relatively high at the environmental temperature of the battery pack 11 without waiting for a long time. The influence of deterioration on the battery cell 13 is small.

  Therefore, according to the present invention, it is possible to provide a charging device that can start appropriate charging without being affected by the environmental temperature of the secondary battery.

  In the present embodiment, when the temperature Ts of the battery cell 13 of the battery pack 11 decreases, the change rate C of the temperature is equal to or less than the set change rate Cs as a condition for starting charging with the change rate C. Further, when the rate of change C is 0, that is, when the temperature Ts of the battery cell 13 is equal to the environmental temperature of the battery pack 11, the battery cell 13 is conditioned on the condition that the temperature Ts of the battery cell 13 is equal to or lower than the second limit temperature Tm. If the temperature Ts 13 is equal to or lower than the second limit temperature Tm, charging can be started.

  In this embodiment, the temperature Ts of the battery cell 13 of the battery pack 11 does not affect the deterioration of the battery cell 13 even when the battery cell 13 is charged, and the first limit temperature Tu that increases the charging efficiency. In the following cases, charging was started regardless of the rate of change C, but this can be made unnecessary. However, when the temperature Ts of the battery cell 13 is equal to or lower than the first limit temperature Tu and there is no influence on the charging efficiency and the deterioration of the battery cell 13 due to charging, the determination with the change rate C is not necessary. Since it is possible to start charging without waiting for a certain period of time (in this embodiment, for example, 5 minutes), it is desirable to make a determination based on the first limit temperature Tu.

It is sectional drawing of the charging device which concerns on this invention. It is a block diagram which shows roughly the structure of the electric circuit in the Example of the charging device which concerns on this invention. It is a graph which shows the characteristic of the temperature of a battery cell. It is a flowchart which shows the process until it starts charge in a charge control circuit. It is a graph which shows the relationship between the characteristic of the temperature of a battery cell, and the conventional charge start temperature.

Explanation of symbols

10 Charging device 13 Battery cell (as secondary battery) Ts Temperature of battery cell C Change rate Cs Set change rate Tu First limit temperature (as limit temperature)

Claims (2)

  A charging device for charging a secondary battery, wherein the secondary battery is charged when a change rate when the temperature of the secondary battery is detected and the temperature is decreased is equal to or less than a preset change rate. The charging device characterized by starting. 2. The charging device according to claim 1, wherein when the temperature of the secondary battery becomes equal to or lower than a preset limit temperature, charging of the secondary battery is started regardless of the rate of change.

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