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Timestamp: 2020-04-05 00:46:03
Document Index: 137721805

Matched Legal Cases: ['art 52', 'art 54', 'art 52', 'art 52', 'art 52', 'art 54', 'art 52', 'art 54', 'art 52', 'art 52']

Battery charger and battery charging method - Makita Corporation
United States Patent 6476584
09/842324
H01M10/44; H02J7/00; H01M10/34; (IPC1-7): H02J7/16
320/152, 320/151, 320/153, 320/150
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6278261 Battery charging device and charging method thereof 2001-08-21 Sakakibara 320/150
6275009 Battery charging device 2001-08-14 Sakakibara et al. 320/134
6225785 Electrical safety test apparatus and test method for rechargeable lithium batteries 2001-05-01 Muramatsu et al. 320/150
6191560 Battery charger 2001-02-20 Sakakibara 320/150
6133713 Method for charging batteries 2000-10-17 Brotto 320/150
6124698 Battery charger 2000-09-26 Sakakibara 320/110
6075347 Battery charger and charging method 2000-06-13 Sakakibara 320/150
6008628 Method for charging batteries 1999-12-28 Brotto 320/137
5912547 Battery charging method and apparatus with thermal mass equalization 1999-06-15 Grabon 320/150
5909101 Battery charger detecting full charge of batteries using a thermostat and thermistor in a battery pack 1999-06-01 Matsumoto et al. 320/110
5886527 Method and device for monitoring deterioration of battery 1999-03-23 Ito 324/431
5767659 Batteries and battery systems 1998-06-16 Farley 320/106
5739673 Control device for the charging of at least one battery 1998-04-14 Le Van Suu 320/31
5659239 Method and apparatus for charging sealed nickel-cadmium batteries 1997-08-19 Sanchez et al. 320/22
5652500 Charge control apparatus for battery pack which uses rate of change of battery temperature adjusted by correction factor 1997-07-29 Kadouchi et al. 320/15
5592070 Battery charger having a temperature sensor and a rechargeable battery charging method 1997-01-07 Mino 320/35
5497068 Secondary battery charging circuit 1996-03-05 Shiojima 320/35
5480734 Rechargeable accumulator 1996-01-02 Schulz et al. 429/7
5241259 Method and apparatus for rapidly charging a battery at high temperature 1993-08-31 Patino et al. 320/35
4775735 Amine thiocyanates as accelerators for cure of polyepoxide-polyimine materials 1988-10-04 Inakagata 320/35
4370606 Charging apparatus 1983-01-25 Kakumoto et al. 320/35
4308493 Charging of alkaline storage batteries 1981-12-29 Köthe et al. 320/35
3852652 RAPID BATTERY CHARGING SYSTEM AND METHOD 1974-12-03 Jasinskl 320/35
DE3736069A1 1989-05-11
DE4200693C1 1993-05-06
DE200693
EP0863599 1998-09-09 Method for charging maintenance-free nickel metal hydride batteries
JP05244729 METHOD OF CHARGING BATTERY
JP06121468
JP070077865
JP07123604 CHARGER FOR SECONDARY BATTERY
JP07153497
JP07284235
JP18298140
JP08327711 RESIDUAL-CAPACITY MEASURING APPARATUS FOR STORAGE BATTERY
JP10014125
JP2000278875 CHARGING DEVICE
WO1991008604A1 1991-06-13 FAST BATTERY CHARGING SYSTEM AND METHOD
WO1994021022A1 1994-09-15 A BATTERY WITH MEMORY FOR STORING CHARGE PROCEDURE
WO1995009471A1 1995-04-06 METHOD FOR HIGH-SPEED CHARGING OF SECONDARY BATTERIES AND APPARATUS THEREFOR
WO1998012789A1 1998-03-26 BATTERY CHARGING METHODS AND APPARATUSES
JP2000278756A 2000-10-06
JPH05244729A 1993-09-21
JPH1014125A 1998-01-16
DD200693A1 1983-06-01
JPH0777865A 1995-03-20
JPH07284235A 1995-10-27
JPH07153497A 1995-06-16
JPH08327711A 1996-12-13
JPH07123604A 1995-05-12
JPH08298140A 1996-11-12
JPH06121468A 1994-04-28
European Search Report of European Patent Application No. EP 00 10 5940 (00105940.1-2207) dated Oct. 3, 2001.
European Search Report of European Patent Application No. EP 00 10 5941 (00105941.9-2207) dated Oct. 3, 2001.
This application is a Continuation-in-part of U.S. patent application Ser. No. 09/527,126, now U.S. Pat. No. 6,225,786, which claims priority to Japanese patent application Ser. No. 11-081247.
1. An apparatus comprising: a battery pack comprising at least a first block of battery cells, a second block of battery cells, a first battery temperature sensor in communication with the first block of battery cells and a second battery temperature sensor in communication with the second block of battery cells, and a battery charger comprising a current supply arranged and constructed to supply charging current to the battery pack and a processor arranged and constructed to (i) calculate battery temperature increase rates based upon signals from the first and second battery temperature sensors, (ii) select charging currents that will be supplied by the current supply to the first and second blocks of battery cells based upon battery temperature and the calculated battery temperature increase rate, and (iii) alternately supply the selected charging currents to the respective first and second block of battery cells.
2. An apparatus as in claim 1, wherein the processor is further arranged and constructed to terminate the supply of charging current to the respective first and second blocks of batteries based upon a determination that relatively low charging currents have been repeatedly supplied to the respective first and second blocks of batteries over a series of intervals.
4. The method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising: supplying a first charging current to the first block of battery cells while monitoring battery temperature and battery temperature increase rate of the first block of battery cells, adjusting the first charging current based upon the battery temperature and the battery temperature increase rate of the first block of battery cells in order to avoid overheating the first block of battery cells, supplying a second charging current to the second block of battery cells while monitoring battery temperature and battery temperature increase rate of the second block of battery cells, and adjusting the second charging current based upon the battery temperature and the battery temperature increase rate of the second block of battery cells in order to avoid overcharging the second block of battery cells.
5. A method as in claim 4, further comprising: terminating the supply of the first charging current to the first block of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the first block of battery cells over a series of intervals, and terminating the supply of the second charging current to the second block of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the second block of battery cells over a series of intervals.
6. A method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising: independently monitoring battery temperature and battery temperature increase rate of the respective first and second block of battery cells, selecting a first charging current from a look up table using the battery temperature and battery temperature increase rate of the first block of battery cells as indices for the look up table, selecting a second charging current from the look up table using the battery temperature and battery temperature increase rate of the second block of battery cells as indices for the look up table, alternately supplying the selected charging currents to the first block of battery cells and the second block of battery cells while continuing to monitor the battery temperature and battery temperature increase rate of the first and second blocks of battery cells at frequent intervals, selecting a first new charging current from the look up table when the battery temperature and/or the battery temperature increase rate of the first block of battery cells changes, and selecting a second new charging current from the look up table when the battery temperature and/or the battery temperature increase rate of the second block of battery cells changes.
7. A method as in claim 6, further comprising terminating charging of the first block of battery cells when the battery temperature increase rate of the first block of battery cells is relatively high and relatively low charging current has been supplied to the first block of battery cells at a relatively high frequency, and terminating charging of the second block of battery cells when the battery temperature increase rate of the second block of battery cells is relatively high and relatively low charging current has been supplied to the second block of battery cells at a relatively high frequency.
8. A method as in claim 7, wherein the new charging current selection steps further comprise selecting a lower charging current when the battery temperature and/or battery temperature increase rate increases.
11. An apparatus adapted to charge a removable battery pack comprising at least a first block of battery cells, a second block of battery cells, a first battery temperature sensor coupled to the first block of battery cells, a second battery temperature sensor coupled to the second block of battery cells, and at least one charging terminal comprising: a controller arranged and constructed to couple to the first and second battery temperature sensors and the at least one charging terminal of the removable battery pack, wherein the controller comprises a memory storing a program containing instructions to: calculate battery temperature and battery temperature increase rate of the first and second blocks of battery cells based upon signals received from the respective first and second temperature sensors, select a first charging current based upon the battery temperature and the battery temperature increase rate of the first block of battery cells and supplying the first charging current to the first block of battery cells, and select a second charging current based upon the battery temperature and the battery temperature increase rate of the second block of battery cells and supplying the second charging current to the second block of battery cells, wherein the first and second blocks of battery cells are alternately charged.
12. An apparatus as in claim 11, wherein the stored program further comprises instructions to: terminate the supply of the first charging current to the first block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the first block of battery cells over a series of intervals, and terminate the supply of the second charging current to the second block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the second block of battery cells over a series of intervals.
13. An apparatus as in claim 12, wherein the stored program further comprises instructions to terminate the supply of current to the first block of battery cells if the current being supplied to the first block of battery cells falls below a predetermined current value over a series of consecutive intervals.
15. A battery charger adapted to supply current to a rechargeable battery pack comprising a first block of battery cells, a second block of battery cells, a first temperature sensor coupled to the first block of battery cells, a second temperature sensor coupled to the second block of battery cells, a first charging terminal and a second charging terminal, comprising: a source of charging current, a first terminal arranged and constructed to couple to the first battery temperature sensor, a second terminal coupled to the source of charging current and arranged and constructed to conduct charging current via the first charging terminal to the first block of battery cells, a third terminal arranged and constructed to couple to the second battery temperature sensor, a fourth terminal coupled to the source of charging current and arranged and constructed to conduct charging current via the second charging terminal to the second block of battery cells, and a controller coupled to the first and third terminals and the source of charging current, the controller being arranged and constructed to select the amount of charging current supplied to the second and fourth terminals based at least upon battery temperature signals received from the first and third terminals.
16. An apparatus as in claim 15, wherein the controller is further arranged and constructed to independently terminate the supply of charging current to the respective first and second blocks of battery cells based upon a determination that relatively low charging currents have been repeatedly supplied to the respective first and second blocks of battery cells over a series of intervals.
19. A battery charging system for charging a detachable battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising: first means for detecting a battery temperature and battery temperature increase rate of the first block of battery cells and the second block of battery cells, second means for storing a map of allowable current values based upon the detected battery temperatures and battery temperature increase rates, third means for selecting an allowable charging current from the second means based upon the detected battery temperatures and battery temperature increase rates, and fourth means for alternately supplying the selected allowable charging currents to the respective first and second blocks of battery cells.
20. A battery charging system as in claim 19, further comprising fifth means for terminating the supply of charging current to the first block of battery cells based upon a determination that relatively low charging current has been repeatedly supplied to the first block of battery cells over a series of intervals.
21. A method for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising: independently monitoring respective battery temperatures of the first and second block of battery cells, using a processor to select allowable charging currents based upon detected battery temperatures of the respective first and second blocks of battery cells, alternately supplying selected charging currents to the respective first and second blocks of battery cells while continuing to independently monitor the battery temperatures of the respective first and second blocks of battery cells, and independently adjusting the selected charging currents based upon changes in the detected battery temperatures of the respective first and second blocks of battery cells.
22. A method as in claim 21, further comprising terminating the supply of charging currents to the first block of battery cells when the battery temperature of the first block of battery cells is relatively high and a relatively low charging current has been supplied to the first block of battery cells over a plurality of consecutive intervals.
24. An apparatus for charging a battery pack comprising at least a first block of battery cells and a second block of battery cells, comprising: means for independently monitoring respective battery temperatures of the first and second block of battery cells, a processor for selecting allowable charging currents based upon detected battery temperatures of the respective first and second blocks of battery cells, means for alternately supplying selected charging currents to the respective first and second blocks of battery cells while continuing to independently monitor the battery temperatures of the respective first and second blocks of battery cells, and means for independently adjusting the selected charging currents based upon changes in the detected battery temperatures of the respective first and second blocks of battery cells.
25. An apparatus as in claim 24, further comprising means for terminating the supply of charging currents to the first block of battery cells when the battery temperature of the first block of battery cells is relatively high and a relatively low charging current has been supplied to the first block of battery cells over a plurality of consecutive intervals.
The present invention has been made to solve the above-stated problems and an object of this invention is to provide a battery charger and a battery charging method capable of appropriately charging a battery in a short time while avoiding overheating the battery during charging.
Battery chargers and battery charging methods according to the preferred embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.
As shown in FIG. 2, the battery pack 50 containing a nickel metal hydride battery cell consists of a generally cylindrical fitted part 52 and a generally prismatic base 55. A key-shaped key part 54 is formed on the side of the fitted part 52 and the first input terminal t1 connected to the positive electrode of the battery, the second input terminal t2a connected to the negative electrode thereof and the third terminal t3 connected to a temperature sensor consisting of a thermistor and these terminals are arranged on the upper portion of the fitted part 52.
As shown in FIG. 1, the battery charger 10 charging the battery packs 50 is provided with a fitting hole 12 into which the fitted part 52 of the battery pack 50 is fitted. A keyway 14 for introducing the key part 54 of the fitted part 52 is formed on the sidewall of the fitting hole 12. The fitting hole 12 is resin molded integrally with a housing 16 forming the battery charger 10. In this embodiment, the key part 54 is provided at the fitted part 52 of the battery pack 50 and the keyway 14 is provided at the fitting hole 12 of the battery charger 10, thereby preventing the battery pack 50 from being installed in a wrong direction. The first to third output terminals, which are not shown, are provided at the bottom of the fitting hole 12 to contact with the first to third terminals t1, t2a and t3 of the battery pack 50, respectively. An LED lamp 18 is provided on the upper portion of the battery charger 10 to indicate that the battery is being charged.
As shown in FIG. 3, the battery-powered drill 70 is provided with a fitting hole 72 into which the fitted part 52 of the battery pack 50 is fitted, and is constructed to rotate a chuck 76 by a motor, which is not shown, when supplied with power from the first input terminal t1 and the second input terminal t2a of the battery pack 50. When the battery-powered drill 70 is used, a plurality of batteries in the battery pack 50 that are completey charged are sequentially used so that the battery-powered drill 70 can continuously operate. To this end, the battery charger in this embodiment is designed so as to be capable of quickly charging the battery pack 50 in about 30 minutes.
The operation principle of the battery charger in the first embodiment will be described in more detail with reference to FIG. 5. In FIG. 5, the vertical axis indicates battery temperature rise values and the horizontal axis indicates charging time. A curve L therein shows temperature rise values at the time of the completion of battery charge corresponding to the charging time while the battery is charged so that the temperature rise value may be constant. The curve L indicates, for instance, that if current is controlled so that the battery temperature which starts at 20° C. may reach 53° C. (a temperature rise value of 33 degrees), charging time is 20 minutes, if current is controlled so that the battery temperature may reach 43° C. (a temperature rise value of 23 degrees), charging time is 30 minutes and that if current is controlled so that the battery temperature may reach 78° C. (a temperature rise value of 58 degrees), charging time is 10 minutes.
That is, it is possible to obtain a temperature rise value (gradient) from the charge completion time and the battery temperature rise value at the time of the completion of battery charge based on the curve L. For example, to complete battery charge in 20 minutes, battery charge may be conducted so as to have a temperature gradient (temperature rise value) indicated by a straight line a which connects 0 deg. in FIG. 5 and 33 deg. on the curve L. In this case, battery charge is completed almost exactly in 20 minutes when the battery temperature becomes 53° C. (a temperature rise value becomes 33 deg.).
The same thing is true for a case where battery charge is completed in 20 minutes at an outside air temperature of 10° C. and a battery temperature of 10° C. Namely, the battery may be charged so as to have a temperature gradient (temperature rise value) indicated by the solid line a which connects 0 deg. in FIG. 5 and 33 deg. on the curve L. In this case, battery charge is completed at a temperature of 43° C. (a temperature rise value of 33 deg.).
Likewise, in case of completing battery charge in 20 minutes at an outside temperature of 30° C. and a battery temperature of 30° C., the battery may be charged so as to have a temperature gradient (temperature rise value) indicated by the solid line a which connects 0deg. in FIG. 5 and 33 deg. on the curve L. In this case, battery charge is completed at a temperature of 63° C. (a temperature rise value of 33 deg.).
FIG. 6 shows a simulation result when charging a nickel metal hydride battery in 25 minutes so that the battery temperature of 20° C. becomes 50° C. To make a temperature rise value constant, it is necessary to frequently adjust a charging current value. FIG. 6 indicates that the current value is relatively high in the first half of battery charge and gradually lower in the second half of battery charge. Here, the charging current is greatly decreased at a temperature of about 50° C., which indicates that the nickel metal hydride battery is completed with charge. In this embodiment, if this phenomenon is detected, battery charge is completed.
FIG. 7 shows a simulation result for another nickel metal hydride battery. When the nickel metal hydride battery is fully charged, a phenomenon known as “overshoot” in which battery temperature suddenly rises due to the past charging record, not due to the present charging current, may occur to the nickel metal hydride battery. When the overshoot occurs, the temperature rise value cannot be made less than a constant value even if the current value is lowered. In this embodiment, battery charge can be completed even if this phenomenon is detected.
First, the control section 36 detects the temperature of the battery pack 50 through the temperature detecting section 38 (in S12). Here, it is assumed that an outside air temperature and a battery temperature is 20° C. Next, charging time and charge completion time are checked (in S14). The battery charger in this embodiment is constituted to switch battery charge between quick charge (20-minute charge) and normal charge (30-minute charge). If battery charge is set at the quick charge, the storage section 39 which holds the values of the curve L described above with reference to FIG. 5 is retrieved to thereby obtain a battery temperature of 53° C. at the time of charge completion. Thereafter, a temperature gradient is calculated (in S16). Here, the gradient of the straight line a connecting 0 deg. and 33 deg. on the curve L shown in FIG. 5 is obtained.
Next, it is determined whether the current value is less than a predetermined value (in S22). As described above with reference to FIG. 6, if battery charge is completed and the current value becomes less than the predetermined value (“Yes” in S22), charge processing is ended. If the current value is more than the predetermined value (“No” in S22), it is further determined whether a predetermined temperature gradient can be maintained by adjusting the current value, i.e., whether overshoot stated above with reference to FIG. 7 has occurred (in S24). If overshoot has occurred (“No” in S24), the processing is ended. If overshoot has not occurred (“Yes” in S24), the processing goes to a step 26, whereafter the battery is charged with the current value determined in the step 20 and the charge processing is continued further.
FIG. 10 shows the change of the border line B in accordance with the battery temperature. In FIG. 10, the border line B indicates that outside air temperature (20° C.) is equal to the battery temperature. A border line B′ indicates that the battery temperature (20° C.) is higher than the outside air temperature (15° C.). In this case, the border line B′ is shifted downward from the border line B by 5° C.
In case of charging the battery at a temperature of, for example, 20° C. at an outside air temperature of 15° C., the battery charger 110 calculates a pattern in which a temperature rise value at the time of the completion of charge is decreased by 5° C. is calculated as stated above with reference to FIG. 10 and charges the battery in accordance with this pattern. Conversely, if the outside air temperature is 25° C. and the battery temperature is 20° C., the battery charger 110 calculates a pattern in which a temperature rise value at the time of the completion of charge is increased by 5° C.
First, the control section 136 detects the temperature of the battery pack 150 from the temperature detecting section 138 (in S112). Here, it is assumed that outside air temperature is 20° C. and battery temperature is 25° C. Next, charging time and battery temperature at the time of the completion of charge are checked (in S114). In this case, when charging time is 20 minutes, the final temperature rise value of 35 degrees (30 deg. +5 deg.) is obtained. Thereafter, a temperature rise pattern is calculated (in S116).
Next, it is determined whether the current value is less than a predetermined value (in S122). As in the case of the first embodiment, if battery charge is completed and the current value becomes less than the predetermined value (“Yes” in S122), charge processing is ended. On the other hand, if the current value is more than the predetermined value (“No” in S122), it is further determined whether a predetermined temperature gradient can be maintained by adjusting the current value, i.e., whether overshoot has occurred (in S124). If overshoot has occurred (“No” in S124), the processing is ended. If overshoot has not occurred (“Yes” in S124), the processing goes to a step 126, whereafter the battery is charged with the current value determined in the step 120 and the charge processing is continued.
The configurations of a battery charger 210 and battery packs 250A and 250B for the battery charging method in the third embodiment will be described with reference to FIG. 13. The battery pack 250A is provided with a ROM 258a which stores a target temperature value (B1 in FIG. 15) which the battery pack 250A is intended to reach. The battery pack 250B is provided with a ROM 258b which stores a target temperature value (B2 in FIG. 15) which the battery pack 250B is intended to reach. It is noted that the target temperature values B1 and B2 are expressed by a formula of Y=β/(X+α)+γ and that the values of coefficients α, β and γ are written in the ROM 258a and ROM 258b, respectively.
Meanwhile, a control circuit 230 in the battery charger 210 is provided with a ROM reader 231 for reading out the contents of the above-stated ROMs 258a and 258b. A storage section 239 contains an equation for generating a temperature rise pattern. The remaining constituent elements are the same as those in the first embodiment described above with reference to FIG. 4. No description thereto will be, therefore, given herein.
First, the control section 236 of the battery charger 210 detects the temperature of the battery pack 250A from a temperature detecting section 238 (in S212). Here, it is assumed that the battery temperature is 20° C. Next, the coefficients α,β and γ for generating the target temperature value B1 are read out from the ROM 258a of the battery pack 250A and a curve of the target temperature value B1 shown in FIG. 15 is calculated (in S213). Then, charging time and battery temperature at the time of the completion of battery charge are checked (in S214). Here, the battery charger 210 is constructed to permit the operator to switch battery charge between quick charge and normal charge. In quick charge, a battery temperature rise value of up to 30 deg. is allowed. In normal charge, the battery charge is to be completed with a temperature rise of not more than 25 deg. If normal charge is selected, charging time of 25 minutes is confirmed from the temperature rise value of 25 deg. at the time of the completion of charge. On the other hand, if quick charge is set, charge time of 20 minutes is confirmed. Thereafter, a temperature gradient pattern is calculated (in S216). If it is confirmed that charge time is 20 minutes in quick charge, an upwardly rounded curve (temperature rise pattern) j is calculated based on the equation in the storage section 239 from a segment i connecting 0 deg. and 30 deg. in PIG. 15. In the third embodiment, the temperature rise pattern is calculated based on the equation. It is also possible to store a plurality of patterns instead of the equation and to relate the patterns to thereby obtain a pattern.
Next, it is determined whether the current value is less than a predetermined value (in S222). As in the case of the first embodiment, if battery charge is completed and the current value becomes less than the predetermined value (“Yes” in S222), charge processing is ended. On the other hand, if the current is more than the predetermined value (“No” in S222), it is further determined whether the temperature gradient can be maintained by adjusting the current value, i.e., whether overshoot has occurred (in S224). If overshoot has occurred (“No” in S224), processing is ended. If overshoot has not occurred (“Yes” in S224), processing goes to a step 226, whereby the battery is charged with the current value determined in the step 220 and charge processing is continued further.
FIG. 16 shows the configurations of a control circuit 30 and the battery pack 50 in the battery charger 10. The battery pack 50 houses 20 1.2V nickel metal hydride battery cells and can thereby output 24V between the first terminal t1 and the second terminal t2. The intermediate terminal t3 is provided between the first to tenth battery cells and the eleventh to 20th battery cells. By applying a voltage between the first terminal t1 and the intermediate terminal t3, the first to tenth battery cells (to be referred to as “block A” hereinafter) can be charged. Also, by applying a voltage between the intermediate terminal t3 and the second terminal t2, the eleventh to 20th battery cells (to be referred to as “block B” hereinafter) can be charged.
On the other hand, the control circuit 30 of the battery charger 10 consists of a temperature detecting section 38 detecting battery temperatures from output values obtained from temperature sensors (thermistors) 56a (block A-side sensor) and 56b (block B-side sensor), a storage section 39 storing current value control information such as a map to be described later, a control section 36 differentiating the temperature values outputted from the temperature detecting section 38, obtaining a temperature rise value, obtaining a current value with which battery cells are chargeable while suppressing the temperature rise value and outputting the current value as a current command value to a charging current control section 34, the charging current control section 34 controlling a power supply circuit 32 based on the current command value from the control section 36 and adjusting battery charging current, the power supply circuit 32 applying a voltage between the first terminal t1 and the intermediate terminal t3 of the battery pack 50 to thereby charge the block A or applying a voltage between the intermediate terminal t3 and the second terminal t2 to thereby charge the block B, and a current switch control section 37 switching battery charge by the power supply circuit between the block A and the block B.
This battery charger gives weight to the map regions so as to appropriately determine the completion of charge. That is, “1” is added to regions (1), i.e., I42, I43, I34, I35 and I36 which tend to occur in the initial charge completion period. To regions (2), i.e., I51, I52, I53, I44, I45, I46, I54, I55 and I56 which tend to occur in the medium charge completion period, “2” is added. To regions (3), i.e., 161, I62, I63, I64, I65 and I66 which tend to occur in the final charge completion period, “3” is added. By doing so, it is detected that the battery cell can be accurately charged up to a target capacity.
When a predetermined time (20 seconds) pass, the charge target block is switched (in S18). In this embodiment, the control section 36 controls the current switch control section 37, whereby the charged terminals of the power supply circuit 32 are switched from the first terminal t1—intermediate terminal t3 to the intermediate terminal t3—the second terminal t2 and the block B charge is started (in S30 and S32). When a predetermined time (20 seconds) passes, the block A charge is started (in S18).
While alternately switching the charge target block between the blocks A and B, charge is conducted for 20 seconds apiece. In the final charging period, if the battery temperature and the battery temperature change value are in the regions which tend to occur in the initial charge completion period (final charging period region (1), i.e., I42, I43, I34, I35 and I36 (“In” in S36), the block A counter is incremented by “1” while block A is being charged and the block B counter is incremented by “1” while block B is being charged (in S42). If they are in the regions which tend to occur in the medium charge completion period (final charging period region (2)), i.e., I51, I52, I53, I44, I45, I46, I54, I55 and I56 (“In” in S38), the counter is incremented by “2” (in S44). Further, if they are in the regions which tend to occur in the final charge completion period (final charging period region (3)), i.e., I61, I62, I63, I64, I65 and I66 (“In” in S40), the counter is incremented by “3” (in S46). Then, it is determined whether the sum of count values exceed a preset value (10) (in S50). If the battery temperature and the battery temperature change value continuously belong to the above-stated final charging period regions and the sum of the count values exceeds the preset value of 10 (“Yes” in S50), then the charge of the relevant block (e.g., the block A) is completed (in S56). Thereafter, until the charge of the block B is completed, i.e., the block B counter becomes 10 (“No” in S58), battery charge is continued (in S54). If the charge of the block B is completed (“Yes” in S58), charge processing is completed.
FIG. 19 shows the configuration of a battery charger 110 in the second embodiment. The battery charger in the embodiment which has been described above with reference to FIG. 16 charges battery cells after dividing the battery pack 50 into the block A and the block B. The battery charger 110 in the second embodiment, by contrast, charges the overall battery pack 50, i.e., simultaneously charges battery cells in the block A and those in the block B at the start of battery charge as shown in FIG. 19(A). In the final charging period, as shown in FIG. 19(B), the battery cells in the block A and those in the block B are separately charged. (FIG. 19(B) shows a state in which the block A is being charged.) Namely, a power supply circuit 132 in the second embodiment is constituted to switch potential between a potential of 36V for charging the battery pack with rated 24V and a potential of 18V for charging the battery pack (blocks A and B) with 12V. The battery charger in the second embodiment is provided with a temperature sensor 56a for detecting battery temperatures in the block A and a temperature sensor 56b for detecting battery temperatures in the block B.
The control section of a control circuit (see FIG. 19) checks a block A counter indicating the progress of the charge of the block A (first to tenth battery cells) and a block B counter indicating the progress of the charge the block B (eleventh to 20th battery cells) (in S112) and determines whether the sum of the count values is not more than 3, i.e., whether the blocks are in an initial charging period (in S114). In case of the initial charging period (“No” in S114), the processing goes to a step 122, where the map M2 for simultaneously charging both the block A and the block B is selected (in S122). First, the absolute temperature T of nickel metal hydride battery cells in the block A is detected (in S124). Next, the inputted absolute temperature T is differentiated and a change in battery temperature dT/dt is calculated (in S126). If the result of the determination of the step 128 is “Yes”, then the absolute temperature T of the nickel metal hydride battery cells in the block B is detected (in S130). Next, the inputted absolute temperature T is differentiated and a change in battery temperature dT/dt is calculated (in S132). Based on the absolute temperature T and the change in temperature dT/dt, an optimum charging current is selected from the above-stated map M2 with reference to FIG. 21 (in S134). In the initial charging period, the absolute temperature T is low and the change in battery temperature dT/dt is small, so that a relatively high current is retrieved.
If the charging period is closer to the final charging period and the sum of the count value of the block A and that of the block B exceeds 3 (“Yes” in S 114), then charge operation starts to separately charge the block A and the block B. In this case, the map M1 for separate charge shown in FIG. 21 is first selected (in S116) and it is determined which block is set as a charge target block, the block A or the block B (in S120). If the block A is set as the charge target block, the processing goes to a step 124, where the absolute temperature T of the nickel metal hydride battery cells in the block A is detected (in S 124). Next, the inputted absolute temperature T is differentiated and a change in battery temperature dT/dt is calculated (in S126). Thereafter, based on the absolute temperature T and the change in temperature dT/dt, an optimum charging current is selected from the above-stated map Ml with reference to FIG. 21 (in S134).
Then, the control section 136 determines whether the absolute temperature and the change in temperature enter final charging period regions in the map in steps 136 to 148. After it is determined whether the sum of the count values exceeds 10 (“No” in S150), the block A is charged with the current value retrieved in the step 134 as shown in FIG. 19(B) (in S152 and S154).
While alternately switching the block between the block A and the block B, battery charge is conducted for 20 seconds apiece. In the final charging period, if the battery temperature and the temperature rise value enter regions which tend to occur in the initial charge completion period (final charging period region (1), i.e., I42, 143, I34, I35 and I36 (“In” in S136), then the block A counter is incremented by “1” during the charge of the block A and the block B counter is incremented by “1” during the charge of the block B (in S142). If they enter regions which tend to occur in the medium charge completion period (final charging period region (2)), i.e., I51, I52, I53, I44, I45, I46, I54, I55 and 156 (“In” in S138), then the counter is incremented by “2” (in S144). Further, if they enter regions which tend to occur in the final charge completion period (final charging period region (3)), i.e., I61, I62, I63, I64, I65 and I66 (“In” in S140), then the counter is incremented by “3” (in S146). In the determination as to whether the sum of the count values exceed a preset value (10) (in S150), if the absolute temperature and the change in temperature continuously enter the above-stated final charging period regions and the sum of the count values exceeds the preset value of 10 (“Yes” in S150), then the charge of the corresponding block (e.g., the block A) is completed (in S156). Then, until the charge of the block B is completed, that is, until the count value of the block B becomes 10 (“No” in S158), battery charge is continued (in S154). Thereafter, if the charge of the block B is completed (“Yes” in S158), charge processing is completed.
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