JP3986975B2 - Multistage charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multistage charging apparatus that charges in multiple stages by changing a current value while monitoring a terminal voltage of a secondary battery such as a sealed lead-acid battery.
[0002]
[Prior art]
For example, a secondary battery that can be repeatedly charged and discharged is used as a main power source of an electric vehicle or a portable electric device. For example, lead batteries and lithium batteries are known as secondary batteries, but lead batteries with relatively large capacity and low cost are widely used in electric vehicles and the like.
[0003]
The lead battery uses lead (Pb) as the negative electrode active material, lead dioxide (Pb02) as the positive electrode active material, and sulfuric acid (H2SO4) as the electrolyte, and generates an electromotive force of about 2.1 V during discharge. And at the time of charge, since the lead sulfate produced | generated at the time of discharge returns to lead and lead dioxide, charging / discharging can be performed repeatedly.
[0004]
As a lead battery charging method, for example, a constant voltage charging method, a constant current charging method, a two-stage constant current charging method, and the like are known. In the two-stage constant current charging method, since a long charging time is required, a technique for charging in more stages has been developed (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-11-89106
[0006]
The conventional multi-stage charging method will be briefly described with reference to FIG. 13. Whether the battery terminal voltage has reached a predetermined threshold Th while constant current charging is performed at the maximum current value in the first stage of charging. To monitor. When the terminal voltage reaches the threshold Th, the process proceeds to the second stage charging, and the current value is decreased to perform constant current charging. When the terminal voltage reaches the threshold Th again, the process proceeds to the third stage of charging, and the charging is continued by further reducing the current value. Although depending on the depth of discharge before charging, the time required from the start of charging to the completion of charging is about 8 hours.
[0007]
[Problems to be solved by the invention]
When charging is performed in a state where the SOC (State Of Charge) is low, the conventional multistage charging method can charge the lead battery while gradually switching the current value as planned. However, if charging is performed in a state where the SOC is high, the terminal voltage may instantaneously exceed the threshold value Th in the first stage charging, and even if the current value is decreased in the second stage and the third stage. The terminal voltage does not drop below the threshold value, and the charging stage may be switched more and more.
[0008]
As shown in FIG. 14, when the SOC is large, the terminal voltage of the lead battery rapidly rises due to the first stage charging. When the terminal voltage reaches the threshold Th, the current value is decreased by switching from the first stage charge to the second stage charge. However, even if the current value is decreased, the terminal voltage does not decrease immediately due to a response delay, and the state where the threshold value Th is exceeded continues for a while. For this reason, the current value is quickly switched from the second stage to the third stage and from the third stage to the fourth stage. Therefore, there is no time for performing scheduled charging at each stage, the current value decreases, and charging may take a long time, and sufficient charging may not be performed.
[0009]
In addition to the response delay, if a surge voltage is superimposed due to noise or the like during charging, the terminal voltage instantaneously exceeds the threshold value Th, which may switch the charging stage.
[0010]
Since charging in a shallowly discharged state increases battery life compared to charging in a deeply discharged state, stable charging with a large SOC is more important.
[0011]
This invention is made | formed in view of the above various subjects, The objective is to provide the multistage charging device which can perform the stable charge. Further objects of the present invention will become clear from the description of the embodiments described later.
[0012]
[Means for Solving the Problems]
  In order to solve the above problems,ClearlyThe following multi-stage charging apparatus is a multi-stage charging apparatus that charges in multiple stages while monitoring the terminal voltage of the secondary battery.It is determined whether or not the terminal voltage has reached a predetermined threshold voltage. When it is determined that the terminal voltage has reached the predetermined threshold voltage, a change rate dv / dt of the terminal voltage is calculated, and this change rate dv / When dt is compared with a predetermined threshold value set to a positive value and it is determined that the rate of change dv / dt exceeds the predetermined threshold value,It is characterized by comprising control means for once reducing the current value to be lower than the current value due to the next stage charge, and then starting the next stage charge.
[0013]
  BookIn the invention, the current value is once lowered to a value (including 0) lower than the next-stage charging current value without immediately shifting to the next-stage charging, and the next-stage charging is performed after the terminal voltage change of the battery has settled. Let it begin. Since the current value in the voltage stabilization period is set lower than the current value in the next stage, the current value increases at the start of charging in the next stage. Thereby, it is possible to prevent the charging stage from being switched immediately due to a response delay of the terminal voltage or the like.
[0014]
  The control means reduces the current value to a current value lower than the current value due to charging in the next stage, and then compares the rate of change dv / dt with another threshold value set to 0 or a negative value, and the rate of change dv / When it is determined that dt has exceeded another threshold, the next stage charging can be started.
[0020]
  The present inventionOtherThe multi-stage charging device according to the aspect includes a control unit connected to a monitoring unit that detects a charge / discharge state of the secondary battery, and a charge that performs predetermined charging of the secondary battery (1) according to a control signal from the control unit And the control means is based on the charge / discharge state detected by the monitoring means., One of several charging methods prepared in advanceDetermine the charging method and control the operation of the charging means based on the determined charging methodAs one of a plurality of charging methods, it is determined whether or not the terminal voltage has reached a predetermined threshold voltage (S4), and when it is determined that the terminal voltage has reached a predetermined threshold voltage The change rate dv / dt of the terminal voltage is calculated, and the change rate dv / dt is compared with a predetermined threshold value set to a positive value (S5), and the change rate dv / dt exceeds the predetermined threshold value. If determined, a charging method is included in which the current value is once lowered to a current value lower than the current value due to the next stage charge and then the next stage charge is started.It is characterized by that.
[0021]
The monitoring means monitors the charge / discharge state by detecting the terminal voltage of the secondary battery, the charging current value, and the like. The control means selects an optimal charging method from a plurality of charging methods prepared in advance based on the charge / discharge state signal (data) input from the monitoring means. As a charging method, for example, a method in which the current value is once lowered to a current value lower than the current value due to the next stage charge and then the next stage charge is started, or the next stage charge is changed according to the terminal voltage change rate dv / dt. A method of switching to the charging of the stage, a method of gradually increasing the charging current of the predetermined stage from a current value lower than a predetermined current value to a predetermined current value, a voltage for switching from the previous stage charging to the next stage charging Examples include a method of changing the threshold value according to the charging current value, and one or a plurality of charging methods can be selected from the plurality of charging methods and can be charged by the charging means. .
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
1. First embodiment
[0024]
1st Embodiment is described based on FIGS. 1-3. FIG. 1 is a functional block diagram of a multistage charging apparatus that is also referred to in other embodiments described later.
[0025]
The lead battery 1 is formed by connecting a plurality of battery cells (battery modules) in series, and the positive electrode and the negative electrode are respectively connected to the charging circuit 2 via conductive wires. The charging circuit 2 charges the lead battery 1 in accordance with a control signal from the controller 10. The charging circuit 2 generates a predetermined constant current using, for example, the commercial power supply 3 and supplies it to the lead battery 1. The ammeter 4 detects the current value of the charging current and inputs it to the controller 10. The voltmeter 5 detects the terminal voltage of the lead battery 1 and inputs it to the controller 10. The temperature sensor 6 detects the temperature of the lead battery 1 and inputs it to the controller 10.
[0026]
The controller 10 connects, for example, a central processing unit (CPU) 11, a read only memory (ROM) 12, a random access memory (RAM) 13, an input / output unit 14, a display driver 15, an operation driver 16 and the like through a bus 17. It is configured as a microcomputer system. The CPU 11 performs later-described control based on a program stored in the ROM 12. The RAM 13 temporarily stores values during calculation and terminal voltages, current values, and battery temperatures input from the outside via the input / output unit 14. The display driver 15 performs a predetermined display on the display unit 20 such as a display panel. The operation driver 16 transmits an operation signal input from the operation unit 21 such as a keyboard switch to the CPU 11. In addition, the structure of the controller 10 is an illustration, Comprising: This invention is not limited to this. For example, it can be realized as a hardware circuit without using a microcomputer.
[0027]
Next, the charging operation of this embodiment will be described with reference to FIG. First, in the initial stage immediately after the start of charging, the first stage charging is performed. In the first stage, charging is performed with a constant current of a predetermined current value i1 (i1 is set to the maximum value throughout all stages). Thereby, the terminal voltage of the lead battery 1 starts to rise and exceeds the threshold value Th1 at time T1.
[0028]
Here, in the present embodiment, even when the terminal voltage reaches the threshold value Th1, the switching determination of the charging stage is not performed immediately, and the threshold value Th1 is exceeded even after the delay time by the noise filter, or continuously for a predetermined time. When the threshold Th1 is exceeded, it is determined that the terminal voltage has reached (exceeded) the threshold Th1. Δt1 in the figure indicates a delay time due to a noise filter or a timer. Thus, even if the terminal voltage instantaneously exceeds the threshold Th due to the superposition of the surge voltage, the switching determination is not performed and stable charge control can be performed.
[0029]
At time T2, the charging cycle is determined to be shifted from the first stage to the second stage. Here, it is determined whether or not the voltage change rate dv / dt detected at time T2 exceeds the second threshold Th2, and the voltage change rate dv / dt is a second threshold Th2 (a positive value close to 0). ), That is, when the voltage is changing rapidly (more precisely, when the voltage is rising rapidly), the current value is set to 0 or 0 once without going to the second stage. The charging pause period is started by lowering the current value iL to a near low value.
[0030]
During this charging suspension period (T2-T4), the terminal voltage of the lead battery 1 gradually decreases, and a state in which the voltage change is small is settled. When the voltage change rate dv / dt exceeds the third threshold Th3 (Th3 is a negative value, Th3 <Th2) at time T4, the charging suspension period ends. This charging suspension period is about several tens of seconds. After the end of the charging suspension period, second-stage charging is started, and constant current charging is performed with a current value i2 set lower than the first-stage current value i1.
[0031]
When the terminal voltage of the lead battery 1 exceeds the first threshold Th1 at time T5, the terminal voltage exceeds the first threshold Th1 and the voltage change rate dv / dt is also at time T6 after the lapse of Δt2. When it is smaller than the second threshold Th2, the charging is suspended and the third stage charging is performed. If the voltage change rate dv / dt is larger than the second threshold Th2 at time T6, the current value is 0 or low so that the next stage charging starts after the terminal voltage settles as described above. The charge is lowered to the value iL, and charging in the third stage is started after a charging suspension period. The delay time Δt2 may be the same value as the initial delay time Δt1, or may be different depending on, for example, the charging stage, the voltage change rate dv / dt, and the like.
[0032]
Based on the flowchart of FIG. 3, the charge control process by the controller 10 will be described. Note that the flowchart shown in the figure shows an outline of the process and is different from an actual program. Step is abbreviated as “S”.
[0033]
First, after performing an initialization process or the like, first-stage charging with a predetermined current value i1 is started (S1). Next, it is determined whether or not a charging end condition is satisfied (S2). However, since the charging end condition is not satisfied at the start of charging, the process proceeds to S3.
[0034]
Then, based on the ambient temperature (battery temperature) detected by the temperature sensor 6, the first threshold Th1 is calculated (S3), and it is determined whether or not the current terminal voltage exceeds the first threshold Th1 (S3). S4). The first-stage charging is continued until the terminal voltage exceeds the first threshold Th1 (S4: NO).
[0035]
At time T2, when the terminal voltage exceeds the first threshold Th1 (S4: YES), the terminal voltage change rate dv / dt is calculated, and the voltage change rate dv / dt exceeds the second threshold Th2. It is determined whether or not (S5). When the voltage continues to rise rapidly, dv / dt> Th2 is established. Conversely, when the voltage is constant or decreased, dv / dt <Th2 is established. If the voltage change rate dv / dt does not exceed the second threshold Th2 (S5: NO), the current value i2 is changed to the next stage (second stage).
[0036]
However, at the initial stage of charging in a state where the SOC is large, the voltage rapidly increases. Therefore, “YES” is determined in S5, and the process proceeds to S7. Then, the current value is reduced to 0 (or a low value iL close to 0), charging is paused (S7), and the rapid change of the terminal voltage is waited for (S8). That is, until it is determined that the voltage change rate dv / dt exceeds the third threshold value Th3 set to a negative value, the next stage charging is not started, and the voltage change rate dv / dt is set to the third threshold value Th3. Is exceeded, the second-stage current value i2 is changed to start the second-stage charging (S9). The above charging process is repeated until the charging end condition is satisfied. Although illustration is omitted, by setting a delay of Δt in all determination steps, it is possible to eliminate the influence of an instantaneous voltage change due to a surge voltage or the like.
[0037]
As described in detail above, according to the present embodiment, even when the transition condition for shifting from the previous stage to the next stage is satisfied, the current value is temporarily changed to the next stage instead of immediately shifting to the next stage charging. To lower the current value to a value lower than the current value (for example, a current value iL close to 0 or substantially zero), and after starting the charging rest period (T2-T4), The charging of the next stage can be performed after the rapid change of the terminal voltage has subsided. As a result, it is possible to prevent the charging stage from being switched before sufficient charging is performed as in the prior art, and stable charging can be performed. Although the time required for charging becomes longer by the charging suspension time, the charging suspension time is about several tens of seconds, which is negligible in use compared to the total charging time (about 8 hours).
[0038]
In this embodiment, since the charging stage is switched based on the voltage change rate dv / dt, unlike the switching determination based on whether or not the threshold value Th is simply reached as in the conventional technique, the terminal voltage changes. The charging stage can be switched accordingly.
[0039]
Furthermore, in this embodiment, when a predetermined delay time Δt by a noise filter, a timer, or the like is set, and the transition condition is satisfied only during the period of Δt, it is determined that the transition condition is satisfied. Stable charge control can be performed without being affected by changes.
[0040]
2. Second embodiment
[0041]
Next, a second embodiment of the present invention will be described with reference to FIGS. The feature of this embodiment is that control is performed so as not to shift to the next stage during the terminal voltage decrease period.
[0042]
FIG. 4 is a characteristic diagram showing the charging operation according to the present embodiment. In the initial stage of charging, the first stage charging is performed with a predetermined current value i1.
[0043]
When the terminal voltage exceeds the first threshold value Th1 at time T11 and the voltage change rate dv / dt is greater than the second threshold value Th2, the current flows at time T12 after the predetermined delay time Δt1 has elapsed. The value is decreased from i1 to i2, and the second stage charging is started immediately.
[0044]
Here, during the period from time T11 to time T13, the terminal voltage is higher than the first threshold value Th1, but during the synchronization, the terminal voltage is gradually decreased and is set to a low positive value. Since the voltage change rate dv / dt does not exceed the threshold value Th2 of 2, the charging stage transition condition is not satisfied. Accordingly, the second stage charging is continued.
[0045]
At time T14 after time T13 has elapsed, the terminal voltage is inverted and gradually increases. At time T15, the terminal voltage reaches the first threshold Th1, and at time T16 after a predetermined delay time Δt2, the terminal voltage exceeds the first threshold Th1 and the voltage change rate dv / dt is When the second threshold Th2 is exceeded, the condition for transition to the next stage is satisfied. Therefore, at time T16, the current value is decreased from i2 to a smaller i3, and the third stage charging is started.
[0046]
In other words, in the present embodiment, instead of the charging suspension period, by prohibiting the transition during the falling period of the terminal voltage, the next stage charging is started after the previous stage charging is sufficiently performed. I have to.
[0047]
FIG. 5 is a flowchart showing the charging control process according to the present embodiment. In S11 to S14, processing similar to S1 to S4 described with reference to FIG. 3 is performed. That is, after the initial setting, charging in the first stage is started (S11), it is determined whether the charging end condition is satisfied (S12), the first threshold Th1 is set according to the battery temperature (S13), It is monitored whether the terminal voltage exceeds the first threshold Th1 (S14).
[0048]
When the terminal voltage exceeds the first threshold Th1 (S14: YES), the terminal voltage exceeds the first threshold Th1, and the voltage change rate dv / dt exceeds the second threshold Th2. It is determined whether or not (S15). When both conditions are satisfied (S15: YES), the current value is decreased and the process proceeds to the next stage charging (S17).
[0049]
On the other hand, when the terminal voltage does not exceed the first threshold Th1 or the voltage change rate dv / dt does not exceed the second threshold Th2 (S14: NO), the terminal voltage is This is the case when it is going down or rising very slowly. Therefore, next, it is determined whether or not a predetermined time has elapsed with the terminal voltage exceeding the first threshold Th1 (S16). When the period during which the terminal voltage exceeds the first threshold Th1 continues for a predetermined time set to, for example, about several seconds to about several tens of seconds, preferably about 5 to 10 seconds (S16: YES), the process proceeds to the next stage. The condition is satisfied, and the process proceeds to S17 to start the next stage charging.
[0050]
Also in the present embodiment configured as described above, since the charging of the previous stage is waited until the charging of the previous stage is sufficiently performed, the charging of the next stage is performed, so that stable charging can be performed.
[0051]
3. Third embodiment
[0052]
Next, FIGS. 6 and 7 show a third embodiment of the present invention. The feature of this embodiment is that the charging current is gradually increased by a so-called soft start method.
[0053]
As shown in FIG. 6, at each charging stage in the present embodiment, a charging increase curve is set so that the charging current gradually increases to a preset current value. Therefore, as shown in the upper side of FIG. 6, the change in the terminal voltage is gradual.
[0054]
For convenience of explanation, the delay time Δt described in the above embodiment is omitted. If the terminal voltage exceeds the first threshold Th1 at time T21, even if the charging current at the first stage does not reach the predetermined current value i1, the charging at the second stage is immediately performed. Transition.
[0055]
Even in this embodiment configured as described above, when the charging from the previous stage to the next stage is performed, the charging current gradually increases from 0, substantially 0, or a low value close to 0. Immediately after the transition, there is a short charging suspension period, and the current value can be gradually increased while waiting for the terminal voltage to stabilize. Thereby, stable charge can be performed.
[0056]
Note that, as shown in FIG. 7, the current value may be increased stepwise instead of increasing the current value in a curved shape.
[0057]
4). Fourth embodiment
[0058]
Based on FIG. 8, a fourth embodiment of the present invention will be described. The feature of this embodiment is that the charge control process described above with reference to FIG. 3 is simplified.
[0059]
S21 to S24 in FIG. 8 perform the same processing as S1 to S4 in FIG. When the terminal voltage exceeds the first threshold Th1 (S24: YES), the current value is immediately reduced to 0 or a value iL close to 0 regardless of the voltage change rate dv / dt (S25). Then, for example, after the charging suspension period is continued for a predetermined time set to about several tens of seconds (S26), the current value is switched to start the next stage charging (S27).
[0060]
In the present embodiment configured as described above, since the transition to the next stage charging is performed after a charging suspension period without looking at the voltage change rate dv / dt, the structure is simpler than that of the first embodiment, and stable. Charging can be realized.
[0061]
5. Fifth embodiment
[0062]
Based on FIG.9 and FIG.10, the 5th Embodiment of this invention is described. The feature of this embodiment is that it is configured in a multistage charging apparatus suitable for an electric vehicle.
[0063]
The electric vehicle 30 is equipped with a lead battery 31 and is driven by an electric motor using the lead battery 31 as a power source. Since it is not the gist of the invention, description of the electric motor, the control circuit of the electric motor, the control system, etc. will be omitted.
[0064]
The charge / discharge state of the lead battery 31 is monitored by a charge monitor 32. The charge / discharge monitoring data detected by the charge monitor 32 is transmitted to the controller 42 described later via the connection unit 34.
[0065]
A charging stand 40 for charging the electric vehicle 30 includes a charging circuit 41 and a controller 42. The charging circuit 41 supplies, for example, a current generated by using a three-phase 200 V commercial power supply 50 to the lead battery 31 via the connection unit 33.
[0066]
The configuration of the controller 42 will be described with reference to FIG. The controller 42 is preferably configured as a microcomputer system. Based on the charge / discharge monitoring data input from the charge monitor 32 (S31), the controller 42 selects one or more charge methods suitable for the current charge state from among a plurality of charge methods prepared in advance. Select (S32). And the controller 42 performs charge control by outputting the control signal according to the selected charging method to the charging circuit 41 (S33).
[0067]
Here, various methods can be adopted as the plurality of charging methods. For example, the following methods can be prepared.
(1) A control method for setting a charging suspension period when shifting from the previous stage to the next stage.
(2) A control method in which a charging suspension period is not set when shifting from the previous stage to the next stage.
(3) A control method for shifting to the next stage based on the voltage change rate dv / dt.
(4) A control method for shifting to the next stage depending on whether or not the terminal voltage has exceeded the first threshold Th1.
(5) A control method that does not shift to the next stage while the terminal voltage is decreasing.
(6) A control method for setting the delay time Δt for determining whether or not the transition condition is satisfied.
(7) A control method for gradually changing the charging current.
(8) A control method for rapidly changing the charging current.
(9) A control method for setting a substantially common first threshold Th1 in all charging stages.
(10) A control method for setting the first threshold Th1 in accordance with each charging stage.
[0068]
A plurality of control methods listed above are stored in advance in the memory of the controller 42. All the control methods (1) to (10) may be provided in advance, or only a part may be provided.
[0069]
The controller 42 controls the charging of the lead battery 31 according to one selected control method or by appropriately combining a plurality of selected control methods. Thereby, it can charge with the optimal method according to the charging / discharging state of the lead battery 31. FIG. It should be noted that the controller 42 can discard the already selected charging method based on the data from the charging monitor 32 and select a charging method again. Unlike the portable electric equipment for consumer use, the lead battery 31 of the electric vehicle 30 may be forced to deep discharge in a short time depending on the running state, and the state of the lead battery 31 varies variously. There is. According to the present embodiment, an optimal charging method can be appropriately selected according to the traveling state of the electric vehicle 30, that is, the usage state of the lead battery 31.
[0070]
The charging stand 40 may be eliminated, and the charging circuit 41 and the controller 42 may be provided in the electric vehicle 30. The controller 42 may be shared with an engine control unit (ECU). Further, not only the charge / discharge monitoring data from the charge monitor 32 but also the charging method is selected in consideration of signals detected from other sensors such as vehicle speed, acceleration, torque, electric motor rotation speed, motor temperature, etc. You may make it do.
[0071]
6). Sixth embodiment
[0072]
Based on FIG.11 and FIG.12, the 6th Embodiment of this invention is described. The feature of this embodiment is that the first threshold value Th1 can be set according to the current value at each charging stage.
[0073]
The other steps except S43 shown in FIG. 8 perform the same processing as the corresponding steps in FIG. Therefore, the new step S43 will be described. In S43, the first threshold Th1 is set according to the current value of each charging stage. The battery temperature is taken into account for the calculation of the first threshold Th1.
[0074]
As shown in FIG. 12, in the first stage charging, the first threshold Th1 (1) is set, and the first threshold Th1 (1) is compared with the terminal voltage. On the other hand, when the charging is shifted to the second stage charging, another first threshold value Th1 (2) set to a value slightly higher than the first threshold value Th1 of the first stage is used. The first threshold Th1 is compared with the terminal voltage.
[0075]
Similarly, in each subsequent charging stage, the first threshold Th1 (3), Th1 (4), etc. can be set for each stage. However, it is not necessary to set different first threshold values Th1 at all stages, and different first threshold values Th1 may be set only at some stages among all charging stages.
[0076]
A person skilled in the art can make various additions and modifications within the scope of the gist of the present invention described in each embodiment. For example, those skilled in the art can appropriately combine the above embodiments. Further, the lead battery has been described as an example, but the present invention can be applied when the battery can be used for other types of batteries. Furthermore, the present invention is not limited to an electric vehicle, and can be applied to portable electric devices such as refrigerators and washing machines used outdoors, portable power supply devices, construction machines, ships, robots, and the like.
[Brief description of the drawings]
FIG. 1 is a functional block diagram of a multi-stage charging apparatus that is preferably used in each embodiment of the present invention.
FIG. 2 is a characteristic diagram showing a charging operation according to the first embodiment.
FIG. 3 is a flowchart showing a charging control process.
FIG. 4 is a characteristic diagram showing a charging operation according to the second embodiment.
FIG. 5 is a flowchart showing a charging control process.
FIG. 6 is a characteristic diagram showing a charging operation according to the third embodiment.
FIG. 7 is a characteristic diagram showing a modification of the third embodiment.
FIG. 8 is a flowchart showing a charging control process according to a fourth embodiment.
FIG. 9 is a functional block diagram when the multistage charging apparatus according to the fifth embodiment is applied to an electric vehicle.
FIG. 10 is a flowchart showing a charging control selection process for selecting a charging method.
FIG. 11 is a flowchart showing a charging control process according to the sixth embodiment.
FIG. 12 is a characteristic diagram showing a charging operation.
FIG. 13 is a characteristic diagram showing a multi-stage charging method according to the prior art.
FIG. 14 is a characteristic diagram showing a state in which charging stages are switched one after another in the prior art.
[Explanation of symbols]
1 Lead battery
2 Charging circuit
3 Commercial power
4 Ammeter
5 Voltmeter
6 Temperature sensor
10 Controller
30 Electric car
31 Lead battery
32 Charging monitor
33 connections
34 connections
40 Charging stand
41 Charging circuit
42 Controller
50 Commercial power supply

Claims (3)

In a multistage charging device that charges in multiple stages while monitoring the terminal voltage of the secondary battery (1),
It is determined whether the terminal voltage has reached a predetermined threshold voltage (S4),
When it is determined that the terminal voltage has reached the predetermined threshold voltage, a change rate dv / dt of the terminal voltage is calculated, and the change rate dv / dt and a predetermined threshold set to a positive value are calculated. Compare (S5),
If it is determined that the rate of change dv / dt has exceeded a predetermined threshold, the current value is once lowered to a current value lower than the current value due to the next stage charge (S7), and then the next stage charge is started (S9). ), A multi-stage charging device comprising a control means (10). The control means (10) compares the rate of change dv / dt with another threshold value set to 0 or a negative value after reducing the current value to a value lower than the current value due to the charging of the next stage. (S8) The multistage charging device according to claim 1, wherein when it is determined that the rate of change dv / dt exceeds the another threshold value, the next-stage charging is started. Control means (42) connected to monitoring means (32) for detecting the charge / discharge state of the secondary battery (31);
Charging means (41) for performing predetermined charging on the secondary battery (1) in response to a control signal from the control means (42),
The control means (42) determines one charging method from a plurality of charging methods prepared in advance based on the charge / discharge state detected by the monitoring means (32) (S32). Control the operation of the charging means based on the charging method , and
As one of the plurality of charging methods,
It is determined whether the terminal voltage has reached a predetermined threshold voltage (S4),
When it is determined that the terminal voltage has reached the predetermined threshold voltage, a change rate dv / dt of the terminal voltage is calculated, and the change rate dv / dt and a predetermined threshold set to a positive value are calculated. Compare (S5),
If it is determined that the rate of change dv / dt has exceeded a predetermined threshold, the current value is once lowered to a current value lower than the current value due to the next stage charge (S7), and then the next stage charge is started (S9). ) A multi-stage charging device including a charging method .

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