JP3752249B2 - Secondary battery charger - Google Patents

Description

  The present invention relates to a charging device for charging a secondary battery such as a nickel-cadmium battery, a nickel-hydrogen metal battery, or a lead storage battery.

In charging a secondary battery, it is important to know how much the secondary battery is charged with respect to the storage capacity of the secondary battery during the charging process.
However, in the past, there was no way to know this, and conventional secondary battery chargers charged secondary batteries by detecting abnormal phenomena (temperature rise, -ΔV characteristics, etc.) that occurred in the secondary battery. (For example, refer to Patent Document 1).

  However, in such a charging method, the secondary battery is excessively charged, resulting in a defect in the internal structure of the secondary battery necessary for repeated charging / discharging, and as a result, the cycle life of the secondary battery is shortened. There was a problem.

  Therefore, in view of such problems, the present applicant and the applicant of the present invention regularly check whether the secondary battery has reached a fully charged state (a state where the charging rate is 100%). A charging device for a secondary battery has been invented that can be appropriately and rapidly charged without damaging the structure (see Patent Document 2).

The secondary battery charging device charges the secondary battery while alternately repeating main charging for supplying a large current to the secondary battery and checking the fully charged state of the secondary battery.
In the main charging, a predetermined charge application voltage value higher than the full charge equilibrium voltage value is applied to the secondary battery (when the applied voltage is increased by applying a voltage to the secondary battery having a charge rate of approximately 0%). A predetermined charging applied voltage value corresponding to a current peak value outside the irreversible chemical reaction region when the charging current increase rate with respect to the applied voltage decreases and the charging current stops increasing is applied for a predetermined time. To charge the secondary battery.

In addition, in the check of the fully charged state of the secondary battery, the current value flowing in the secondary battery is detected while the fully charged equilibrium voltage value is applied to the secondary battery for a short time, and the current value and the charge are charged. Comparing with the completion determination reference value, it is checked whether or not the secondary battery has reached a fully charged state.
When the detected current value is larger than the charge completion determination reference value, it is determined that the secondary battery has not yet reached the full charge state, and the main charge is performed again, while the detected current value is When the charge completion determination reference value or less, it is determined that the secondary battery has reached a fully charged state, and the charging of the secondary battery is stopped here.

JP-A-8-9563

Japanese Patent No. 3430439

  As described above, the charging device disclosed in Patent Document 2 periodically applies a full charge equilibrium voltage value to the secondary battery, and determines whether or not the charging rate of the secondary battery has reached 100%. While checking, the secondary battery is charged. However, for the following reason, the same type (for example, nickel-cadmium battery, nickel-hydrogen metal battery, etc.) and the same model number (for example, AA type or It was later found that some secondary batteries (such as AAA type) did not reach a charging rate of 100%.

  The reason for this is that even with secondary batteries of the same type and the same model number, the storage capacity and the full charge equilibrium voltage value differ slightly depending on the manufacturer, model, usage history, etc. Some manufactured secondary batteries have the same type, model number, manufacturer, model, etc., but have different storage capacities and full charge equilibrium voltage values. For this purpose, when the secondary battery of the same type and the same model number is charged in the charging device disclosed in Patent Document 2, the actual full charge equilibrium voltage value of the secondary battery and the charging device are set. The rechargeable battery is slightly different from the full charge equilibrium voltage value, and the rechargeable battery is only charged to about 90%, and the rechargeable battery is overcharged to over 100%. There was also.

  In view of the above, in the present invention, regardless of the type or model number of the secondary battery, any secondary battery can be charged so that the charging rate is approximately 100%. It is an object of the present invention to provide a rechargeable battery charging device.

The above is a problem to be solved by the present invention. Next, means for solving this problem will be described.
First, as described in claim 1, a charging voltage supply unit that supplies a charging voltage to the secondary battery, a current detection unit that detects a current value of a charging current passed through the secondary battery, and a secondary battery A charging control device for controlling charging, wherein the charging control device includes a minimum check voltage value lower than a rated full charge equilibrium voltage value of the secondary battery, and the full charge equilibrium voltage. Storage means for storing a predetermined charge application voltage value exceeding a value but not reaching the irreversible chemical reaction region, a voltage value of a predetermined step size, and a voltage of the predetermined step size to the check voltage value so far An increment means for adding a value to set a new check voltage value; a switching means for switching the charge voltage supplied from the charge voltage supply means to the predetermined charge application voltage value or the check voltage value; and the current detection hand A first determination unit that determines whether or not the current value detected by the step is equal to or less than a predetermined reference criterion, and from the previous positive determination to the current positive determination by the first determination unit Second determining means for determining whether or not the required time between the two times exceeds r (r is a real number greater than or equal to 1) times the required time between the previous positive determination and the previous positive determination. The charging of the secondary battery is controlled according to the following first to eighth steps.
(First Step) A secondary battery is applied for a minute time at the minimum check voltage value, and a current value flowing through the secondary battery is detected by the current detection means during the minute time.
(Second step) The detected current value is determined by the first determining means, and if the current value exceeds the determination reference value, the process proceeds to the next third step. If the value is equal to or less than the determination reference value, the process jumps to the fourth step.
(Third Step) After switching the charging voltage to the predetermined charging application voltage value by the switching means and applying a secondary battery at the predetermined charging application voltage value for a predetermined time, the charging voltage is reduced to the minimum by the switching means. Switch to the check voltage value and return to the first step.
(Fourth Step) A new check voltage value is set by adding the voltage value of the predetermined step size to the previous check voltage value by the increment means.
(Fifth step) The switching means switches the charging voltage to the predetermined charging applied voltage value, and after the secondary battery is applied for a predetermined time at the predetermined charging applied voltage value, the charging voltage is changed to the new voltage by the switching means. The current value flowing through the secondary battery is detected by the current detection means while the secondary battery is applied with the new check voltage value for a short time.
(Sixth step) The detected current value is determined by the first determining means, and if the current value exceeds the determination reference value, the process returns to the fifth step, while the current value is If it is below the criterion value, the process proceeds to the next seventh step.
(Seventh Step) The second determination means determines the required time from the previous positive determination by the first determination means to the current positive determination, and the previous positive determination by the first determination means. If the required time from the current positive determination to the current positive determination is less than r times the required time from the previous positive determination to the previous positive determination, the process returns to the fourth step, while the first determination means If the required time from the previous affirmative determination to the current affirmative determination exceeds r times the required time from the previous affirmative determination to the previous affirmative determination, a charge stop signal is output.

  According to a second aspect of the present invention, when the charging stop signal is output in the seventh step, the switching means switches the charging voltage to the predetermined charging application voltage value, and the predetermined charging application After the secondary battery is applied at the voltage value for the second predetermined time, the charging of the secondary battery is completed.

  According to a third aspect of the present invention, the required time is measured by counting the number of times of switching to the check voltage value by the switching means.

The above is the solution of the present invention, and the effects of the present invention will be described next.
First, according to the invention of claim 1, regardless of the type or model number of the secondary battery, the charging rate can be determined while searching for the full charge equilibrium voltage value of any secondary battery. Can be charged to be approximately 100%, and the reliability is improved. Furthermore, this charging device is also effective for a secondary battery whose internal structure is partially destroyed and deteriorated, and finds the current full charge equilibrium voltage value of the secondary battery to obtain the current storage capacity. On the other hand, charging can be performed so that the charging rate is approximately 100%.

  And according to invention of Claim 2, while having the same effect as invention of Claim 1, it can charge so that a charging rate may approach 100% further, and reliability improves.

  The invention of claim 3 also has the same effect as that of the invention of claim 1 or claim 2.

The charging device 1 of the secondary battery described below has the highest applied voltage (predetermined charge applied voltage value) E _s outside the irreversible chemical reaction region D so as not to damage the internal structure of the secondary battery during charging. To apply a large current to the secondary battery 10 and periodically switch the applied voltage to the fully charged equilibrium voltage value E _eq to check whether the secondary battery 10 has reached a fully charged state. There is a feature in what to do. In the full charge state check at the full charge equilibrium voltage value E _eq , the full charge state can be determined instantly and accurately. According to this charging device 1, the time until the completion of charging is reduced to about 30 minutes. In addition, it can be charged properly to a fully charged state without causing excessive chemical reaction (redox reaction), and as a result, the cycle life can be increased to 5000 times or more without damaging the internal structure of the secondary battery. Can be improved.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a secondary battery charging device 1, which includes a power supply unit 2, an operation unit 3, an arithmetic control unit 4, a voltage / current control unit 5, a voltage A supply unit 6, a display unit 7, a current detection unit 8, and a voltage detection unit 9 are provided.

The power supply unit 2 includes a transformer and a rectifier circuit that converts commercial AC electricity into direct current, and the operation unit 3 includes operation buttons for a user to perform a start operation and the like. The arithmetic control unit 4 is a charge control means for controlling the charging of the secondary battery 1, and the arithmetic control unit 4 includes a full-charge equilibrium voltage value E _eq (see FIG. 2) of the secondary battery 10, A predetermined charge application voltage value E _s exceeding the full charge equilibrium voltage value E _eq of the battery (see FIG. 2). Storage means (memory corresponding to the current peak value I _so outside the irreversible chemical reaction region D) when the rate of increase (ΔI / ΔE) decreases and the charging current stops increasing The arithmetic control unit 4 stores a program for determining whether or not the secondary battery 10 has reached a fully charged state.

The voltage / current control unit 5 performs switching control of the voltage and current applied to the secondary battery 10 based on the command from the arithmetic control unit 4. That is, voltage and current control unit 5 constitutes a switching means for switching the charging voltage of the secondary battery 10 to a predetermined special charging voltage E _s or equilibrium voltage E _eq at full charge or the like. The voltage supply unit 6 supplies the charging voltage determined by the voltage / current control unit 5 to the secondary battery 10, while stopping charging according to an end instruction from the calculation control unit 4. The display unit 7 is configured by a display lamp or the like that displays charging or completion of charging.

The current detection unit 8 detects the current value of the charging current passed through the secondary battery 10, and the voltage detection unit 9 determines the voltage value applied to the secondary battery 10 or the charging voltage of the secondary battery 10. Then, the detected current value and the detected voltage value are sent to the arithmetic control unit 4.
In the present embodiment, as an example of the notification means, the display unit 7 is configured to notify the user of the completion of charging or the like through vision. However, the notification unit may be configured to notify by voice or the like. The configuration is not particularly limited.

Next, the characteristics of the charging voltage and the charging current of the secondary battery 10 which are basic in describing the charging method of the present invention will be described based on the graph of FIG.
The horizontal axis of the graph in FIG. 2 represents the battery terminal voltage (applied voltage) E (V), and the vertical axis represents the charging current I (mA). Each characteristic is shown.

A graph α indicated by a broken line in FIG. 2 indicates a voltage-current characteristic during charging of the secondary battery 10 having a charging rate of approximately 0%. In this case, a voltage E _α lower than the standard voltage E ⁰ (nominal voltage). Even if is applied, charging current begins to flow. The applied voltage (battery terminal voltage) when this charging current begins to flow is the open circuit voltage, and this open circuit voltage increases as the charging rate increases.

The graph β shown by the one-dot chain line in FIG. 2 shows the voltage-current characteristics during charging of the secondary battery 10 having a charging rate of about 50%, and the applied voltage was increased (from 0 (V)). secondary battery open-circuit voltage E _beta the charging current begins to flow 10 when the charging rate is higher than the open circuit voltage E _alpha of approximately 0% of the secondary battery 10.

A graph γ indicated by a two-dot chain line in FIG. 2 indicates a voltage-current characteristic during charging of the secondary battery 10 having a charging rate of about 90%, and the open circuit voltage is E _γ (E _γ > E _β ). . A graph δ shown by a solid line in FIG. 2 shows the voltage-current characteristics during charging of the secondary battery 10 having a charging rate of approximately 100% (less than 100%), and the open circuit voltage is E _δ (E _δ > _Eγ ). And the value of the open circuit voltage of the secondary battery 10 with a charging rate of 100% (in a fully charged state) is a full charge equilibrium voltage value E _eq (E _eq > E _δ ).

When the secondary battery 10 exceeds the open circuit voltage E _α , E _β , E _γ , E _δ, etc. according to the charging rate, the charging current increases substantially in proportion to the applied voltage, and a predetermined voltage (voltage-current) After passing the inflection point in the curve, the rate of increase in charging current (ΔI / ΔE) with respect to the applied voltage decreases, and eventually the charging current does not increase at all even if the applied voltage is increased. I _so is reached.

Thus, the increase rate of charging current to the applied voltage (ΔI / ΔE) is the applied voltage value corresponding to the current peak value I _so of when it becomes zero becomes E _s, the charging applied voltage value E _s This predetermined The voltage value is specific to the secondary battery 10 determined by the type of the secondary battery 10 and the deterioration state of the secondary battery 10.

When the voltage exceeds the predetermined special charging voltage E _s is applied, the secondary battery 10, the process proceeds redox reaction of the active material is further internally sparked electrolysis reaction, appears negative resistance characteristic Thus, an unintended exothermic reaction or an abnormality such as swelling may possibly lead to destruction of the internal structure of the secondary battery 10. Even if it does not reach that point, the irreversible chemical reaction is extended and the cycle life of the secondary battery 10 is greatly affected. The region defined by the relationship between the charging current and the applied voltage, where such an irreversible chemical reaction that adversely affects the secondary battery 10 occurs, is an irreversible chemical reaction region D indicated by hatching in FIG.

  Therefore, in the charging of the secondary battery 10, until the secondary battery 10 is fully charged (charging rate 100%), the relative value of the charging current with respect to the applied voltage exceeds the reaction watershed Ld and enters the irreversible chemical reaction region D. It is necessary to control the applied voltage so as not to occur.

By the way, the storage capacity of the secondary battery 10 is obtained by the product of the charging current and the charging time. For this reason, if it is going to shorten charging time, it is necessary to increase charging current.
As shown in FIG. 2, the charging rate is to apply the equilibrium voltage E _eq at full charge to approximately 0% of the secondary battery 10, as the charging rate is increased, the charging current flowing through the secondary battery 10 is I _EQO It decreases from (<I _so ). When the secondary battery 10 reaches the fully charged state (charging rate 100%), the charging current becomes 0 (mA), so that it is easy to determine the fully charged state. However, in the charging with the full charge equilibrium potential E _eq , the charging current is lower and the charging time is considerably longer than in the charging with the predetermined charging application voltage value E _s .

Therefore, in the main charging, the secondary battery 10, by applying an irreversible chemical reaction region D outside the highest charging current (current peak value I _so) can flow a predetermined special charging voltage E _s, the Whether or not the secondary battery 10 has reached a fully charged state by passing a large current through the secondary battery 10 and periodically switching the voltage value applied to the secondary battery 10 to the full charge equilibrium voltage value E _eq This check will be performed.
Incidentally, the value of the applied voltage for the large current charging is not limited to said predetermined special charging voltage E _s corresponding to the current peak value I _so, the voltage value corresponding to the slightly lower current value than that (<E _s )

Next, a first embodiment of the charging device 1 for a secondary battery will be described.
The charging device 1 of the secondary battery according to the first embodiment includes a basic configuration of the charging device 1 of the secondary battery according to the second embodiment described later and the charging device 1 of the secondary battery according to the third embodiment. Become.

The secondary battery charging apparatus 1 according to the first embodiment is configured as shown in FIG. 1, and the arithmetic control unit 4 is applying the secondary battery 10 at the fully charged equilibrium voltage value E _eq. A determination program that is a determination means for comparing and determining a check current value i detected by the current detection unit 8 and a charge completion determination reference value J (for example, 10 (mA)) set in advance is incorporated.

Next, the flow of charging by the charging device 1 according to the first embodiment will be described with reference to FIG.
First, when the type of the secondary battery 10 to be charged by the user is input from the operation unit 3 to the calculation control unit 4, the secondary battery 10 is stored in a table stored in advance in the storage means in the calculation control unit 4. A predetermined charge application voltage value E _s and a full charge equilibrium voltage value E _eq corresponding to the type are respectively selected.

The predetermined special charging voltage E _s and the full charge balanced voltage value E _eq, Ni - cadmium battery, a nickel - type and storage capacity of the secondary battery such as hydrogen battery, a unique value determined by the model number, for example, nickel - for cadmium battery, the equilibrium voltage _{E eq} at full charge of about 1.41 (V), the predetermined special charging voltage _{E s} is selected as the higher also about 1.80 (V) it.

Next, the user by operating the operating unit 3, the charging is started (step A1), the secondary battery 10 is a predetermined time T ₁ at a predetermined special charging voltage E _{s (e.g.,} 55 seconds) to continue (Step A2). After the predetermined time _{T 1} elapses, the applied voltage is switched to the full-charge balanced voltage value _{E eq} (step A3), the secondary battery 10 minute time at this full charge balanced voltage value _{E eq T 2} (e.g., 5 (Second)) While the voltage is being applied, the current detection unit 8 detects the current value i flowing in the secondary battery 10 (step A4).

  Then, the determination program compares the detected current value i with the determination reference value J (step A5). If the current value i is larger than the determination reference value J, the process proceeds to step A2. Returning and repeating the above-described flow (charging control), on the other hand, if the current value i is equal to or less than the determination reference value J, it is determined that the secondary battery 10 has reached a fully charged state, and charging is stopped here. (Step A6).

As described above, according to the charging device 1 according to the first embodiment, the secondary battery 10 is appropriately brought into a fully charged state without causing an excessive chemical reaction (oxidation-reduction reaction) inside the secondary battery 10. Can be charged. Moreover, according to this charging device 1, since it can prevent damaging the internal structure of the secondary battery 10, a cycle life can be improved significantly. Further, the charging device 1 is a Lord charging, by applying a equilibrium voltage E _eq at full charge over a predetermined special charging voltage E _s to the secondary battery 10, a fairly large charging current to the secondary battery 10 As a result, the charging time can be greatly shortened.

As described above, the charging device 1 according to the first embodiment periodically applies the full charge equilibrium voltage value E _eq to the secondary battery 10 and checks whether or not the charging rate has reached 100%. However, the secondary battery 10 is being charged. However, for the following reason, the same type (for example, nickel-cadmium battery, nickel-hydrogen metal battery, etc.) and the same model number (for example, AA type or It was later found out that some secondary batteries 10 (such as AAA type) had a charge rate of less than 100%.

The reason for this is that even for secondary batteries 10 of the same type and the same model number, their storage capacity and full charge equilibrium voltage value are slightly different due to differences in manufacturers, models, usage histories, etc. Some foreign-made secondary batteries 10 have the same type, model number, manufacturer, model, etc., but have different storage capacities and full charge equilibrium voltage values E _eq . For this reason, when the secondary battery 10 of the same type and the same model number is charged by the charging device 1 according to the first embodiment, the actual full-charge equilibrium voltage value of the secondary battery 10 and the charging device 1 Is slightly different from the full charge equilibrium voltage value E _eq set to 1, a certain secondary battery 10 is charged only up to about 90%, and a certain secondary battery 10 has a charging rate of 100%. In some cases, the battery was overcharged.

  Accordingly, the secondary battery charging apparatus 1 according to the second embodiment has been improved as follows in view of such a point.

  The charging device 1 according to the second embodiment is also configured as shown in FIG. 1, and the configuration other than the calculation control unit 4 and the voltage / current control unit 5 is the same as that of the charging device 1 of the first embodiment. It is substantially the same.

The storage means (memory) of the arithmetic control unit 4 measures the minimum check voltage value E ₁ lower than the rated full charge equilibrium voltage value of any secondary battery 10 to be measured, and exceeds the full charge equilibrium voltage value. A predetermined charge application voltage value E _t (≦ E _s ) and a voltage value ΔE having a predetermined step size that do not reach the irreversible chemical reaction region D in any target secondary battery 10 are stored.
In addition, when a condition described later is satisfied, the arithmetic control unit 4 adds a voltage value ΔE having the predetermined step size to the check voltage value E _c so far, thereby obtaining a new check voltage value E _{c + 1} (= An increment program for setting E _c + ΔE) is incorporated. Here, the check voltage value E _c is a voltage value obtained by incrementing the voltage value ΔE from the minimum check voltage value E ₁ c times (c is an integer of 1 or more), and may be expressed as E _{c + 1} = E ₁ + ΔE · c. it can.

Furthermore, the calculation control unit 4 receives the current reference value i detected by the current detection unit 8 while the secondary battery 10 is being applied with the check voltage value E _c as the determination reference value K (for example, 1 ( mA)) a first determination program for determining whether or not the following is satisfied, and a previous positive determination by the first determination program (detected when the check voltage value E _c-1 is applied to the secondary battery 10) and the detected current value i is less than the determination reference value K when the current value i is the application of the check voltage E _c to the affirmative determination (secondary battery 10 of this from determination) with the following criterion value K were of until determination), a measuring program for counting the switching circuit number to check voltage E _c by the voltage and current control unit 5, the check voltage to the current positive determination from the previous affirmative determination by the first judging program switching circuit number of the value E _c is And s times a second determination program (the r 1 or more real) r of the switching circuit number to check voltage E _c-1 to positive determination previous from positive determination determines whether exceeds the fold, is incorporated It is. However, the measurement by the measurement program and the determination by the second determination program are performed when c ≧ 2.

As described above, the calculation control unit 4 of the charging device 1 according to the second embodiment includes the increment program that is the increment means, the first determination program and the second determination program that are the determination means, and the measurement that is the measurement means. A program is stored.
The measurement program and the second determination program are not limited to the above configuration, and the measurement program is configured to measure the time required from the previous affirmative determination to the current affirmative determination by the first determination program. The program determines whether or not the required time from the previous positive determination to the current positive determination by the first determination program exceeds r times the required time from the previous positive determination to the previous positive determination. It is good also as a structure.

The voltage-current control unit 5 is a switching means, the charging voltage of the secondary battery 10, for checking the predetermined fully charged state special charging voltage E _t or the secondary battery 10 for charging Switch to the check voltage value E _c (including the minimum check voltage value E ₁ ).

Next, an outline of charging by the charging device 1 according to the second embodiment will be described.
The charging by the charging device 1 according to the second embodiment will be described as an example of a high jump in track and field competition. Here, a player who does not know the high jump ability accurately (secondary battery whose full charge equilibrium voltage value is not accurately known). Battery).

First, the height of the bar is set to the minimum height (minimum check voltage value E ₁ ) and the competition (charging) is performed, and the athlete clears this minimum height (detected by the determination by the first determination program). When the current value i is determined to be equal to or less than the determination reference value K), the number of trials required until the current value i is cleared is recorded. In the normal high jump rule, there are up to 3 attempts, but the rule here is the number of attempts required to clear the height at the previous height (check voltage value E _c ). Within r times. For example, if r is 1, and 10 trials are required before the height is cleared at the previous height (check voltage value E _c ), the bar height (voltage value) is set to the predetermined height. At the current height (new check voltage value E _{c + 1} ) after increasing (the voltage value ΔE of a predetermined step size), the number of trials is up to 10 times, and when it exceeds 10 times (judgment by the second judgment program) Therefore, the competition (charging) shall end.

FIG. 4 is an enlarged view of a portion indicated by an arrow P in FIG. 2, and a nickel-hydrogen battery will be described as an example.
The voltage-current characteristic changes in the direction of the arrow in FIG. 4 as charging progresses (as the charging rate increases), and the straight line along the reaction water basin Ld is a straight line with a charging rate of 100%. Become.
First, by setting the minimum check voltage E ₁ to 1.40 (V), a charge of a predetermined special charging voltage that does not reach the but irreversible chemical reaction region D than the full-charge balanced voltage value E _eq, the go repeatedly and check the state of charge by the lowest check voltage E _1. According the number of checks by the lowest check voltage E ₁ increases, the detected electric current i during check decreases so that it descends along the bold line on 1.40 (V) in FIG. Then, for example, in check by the lowest check voltage E ₁ of the 20 th, the detected current value i is less than or equal to the determination reference value K.

The next check voltage value E ₂ is increased by 0.01 (V) from the minimum check voltage value E ₁ to 1.41 (V). In the first charge state check using this check voltage value E ₂ , the nickel- 2 (mA) weak current flows in the hydrogen battery, according to the number of checks by the check voltage E ₂ increases, the detected electric current i during check continue to decrease, 1.41 in FIG. 4 (V) It descends along the thick line above. For example, it is assumed that the detected current value i is determined to be equal to or less than the determination reference value K in the third charge state check. The number of checks to the detected current value i is determined to be equal to or smaller than the determination reference value K (3 times) the current value i detected by the previous lowest check voltage E ₁ is determined to be equal to or lower than the determination reference value K It is less than the number of checks (20 times) until it is completed, and therefore charging is continued.

Then, set the check voltage _{E 3} from check voltage _{E 2} to 0.01 (V) up to 1.42 (V), in the initial state of charge check by the check voltage _{E 3} are nickel - hydrogen battery about 2 current flow (mA) in accordance with the number of checks by the check voltage E ₂ increases, the current value is detected at the time of check i is gradually reduced, in FIG. 4 1.42 (V) above It goes down along the thick line. For example, it is assumed that the detected current value i is determined to be equal to or less than the determination reference value K in the third charge state check. The detected current value i is determined to the number of checks (3 times) the current value i detected by the previous check voltage E ₂ is equal to or less than the determination reference value K is determined to be equal to or smaller than the determination reference value K This is the same as the number of checks up to (3), and therefore charging is continued in this case as well.

  Thereafter, the state of charge is checked in the same manner, and the number of checks until the detected current value i is determined to be equal to or less than the determination reference value K with a check voltage value of 1.47 (V) is 1 before that. When the check voltage value of .46 (V) exceeds the number of checks until the detected current value i is determined to be equal to or less than the determination reference value K, the charging of the nickel-hydrogen battery is stopped here. By charging the secondary battery in this way, the charging rate of the secondary battery becomes approximately 100%.

Next, the flow of charging by the charging device 1 according to the second embodiment will be described with reference to FIG.
First, when the user sets the secondary battery 10 in the charging device 1 and operates the operation unit 3, the secondary battery 10 is rated for the secondary batteries of all types and all model numbers to be measured by the charging device 1. A minute time T ₂ (for example, 5 (seconds)) is applied at a minimum check voltage value E ₁ (for example, 1.40 (V)) lower than the full charge equilibrium voltage value (step B1).

The lowest check voltage E ₁ in the secondary battery 10 while short time T ₂ applied, by detecting the current value i of the current detector 8 is flowing through the secondary battery 10 (step B2), the The first determination program determines the detected current value i (step B3).

If the detected current value i is beyond the criterion value K (step B3), by switching the charging voltage to the predetermined special charging voltage E _t by the voltage-current control unit 5, the predetermined charging voltage applied predetermined time of the secondary battery 10 with the value _{E t T 1} (e.g., 55 seconds) is applied (step B4). It charges the secondary battery 10 at this predetermined special charging voltage E _t, after a predetermined time applying T _1, by switching the charging voltage to the lowest check voltage E ₁ by the voltage-current control unit 5, again Return to step B1.

On the other hand, if the detected current value i is equal to or smaller than the determination reference value K (step B3), the check voltage value E _c (including the minimum check voltage value E ₁ ) is obtained by the increment program of the arithmetic control unit 4. The voltage value ΔE (for example, 0.01 (V)) of the predetermined step width is added to set a new check voltage value E _{c + 1} (= E _c + ΔE) (step B5), and the voltage / current control unit 5 by switching the charging voltage to the predetermined special charging voltage E _t by, the predetermined charging applied voltage value E _t secondary battery 10 for a predetermined time T _{1 (e.g.,} 55 seconds) is applied (step B6 ).

Then, after the predetermined time T ₁ elapses, the voltage / current control unit 5 switches the charging voltage to the new check voltage value E _c , and the secondary battery 10 is connected to the new check voltage value E _{c + 1} for a short time T _2. applying (step B7), during this short time T _2, by detecting the current value i of the current detector 8 is flowing through the secondary battery 10 (step B8), and the detection by the first judging program The current value i is determined (step B9).

If the detected current value i exceeds the determination reference value K (step B9), the process returns to step B5. On the other hand, if the current value i is equal to or less than the determination reference value K (step B9), From the previous affirmative determination (determination that the detected current value i is equal to or less than the determination reference value K) by the first determination program by the second determination program to the current affirmative determination (the detected current value i is equal to or less than the determination reference value K) switched until determination) determines switching circuit speed _{N c} to check voltage _{E c} (step B10).

The number of times of switching N _c to the check voltage value E _c from the previous affirmative determination to the current affirmative determination by the first determination program is the check voltage value E _c− between the previous affirmative determination and the previous affirmative determination. if less r times the switching circuit number N _c-1 to ₁ (step B10), returns to the step B6, whereas, check voltage between the previous affirmative determination by the first judging program to the present affirmative judgment if switching circuits speed N _c to E _c is has exceeded the r times the switching circuit speed N _c-1 of the check voltage E _c-1 between the positive determination of the second last until a positive determination in the previous (step B10), A charge stop signal is output (step B11), and charging of the secondary battery 10 is stopped (step B12).

In addition, when the charge stop signal is output in Step B11, the charging of the secondary battery 10 may be stopped immediately, or the charging of the secondary battery 10 may be stopped after a certain time has elapsed. Also good. In the latter case, when the charge stop signal is output, for example, by switching the charging voltage to the predetermined special charging voltage E _t by the voltage-current control unit 5, in the predetermined special charging voltage E _t after the secondary battery 10 has a second predetermined time T ₃ is applied to complete the charging of the secondary battery 10. Alternatively, when the charge stop signal is output, and the voltage application for a predetermined time T ₁ by the predetermined special charging voltage E _t, the cycle consisting of the voltage application minute time T ₂ and by the check voltage E _c You may comprise so that charge of the secondary battery 10 may be completed after repeating predetermined times.
By charging in this way, the secondary battery 10 can be charged so that the charging rate further approaches 100%.

  With the configuration as described above, according to the charging device 1 of the second embodiment, regardless of the type or model number of the secondary battery 10, any secondary battery 10 can be used. Thus, charging can be performed such that the charging rate is approximately 100% while searching for the full charge equilibrium voltage value of the battery, and reliability is improved. Furthermore, the charging device 1 is also effective for a secondary battery 10 whose internal structure is partially destroyed and deteriorated. The current full-charge equilibrium voltage value of the secondary battery 10 is searched for, Charging can be performed so that the charging rate is approximately 100% with respect to the storage capacity.

Next, a charging theory by the charging device 1 according to the second embodiment will be described.
As shown in FIG. 6, there are three examples of general forms of functions having asymptotic characteristics that approach a constant value. Among these, the function (b) in FIG. 6 does not apply to the charging by the charging device 1 according to the second embodiment, so the functions (a) and (c) in FIG. 6 are examined.
First, the function (a) in FIG. 6 will be described. As shown in FIG. 7, when the potential at the time of saturation in a fully charged state with a charging rate of 100% is V _{eq, f} , the electromotive voltage V _eq (t ) Is represented by the following formula (a-1).

Here, when the electromotive voltage at time t = t ₁ is V _eq (t ₁ ), the following equation (a-2) is established.

  If the check voltage value is increased by ΔV from this state to set a new check voltage value, and the time required for the battery electromotive voltage to equilibrate to the new check voltage value is Δt (tn), the following equation (a-3) ) Holds.

  When this formula (a-3) is rearranged, the following formula (a-4) is obtained. This formula (a-4) is expressed by formula (a-5) using formula (a-2). .

Battery voltage V _eq (t ₂ + 2Δt (t ₁ )) at time 2Δt (t ₁ ) from time t = t ₂ shown in equation (a-3) is calculated and compared with V _eq (t ₂ ) + ΔV. .
That is, the following equation (a-6) in which t = t ₁ + 3Δt (t ₁ ) is substituted into equation (a-1) and t = t ₂ is substituted into equation (a-1) and ΔV is added. It becomes a comparison with the following formula (a-7).

If the formula (a-6) is larger than the formula (a-7), the base point is t = t ₂ and charging continues. On the other hand, if the formula (a-6) is smaller than the formula (a-7), the charging is terminated, and the terminated battery electromotive voltage is defined by the formula (a-6). Here, the following formula (a-8) is a calculation formula obtained by subtracting the formula (a-7) from the formula (a-6).

As a specific example, assume that a certain secondary battery has the following constants.
V _{eq, f} = 1.417 (V), V _eq (t ₀ ) = 1.385 (V), constant λ is a constant determined by the charging current, and increase in comparison voltage is ΔV = 0.01 (V) . In the case of the time-voltage pattern of FIG. 8, the calculation base point is time t = t ₁ . (Even if the check start voltage is 1.38 (V), the object of control is the time t = t ₁ or later in the case of the figure.)
Substituting these values into the equation (a-8) gives the following equation (a-9).

  Based on the above calculation formula, an example when the constant r related to the determination in the second determination program is set to r = 2 in the charging device 1 according to the second embodiment will be described.

As shown in FIG. 9, first, the minimum check voltage value is set to 1.39 (V), and charging of the secondary battery is started. When charging proceeds and the electromotive voltage of the secondary battery reaches 1.39 (V), charging stops in equilibrium.
Next, when the check voltage value is increased by 0.01 (V) to 1.40 (V), after a certain period of time (in the example of FIG. 9, the dimensionless time is 0.463), the battery electromotive voltage Reaches 1.40 (V). Further, the check voltage value is increased by 0.01 (V) to 1.41 (V), and the time required to reach 1.41 (V) from 1.40 (V) (zero in non-dimensionalized time). , 887), the charging is terminated when time has elapsed. The battery electromotive voltage at this time is 1.4158 (V), reaching 99.9% of the original fully charged electromotive voltage.

  As long as the charging characteristics of the secondary battery are in this pattern, this control method can be brought close to the fully charged electromotive voltage even if there is a difference in the electromotive voltage. Full charge is possible regardless of.

Next, the function (c) in FIG. 6 will be described.
As shown in FIG. 10, the outline of charging in this case will be described. At time t = t ₁ , the battery voltage is balanced with the check voltage value, and the voltage at that time becomes V _eq (t ₁ ). Next, the check voltage value is increased by ΔV, a new check voltage value is set, and charging is continued and the time until equilibration is assumed to be Δt (t ₁ ). The equilibrium voltage there is V _eq (t ₁ ) + ΔV. Further, the check voltage value is increased by ΔV, a new check voltage value is set, and charging is continued. At this time, the charging is terminated if the equilibrium does not occur even after 2Δt (t ₁ ) has elapsed. When balanced, the elapsed time is Δt (t ₂ ), and the balanced voltage at that time is V _eq (t ₁ ) + 2ΔV. Then, the check voltage value is increased by ΔV and the above process is repeated.

  When the above charge control is mathematically deduced, the potential curve shown in FIG. 10 follows the following equation (b-1).

When time t = t ₁ , the following expression (b-2) is obtained by substituting into the expression (b-1).

  From this time, the time required for the voltage to increase by ΔV is calculated.

  When the above equation (b-3) is modified, the following equation (b-3 ′) is obtained.

  Further, when the formula (b-2) is modified, the following formula (b-2 ') is obtained.

Based on the above calculation formula, an example will be described when the constant r related to the determination in the second determination program is set to r = 2 in the charging device 1 according to the second embodiment.
When the check voltage value is increased by 0.01 (V), the time required to clear the height of the bar (check voltage value) differs depending on the charging step (degree of charging). When the time has doubled, calculate the equilibrium voltage when charging is stopped.

  In FIG. 11, when the minimum check voltage value, which is the height of the first bar, is set to 1.40 (V) and the check voltage value is increased from 1.40 (V) to 1.41 (V), It takes 1.299 in dimensionless time to clear. In addition, when 1.43 (V) to 1.44 (V) is cleared at the minimum time (0.673 in dimensionless time) in the table of FIG. It takes a long time to clear the check voltage value, and it is impossible to clear the check voltage. Therefore, when the charging is stopped within the limit of twice the required time finally cleared, the achievement level is calculated as the target value, which is the lowest value in the table of FIG. As can be seen from this table, according to this charging method, 99.97% of the original full-voltage electromotive voltage is reached at the end of charging.

  The above is the description when the constant r related to the determination in the second determination program is set to r = 2 in the charging device 1 according to the second embodiment. The constant setting r is not limited as long as it is 1 or more. When this constant r is set to r = 1, charging stops near the inflection point (voltage value at time t = tc) of the voltage curve in FIG. 10, and the charging rate of the secondary battery at the end of charging is About 80%. The charging method having such a setting is also effective, charging can be performed without reaching the irreversible reaction region D, and the cycle life can be dramatically extended to exceed 5000 times.

The block diagram which shows the control structure of the charging device 1 of a secondary battery. The graph which shows the current-voltage characteristic for every charging rate of the secondary battery. The flowchart which shows the charge control by the charging device 1 of 1st Embodiment. The figure which expanded the part of the arrow P in FIG. The flowchart which shows the charge control by the charging device 1 of 2nd Embodiment. The figure which shows the function with the asymptotic characteristic which approaches a fixed value. The figure which shows the asymptotic characteristic of the function shown to (a) in FIG. The figure which shows the asymptotic characteristic of the function shown to (a) in FIG. The table | surface which shows determination of the charge completion state when incrementing a check voltage value. The figure which shows the asymptotic characteristic of the function shown to (c) in FIG. The table | surface which shows determination of the charge completion state when incrementing a check voltage value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging apparatus 2 Power supply part 3 Operation part 4 Operation control part 5 Voltage / current control part 6 Voltage supply part 7 Display part 8 Current detection part 9 Voltage detection part 10 Secondary battery

Claims (3)

A charging voltage supply means for supplying a charging voltage to the secondary battery; a current detection means for detecting a current value of a charging current passed through the secondary battery; and a charge control device for controlling the charging of the secondary battery. In the secondary battery charger,
The charge control device includes:
A minimum check voltage value lower than the rated full charge equilibrium voltage value of the secondary battery, a predetermined charge application voltage value exceeding the full charge equilibrium voltage value but not reaching the irreversible chemical reaction region, and a voltage having a predetermined step size Storage means for storing values;
Increment means for setting a new check voltage value by adding the voltage value of the predetermined step size to the previous check voltage value;
Switching means for switching the charging voltage supplied from the charging voltage supply means to the predetermined charging application voltage value or the check voltage value;
First determination means for determining whether or not a current value detected by the current detection means has become equal to or less than a predetermined reference criterion value;
The required time from the previous positive determination to the current positive determination by the first determination means is r (r is a real number of 1 or more) times the required time from the previous positive determination to the previous positive determination. Second determination means for determining whether or not
Comprising
A charging device for a secondary battery that controls charging of the secondary battery according to the following first to eighth steps.
(First Step) A secondary battery is applied for a minute time at the minimum check voltage value, and a current value flowing through the secondary battery is detected by the current detection means during the minute time.
(Second step) The detected current value is determined by the first determining means, and if the current value exceeds the determination reference value, the process proceeds to the next third step. If the value is equal to or less than the determination reference value, the process jumps to the fourth step.
(Third Step) After switching the charging voltage to the predetermined charging application voltage value by the switching means and applying a secondary battery at the predetermined charging application voltage value for a predetermined time, the charging voltage is reduced to the minimum by the switching means. Switch to the check voltage value and return to the first step.
(Fourth Step) A new check voltage value is set by adding the voltage value of the predetermined step size to the previous check voltage value by the increment means.
(Fifth step) The switching means switches the charging voltage to the predetermined charging applied voltage value, and after the secondary battery is applied for a predetermined time at the predetermined charging applied voltage value, the charging voltage is changed by the switching means to the new The current value flowing through the secondary battery is detected by the current detection means while the secondary battery is applied for a very short time with the new check voltage value.
(Sixth step) The detected current value is determined by the first determining means, and if the current value exceeds the determination reference value, the process returns to the fifth step, while the current value is If it is below the criterion value, the process proceeds to the next seventh step.
(Seventh Step) The second determination means determines the required time from the previous positive determination by the first determination means to the current positive determination, and the previous positive determination by the first determination means. If the required time from the previous determination to the current positive determination is less than r times the required time from the previous positive determination to the previous positive determination, the process returns to the fourth step, while the first determination means If the required time from the previous affirmative determination to the current affirmative determination exceeds r times the required time from the previous affirmative determination to the previous affirmative determination, a charge stop signal is output.   When the charging stop signal is output in the seventh step, the switching means switches the charging voltage to the predetermined charging applied voltage value, and the secondary battery is set to the second predetermined charging voltage value by the predetermined charging applied voltage value. The charging device of the secondary battery according to claim 1, wherein the charging of the secondary battery is completed after the time application.   The secondary battery charging device according to claim 1, wherein the required time is measured by counting the number of times of switching to the check voltage value by the switching unit.

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