JP2003223934A - Charging method, storage battery system, and air conditioning system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of performing overcharging appropriately also for a secondary battery with a large internal resistance concerning multistage constant-current charging of the secondary battery. <P>SOLUTION: Opportunity to change to a 2nd-step charging from a 1st-step charging is found in comparison of storage battery voltage VB with detection voltage V<SB>1</SB>(S12, S13). And the opportunity to end the charging of the last stage is found in whether a charge-amount accumulation value ΣQ has reached k (>1) times of a rated capacity Z (S16) or not. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for charging a secondary battery such as a lead storage battery.

[0002]

2. Description of the Related Art Various charging methods for charging a secondary battery (storage battery) have been devised. State of charge of secondary battery (hereinafter "S
Even if “OC” (also referred to as “State Of Charge”) is increased, the battery is not charged with a constant current over the entire charging period so that an abnormal increase in the battery voltage is less likely to occur, and the charging is performed stepwise after the start of charging. It is desirable that the battery be charged using a charging current that is reduced to a minimum (such charging is referred to herein as "multi-stage constant current charging").

It is desirable that the charging current at the final stage, which is the charging at the highest SOC, does not exceed a predetermined charging current. The SOC at the final stage is 90, for example.
% (The rated capacity is 100%: for example, if the rating of the lead storage battery is 70 Ah, the discharge capacity is 63 Ah).

The charging current at the final stage varies depending on the type of secondary battery to be charged. For example, in the case of a lead storage battery, the charging current at the final stage is 0.025 to 0.05 CA.
(If the rated capacity of the lead storage battery is 70 Ah, 1.75 ~
It is set to about 3.5A). Further, when charging is performed with three-stage current, the charging currents of the first and second stages are 0.25 CA and 0.1 CA, respectively (17.5 A and 7 A if the rated capacity of the lead storage battery is 70 Ah, respectively). ) Is set to about.

In charge and discharge that is repeated on a daily basis,
By grasping the discharge amount P between charging and charging, an incomplete charging with a charging amount x · P (x is a predetermined coefficient of about 1) proportional to the discharging amount P and not making SOC 100% is adopted. (Referred to as “normal charging” in the present specification). As a result, the charging efficiency can be improved while ensuring a predetermined discharge amount to some extent. Further, when the secondary battery is a lead storage battery, it is possible to prevent a decrease in battery life due to corrosion of the positive electrode plate.

However, when only normal charging is adopted and charging / discharging is repeated, the discharge capacity gradually decreases. In order to recover this, overcharge is performed periodically, for example, once a week when charging / discharging is repeated once a day. In the overcharge, for example, the fixed amount of charge Q ₀ is charged subsequently to the final stage of the normal charge (referred to as “periodic overcharge” in the present specification).

Furthermore, when the discharge capacity is extremely decreased, for example, the SOC is decreased to about 0%, each time,
Overcharge (referred to herein as "overcharge each time"). In particular, when a lead storage battery is used as an auxiliary power source for an air conditioner, the load on the air conditioner varies greatly depending on the season, so that the SOC tends to decrease significantly. Therefore, it is important to overcharge the air conditioner each time.

FIG. 6 is a flow chart illustrating a method of overcharging each time multi-stage constant current charging is adopted. It is assumed that the discharge amount P before the charging to be performed from now on is previously obtained. In step S1, first-stage charging is performed. In the above example, charging is performed with a charging current of 0.25 CA. The first stage aims at charging until the SOC reaches 80%.

The state of SOC is generally the voltage V of the secondary battery.
_It can be roughly grasped by _B. FIG. 7 is a graph illustrating the relationship between the SOC percentage and the storage battery voltage V _B. The graph R ₀ shown by the solid line shows the relationship of a normal secondary battery. Here, the detection voltage V ₁ is SOC of 80 when a normal secondary battery is charged with the charging current of the first stage.
It is a value taken by the voltage V _B when it is%. Since such a relationship is known, if it is detected that the storage battery voltage V _B has reached a predetermined detection voltage V ₁ , S is detected in a normal secondary battery.
It turns out that the OC reached almost 80%. The detection of the end of the first-stage charging by the voltage V _B is excellent in that it is simple.

Returning to FIG. 6, in step S2 the storage battery voltage V
_It is determined whether _B is equal to or higher than the detection voltage V ₁ . If a negative determination is made, step S1 is repeatedly executed. By repeating steps S1 and S2, SO
Charging is performed with a relatively large charging current until C reaches almost 80%.

If a positive determination is made in step S2, the process proceeds to step S3, the charging current is reduced, and the second stage charging is performed. In the above example, 0.1 CA
Charging is performed with the charging current of. At the same time, a charge amount integrated value ΣQ obtained by integrating the charge amounts from the start of the second stage charging is obtained.

In each overcharge, the secondary battery is shifted from the SOC of almost 0% to the overcharge state. On the other hand, in the first-stage charging, the SOC should be almost 80%. Therefore, in the second stage and the third stage, charging is performed with a charging amount that is 20% of the rated capacity in total. Here is the second
It is assumed that the charge amounts Q ₁ and Q ₂ are adopted in the third stage and the third stage, respectively (where Q1 + Q2 = 0.2Z: Z is the rated capacity). The charge amounts Q ₁ and Q ₂ are set equal, for example.

In the second stage charging, it is determined in step S4 whether the charge amount integrated value ΣQ exceeds Q ₁ . If a negative determination is made in step S4, step S3
Return to. By repeating steps S3 and S4, charging is performed with a smaller charging current than the first-stage charging.

If a positive determination is made in step S4, the process proceeds to step S5, the charging current is reduced, and the third stage charging is performed. In the above example, for example, 0.
Charging is performed with a charging current of 05 CA. Also at this time, the charge amount integrated value ΣQ is continuously obtained.

Then, the routine proceeds to step S6, where it is judged if the charge amount integrated value ΣQ becomes equal to or more than Q ₁ + Q ₂ . If a negative determination is made in step S6, step S
Return to 5. By repeating steps S5 and S6,
Charging is performed with a smaller charging current than the second-stage charging. When a positive determination is made in step S6, the overcharge ends each time.

[0016]

However, in each overcharge, the measurement of the storage battery voltage V _B and the charge amount Q ₁ ,
Only Q ₂ is managed, and the amount of charge actually charged is not directly related to the amount of discharge P. In overcharging each time, since the SOC is almost a% (a is almost zero), overcharging is performed. Therefore, considering that the discharge amount P should be substantially equal to the rated capacity Z, the charging amount is Z. (A / 1
00) -Z is expected to exceed. However, the termination of the first-stage charging triggered by the affirmative determination in step S2 does not necessarily mean that the SOC is charged to 80%.

The graph R ₁ shown by the broken line in FIG. 7 shows the relationship of the secondary battery whose internal resistance increased due to repeated charging and discharging. For example, in a lead-acid battery, if lead sulfate accumulated by discharging is not decomposed by charging,
Internal resistance rises.

As can be understood by comparing the graphs R ₀ and R ₁ , the higher the internal resistance, the lower the percentage of SOC when the storage battery voltage V _B takes a predetermined detection voltage V ₁ . Here, the graph R ₁ exemplifies a case where the storage battery voltage V _B reaches the detection voltage V ₁ even though the SOC reaches only 60%.

Therefore, when a secondary battery having a large internal resistance and having the relationship shown by the graph R ₁ is overcharged each time, the SOC becomes 60 when the charging step shifts from step S2 to step S3. Only% charged. Therefore, when a positive determination is made in step S6,
That is, even if overcharging is completed each time, the SOC of the secondary battery has reached up to almost 80%.

FIG. 8 is a graph showing the state of overcharge each time for two secondary batteries having different internal resistances. The horizontal axis represents time and the vertical axis represents the storage battery voltage V _B. A graph L ₀ shows a normal secondary battery, and a graph L ₁ shows a secondary battery having a large internal resistance. In both cases, the time when the first charging is started is 0.
In addition, it is assumed that the two types of secondary batteries are discharged with the same amount of discharge before the current charging. In addition, since the magnitude of the charging current is determined in the second-stage charging and the third-stage charging for charging the charge amounts Q ₁ and Q ₂ , respectively, for both graphs L ₀ and L ₁ , the period T It is being carried out at ₂₀ , T ₃₀ . Here, the case of Q ₁ = Q ₂ is illustrated, and since the charging current during the third-stage charging is smaller than the charging current during the second-stage charging, the period T ₃₀ is less than the period T ₂₀ . Has been taken longer.

In a normal secondary battery, as shown in the graph L ₀ , the storage battery voltage V _B reaches the detection voltage V ₁ at the time t ₀₁ when the period T ₀₁ has elapsed from the start of charging, and the first
Switch from tier charging to second tier charging. And time t ₀₁
At time t ₀₂ when the period T ₂₀ has passed from the second stage charging to the third stage charging. Furthermore, from time t ₀₂ , period T
_At time t _{03 when 30} has elapsed, the third-stage charging is completed, and thus the overcharging is terminated each time.

On the other hand, in the secondary battery having a large internal resistance, as shown in the graph L ₁ , the period T from the start of charging is increased.
_At time t _{11 when 11} (<T ₀₁ ) has elapsed, the storage battery voltage V
_B reaches the detection voltage V ₁ , and the first-stage charging is switched to the second-stage charging. The switched at time t ₁₂ to time T ₂₀ elapses from the time t _{1 1} from the second-stage charging to the third stage charging. A third stage charging at time t ₁₃ to time T ₃₀ elapses from the time t _12, and thus overcharge each ends.

The present invention has been made in view of the above circumstances, and in the multi-stage constant current charging of a secondary battery, the voltage of the secondary battery is used as a reference for shifting from the first-stage charging to the second-stage charging. Provided is a method for appropriately overcharging a secondary battery having a large internal resistance. Such a technique can be applied to a storage battery system including the secondary battery. Therefore, it is also applicable to an air conditioning system including the storage battery system.

[0024]

[Means for Solving the Problems] Claim 1 of the present invention
A charging method for charging a secondary battery (220), which is used by repeating charging and discharging alternately, by using a charging current that gradually decreases, (a) the secondary battery the voltage (V _B), as a trigger to lead to the detection voltage (V ₁₎ corresponding to a predetermined value of the ratio of the charged state to the rated capacity of the secondary battery (SOC) (S12), the charging current (I Step of reducing the size of _C ) (S13)
And (b) when the integrated value (ΣQ) of the charge amount reaches the charge amount obtained by the product of the rated capacity (Z) of the secondary battery and the first coefficient (k) larger than 1. , A step (S16) of terminating the final stage charging.

According to claim 2 of the present invention,
The charging method according to claim 1, wherein the step (a) is performed.
And (c), the integrated value (ΣQ) of the charge amount is the discharge amount (P) discharged before the charge and the second coefficient (y) smaller than 1. ), The magnitude of the charging current (I _C ) is reduced when the amount of charge (y · P) obtained by multiplying is increased (S1).
4, S15).

According to claim 3 of the present invention,
The charging method according to claim 1, wherein the step (a) is performed.
And step (b), which further includes (c) a step (S24, S26) of additionally charging a predetermined fixed charge amount (Q ₁ + Q ₂ ).

According to claim 4 of the present invention,
The charging method according to claim 3, wherein the fixed charge amount is divided and charged with charging currents having different magnitudes.

According to claim 5 of the present invention,
The charging method according to any one of claims 1 to 4, wherein the secondary battery is a lead storage battery.

According to claim 6 of the present invention,
A storage battery system (2) comprising the lead storage battery, wherein the charging method according to any one of claims 1 to 5 is adopted.
00).

According to claim 7 of the present invention,
An air conditioning system (100, 200, 300) comprising the storage battery system according to claim 6.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION A. Configuration to which the present invention is applicable. FIG. 1 is a block diagram showing a configuration of a storage battery unit 200 in which the charging method according to the present invention is adopted and an air conditioning system including the storage battery unit 200.

The air conditioning system is an outdoor unit 10
0, an indoor unit 300 is also provided. The outdoor unit 100 includes a compressor 103, and the indoor unit 300 performs an air conditioning operation on an interior (not shown) using a refrigerant (not shown) compressed here.

The storage battery unit 200 includes a storage battery 220 to be charged / discharged, a bidirectional converter 210 for executing charging / discharging for the storage battery 220, and a charging / discharging control unit 230 for controlling charging / discharging.

The outdoor unit 100 further includes an AC / DC converter 101 and an inverter 102. AC
The / DC converter 101 is, for example, a three-phase AC commercial power source 4
00, AC / DC conversion, and inverter 1
02 or the bidirectional converter 210, DC power is supplied. The inverter 102 is operated by using the DC power supplied from the bidirectional converter 210 and the DC power supplied from the AC / DC converter 101 together to drive the compressor 103.

The storage battery unit 200 receives DC power from the AC / DC converter 101 during a time period when the electricity charge is low, and charges the built-in storage battery 220 via the bidirectional converter 210. At this time, the inverter 10
2 is not driven. On the other hand, the AC / DC converter 10 is not charged during the time period when the inverter 102 is operating.
Storage battery unit 2 with DC power supplied by 1
00 supplies DC power to the inverter 102. Of course,
The storage battery unit 200 does not need to constantly supply the DC power to the inverter 102, and may supply the power during a part of the time period in which the inverter 102 is operated.

The storage battery 220 is configured as an assembled battery, for example, and is configured by connecting a plurality of unit cells 221 which are lead storage batteries in series. However, in the present invention, it is not essential that the storage battery 220 is an assembled battery, and the storage battery 220 may be composed of a single battery. Further, a secondary battery other than a lead storage battery may be adopted, but a lead storage battery is mentioned as a secondary battery suitable for multi-stage constant current charging.

FIG. 2 is a circuit diagram showing a configuration of a portion related to charging / discharging of the storage battery 220. Here, the inverter 102
However, the configuration of supplying DC power from the AC / DC converter 101 is omitted.

The bidirectional converter 210 includes a charging converter 211 for charging and a converter 212 for discharging.
And a charging / discharging changeover switch 213 that is switched between when the storage battery 220 is charged and when it is discharged. That is, at the time of charging, under the control of the charge / discharge control unit 230, the AC / DC converter 101 is controlled by the charging converter 211 via the charging / discharging changeover switch 213.
The storage battery 220 is charged with the electric power obtained from Further, at the time of discharging, under the control of the charge / discharge control unit 230, the storage battery 220 is discharged to the inverter 102 by the discharge converter 212 via the charge / discharge changeover switch 213.

The charge current and the voltage of the storage battery 220 are monitored by the charge / discharge control unit 230 as needed. The charge / discharge control unit 230 has a function of causing the bidirectional converter 210 to control a charge / discharge current to a constant current, a function of switching a charge / discharge current value, and a function of managing integration of charge / discharge amounts. The charge / discharge control unit 230 further has a timer function for measuring the elapsed time from a predetermined timing. These functions are shown in Fig. 2 as "constant current control function".
It is shown as "charge / discharge current switching function", "charge / discharge amount integrated management function", and "timer function".

B. First embodiment. FIG. 3 is a flowchart showing the charging method according to the first embodiment of the present invention. Here, only the process of gradually reducing the charging current I _C from the start of overcharging to the end of charging is described. The gradual reduction of the charging current is performed by the charging converter 211 based on the “constant current control function” and the “charging / discharging current switching function” of the charging / discharging control unit 230. Further, similarly to the conventional technique, the discharge amount P discharged before the charging and the charge amount integrated value ΣQ are obtained, and these are realized by the charge / discharge control unit 230 based on the “charge / discharge amount integrated management function”. To be done. However, in this embodiment, the charge amount integrated value ΣQ is calculated by starting charge of overcharge each time, that is, integrating the charge amount from the beginning of the first-stage charge.

When the charging is started, first, in step S11, the magnitude of the charging current I _C is set to the current value I ₁ for the first-stage charging. As in the conventional case, the current value I ₁
Is set to an amount of current corresponding to, for example, 0.25 CA. Next, in step S12, whether the voltage of the storage battery 220 (storage battery voltage) V _B has reached the detection voltage V ₁ corresponding to a predetermined value of the SOC of the storage battery 220, for example, 80%, that is, the voltage V _B is the detection voltage V ₁ It is determined whether or not the above. If a negative determination is made, the process returns to step S11, and if a positive determination is made, the process proceeds to step S13. When the once set charging current value is maintained until it is newly set, the process may return to step S12 when a negative determination is obtained in step S12.

In step S13, the charging current I _C is set to the current value I ₂ (<I ₁ ) for the second stage charging. For example, as in the conventional case, the current value I ₂ is set to the amount of current corresponding to 0.1 CA.

As described above, the voltage V_BIs the detection voltage V₁
Charging current I _CThe size of
Let Until then, step S12 (or step further)
S11) is repeatedly executed, and the first-stage charging continues
There is. Therefore, the charging current I can be easily determined._CLine switching
I can.

Next, in step S14, it is judged whether or not the integrated charge amount value ΣQ exceeds the charge amount y · P obtained by multiplying the discharge amount P discharged before the charge by a predetermined coefficient y. To be done. Here, y is a predetermined coefficient smaller than 1, and is set to 0.92, for example. Step S14
If a negative determination is made in step S13, the process returns to step S13, and if a positive determination is made, the process proceeds to step S15. When the once set charging current value is maintained until it is newly set, the process may return to step S14 when a negative determination is obtained in step S14.

In step S15, the charging current I _C is set to the current value I ₃ (<I ₂ ) for the third stage charging. For example, as in the conventional case, the current value I ₂ is 0.025 to 0.0
The current amount is set to a magnitude corresponding to 5 CA.

As described above, the integrated charge amount value ΣQ is
When the charge amount y · P is exceeded, the magnitude of the charge current I _C is reduced. Until then, step S14 (or further step S13) is repeatedly executed, and the second stage charging is continued.

Next, in step S16, it is determined whether or not the charge amount integrated value ΣQ reaches the charge amount k · Z. Here, Z is a known rated capacity in advance, for example, the storage battery 220
It is the minimum guaranteed capacity in the specifications of. The coefficient k takes a value larger than 1. If a negative determination is made in step S16, the process returns to step S15, and if a positive determination is made, charging ends. When the value of the charging current once set is maintained until it is newly set, the process may return to step S16 when a negative determination is obtained in step S16.

As described above, the charge amount integrated value ΣQ is
Overcharging is terminated each time the charged amount k · Z, which is larger than the rated capacity, is reached. Until then, step S16
(Or further step S15) is repeatedly executed,
The third-stage charging continues.

As described above, in each overcharge,
By obtaining the storage battery voltage V _B as a reference for shifting from the first-stage charging to the second-stage charging in which charging is performed with a large current, it is possible to easily obtain the trigger for the reduction of the charging current. Moreover, since the battery is charged with a charge amount k · Z larger than the rated capacity, the standard for shifting from the first-stage charging to the next-stage charging is erroneously determined due to an increase in the internal resistance of the secondary battery. However, it is possible to reliably perform overcharge with respect to the rated capacity.

In particular, by the processing of steps S14 and S15, the charge amount integrated value ΣQ becomes the discharge amount P discharged before charging.
And the charge amount y · P obtained by multiplying by a coefficient y smaller than 1.
As a result, the magnitude of the charging current I _C is reduced. Therefore, the SOC of the storage battery 220 can be charged not with an unnecessarily small current but with an appropriate amount of current according to the amount of discharge.

C. Second embodiment. The rated capacity Z is the minimum guaranteed capacity in the specifications of the storage battery 220. Therefore, even if the storage battery 220 is manufactured and distributed as having the rated capacity Z, the storage battery 220 may have a capacity larger than the rated capacity Z. In such a case, at least the charge amount k · Z is secured and charged by the first embodiment, but the SOC of the storage battery 220 may remain low. Therefore, even if overcharge is performed each time, the storage battery 220 may actually fall into an incompletely charged state.

FIG. 4 is a graph showing the state of the storage battery voltage V _B when overcharging is performed each time using the first embodiment. A graph L ₂ shows a state of a secondary battery having a rated capacity Z, and a graph L ₃ shows a state of a secondary battery having a capacity larger than the rated capacity Z. Both are first
The time when charging starts is set to 0. Further, it is assumed that the two types of secondary batteries are discharged with the same discharge amount P before the current charging.

In the secondary battery having the rated capacity Z, as shown in the graph L ₂ , at the time t ₂₁ when the period T ₂₁ has elapsed from the start of charging, the storage battery voltage V _B becomes the predetermined detection voltage V ₁ And the first-stage charging is switched to the second-stage charging. Then, the time t when the period T ₂₂ has elapsed from the time t _{21
At 22} , the second-stage charging is switched to the third-stage charging.
A third stage charging at time t ₂₃ to time T ₂₃ elapses from the time t _22, and thus overcharge each ends.

On the other hand, in a secondary battery having a capacity larger than the rated capacity Z, as shown in the graph L ₃ , the storage battery voltage at the time t _{31 when the} period T ₃₁ (> T ₂₁ ) has elapsed from the start of charging. When V _B reaches the predetermined detection voltage V ₁ , the first-stage charging is switched to the second-stage charging. SOC shown in FIG.
The relationship between the percentage of the storage battery voltage V _B and the percentage of the storage battery voltage V _B does not depend so much on the capacity of the secondary battery. Therefore, when the same charging current I ₁ is charged, the charging time of the secondary battery having a large capacity becomes longer.

The period T ₃₂ required for the second stage charging is shorter than the period T ₂₂ . This is because the charge amount integrated value ΣQ after the overcharge is started is the charge amount y in the determination of step S14.
This is because the amount of charge in the first-stage charging is larger as the capacity of the secondary battery is larger on the basis of whether P is exceeded.

For example, I₁= 17.5A, I₂= 7A
T₃₁/ T_{twenty one}= 5/4, T ₃₂/ T_{twenty two}= 0.5 /
3 (17.5 x 5 + 7 x 0.5 = 17.5 x 4 + 7 x 3).

Thereafter, in step S16, the charge amount product
Charged until the calculated value ΣQ reaches the charge amount k · Z. Second stage
The accumulated charge amount ΣQ charged by the end of charging is the secondary
Since it is y · P regardless of the capacity of the battery, the third stage charging
The charging time at does not depend on the capacity of the secondary battery. Yo
And a secondary battery with a capacity larger than the rated capacity Z is _{twenty three}
Period T equal to₃₃The third stage charging is performed at time t₃₃To
Then, the third-stage charging is completed, and accordingly, the overcharging is completed each time.

Storage battery voltage V _B after time t _{33 in} graph L ₃
As can be seen from the change of 1, the secondary battery having a capacity larger than the rated capacity Z is not overcharged. The present embodiment proposes a charging method that increases the possibility of overcharging a secondary battery having a capacity larger than the rated capacity Z and does not excessively charge the secondary battery having the rated capacity Z. To do.

FIG. 5 is a flow chart showing a charging method according to the second embodiment of the present invention. Here, only the process of gradually reducing the charging current I _C from the start of overcharging to the end of charging is described. Also in this embodiment, as in the first embodiment, the charge amount integrated value ΣQ
Will accumulate the amount of charge from the start of overcharge each time.

First-stage charging is performed in the same manner as in the first embodiment. That is, steps S11 and S12 are executed. After a positive determination is obtained in step S12, the process proceeds to step S21, the timer function of the charge / discharge control unit 230 is used to temporarily reset the timer and start counting.

In step S13, the charging current is reduced in the same manner as in the first embodiment. And step S24
Then, it is determined whether the timer has counted up.
Since the charging current is constant during the first-stage charging, by fixing the time until the count up, step S2
4 substantially fulfills the function of charging the fixed charge amount Q ₁ in the second stage charging, similarly to step S4 of FIG. In the present embodiment, in order to use the charge amount integrated value ΣQ in the determination of step S16, which will be described later, the charge amount is added from the start of overcharge each time, so step S24 is used instead of step S4. However,
If a function for accumulating the charge amount from the start of overcharging each time is separately provided, the judgment in step S4 is used, and the step S2 is used.
1 can be omitted.

Further, in step S22, the timer is once reset and counting is started. And step S1
In 5, the charging current is reduced in the same manner as in the first embodiment. Then, in step S26, it is determined whether the timer has counted up. Since the charging current is constant even during the second-stage charging, by fixing the time until the count-up, step S26 substantially fulfills the function of charging the fixed charge amount Q ₂ in the second-stage charging. become. As described above, if the function of integrating the charge amount from the start of overcharge each time is separately provided, the determination of step S6 can be used and step S22 can be omitted.

As described above, the processes of steps S11 to S26 in this embodiment are substantially the same as those shown in FIG.
This is equivalent to the processing of steps S1 to S6 shown in FIG. However, in the present embodiment, step S16 is further executed subsequent to step S26. The process of step S16 is the same as the process described in the first embodiment, and each time it is determined whether the charge amount integrated value ΣQ obtained by integrating the charge amount from the start of overcharge reaches the charge amount k · Z. It

If a negative determination is made in step S16, the process returns to step S15. The timer has already counted up and has not been reset since then. Therefore, when the once set charging current value is maintained until it is newly set, the process may return to step S26. Alternatively, the process may return to step S16.

By the processes of steps S13 to S26, the fixed charge amount (Q ₁ + Q ₂ ) is additionally charged after the first stage charge. Therefore, as compared with the first embodiment, the storage battery 220 having a capacity larger than the rated capacity is
The possibility of performing charging with a higher OC is increased. In the present embodiment, the charging amount that increases as compared with the first embodiment is the charging amount in the first-stage charging. Therefore, a large amount of charge is given to the storage battery 220 having a capacity larger than the rated capacity Z each time during overcharge, while an excessive amount of charge is given to the storage battery 220 having a capacity of the rated capacity Z at each time. Charging will not occur.

By the process of step S16, the storage battery 220 having a large internal resistance can be overcharged each time with a charge amount larger than the rated capacity, as in the first embodiment.

Although it is possible to charge the fixed charge amount (Q ₁ + Q ₂ ) with the same charge current at the same stage, the fixed charge amounts Q ₁ and Q ₂ are changed with different charge currents which are gradually reduced.
It is desirable to charge each battery separately. This is because, as described above, an abnormal increase in battery voltage is unlikely to occur.

By adopting the charging method shown in each of the above-described embodiments, the storage battery unit 200 (see FIG. 1) functions as a storage battery system that is appropriately overcharged. Further, the air conditioning system that employs the storage battery unit 220 (see FIG. 1) can efficiently operate using inexpensive electric power.

[0069]

According to the charging method according to the first aspect of the present invention, the reference voltage for shifting from the first-stage charging to the next-stage charging in which a large current is charged is set to the secondary battery voltage. By obtaining it, it is possible to easily obtain the trigger for the decrease of the charging current. Moreover, since the battery is charged with a larger amount of charge than the rated capacity, the standard for shifting from the first-stage charging to the second-stage charging is erroneously determined due to an increase in the internal resistance of the secondary battery. It is possible to reliably perform overcharge with respect to the rated capacity.

According to the charging method of the second aspect of the present invention, the SOC of the secondary battery can be charged with a current of an appropriate magnitude according to the amount of discharge, rather than an unnecessarily small current. .

According to the charging method of the third aspect of the present invention, it is possible to charge the secondary battery having a larger capacity than the rated capacity by further increasing the SOC. Since the amount of charge in step (a) increases as the capacity of the secondary battery increases, excessive overcharging of a secondary battery having a capacity of about the rated capacity will not occur.

According to the charging method of the fourth aspect of the present invention, the abnormal rise of the secondary battery voltage is unlikely to occur.

According to the charging method of the fifth aspect of the present invention, a secondary battery suitable for multi-stage constant current charging is adopted.

According to the sixth aspect of the present invention, the storage battery system reduces the possibility that the dischargeable amount will deteriorate.

According to the seventh aspect of the present invention, the air conditioning system can be efficiently operated using inexpensive electric power.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration to which the present invention is applicable.

FIG. 2 is a circuit diagram showing a configuration of a portion related to charge / discharge of a storage battery.

FIG. 3 is a flowchart showing a charging method according to the first embodiment of the present invention.

FIG. 4 is a graph illustrating a charging method according to the first embodiment of the present invention.

FIG. 5 is a flowchart showing a charging method according to the second embodiment of the present invention.

FIG. 6 is a graph illustrating a conventional charging method.

FIG. 7 is a graph showing the relationship between storage battery voltage and SOC.

FIG. 8 is a graph illustrating a conventional charging method.

[Explanation of symbols]

200 Storage battery unit 220 Storage battery y, k Predetermined coefficient P Discharge amount V _B Storage battery voltage V ₁ Detection voltage ΣQ Charge amount integrated value

Continued front page    F-term (reference) 5H030 AA01 AA03 AS11 BB01 BB21                       FF41 FF42 FF43

Claims (7)

[Claims] 1. A charging method for charging a secondary battery (220), which is repeatedly charged and discharged alternately by using a charging current that gradually decreases, comprising: (a) the secondary battery. the voltage (V _B), as a trigger to lead to the detection voltage (V ₁₎ corresponding to a predetermined value of the ratio of the charged state to the rated capacity of the secondary battery (SOC) (S12), the charging current (I _(C ) the step of reducing the size of (S13), (b) the integrated value (ΣQ) of the charge amount is the rated capacity (Z) of the secondary battery, and the first coefficient (k) is larger than 1. A charging method comprising a step (S16) of terminating the charging at the final stage when the amount of charge obtained by the product is reached. 2. The method is performed between the step (a) and the step (b), and (c) the integrated value (ΣQ) of the charge amount is the discharge amount (P) discharged before charging. Step (S14, S15) of decreasing the magnitude of the charging current (I _C ) when the amount of charge (y · P) obtained by multiplying the second coefficient (y) smaller than 1 is exceeded. The charging method according to claim 1, further comprising: 3. A step (c) which is executed between the step (a) and the step (b), and (c) additionally charges a predetermined fixed charge amount (Q ₁ + Q ₂ ) (S24, S26). The method further comprising:
The charging method described. 4. The charging method according to claim 3, wherein the fixed charging amount is divided and charged with charging currents having different magnitudes. 5. The charging method according to claim 1, wherein the secondary battery is a lead storage battery. 6. A storage battery system (200), which employs the charging method according to any one of claims 1 to 5 and includes the secondary battery. 7. An air conditioning system (100, 200, 300) comprising the storage battery system according to claim 6.