MXPA97002291A - Ac apparatus - Google Patents

Abstract

The present invention relates to a charging apparatus for control in order to charge a plurality of secondary batteries which are connected in parallel, the charging apparatus comprising: a power source for supplying a charging current to the plurality of secondary batteries; a switching means for interrupting the charging current of one of the secondary batteries, in a certain period, a first comparison means for comparing a voltage difference of a first voltage of the power source, when the charging current is interrupted and a second secondary battery voltage with a first reference voltage, a second comparison means for comparing a negative terminal voltage of one of the secondary batteries with a second reference voltage, and a control means for controlling the charge of the secondary battery. agreement with each of the results of the comparison

Description

"LOADING EQUIPMENT" BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a charging apparatus for charging a secondary battery.

DESCRIPTION OF THE RELATED TECHNIQUE In a charging apparatus that is used to charge a secondary battery such as a lithium battery or the like, generally a constant current charge and a constant voltage load are executed. The charging apparatus using this charging method has a construction, for example, as shown in Figure 10. Figure 11 shows a relationship (output characteristics of the charging apparatus) between a charging voltage V and a charging current I. Figure 12 shows the ratios (charging characteristic curves) between the charging voltage V • charging current I and a charging time T. In a charging apparatus 100, a secondary battery 101 and a current sensing resistor 102 are connected in series with a power source 103. That is, a positive terminal of the secondary battery 101 is connected to a positive terminal of the power source 103. A negative terminal of the secondary battery 101 is connected to one end of the current sensing resistor 102 and the other end of the current sensing resistor 102 is connected to a negative terminal of the power source 103. The positive and negative input terminals of a comparator 104 are connected to both ends of the current sensing resistor 102 and an output terminal of the comparator 104 is connected to the power source 103. In this construction, since a load of a constant current Ibl is finished and a load of a constant voltage Vbl is initiated at the end of the charging of the secondary battery 101, the charging current I is reduced. When the comparator 104 detects that the load current I is equal to or smaller than the predetermined value, a generation of a load continuation signal SE to the power source 103 is stopped, thereby terminating the load. That is, the comparator 104 senses the voltage across the current sensing resistor 102, thereby detecting that the secondary battery 101 has been fully charged. As a above-mentioned current sensing resistor 102 of the charging apparatus 100, a resistance of a low resistance value is used, for example, (R = O.lO) due to a power consumption or similar ratio. However, since the load current I at the end of the charge of the secondary battery 101 is a low current, for example, I = 0.2A, a voltage that is detected by the comparator 104 is an extremely microscopic voltage, such as El = I * R = 20 mV. As a comparator 104 for detecting this microscopic voltage, a high precision comparator wherein the off-center voltage is extremely low has to be used so that there is an inconvenience that it is expensive. Even after the charging is completed, there is a case such that a battery capacity is reduced by a consumption in the battery, a consumption due in the impedance of the power source 103 when the apparatus is on the left in a state arrested, a consumption for example in a main body of the portable telephone or similar. In general, when charging continues even after the end of charging, the event of the battery capacity falling may also be prevented. However, there is a problem such that when a voltage is continuously applied to the secondary battery 100, the battery life is shortened.

Also, when a plurality, for example, of two secondary batteries are connected in parallel and charged by unloading the aforementioned charging apparatus 100, if during the charging of one of the secondary batteries to another secondary battery is connected, there is a problem of such that there is a case where the charge is terminated by wrong discrimination regardless of the fact that one of the secondary batteries is being charged.

OBJECTS AND COMPENDIUM OF THE INVENTION An object of the invention is to provide an inexpensive charging apparatus which prevents a drop in the capacity of the battery without deteriorating a secondary battery. Another object of the invention is to provide a charging apparatus that can prevent erroneous discrimination around the end of a charge, even when a plurality of secondary batteries are connected in parallel. According to one aspect of the invention, a charging apparatus is provided for controlling in order to charge a secondary battery connected by a constant current that is equal to or less than a constant voltage and to charge the secondary battery by a constant voltage that equals a or less than the constant current when a terminal voltage of the secondary battery is raised to the constant voltage comprising: a switching means for interrupting the charging current for a certain period; a comparison means for comparing a voltage difference formerly in first voltage on one side of the power source than the switching means when the charging current is interrupted, and a second voltage on the side of secondary battery with a first voltage reference; and a control means for stopping the load or presenting one end of the load in accordance with the result of the comparison. According to another aspect of the invention, a charging apparatus is provided for controlling the manner of charging a plurality of secondary batteries that are counted in parallel by a constant current that is equal to or less than the constant voltage and for charging the secondary batteries by a constant voltage that is equal to or less than the constant current, when a terminal voltage of each of the secondary batteries rises to the constant voltage, characterized in that it comprises: a switching means for interrupting the load current of one of the secondary batteries during a certain period; a first comparison means for comparing a voltage difference of a first voltage on one side of the power source that the switching means when the charging current is interrupted, and a second voltage on the side of the secondary battery with a first reference voltage; the second comparison means for comparing a negative terminal voltage of one of the secondary batteries with a second reference voltage; and a control means for controlling the load in accordance with each of the results of the comparison. In accordance with the aforementioned construction, since charging is continued or stopped by comparing the charging voltage of the secondary battery and a predetermined reference voltage, the construction can be simplified and a full state of charge can always be maintained. In accordance with the invention, the product costs can be reduced and the reliability of the load can be increased. Since the current sensing resistance required in the conventional apparatus is unnecessary, the number of parts can be reduced. The voltage drop that occurs when the current flows in the current sensing resistor is eliminated. Therefore, the charging time of the secondary battery can be shortened. According to the foregoing, another construction, a direction of the charge current of the secondary battery that has already been charged is detected, when the direction of the charging current is reversed, the charging stops and the apparatus waits , and when the direction of the load current is often reversed, the load is restarted so that discrimination around the end of the load can be prevented. In accordance with the invention, even when a plurality of secondary batteries are charged in parallel, an erroneous decision around the end of the load can be prevented so that the reliability of the load can be raised and a rapid deterioration of the secondary battery can be prevented. The aforementioned objects and features and others of the present invention will become apparent from the following detailed description and the appended claims, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a functional diagram for showing a first embodiment of a charging apparatus of the invention; Figure 2 is a flow chart for explaining an example of operation of the loading apparatus shown in Figure 1; Figure 3 is a first diagram showing the relationships (load characteristic curves) between the charging voltage • current and charging time in the charging apparatus shown in Figure 1; Figure 4 is an amplified diagram of a portion X shown in Figure 3; Figure 5 is a second diagram showing the relationships (load characteristics curves) between the charging voltage • current and charging time of the charging apparatus shown in Figure 1; Figure 6 is an amplified diagram of a portion X shown in Figure 5; Figure 7 is a functional diagram showing a second embodiment of a charging apparatus of the invention; Figure 8 is a flow chart to explain an example of the operation of the loading apparatus shown in Figure 7; Figure 9 is a diagram showing the relationships (load characteristic curves) between the charging voltage current and a charging time of the charging apparatus shown in Figure 7; Figure 10 is a functional diagram showing an example of a conventional loading apparatus; Figure 11 is a diagram showing the relationship (output characteristics of the charging apparatus) between a general output voltage and a charging current; and Figure 12 is a diagram showing the relationships (load characteristic curves) between the charging voltage • current and a charging time of the charging apparatus shown in Figure 7.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY A preferred embodiment of the invention will be described in detail below with reference to the accompanying drawings. Since the embodiment will be described below in a specific preferred example of the invention, several limitations are provided that are technically preferable. However, the scope of the invention is not limited to those embodiments as long as there is particularly no disclosure to limit the invention in the following description.

Figure 1 is a construction diagram showing a first embodiment of a charging apparatus of the invention. In a charging apparatus 10, a secondary battery 11 and a charging current interrupter switch 12 are connected in series with a power source 13. That is, a positive terminal of the secondary battery 11 is connected to a positive terminal of the power source 13. A negative terminal of the secondary battery 11 is connected to one end of the load current interrupter switch 12 and the other end of the load current interrupter switch 12 is connected to a negative terminal of the power source 13. In addition, the negative terminal of the secondary battery 11 is connected to a positive input terminal of a comparator 14. A terminal of a reference power source change switch 16 of the reference power sources 15a and 15b is connected to a negative input terminal of the comparator 14. An output terminal of the comparator 14 is connected in a load control unit 17. The load control unit 17, the load current interrupter switch 12, the reference power source change switch 16 and the presentation unit 18 are switched on.

In this construction, an example of the operation of the load will be described first with reference to a flow chart of Figure 2. First, an output voltage VO of the load source 13 is adjusted and graduated in order to be equal to full charge voltage VbO (refer to Figure 8) of the secondary battery 11, for example, of 8.4V in a state (no charge state) where the secondary battery 11 is not connected. An alternating current connector 19 is connected to an AC power source (AC 100V) and the secondary battery 11 is connected (step STP1). The load control unit 17 operates the reference power source change switch 16 in order to be switched, for example, to one side of the contact (a) of the reference power source 15a (step STP2). The load control unit 17 starts a fast charge and also starts a synchronizer (step STP3, 4) and fast charging ends when the synchronizer stops (step STP5, 6). That is, the load control unit 17 controls the on / off of the load current interrupter switch 12 for a predetermined period or an arbitrary period after starting the fast charge. For example, the load current interrupter switch 12 is switched on for only three minutes after the fast charge has been started, thereby supplying the charging current. After three minutes have elapsed, the load current interrupter switch 12 is turned off, thereby interrupting the charging current. The comparator 14 compares a voltage difference VA between the output voltage VO of the power source 13 at the time when there is no load being supplied to the positive input terminal when the charging current is interrupted and an open battery voltage VB with a reference voltage Ea of the reference power source 15a that is supplied to the negative input terminal, thereby detecting a voltage? V through the load current interrupting switch 12 and generating a detection SD signal to the load control unit 17. When the detection signal SD is at the high level, the load control unit 17 determines that the load is continued, allows the presentation unit 18 to be present "on load", return to step STP3 and repeat the aforementioned processes (step STP7). When the detection signal SD is at the low level, the load control unit 17 decides that the load has stopped and allows the presentation unit 18 to present "load stop" thereby stopping the load (step STP8) . The processes up to the aforementioned steps are related to the example of the loading operation. Figure 3 is a diagram showing the relationships (load characteristic curves) between the charging voltage V • the charging current I of the charging apparatus 10, the voltage difference VA and the charging time T. Figure 4 is an amplified diagram of a portion X of Figure 3. A ratio (output characteristic of the charging apparatus) between the charging voltage V and the charging current I is similar to that of Figure 11. period of interruption of the load current I (period in which the load voltage V decreases), the difference VA of voltage between the output voltage VO of the load source 13 at the time when there is no load and the voltage VB The open battery is supplied to the comparator 14 and compared to the reference voltage Ea of the reference power source 15a. The voltage? V through the load current interrupter switch 12 is detected in the detection signal SD is sent to the load control unit 17. When the detection signal SD is at a low level, that is, when the difference VA of the voltage is equal to or less than the reference voltage Ea, the load stops. The output of the detection signal SD of the comparator 14 is valid only if the period of interruption of the load current I is determined as an invalid detection for a period of time except that period. Therefore, the output of the detection signal SD in the period in which the load current I is not interrupted, is at a high level or a low level depending on a circuit graduation. In construction, as mentioned above, the voltage? V is adjusted, for example, to 80 mV. As a comparator 14 for detecting the voltage V of 80 mV, even if a voltage of about 5 mV is taken into account as a variation of an off-center voltage, it is not an unproblematic level so that a general IC can be used. Since the load control unit 17 does not detect a high exact analog voltage, a cheap IC of a ROM of l k or less, such as a logic circuit, a microcomputer, a chip or the like, can be used. An example of the operation of a recharge after stopping the charge will now be described with reference to the flow chart of Figure 2.

When the charge of the secondary battery 11 is stopped (step STP8), the load control unit 17 operates the reference power source change switch 16 thereby changing for example to the side of a contact (b) of the reference power source 15b (step STP9). A reference voltage Eb of reference source 15b of reference energy and reference voltage Ea of reference voltage 15a are set as Eb (for example, 120 mV) > Ea (for example, 80 mV). The load control unit 17 starts the synchronizer (step STP10). When the synchronizer is stopped (step STP11), the comparator 14 compares the voltage difference VA between the output voltage VO of the power source 13 at the time when there is no load being supplied to the positive input terminal and the voltage open battery with the reference voltage Eb of the reference power source 15b that is supplied to the negative input terminal, thereby detecting the voltage? V through the switch 12 load current switch in the same period as that in steps STP4 and STP5. The detection signal SD is transmitted to the load control unit 17. When the detection signal SD is at the high level, the load control unit 17 decides that the charging again takes place, allows the presentation unit 18 present "on re-charging" to return to step STP2 and repeat the processes mentioned above (step STP12). When the detection signal SD is at the low level, the load control unit 17 determines that the charge stop state continues, allows the presentation unit 18 to continuously present "charge stop", return to step STP10 and repeat the processes mentioned above. When it is established that the comparison process of the comparator 14 is continued even after the stopping of the load, the synchronizer process (step STP10, 11) of the load control unit 17 may be omitted. The above-mentioned steps are related to the example of the re-load operation. Figure 5 is a diagram showing the relationships (load characteristic curves) between the charging voltage • current and charging time of the charging apparatus 10. Figure 6 is an amplified diagram of a portion X in Figure 5. When the capacity of the battery decreases after stopping the load, the voltage difference VA rises compared to that at the time of stopping the load. Accordingly, after a predetermined time following the charging stop has elapsed, the voltage difference VA between the output voltage VO of the power source 13 at the time when there is no load and the open battery voltage VB is supports the comparator 14 for a predetermined period and is compared to the reference voltage Eb of the reference voltage 15b, thereby detecting the voltage? V through the load current interrupting switch 12. The detection signal SD is sent to the load control unit 17. When the detection signal SD is at a high level, namely, when the voltage difference VA is equal to or is higher than the reference voltage Eb, the recharging operation is initiated. As mentioned above, in the charging apparatus 10, since the general comparator can be used to detect the voltage and a general microcomputer can be used to control the charge, the costs of the apparatus itself can be reduced. Charging is continued until the voltage difference VA is graduated to the reference voltage Ea after starting the load. Further, . when the voltage difference VA is adjusted to the reference voltage Eb after the load is stopped, re-charging is started. Consequently, the duration of the secondary battery 11 is not deteriorated and a full state of charge can always be maintained. Even when the two reference energy sources are adjusted and both the arrest of load as the start of re-charging in the first embodiment mentioned above, only the in-charge / charging end can also be presented (if the charging current is continuously supplied). By adjusting a plurality of reference energy sources, for example, a load amount can also be detected by switching a display during charging. Figure 7 is a construction diagram showing a second embodiment of a charging apparatus of the invention. In the embodiment, as a charging apparatus which can charge a plurality of secondary batteries in parallel, a charging apparatus having a function for connecting a secondary battery and charging it and a function for connecting a similar equipment such as a portable telephone or the like having a secondary battery with an output terminal and being charged therein will be described. In a charging apparatus 20, a secondary battery 21A and a load current interrupting switch 22 are connected in series with a power source 23. In addition, a secondary battery 21B constructed in a device 40 such as a portable telephone or the like is connected in parallel with the secondary battery 21a through an output terminal. That is, the positive terminals of the secondary batteries 21A and 21B are connected to a positive terminal of a power source 23, a negative terminal of the secondary battery 21A is connected to one end of the load current interrupter switch 22. The other end of the load current interrupter switch 22, a negative terminal of the secondary battery 21B and a negative terminal of the power source 23 are connected to ground. A resistor 30 is connected in parallel with the load current interrupter switch 22. The negative terminal of the secondary battery 21A is connected in parallel with the positive input terminals of the comparators 24A and 24B. A terminal of a reference power source switching switch 26 of the reference power sources 25A and 25B is connected to a negative input terminal of the comparator 24A. An output terminal of the comparator 24A is connected to a load control unit 27. In addition, a negative terminal of the reference power source 25C is connected to a negative input terminal of the comparator 24B. A comparator output terminal 24B is connected to the load control unit 27. The load current interrupter switch 22, the reference power source change switch 26 and a display unit 28 are connected to the load control unit 27.

In case of charging two secondary batteries in parallel, their battery voltages are usually different. Therefore, the charging apparatus does not charge the secondary battery of a high battery voltage, but only charges the secondary battery of a low battery voltage. For example, when the secondary battery 21B not charged is connected to a synchronizer shown in Figure 9 while the secondary battery 21A is charged by a charging voltage VOA, the charging voltage is adjusted to VOB. Now, assuming that the load voltage VOB is lower than the load voltage VOA, the load of the secondary battery 21A is interrupted at half load and the current flows from the secondary battery 21A to the secondary battery 21B. In this situation, if the comparator 24A is constructed in order to detect a voltage? V through the load current interrupting switch 22, to walk from the fact that the secondary battery 21A is being charged, the comparator 24A detects the extreme of the charge of the secondary battery 21A and an erroneous decision indicative of the end of the charge is presented in the presentation unit 28. Therefore, the comparator 24B is constructed in order to compare the voltage at the negative terminal of the secondary battery 21A with an earth voltage and to detect a reverse current from the secondary battery 21A to the secondary battery 21B. In this construction, an example of the loading operation will now be described with reference to a flow chart of Figure 8. First, in a state (at the time when there is no charge) where the secondary batteries 21A and 21B do not connect, a The output voltage VO of the power source 23 is adjusted and set so as to become a full charge voltage VbO (refer to FIG. 11) of the secondary batteries 21A and 21B, for example, 8.4V. An alternating current connector 29 is connected to an alternating current power source (alternating current 100V) and the secondary battery 21A is connected (step STP21). The load control unit 27 operates the reference power source change switch 26, thereby changing, for example, to one side of the contact (a) of the reference power source 25a (step STP22). The load control unit 27 starts a fast charge and also starts a sincrionizer (step STP23, 24). The comparator 24B senses towards the voltage at the negative terminal of the secondary battery 21A is lower than a ground voltage or not and generates a detection signal SD to the load control unit 27. When the detection SB signal is at the low level, namely, when the voltage at the negative terminal of the secondary 21A battery is higher than the ground voltage. The load control unit 27 terminates the fast charge when the synchronizer is stopped (step STP25, 26, 27). Namely, the load control unit 27 controls the on / off of the load current interrupter switch 22 for a predetermined period or an arbitrary period after the fast charge is started. For example, the load control unit 27 connects the load current interrupter switch 22 which is only connected for three minutes after the rapid charge has been started, supplies a charging current and after three minutes has elapsed, disconnects the load current interrupting switch 22 interrupts the charging current. The comparator 24A compares a voltage difference VA between the output voltage VO of the power source 23 at the time when there is no load that is admitted to the positive input terminal when the charging current is interrupted and an open battery voltage VB with a reference voltage Ea of the reference power source 25a which is admitted to the negative input terminal detects the voltage? V through the load current interruption switch 22, and generates a detection signal SA to the unit 27 of load control. When the detection signal SA is at the high level, the load control unit 27 determines a continuation of the load and allows the presentation unit 28 present "on load" to return to step STP3 and repeat the aforementioned processes (step STP28 ). When the detection signal SA is at low level, the load control unit 27 determines the stopping of the load allows the display unit 28 to present "load stop" and stop charging (step STP29). When the charging of the secondary battery 21A is stopped (step STP29), the load control unit 27 operates the reference power source change switch 26, thereby changing, for example, one side of the contact (b ) of the reference power source 25b (step STP30). A reference voil Eb of the reference power source 25b and the reference voltage Ea of the reference power source 25a are set so that they will be Eb (for example 120 mV) >; Ea (for example, 80 mV). The comparator 24A compares the voltage difference VA between the output voltage VO of the power source 23 while there is no load that is admitted to the positive input terminal and the open battery voltage VB with the reference voltage Eb of the source 25b of reference power that is admitted to the negative input terminal, detects the voltage? V through the load current interrupter switch 22 during the same period as in the steps STP24, STP25 and STP26, which are referred to in FIG. which precedes and transmits the detection signal SA to the load control unit 27. When the detection signal SA is at a high level, the load control unit 27 determines "recharge" allows the presentation unit 28 present "to recharge" to return to step STP22 and repeat the aforementioned processes (STP31). When the secondary battery 21B is connected during the process in steps STP23 to STP28, the comparator 24B admits a voltage (voltage lower than the reference voltage Ec of the source 25c of reference power) in the negative terminal of the battery 21A secondary that is lower than the ground voltage by an impedance resistance r of the load current interrupter switch 22, so as to generate the detection signal SB at the high level towards the load control unit 27.

When the high level detection signal SB is received, the load control unit 27 determines that the current flows inversely from the secondary battery 21A to the secondary battery 21B and immediately terminates the fast charging (steps STP25,32). Namely, the load control unit 27 disconnects the load current interruption switch 22. In this way, the reverse current passes through the resistor 30 and flows inversely. When the fast charge is terminated in the step STP12, the load control unit 27 discriminates by the detection signal SB whether the reverse current through the resistor 30 continues or not (step STP33). When the detection signal SB graduates at the low level, a "V" non-detection synchronizer is started and the voltage detection? V through the load current interrupting switch 22 of the comparator 24A is temporarily stopped (step STP34 ). When the? V non-detection synchronizer is stopped, the load control unit 27 re-starts the voltage detection? V via the load current interrupter switch 22 of the comparator 24A, returns to step STP23 and repeats the aforementioned processes (step STP35).

As long as the high level detection signal SB is admitted from the comparator 24B to the load control unit 27, or when the non-detection? V synchronizer is running, the load current interruption switch 22 is disconnected. . However, by continuing to present the "in charge" of the presentation unit 28 during this period of time, an erroneous choice or charge decision can be prevented. Figure 9 is a diagram showing the relationships (charging characteristic curves) between the charging voltage V • charging current I, the voltage difference VA and the charging time T of each of the secondary batteries 21A and 21B in the loading apparatus 20. A ratio (output characteristics of the charging apparatus) between the charging voltage V and the charging current I is similar to that of Figure 11. As mentioned above, when the secondary battery 21B is switched on during battery charging 21A secondary, current flows inversely from secondary battery 21A to secondary battery 21B. However, the inverse current is graded to Ec / r = 0.2A when it is assumed that the impedance resistance r of the load current interrupter switch 22 is equal to 50 mO and the reference voltage Ec of the power source 25c of reference is equal to 10 mV. Therefore, comparator 24B can detect inverse current generation of 0.2A or more. When the reference voltage Ec of the reference power source 25c is further reduced, the generation of an additional small inverse current can be detected. In addition, the reverse current after the load current switching switch 22 has been switched off flows inversely at the resistance 30. However, assuming now that a resistance R of the resistance 30 equals 100O, the reverse current is graduates at Ec / R = 0. ImA and the switch is switched so that the reverse current from the secondary battery 21A can be detected by a microcurrent. As mentioned above, by disconnecting the load current interrupter switch 22, the reverse current can be reduced to a minimum. When the switch is switched to the charge of the secondary battery 21B, the charging voltage VOB rises. When the load voltage VOB reaches V0, a load current IbB (constant voltage load) decreases. On the other hand, since the charging voltage is reduced to V0, a charging current IbA in the secondary battery 21A begins to flow. The load current IbA rises to the value of the current that was interrupted by the connection of the secondary battery 21B and is started to decrease after that (load state in parallel). The charging current IbA is determined by the charging time of the secondary battery 21B for a period of time through which the switch is switched from the reverse current to the actual load and the current reaches the maximum of the current IbA. Thus, the non-detection synchronizer of? V is activated in such a way that even after the detection signal SB is at the high level of the comparator 24B is released, the state of charge stop is not canceled immediately. Although there is no problem, if the period of non-detection of? V coincides with the constant current charge time period of the secondary 21B battery, it can also be graduated by experiments and examination. In the aforementioned construction, the voltage? V is graduated, for example, to 80 mV. However, the comparator 24A for detecting the voltage V of 80 mV is particularly at an unproblematic level even when a voltage of about 5 mV is considered as a variation of an off-center voltage, so that a general IC can be used. Since the load control unit 27 does not detect a high exact analog voltage, for example, a cheap IC of a ROM of 1K or less, such as a logic circuit, a chip microcomputer or similar device, may be used. As mentioned above, since the charging apparatus 20 can use a general comparator to detect a voltage that a general microcomputer can use to control the charge, the apparatus itself can be done economically. Charging is continued until the voltage difference VA reaches the reference voltage Ea after the charge is started. In addition, after the charging stops, when the voltage difference VA reaches the reference voltage Eb, the re-charging starts. Therefore, the deterioration in the life of the secondary 21A battery does not occur and the full charge state can always be maintained. Even though the above embodiment has been described in relation to a parallel charging of two secondary batteries, even in the case of parallel charging a plurality of (three or more) secondary batteries, providing the aforementioned reverse current detecting means for each of the secondary batteries, a similar effect can be obtained. Having described specific preferred embodiments of the present invention with reference to the accompanying drawings, it should be understood that the invention is not limited to those precise embodiments and that various changes and modifications may be carried out therein by a person skilled in the art. technique without departing from the scope or spirit of the invention as defined in the appended claims.

Claims (14)

R E I V I N D I C A C I O N E S:

1. A charging apparatus for controlling in order to charge a secondary battery connected by a constant current that is equal to or less than a constant voltage and for charging the battery by a constant voltage that is equal to or less than the constant current, when a terminal voltage of the secondary battery rises up to the constant voltage, characterized in that it comprises: a switching means for interrupting a load current during a certain period; a comparison means for comparing a voltage difference between a first voltage on one side of the power source that the switching means when the charging current is interrupted, and a second voltage on the side of the secondary battery with a first voltage reference; and a control means for stopping the load or presetting one end of the load in accordance with the result of the comparison.

2. A charging apparatus according to claim 1, wherein the voltage difference is equal to or less than the first reference voltage, the load is stopped or the end of the charge is presented.

3. A charging apparatus for controlling in order to charge a connected secondary battery makes up the constant current which is equal to or less than a constant voltage and for charging the secondary battery by a constant voltage which is equal to or less than the constant current when a voltage of the The terminal of the secondary battery is raised up to the constant voltage, characterized in that it comprises: a switching means for interrupting a charging current during a certain period; a comparison means for comparing a voltage difference between a first voltage on one side of the power source and the switching means when the charging current is interrupted and a second voltage on the side of the secondary battery when the second voltage reference after a predetermined period of time has elapsed since stopping the load; and a control means for starting a recharge in accordance with the result of the comparison.

4. A charging apparatus according to claim 3, wherein the voltage difference is equal to or higher than the second reference voltage, recharging is initiated.

5. A charging apparatus for controlling in order to charge a plurality of secondary batteries that are connected in parallel by a constant current that is equal to or less than a constant voltage and to charge the secondary batteries by a constant voltage that is equal to or less that the constant current, when a terminal voltage of each of the secondary batteries rises to the constant voltage, characterized in that it comprises: a switching means for interrupting the charging current of one of the secondary batteries during a certain period; a first comparison means for comparing a voltage difference of a first voltage on one side of the power source of the switching means when the charging current is interrupted, and a second voltage on the side of the secondary battery with a first voltage of reference; a second comparison means for comparing a given negative voltage of one of the secondary batteries with a second reference voltage, and a control means for controlling the load in accordance with each of the results of the comparison.

6. A charging apparatus according to claim 5, wherein the charging of one of the secondary batteries is stopped when the negative terminal voltage of one of the secondary batteries is equal to or less than the second reference voltage. A charging apparatus according to claim 5, wherein an operation of the first comparison means is stopped for a predetermined period of time from a period of time when the negative terminal voltage of one of the secondary batteries is equal to or higher than the second reference voltage. 8. A charging method to control in order to charge a secondary battery connected by a constant current that is equal to or less than a constant voltage, and for charging the battery by a constant voltage that is equal to or less than the constant current when a terminal voltage of the secondary battery is raised to the constant voltage, characterized in that it comprises the steps of: interrupting a charging current during a certain period by a switching medium; comparing a voltage difference between a first voltage on one side of the power source that the switching means when the charging current is interrupted and a second voltage on the side of the secondary battery with the first reference voltage; and control in order to stop the load or present one end of the load in accordance with the result of the comparison. 9. A charging method according to claim 8, wherein the voltage difference is equal to or less than the first reference voltage, the load is stopped or the end of the load is presented. 10. A charging method for charging in order to charge a secondary battery connected by a constant current that is equal to or less than a constant voltage to charge the battery by a constant voltage that is equal to or less than the constant current, when a voltage The terminal of the secondary battery is raised to the constant voltage, characterized in that it comprises the steps of: interrupting a charging current for a certain period by the switching means; compare a voltage difference between a first voltage on one side of the power source that the switching medium when the charging current is interrupted and a second voltage on the secondary battery side with a second reference voltage after having elapsed a predetermined period of time from the time the load is stopped; and control in order to start a re-load in accordance with the result of the comparison. A charging method according to claim 10, wherein the voltage difference is equal to or higher than the second reference voltage, and re-charging is initiated. 12. A charging method for controlling in order to charge a plurality of secondary batteries that are connected in parallel by a constant current that is equal to or less than a constant voltage and to charge the secondary batteries by a constant voltage that is equal to or less that the constant current, when a terminal voltage of each of the secondary batteries rises up to the constant voltage, characterized in that it comprises: a switching step to interrupt the charging current of one of the secondary batteries during a certain period by a switching means; a first comparison step to compare a voltage difference of a first voltage on one side of the power source to the switching medium when the charging current is interrupted and a second voltage on the side of the secondary battery with a first voltage reference; a second comparison step for comparing a negative terminal voltage of one of the secondary batteries with a second reference voltage; and a step of controlling to control the load in accordance with each of the results of the comparison that are obtained in the first and second comparison steps. A charging method according to claim 12, wherein the charging of one of the secondary batteries is stopped when the negative terminal voltage of one of the secondary batteries is equal to or less than the second reference voltage. A charging method according to claim 12, wherein an operation in the first comparison step is stopped for a predetermined period of time from the time when the negative terminal voltage of one of the secondary batteries is equal to or greater than higher than the second reference voltage.