JP2015012685A - Power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure vehicle starting performance in a lead-free power storage system.SOLUTION: A secondary battery 10 is a battery for feeding power to the auxiliary machinery in a vehicle. For example, a nickel hydrogen battery is used. A capacitor 20 is connected in parallel to the secondary battery 10. In a management part 30, the capacitor is discharged when an ignition is turned off, and charging is performed from the secondary battery to the capacitor when the ignition is turned on. In the management part 30, when the ignition is turned off, the capacitor may be discharged up to the pre-set voltage capable of allowing deterioration without being completely discharged.

Description

  The present invention relates to an electricity storage system suitable for an idling stop and energy regeneration system.

  Currently, lead batteries are usually used for storage batteries used in idling stop systems and energy regeneration systems. In a lead battery, full charge maintenance is desired in order to suppress performance degradation. Since the lead battery is frequently charged and discharged in the above-described application, the performance deterioration of the lead battery is accelerated, and the battery life is shortened. Particularly in the idling stop system, a considerable amount of discharge is required when the engine is restarted from the idling stop state. Degradation of lead batteries accelerates as the depth of discharge (DOD) increases. In general, the recommended DOD range for lead batteries is 0-10%.

  On the other hand, it is conceivable to suppress the depth of discharge from increasing by increasing the capacity of the lead battery relative to the discharge capacity necessary for power supply. However, when the capacity of the lead battery is increased, the size and mass increase, and the cost also increases.

  Nickel metal hydride batteries and lithium ion batteries have a relatively small influence of discharge depth on battery deterioration, and can be used in a wide DOD range. Generally, the recommended DOD range for nickel metal hydride batteries and lithium ion batteries is 20 to 80%. Therefore, when a nickel metal hydride battery or a lithium ion battery is used instead of the lead battery, the power storage system can be reduced in size and weight.

JP 2011-162112 A

  By the way, when the vehicle engine is started, an instantaneous large current discharge is required. Nickel metal hydride batteries and lithium ion batteries generally increase reaction resistance at low temperatures. Therefore, in a nickel metal hydride battery and a lithium ion battery, if the discharge voltage is lowered, sufficient starting performance may not be obtained.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique for enhancing the starting performance of a vehicle.

  In order to solve the above problems, a power storage system according to an aspect of the present invention includes a secondary battery for supplying power to an auxiliary machine in a vehicle, a capacitor connected in parallel with the secondary battery, and a capacitor when the ignition is turned off. And a management unit that charges the capacitor from the secondary battery when the ignition is turned on.

  According to the present invention, the starting performance of the vehicle can be enhanced.

It is a figure for demonstrating the vehicle-mounted electrical storage system which concerns on embodiment of this invention. FIGS. 2A to 2B are diagrams showing experimental data obtained by examining deterioration characteristics of the electric double layer capacitor with respect to the neglected voltage. It is a figure which shows the structural example of the secondary battery of FIG. 1, a capacitor, and the management part. It is a flowchart for demonstrating the operation | movement at the time of vehicle starting of the vehicle-mounted electrical storage system which concerns on embodiment of this invention. It is a flowchart for demonstrating the operation | movement at the time of parking of the vehicle-mounted electrical storage system which concerns on embodiment of this invention. It is a figure for demonstrating the vehicle-mounted electrical storage system which concerns on a modification.

  Hereinafter, an in-vehicle power storage system according to an embodiment of the present invention will be described. In the following description, it is assumed that the in-vehicle power storage system is mounted on a vehicle having an idling stop function and an energy regeneration function.

  The idling stop function is a function that automatically stops the engine when the vehicle stops and restarts the engine automatically when the vehicle starts. The energy regeneration function is a function of operating an alternator without using fuel by kinetic energy of the vehicle when decelerating and supplying electric power to an in-vehicle power storage system or the like by the energy generated by the alternator. Both functions have the effect of improving fuel consumption.

  In vehicles equipped with an idling stop function, the number of engine starts increases. The engine is usually started by a starter driven by an in-vehicle power storage system. Therefore, as the number of engine starts increases, the power consumption of the battery increases and the number of discharges increases. Further, in a vehicle equipped with an energy regeneration function, power is generated by an alternator intensively when the vehicle is decelerated, and therefore an in-vehicle power storage system capable of efficient charging with a large capacity is required.

  Conventionally, lead batteries are often used in in-vehicle power storage systems. When the lead battery reaches the discharge lower limit voltage due to discharge, the alternator is operated to charge the lead battery. Thereby, it is suppressed that the discharge depth of a lead battery becomes deep, and the deterioration of a lead battery is suppressed. However, such control shortens the idling stop time and reduces the fuel efficiency improvement effect.

  From the viewpoint of protecting the global environment, lead-free power storage systems are being studied, and nickel-metal hydride batteries, lithium ion batteries, and the like are also being considered as alternatives to lead batteries in power storage systems for vehicles. As described above, nickel metal hydride batteries and lithium ion batteries can be used up to a deeper discharge depth than lead batteries, but there is a problem in that the discharge characteristics are drastically lowered at a low temperature of 0 ° C. or lower. In in-vehicle applications, sufficient engine starting performance at low temperatures cannot be secured.

  Therefore, it is conceivable to connect a capacitor with small temperature dependence and excellent instantaneous discharge in parallel with the nickel metal hydride battery and the lithium ion battery. Thereby, the instantaneous voltage drop at the time of large current discharge at low temperature can be suppressed.

  Capacitors have the property of becoming more deteriorated when left in a charged state. Therefore, it is required that the capacitor is left in a discharged state when parked without using the capacitor for a long time. On the other hand, at the time of start-up, it is required to be in a charged state capable of instantaneous discharge.

  FIG. 1 is a diagram for explaining an in-vehicle power storage system (in-vehicle power supply device) 100 according to an embodiment of the present invention. A vehicle on which the in-vehicle power storage system 100 is mounted includes an alternator 200, a starter 300, an electrical component 400, and an electronic control unit (ECU) 500 as members related to the in-vehicle power storage system 100. .

  Alternator 200 generates AC power from an engine (not shown), and further generates kinetic energy during deceleration in a vehicle having an energy regeneration function. In the present embodiment, power generation during deceleration will be mainly described. The alternating current generated by the alternator 200 is converted into direct current by a circuit such as a regulator and a rectifier (not shown), and the electric power of the alternator 200 is supplied to the electrical component 400 and the in-vehicle power storage system 100. In this embodiment, the output voltage from the alternator 200 is designed to be 14-15V.

  The starter 300 is an engine starting motor. The starter 300 is connected to the output system of the in-vehicle power storage system 100 via the starter switch S1. A relay or a semiconductor switch can be used for the starter switch S1. When an ignition switch (not shown) is turned on by the driver's operation, the starter switch S1 is turned on, power is supplied from the in-vehicle power storage system 100 to the starter 300, and the starter 300 is started. When the engine is started by the starter 300, the starter switch S1 is turned off. The time from turning on the starter switch S1 to turning it off is usually within about 1 second.

  The electrical component 400 is a generic name indicating various electric loads mounted in a vehicle such as a headlight, an air conditioner, a defogger, an audio, a meter, a stop lamp, a fog lamp, a winker, a power steering, a power window, and an engine electrical component. In the present specification, it is assumed that the electric component 400 does not include a high-power traveling motor that can be self-propelled. It is assumed that the electrical component 400 includes a relatively low-output travel assist motor that assists in engine travel. That is, it is assumed that the electric assisting device 400 includes a travel assist motor mounted on the mild hybrid vehicle.

  In this embodiment, for convenience of explanation, the alternator 200, the starter 300, and the electronic control unit 500 are handled separately from the electrical component 400. The electrical component 400 is driven by electric power supplied from the alternator 200 or the in-vehicle power storage system 100.

  The electronic control unit 500 is connected to various auxiliary devices, sensors, and switches mounted in the vehicle, and electronically controls the engine and various auxiliary devices. When executing the idling stop function, the electronic control unit 500 detects a stop of the vehicle or a deceleration to a set speed or less based on signals input from a brake, a vehicle speed sensor or the like. The electronic control unit 500 stops the engine when they are detected. Further, when the electronic control unit 500 detects the release of the brake, the electronic control unit 500 determines that the vehicle travel starts. When the start of vehicle travel is detected after the idling stop function is executed and the engine is stopped, the electronic control unit 500 restarts the engine. At that time, the starter switch S <b> 1 is turned on to control power to be supplied from the in-vehicle power storage system 100 to the starter 300, and the starter 300 is operated. In the above description, it is determined that the vehicle starts to travel when the brake is released, but the determination method is an example. For example, the vehicle travel start may be determined based on the state of the vehicle speed sensor or the accelerator.

  The electronic control unit 500 stops the alternator 200 in principle during normal running. Further, when executing the energy regeneration function, the electronic control unit 500 operates the alternator 200 when detecting deceleration of the vehicle based on signals input from a brake, a vehicle speed sensor, and the like. When the stored energy of the in-vehicle power storage system 100 is lower than the set lower limit value, the electronic control unit 500 operates the alternator 200 even during normal travel. The fuel consumption improves as the operation time of the alternator 200 during engine running is reduced.

  The in-vehicle power storage system 100 includes a secondary battery 10, a capacitor 20, a management unit 30, and a connection switching circuit 40. When power is supplied from the in-vehicle power storage system 100 to the starter 300, the secondary battery 10 and the capacitor 20 are connected in parallel. As the secondary battery 10, a battery that can be used up to a region with low deterioration and a deep discharge depth is used. Examples of the secondary battery 10 having a recommended DOD wider than that of the lead battery include a nickel metal hydride battery, a lithium ion battery, and a nickel / cadmium battery. In this embodiment, an example in which a nickel metal hydride battery whose voltage / temperature management is easier than that of a lithium ion battery is considered. Since the nickel hydride battery has a relatively high charge / discharge upper limit temperature, it can be installed in an engine room. Consider an example in which an electric double layer capacitor having a high power storage efficiency per volume is used as the capacitor 20. Electrolytic double layer capacitors cannot be used as a smoothing capacitor because they have a higher internal resistance than ordinary capacitors (smoothing capacitors) used to absorb ripple currents. The battery has a high storage efficiency and can be used in applications close to secondary batteries.

  When constructing a general 12V system as an in-vehicle power source, for example, a secondary battery 10 in which 10 nickel-hydrogen batteries having a nominal voltage of 1.2V are connected in series and an electric double layer capacitor having a rated voltage of 2.5V are provided. It can be constructed by connecting five or six capacitors 20 connected in series in parallel. Further, the secondary battery 10 and the capacitor 20 can further increase the storage capacity by connecting a nickel metal hydride battery and an electric double layer capacitor in parallel. In the present embodiment, the storage capacity of the secondary battery 10 is designed to be 20 Ah or more. For example, it can be realized by connecting four or more series circuits in which ten nickel hydride batteries having a nominal voltage of 1.2 V and a nominal capacity of 5.0 Ah are connected in series. Thereby, the dark current to the vehicle auxiliary machine when the vehicle is left can be secured.

  The management unit 30 manages and controls the secondary battery 10, the capacitor 20, and the connection switching circuit 40. Specifically, the monitoring data of the secondary battery 10 and the capacitor 20 are acquired, and the remaining capacity of the secondary battery 10 and the presence / absence of abnormality are monitored. As the remaining capacity, SOC (State of Charge) defined as the ratio of the remaining charge to the charge capacity is used. The SOC is an index representing a relative charge level, and is often used for control for preventing overcharge and overdischarge. In addition, the management unit 30 discharges the capacitor 20 when the ignition switch is turned off by the driver, and charges the capacitor 20 from the secondary battery 10 when the ignition switch is turned on. As described above, the capacitor has a characteristic of deteriorating when left in a charged state for a long time. When the vehicle is left for a long time, the deterioration is suppressed by discharging the capacitor 20.

  The management unit 30 and the electronic control unit 500 are connected by, for example, a CAN (Controller Area Network), and communicate with each other. The management unit 30 notifies the electronic control unit 500 of the state of the secondary battery 10 and the capacitor 20. For example, normal / abnormal and SOC are notified. Further, when the SOC of the secondary battery 10 or the voltage of the capacitor 20 falls below the set lower limit value, the management unit 30 notifies the electronic control unit 500 of an operation instruction for the alternator 200 in order to charge the in-vehicle power storage system 100. The management unit 30 receives vehicle information from the electronic control unit 500. For example, the operating status of the alternator 200 is received.

  The connection switching circuit 40 is provided between the charge / discharge terminal of the secondary battery 10 and the charge / discharge terminal of the capacitor 20 in the power supply line. The connection switching circuit 40 includes a current limiting resistor R1, a first path switch S2, and a second path switch S3. A relay or a semiconductor switch can be used for the first path switch S2 and the second path switch S3. The first path switch S <b> 2 is inserted between a power supply line connecting the charge / discharge terminal of the secondary battery 10 and the charge / discharge terminal of the capacitor 20. The current limiting resistor R1 and the second path switch S3 are connected in series, and the series circuit is connected in parallel to the first path switch S2. The first path switch S2 and the second path switch S3 are ON / OFF controlled by the management unit 30.

  The connection switching circuit 40 changes state between the parallel connection mode, the connection release mode, and the charge connection mode in accordance with a control signal from the management unit 30. The parallel connection mode is a mode in which the first path switch S2 is controlled to be on and the second path switch S3 is controlled to be off, and the secondary battery 10 and the capacitor 20 are connected in parallel without going through the current limiting resistor R1. The connection release mode is a mode in which the first path switch S2 and the second path switch S3 are controlled to be off, and the secondary battery 10 and the capacitor 20 are electrically disconnected. The charge connection mode is a mode in which the first path switch S2 is turned off and the second path switch S3 is turned on, and the secondary battery 10 and the capacitor 20 are connected via the current limiting resistor R1. The charge connection mode is selected when charging the capacitor 20 from the secondary battery 10 while limiting the current.

  When the secondary battery 10 and the capacitor 20 are left unattended due to the ignition off, the management unit 30 maintains the connection switching circuit 40 in the connection release mode. When the secondary battery 10 and the capacitor 20 are started to be used due to the ignition being turned on, the management unit 30 shifts the connection switching circuit 40 to the charge connection mode. The management unit 30 transitions the connection switching circuit 40 to the parallel connection mode after a set period has elapsed from the start of use (for example, after one second). Thereafter, the parallel connection mode is basically maintained until the ignition is turned off.

  When switching the connection switching circuit 40 from the parallel connection mode to the connection release mode by turning off the ignition, the management unit 30 does not completely discharge the capacitor 20 but discharges it to a preset voltage that can allow deterioration. As described above, the capacitor has a characteristic of deteriorating when left in a charged state for a long time. From this point of view, it is desirable to maintain the capacitor 20 in a completely discharged state when the vehicle is left. On the other hand, the capacitor 20 is charged from the secondary battery 10 when the vehicle is started. At this time, it is desirable that the potential difference between the secondary battery 10 and the capacitor 20 is small. The smaller the potential difference, the smaller the inrush current and the shorter the charging time. Thus, the neglected voltage of the capacitor 20 is in a trade-off relationship between suppression of deterioration of the capacitor 20 and ease of charging at start-up. The present inventor has found through experiments that it is preferable to maintain the neglected voltage of the capacitor 20 at 4 to 6 V in the 12 V system of the secondary battery 10 and the capacitor 20. Hereinafter, a detailed description will be given based on experimental data.

  FIGS. 2A to 2B show experimental data in which the deterioration characteristics of the electric double layer capacitor (EDLC) with respect to the neglected voltage are examined. This experimental data shows data obtained when an EDLC having a rated voltage of 2.5 V is left at a predetermined leaving voltage at an environmental temperature of 50 ° C. for 15000 hours. FIG. 2A is a table showing the relationship between the leaving voltage and the capacity initial ratio after being left. When the neglected voltage is 0.0 V, 0.5 V, and 1.0 V, the capacity initial ratio after leaving is within 98%, and it can be seen that the capacity is hardly decreased from the initial capacity and the deterioration is small. It can be seen that when the neglected voltage is 1.5 V, the initial capacity ratio after leaving is 85% and the deterioration is increased. It can be seen that when the neglected voltage is 2.0 V, the initial capacity ratio after leaving is 65%, and the deterioration is further increased. FIG. 2B is a line graph showing the data of FIG.

  From the above experimental data, it can be said that it is acceptable if the standing voltage of EDLC is up to about 1.0V. When the secondary battery 10 and the capacitor 20 are connected in parallel to construct a 12V power storage system, when the capacitor 20 is mounted in series of 5 EDLCs with a rated voltage of 2.5V, the allowable neglected voltage of the capacitor 20 Becomes 5.0V. In the case of mounting in 6 series, it becomes 6.0V.

  3 is a diagram illustrating a configuration example of the secondary battery 10, the capacitor 20, and the management unit 30 of FIG. The secondary battery 10 is formed by connecting ten nickel hydride battery (NiMH) cells B1 to B10 having a nominal voltage of 1.2 V in series. A shunt resistor Rs is connected in series to the NiMH cells B1 to B10. A temperature sensor 25 is provided in the vicinity of the NiMH cells B1 to B10.

  The capacitor 20 is formed by connecting six electric double layer capacitor (EDLC) cells C1 to C6 having a rated voltage of 2.5 V in series. A self-discharge circuit is connected in parallel to each of the EDLC cells C1 to C6. The self-discharge circuit is formed by connecting a discharge switch and a discharge resistor in series. Specifically, a series circuit of a discharge switch S21 and a discharge resistor R21 is connected in parallel with the EDLC cell C1. The other EDLC cells C2 to C6 are similarly configured.

  The management unit 30 includes a voltage / current detection unit 31, a voltage detection unit 32, a main control unit 33, a switch control unit 34, and a communication unit 35. The voltage / current detector 31 detects the voltage and current of the NiMH cells B1 to B10. FIG. 2 shows a configuration example for detecting the upper voltage, lower voltage, and intermediate voltage of the NiMH cells B1 to B10. In the case of a nickel metal hydride battery, there is no need to strictly equalize and control the cell voltage unlike a lithium ion battery, and therefore it is not always necessary to individually detect the cell voltages of the NiMH cells B1 to B10. The voltage / current detector 31 detects the voltage across the shunt resistor Rs and detects the value of the current flowing through the NiMH cells B1 to B10. The voltage / current detection unit 31 outputs the detected voltage value and current value of the NiMH cells B <b> 1 to B <b> 10 to the main control unit 33.

  The voltage detector 32 is connected to each node of the EDLC cells C1 to C6, and detects each voltage of the EDLC cells C1 to C6. The voltage detector 32 outputs the detected voltage values of the EDLC cells C1 to C6 to the main controller 33.

  The main control unit 33 receives the voltage values and current values of the NiMH cells B1 to B10 from the voltage / current detection unit 31, receives the voltage values of the EDLC cells C1 to C6 from the voltage detection unit 32, and receives the temperature values from the temperature sensor 25. The external signal is received from the communication unit 35. The main control unit 33 controls the NiMH cells B1 to B10, the EDLC cells C1 to C6, and the connection switching circuit 40 based on these data and external signals. Specifically, a switch switching signal is sent to the switch control unit 34 to control on / off of the discharge switches S21 to S26, the first path switch S2 of the connection switching circuit 40, and the second path switch S3. In addition, an instruction signal is sent to the electronic control unit 500 via the communication unit 35.

  When the main control unit 33 detects overdischarge, overcharge, overcurrent, or temperature abnormality based on the voltage value, current value, and temperature value of the NiMH cells B1 to B10, the main control unit 33 notifies the electronic control unit 500 via the communication unit 35. Notify that. The electronic control unit 500 restarts or stops the alternator 200 based on the notification. When a switch (not shown) is provided between the 12V power supply line and the NiMH cells B1 to B10, the main control unit 33 instructs the switch control unit 34 as necessary to turn off the switch. Further, the main control unit 33 instructs the electronic control unit 500 to operate the alternator 200 when the voltage across the NiMH cells B1 to B10 reaches the set lower limit voltage, and instructs the stop of the alternator 200 when the set upper limit voltage is reached.

  When the main control unit 33 detects a breakdown voltage over based on the voltage across the EDLC cells C1 to C6, the main control unit 33 notifies the electronic control unit 500 via the communication unit 35. The electronic control unit 500 stops the alternator 200 based on the notification. When a switch (not shown) is provided between the 12V power supply line and the EDLC cells C1 to C6, the main control unit 33 instructs the switch control unit 34 to turn off the switch. When the main control unit 33 detects an imbalance of the cell voltages of the EDLC cells C1 to C6, the main control unit 33 instructs the switch control unit 34 to turn on the discharge switch of the EDLC cell having a high voltage.

  When the ignition is turned off, the main control unit 33 instructs the switch control unit 34 to turn on the discharge switches S21 to S26. Thereafter, the main control unit 33 sequentially turns off the discharge switches of the EDLC cells whose cell voltage has reached the set leaving voltage. In the present embodiment, the set leaving voltage of the EDLC cell is set in the range of 0.8 to 1.2V. The following description is 1.0V.

  In the ignition-on state, the connection switching circuit 40 is normally controlled in the parallel connection mode. Therefore, normally, when the ignition switch is turned off, the first path switch S2 is on, and the capacitor 20 and the secondary battery 10 are at the same potential.

  In exceptional cases, the power storage system 100 may be operated in a state where the first path switch S2 and the second path switch S3 are turned off, that is, in a state where the capacitor 20 is not used. In this case, when the ignition switch is turned off, it may be less than the set neglect voltage (6 V in the present embodiment) of the capacitor 20 in some cases. In this case, the main control unit 33 turns on the second path switch S3 and charges the EDLC cells C1 to C6 until the cell voltage reaches the set neglect voltage (1.0 V in the present embodiment). Thereafter, the discharge switches of the EDLC cells whose cell voltage has reached the set neglected voltage are sequentially turned off. When all the EDLC cells have reached the set neglected voltage, the second path switch S3 is turned off.

  FIG. 4 is a flowchart for explaining the operation of vehicle-mounted power storage system 100 according to the embodiment of the present invention when the vehicle is started. When the ignition switch is turned on by the driver (Y in S10), the management unit 30 controls the first path switch S2 to be turned off and the second path switch S3 to be turned on (S11). As a result, the secondary battery 10 is precharged to the capacitor 20. When a set time (for example, 1 second) elapses from the start of precharge (Y in S12), the management unit 30 controls the first path switch S2 to be on and the second path switch S3 to be off (S13). The starter switch S1 is turned on in that state (S14).

  FIG. 5 is a flowchart for explaining the operation during parking of the in-vehicle power storage system 100 according to the embodiment of the present invention. When the ignition switch is turned off by the driver (Y in S20), the management unit 30 controls the first path switch S2 and the second path switch S3 to be turned off (S21). Thereby, the secondary battery 10 and the capacitor 20 are electrically disconnected. The management unit 30 turns on the discharge switches S21 to S26 (S22), and discharges the capacitor 20. When the voltage of the capacitor 20 reaches the set leaving voltage (6 V in the present embodiment) (Y in S23), the management unit 30 turns off the discharge switches S21 to S26 (S24).

  As described above, according to the present embodiment, the starting performance of the vehicle can be ensured without using a lead battery by connecting the capacitor 20 in parallel to the secondary battery 10 using a nickel metal hydride battery. Moreover, the capacitor 20 is discharged when the vehicle is left, and the capacitor 20 is precharged from the secondary battery 10 when the vehicle is started, so that the starting performance of the vehicle can be secured while suppressing the deterioration of the capacitor 20.

  In addition, when the capacitor 20 is left unattended, the electric charge remains within a range in which the deterioration can be allowed without being completely discharged. Thereby, the potential difference between the secondary battery 10 and the capacitor 20 at the time of starting can be reduced. Therefore, the precharge time can be shortened. In addition, since the precharge current can be greatly reduced as compared with the case of complete discharge, the specifications of the harness, instrument, etc. can be kept low, and a simple and low cost circuit configuration can be achieved. Further, the reduction of the precharge current is effective in preventing the welding of the relay.

  Further, by providing the connection switching circuit 40, it is possible to precharge the capacitor 20 from the secondary battery 10 while limiting the current. It can be prevented that a large current flows through the secondary battery 10 at the time of pre-charging, the potential difference between both ends of the secondary battery 10 disappears, and the charging current cannot be supplied.

  Moreover, since it is a lead-free power storage system, the environmental impact is small. In addition, the number of replacements can be reduced compared to lead batteries.

  The present invention has been described based on the embodiments. Those skilled in the art will understand that these embodiments are exemplifications, and that various modifications can be made to the combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. By the way.

  FIG. 6 is a diagram for explaining an in-vehicle power storage system 100 according to a modification. The power storage system 100 of FIG. 6 has a configuration in which the connection switching circuit 40 is removed from the power storage system 100 of FIG. Instead, a capacitor switch S4 for electrically disconnecting the capacitor 20 from the secondary battery 10 is provided. As described above, when the capacitor 20 is left as it is, charges remain in a range in which deterioration can be tolerated. Accordingly, the leaving voltage of the capacitor 20 is not 0V but 6V in the above example. Further, if the capacitor 20 is allowed to deteriorate, the voltage can be further increased. Therefore, the potential difference between the secondary battery 10 and the capacitor 20 at the time of starting can be reduced as compared with the case where the neglected voltage is 0V. As a result, it is possible to employ a circuit configuration in which the connection switching circuit 40 that is necessary for reducing the potential difference during precharging is omitted.

  In the above-described embodiment, the vehicle on which the alternator 200 and the starter 300 are mounted has been described. However, a motor generator may be mounted instead of the alternator 200 and the starter 300. In this case, the motor generator is used not only for restarting from the idling stop state but also for the initial start. When both the starter and the motor generator are mounted, the motor generator is used for restart from the idling stop state, and the starter is used for the initial start.

  Moreover, although the above-mentioned embodiment demonstrated the example which mounts an electrical storage system in the vehicle which has an idling stop and an energy regeneration system, it is not limited to mounting to the vehicle which has these functions.

  100 onboard power storage system, 200 alternator, 300 starter, 400 electrical component, 500 electronic control unit, 10 secondary battery, B1-B10 nickel-hydrogen battery cell, Rs shunt resistor, 20 capacitor, 25 temperature sensor, C1-C6 EDLC cell , S21 to S26 discharge switch, R21 to R26 discharge resistance, 30 management unit, 31 voltage current detection unit, 32 voltage detection unit, 33 main control unit, 34 switch control unit, 35 communication unit, 40 connection switching circuit, S1 starter switch , S2 first path switch, S3 second path switch, R1 current limiting resistor, S4 capacitor switch.

Claims (7)

A secondary battery for supplying power to an auxiliary machine in the vehicle;
A capacitor connected in parallel with the secondary battery;
A management unit for discharging the capacitor when the ignition is turned off, and charging the capacitor from the secondary battery when the ignition is turned on;
A power storage system comprising: A parallel connection mode for connecting the secondary battery and the capacitor in parallel; a charge connection mode for limiting a charging current from the secondary battery to the capacitor; and a connection for electrically disconnecting the secondary battery and the capacitor. A connection switching circuit having a release mode,
The management unit transitions the connection switching circuit to the connection release mode when the ignition is turned off, and transitions the connection switching circuit to the charge connection mode when the ignition is turned on. The power storage system according to claim 1, wherein the connection switching circuit is shifted to the parallel connection mode.   3. The power storage system according to claim 1, wherein when the ignition is turned off, the management unit does not completely discharge the capacitor but discharges the capacitor to a preset voltage that can allow deterioration. 4.   The power storage system according to any one of claims 1 to 3, wherein the management unit controls the voltage of the capacitor to be maintained at 4 to 6 V in an ignition-off state. The capacitor is composed of five or six electric double layer capacitors having a rated voltage of 2.5 V connected in series,
5. The power storage system according to claim 1, wherein the secondary battery is configured by connecting ten nickel hydride battery cells having a nominal voltage of 1.2 V in series.   The power storage system according to claim 5, wherein the secondary battery has a capacity of 20 Ah or more.   The power storage system according to any one of claims 1 to 6, wherein a motor for starting an engine is included in the auxiliary machine that supplies power from the secondary battery and the capacitor.

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