JP7416510B2 - charging system - Google Patents

Description

The present invention relates to a charging system.

In recent years, out of consideration for the global environment, engine-driven vehicles that are driven by an internal combustion engine have been replaced by electric vehicles that are driven by a motor, hybrid vehicles that are driven by an engine and a motor, or plug-in hybrid vehicles that can be charged using a charger. It's coming. In particular, as the performance of the electric vehicle or plug-in hybrid vehicle improves, the number of battery power sources, that is, the number of battery modules installed per electric vehicle tends to increase.

Japanese Patent Application Publication No. 2020-129863

In the motor system equipped with a battery power source and a motor mounted on a conventional electric vehicle, various efforts have been made to extend the cruising distance per charge of the electric vehicle. It does not match the cruising distance of a self-driving car on a single full tank of fuel.

The present invention has been made in view of this background, and an object of the present invention is to provide a technology that can efficiently control charging.

The main invention of the present invention for solving the above problems is a charging system that includes a charging circuit, a plurality of battery modules, and a balance circuit that balances and controls remaining capacity imbalance among the plurality of battery modules. A charging sequence in which charging is selectively and individually controlled in order of battery modules having a relatively large remaining capacity, and a balance sequence in which the balance control is performed are alternately switched.

Other problems disclosed in the present application and methods for solving the problems will be made clear by the section of the embodiments of the invention and the drawings.

According to the present invention, charging can be efficiently controlled.

FIG. 2 is a graph diagram of a charging voltage waveform and a charging current waveform showing a method of charging a lithium ion secondary battery cell according to the present embodiment. FIG. 2 is a circuit block diagram showing a charging system that connects three battery modules 2 in series and charges them according to the present embodiment. FIG. 2 is a circuit block diagram showing a charging system that connects three battery modules 2 in parallel and charges them according to the present embodiment. FIG. 1 is a circuit block diagram showing a charging system 100 according to the present embodiment. It is a circuit block diagram of charging system 100 (a) showing state a which is one state of charging system 100 concerning this embodiment. It is a circuit block diagram of charging system 100 (b) which shows state b which is one state of charging system 100 concerning this embodiment. It is a flowchart figure showing an outline of control of main controller 4 of charging system 100 concerning this embodiment.

As shown in FIG. 1, the lithium ion secondary battery cell is first charged with a predetermined constant current (CC charging), and the charging voltage increases as the remaining capacity of the lithium ion secondary battery cell increases. After reaching a predetermined voltage value, charging is performed at a constant voltage while gradually reducing the charging current to maintain the predetermined voltage value (CV charging). There is generally a charging method called CCCV charging that determines the state as fully charged and stops charging. The CV value is proportional to the number of lithium ion secondary battery cells to be charged or the number of battery modules having lithium ion secondary battery cells connected in series, and it is necessary to increase the CC value in order to shorten the charging time. The output voltage rating of the charging circuit related to the CV value and the output current rating of the charging circuit related to the CC value directly affect the increase in cost.

For charging an electric vehicle equipped with a plurality of battery modules each including a plurality of lithium ion secondary battery cells, for example, as shown in FIG. 2, three battery modules 2 each having a lithium ion secondary battery cell group 1 There is a method in which three battery modules 2 are connected in series to form two groups of battery modules, and a charging circuit 3 is connected to the two groups of battery modules to charge the three battery modules 2 at once.

In the charging system 100, as shown in FIG. 4, three battery modules 2 each having a lithium ion secondary battery cell group 1 are connected to a charging circuit 3 via a switch 6. Here, all of the switches 6 are in the off state, but the main controller 4 sends an instruction signal 5 or an instruction signal 7 to turn on or off the switch 6 or charge the charging circuit 3 according to a flowchart described later. Manipulate current output or stop.

Although the switch 6 is schematically illustrated as a contact switch in FIG. 4, a semiconductor switch such as an FET may also be used.

Regarding the charging of an electric vehicle equipped with a plurality of battery modules made up of lithium ion secondary battery cells, for example, as shown in FIG. There is a method of connecting the battery modules 2 in parallel to form two groups of battery modules, connecting the charging circuit 3 to the two groups of battery modules, and charging the plurality of battery modules 2 at once.

As shown in FIG. 5, the charging system 100(a) according to the present embodiment charges one of the three battery modules 2 via the switch 6 which is turned on or off. Circuit 3 is connected. As a result, CCCV charging is executed by the charging circuit 3, and only one battery module 2 among the three battery modules 2 is selectively and individually charged.

As shown in FIG. 6, in the charging system 100(b) according to the present embodiment, three battery modules 2 each having a lithium ion secondary battery cell group 1 are connected in parallel via switches 6 that are all turned on. When there is an unbalance in remaining capacity among the three battery modules 2, current flows back and forth between the three battery modules, and the voltages are balanced autonomously. At this time, the charging circuit 3 does not output charging current and is in a stopped state.

Next, the control of the main controller 4 of the charging system 100 will be explained using the flowchart of FIG. 7.

The main controller 4 of the charging system 100 detects the remaining capacity of the three battery modules 2 in Step 1, and detects the remaining capacity of the three battery modules 2 among the three battery modules 2 in Step 2. Select battery module 2. The remaining capacity can be detected by the main controller 4 directly detecting the voltage appearing at the terminals of the battery module 2, or by communicating with a module controller in the battery module 2 (not shown) to detect the voltage of the lithium ion secondary battery cell group 1. Any method of acquiring value information may be used.

The main controller 4 of the charging system 100 moves to the charging sequence of Step 3, in which the battery module 2 with the relatively highest remaining capacity among the three battery modules 2 selected in Step 2 is charged. The charging sequence is performed in state a shown in FIG. 5, that is, in the configuration of charging system 100(a). Note that FIG. 5 shows a state in which the center one among the three battery modules 2 is selected. The charging method in the charging sequence is that the charging circuit 3 of the charging system 100 inputs an AC voltage, which is a commercial power source, converts it to a DC voltage and performs desired CCCV charging. Unlike the method of collectively charging three connected battery modules 2, CC charging and CV charging for selectively and individually charging one battery module 2, that is, the output voltage rating of the charging circuit 3 and Since the output current rating is adjusted to one battery module 2, the cost does not increase; that is, the cost can be significantly reduced compared to a charging system that charges the same number of battery modules.

In Step 4, the main controller 4 of the charging system 100 uses a communication signal (not shown) to determine whether the charging circuit 3 has detected an abnormal state during charging, for example, a group of lithium ion secondary battery cells in the battery module 2. 1 is in an overvoltage state or a high temperature state. If it is determined in Step 4 that there is no abnormality, the process proceeds to Step 5, in which it is detected whether or not the charging circuit 3 has completed charging the battery module 2. In Step 5, if the charging circuit 3 determines that the battery modules 2 have not been selectively and individually charged, the process returns to Step 3, while the charging circuit 3 determines that the battery modules 2 have been selectively and individually charged. When it is determined that the battery 2 is fully charged, the charging circuit 3 stops outputting the charging current, moves to Step 6, and executes a balance sequence. The balance sequence is performed in state b shown in FIG. 6, that is, in the configuration of charging system 100(b). The main controller 4 turns on all the switches 6 to connect the three battery modules 2 in parallel. At this time, current flows between the one battery module 2 that was fully charged in Step 5 and the remaining two battery modules 2 that are not fully charged, and the voltages are balanced and autonomously balanced. In other words, the remaining capacity of the remaining two battery modules 2 that were not fully charged approaches 100% due to the balance sequence.

The main controller 4 of the charging system 100 determines whether an abnormal state is detected during balance in Step 7, for example, whether the lithium ion secondary battery cell group 1 in the battery module 2 is in an overvoltage state or an overcurrent state. It detects whether or not the temperature is high. If it is determined in Step 7 that there is no abnormality, the process moves to Step 8 to determine whether or not balancing has been completed, that is, the remaining capacity difference, that is, the voltage difference between the three parallel-connected battery modules 2 is below a predetermined value. Detect whether or not. In Step 8, if it is determined that the balance is not completed, the process returns to Step 6, while if it is determined that the balance is completed, the process proceeds to Step 10, and in the charging sequence of Step 3, the process returns to Step 6. Detect whether or not. If it is determined that all of the three battery modules 2 have been fully charged, the control of the charging system 100 is terminated; on the other hand, if it is determined that all of the three battery modules 2 are not fully charged, the process returns to Step 1, The charging sequence of selecting and individually charging battery modules 2 with a relatively large remaining capacity in Steps 1 to 3 and the balance sequence of Step 6 are repeated until all three battery modules 2 are fully charged.

Since a lithium ion secondary battery generally used for driving a motor of an electric vehicle has a low internal resistance, the time required for the above-mentioned balancing is relatively extremely short compared to the normal charging time by CCCV charging. Therefore, even if the charging time for one battery module 2 is relatively long without increasing the output current rating of the charging circuit 3, battery modules 2 with relatively large remaining capacity can be selectively and individually charged in Steps 1 to 3. By combining the charging sequence that shortens the charging time by doing this, and the short-time balance sequence of the three battery modules 2 in Step 6, it is possible to reduce the cost of the charging circuit and shorten the total charging time of the three battery modules 2. It is possible to achieve both.

On the other hand, if it is determined in Step 4 that the abnormal state is present, the process proceeds to Step 9 and the entire sequence, that is, the charging sequence and the balance sequence, is interrupted. At this time, the charging system 100 has the configuration of the charging system 100 in which all the switches 6 shown in FIG. respond and ensure safety.

Although the present embodiment has been described above, the above embodiment is for facilitating understanding of the present invention, and is not for construing the present invention in a limited manner. The present invention may be modified and improved without departing from the spirit thereof, and the present invention also includes equivalents thereof.

2 Battery module 4 Main controller 100 Charging system

Claims (2)

charging circuit;
multiple battery modules;
a balance circuit that balances and controls remaining capacity imbalance among the plurality of battery modules;
Equipped with
A charging system that alternately switches between a charging sequence in which charging is selectively and individually controlled in order of battery modules having a relatively large remaining capacity, and a balance sequence in which the balance control is performed. The charging system according to claim 1, wherein the charging sequence and the balancing sequence are interrupted when an abnormality in at least one battery module among the plurality of battery modules is detected.

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