Automatic equalization charging circuit and charging method for single string battery in lithium ion battery pack

Abstract

The present invention relates to an automatic equalizing charging circuit for a single string of batteries in a lithium-ion battery pack and a charging method thereof, and belongs to the field of lithium battery charging. The technical solution adopted by the present invention is that it includes a PLC controller, a human-computer interaction display screen and a charging circuit, and the human-computer interaction display screen is connected to the interactive interface of the PLC controller. The charging circuit includes a connecting plug connected to the AC mains, an AC circuit breaker, a battery type selection relay, a charging current selection relay, a charger and a charging relay, and the live wire of the AC circuit breaker, the battery type selection relay, the charging current selection relay and the charger are connected in series. The battery cell and the charging current can be selected by the human-computer interaction display screen, and different charging rates can be switched to achieve the purpose of automatic equalizing charging of a single string of battery cells. The charging efficiency of a single string of battery cells is improved quickly.

Description

Technical Field

[0001] The invention relates to an automatic equalization charging circuit for a single-string battery in a lithium-ion battery pack and a charging method thereof, belonging to the field of lithium battery charging. Background Art

[0002] With the rapid development of lithium-ion batteries, the application scope of lithium-ion battery packs is also expanding. Currently, the commonly used lithium-ion batteries are lithium iron phosphate and ternary lithium. However, due to the influence of lithium-ion production technology, the consistency problem of lithium-ion voltage and capacity cannot be fundamentally solved. As the use time of lithium-ion battery packs accumulates, the deviation of voltage and capacity between each string will become larger and larger, which will eventually lead to a reduction in the capacity of lithium-ion batteries and a shortened service life.

[0003] In order to solve the consistency problem of lithium-ion battery packs and extend the life of lithium-ion battery packs, it is necessary to charge the single-string battery packs separately and maintain the voltage and capacity so that the voltage and capacity of the single-string battery packs can be the same again.

[0004] The current conventional method is to use a single-string charger to charge a single string of batteries. After full, the batteries are manually replaced with the next string. This is inefficient and requires human supervision. Summary of the invention

[0005] The purpose of the patent of this invention is to provide an automatic balanced charging circuit for a single string of batteries in a lithium-ion battery pack and a charging method thereof, which can realize automatic balanced charging of a single string of batteries in a lithium-ion battery pack, improve the efficiency of single string charging, and improve the consistency of the lithium-ion battery pack.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is a single string battery automatic equalization charging circuit in a lithium ion battery pack, comprising a PLC controller, a human-machine interactive display screen and a charging circuit, wherein the human-machine interactive display screen is connected to an interactive interface of the PLC controller;

[0007] The charging circuit includes a connection plug connected to the AC mains, an AC circuit breaker, a battery type selection relay, a charging current selection relay, a charger and a charging relay. The live wire of the AC circuit breaker, the battery type selection relay, the charging current selection relay and the charger are connected in series. Two battery type selection relays are provided, corresponding to the lithium iron phosphate battery pack and the ternary lithium battery pack respectively. Each battery type selection relay is connected to two groups of charging current selection relays.

[0008] The positive pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the positive pole of a single string of batteries in the lithium battery pack to be charged. The negative pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the negative pole of the single string of batteries in the lithium battery pack to be charged. The control wiring of the battery type selection relay, the charging current selection relay and the charging relay is connected to the PLC controller.

[0009] Preferably, the human-machine interactive display screen has display, touch input and output functions, the touch input realizes the selection of battery type and charging current, and the charging of a single string of batteries is started through the human-machine interactive display screen.

[0010] Preferably, the charger is provided with a full charge signal feedback output interface, which is connected to the PLC controller. After the charger detects that a single battery is fully charged, it sends out a full charge signal through the full charge signal feedback output interface. The PLC controller receives the signal and sends a signal to stop charging the battery.

[0011] Preferably, the battery type of batteries of different materials is selected through the battery type selection relay, and the current is selected through the charging current selection relay, thereby starting the built-in different chargers for output to charge the single string of batteries. When the single string of batteries in the lithium battery pack to be charged is fully charged, the PLC controller switches the charging relay to the next single string of batteries for charging.

[0012] Preferably, the lithium-ion battery pack contains 16 single-string batteries connected in series, and the charging relays connected to the positive poles of the 16 single-string batteries are respectively charging relays K1, K2, K3, ... K16, and the negative pole of the last single-string battery is connected to the charging relay K17. There are four groups of chargers, namely 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger. The charging current selection relays correspond to four groups of chargers, namely charging current selection relay K20, charging current selection relay K21, charging current selection relay K22 and charging current selection relay K23, and the two battery type selection relays are battery type selection relay K18 and battery type selection relay K19.

[0013] Further preferably, the battery type selection relay K18 and the battery type selection relay K19 are connected in parallel to the live wire of the AC circuit breaker, the charging current selection relay K20 and the charging current selection relay K21 are connected in parallel to the battery type selection relay K18, the charging current selection relay K22 and the charging current selection relay K23 are connected in parallel to the battery type selection relay K19, the charging current selection relay K20 is connected to a 3.6V3A lithium iron phosphate charger, the charging current selection relay K21 is connected to a 3.6V5A lithium iron phosphate charger, the charging current selection relay K22 is connected to a 4.2V3A ternary lithium charger, and the charging current selection relay K23 is connected to a 4.2V5A ternary lithium charger.

[0014] Further preferably, the positive poles of the DC output ends of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are connected together, and then 16 positive charging lines are led out and connected in series with the charging relays K1, K2, K3,...K16 and the positive poles of 16 single-string batteries, and the negative poles of the DC output ends of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are connected together, and then 16 negative charging lines are led out and connected to the charging relays K2, K3, K4,...K17 and the negative poles of 16 single-string batteries, respectively.

[0015] Further preferably, the neutral line of the AC circuit breaker is connected to the AC input neutral line interface of the 4.2V5A ternary lithium charger, the AC output neutral line interface of the 4.2V5A ternary lithium charger is connected to the AC input neutral line interface of the 4.2V3A ternary lithium charger through a wire, the AC output neutral line interface of the 4.2V3A ternary lithium charger is connected to the AC input neutral line interface of the 3.6V5A lithium iron phosphate charger through a wire, and the AC output neutral line interface of the 3.6V5A lithium iron phosphate charger is connected to the AC input neutral line interface of the 3.6V3A lithium iron phosphate charger through a wire.

[0016] The method for charging according to the automatic equalization charging circuit of a single string of batteries in a lithium-ion battery pack comprises the following steps:

[0017] 1) Start the charging circuit through the human-computer interactive display screen, select the battery type to be charged as lithium iron phosphate battery or ternary lithium battery, select the charging current according to the battery type, and transmit the selected battery type and charging current control signal to the PLC controller;

[0018] 2) The PLC controller sends a closing signal to the battery type selection relay K18 or the battery type selection relay K19 according to the battery type and charging current selected on the human-computer interaction display screen, sends a closing signal to one of the charging current selection relays K20, K21, K22 and K23; and sends a closing signal to two adjacent charging relays among the charging relays K1, K2, K3, ..., K16, K17;

[0019] 3) The PLC controller controls the two charging relays connected to the positive and negative poles of a single string of batteries in the lithium-ion battery pack to close, and the charging line of the single string of batteries is connected for charging;

[0020] 4) The charger constantly detects the voltage of a single battery string during charging. When the required charging voltage is reached and the charging current is reduced to the full current of a single battery string, the charger sends a full charge signal to the PLC controller.

[0021] 5) The PLC controller controls the charging relays connected to the positive and negative poles of a single string of batteries to disconnect, and then closes the two charging relays connected to the positive and negative poles of another single string of batteries to charge the single string of batteries;

[0022] 6) Repeat steps 3, 4 and 5 to fully charge all single-string batteries in all ion battery packs. The PLC controller sends a disconnect signal to the battery type selection relay, the charging current selection relay and the two charging relays used for the last charging, and the charging is completed.

[0023] Preferably, after the last single string of batteries is fully charged, a delay of 5 seconds is performed to close the two charging relays connected to the positive and negative electrodes of the next single string of batteries.

[0024] The battery and charging current are selected through the human-machine interactive display screen, and the operation is started through the human-machine interactive display screen; a single-string automatic equalization charging execution circuit for 1-16 lithium-ion battery packs with different charging rates is designed, that is, the charging type is selected through the battery type selection relay, and the current is selected through the charging current selection relay, and then the built-in 4 different chargers are started to output to charge the single-string battery. When the single-string battery is fully charged, the charger will send a signal to the PLC, and the PLC will control the single-string charging relay to switch to the next string of batteries for charging until the end. The charging efficiency of a single-string battery is improved quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a connection relationship diagram between the PLC and the human-machine interactive display screen of the present invention,

[0026] Figure 2 The connection diagram of the single-pass battery and the charger of the present invention,

[0027] Figure 3 is a flowchart of the charging method of the present invention,

[0028] Figure 4 is a human-computer interaction display screen interface diagram of the present invention,

[0029] Reference numerals:

[0030] 1. Human-computer interaction display screen, 2. PLC controller, 3. AC circuit breaker, 4. 3.6V3A lithium iron phosphate charger, 5. 3.6V5A lithium iron phosphate charger, 6. 4.2V3A ternary lithium charger, 7. 4.2V5A ternary lithium charger 8. Connection plug. DETAILED DESCRIPTION

[0031] The specific contents of the invention are further described below:

[0032] The automatic equalization charging circuit of a single string of batteries in a lithium-ion battery pack of the present invention is as follows: Figure 1 As shown in the figure, it includes a PLC controller, a human-computer interaction display screen and a charging circuit. Figure 1 In the process, the human-machine interactive display screen is connected to the interactive interface of the PLC controller.

[0033] Charging circuit such as Figure 2 As shown, it includes a connection plug connected to the AC mains, an AC circuit breaker, a battery type selection relay, a charging current selection relay, a charger and a charging relay. The live wire of the AC circuit breaker, the battery type selection relay, the charging current selection relay and the charger are connected in series. The two battery type selection relays correspond to the lithium iron phosphate battery pack and the ternary lithium battery pack, respectively, and each battery type selection relay corresponds to two groups of charging current selection relays. The positive pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the positive pole of a single string of batteries in the lithium battery pack to be charged. The negative pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the negative pole of a single string of batteries in the lithium battery pack to be charged. The control wiring of the battery type selection relay, the charging current selection relay and the charging relay is connected to the PLC controller.

[0034] The mains power is connected to the equalizing charging circuit via a connection plug and a 220V AC circuit breaker.

[0035] The charger is provided with a full charge signal feedback output interface, which is connected to the PLC controller. After the charger detects that a single battery is fully charged, it sends out a full charge signal through the full charge signal feedback output interface. The PLC controller receives the signal and sends a signal to stop charging the battery.

[0036] The battery type selection relay is used to select the battery type of batteries of different materials, and the charging current selection relay is used to select the current, thereby starting the built-in different chargers to output and charge the single string of batteries. When the single string of batteries in the lithium battery pack to be charged is fully charged, the PLC controller switches the charging relay to the next single string of batteries for charging.

[0037] The human-machine interactive display screen has display, touch input and output functions. The display screen displays the battery type selection box and the current type selection box as the touch input interface. The human-machine interactive display screen is connected to the PLC controller via a data line to realize information exchange and control data transmission. Touch input realizes the selection of battery type and charging current, and starts charging of a single string of batteries through the human-machine interactive display screen. The human-machine interactive display screen is connected to the PLC controller via a data line to realize information exchange and control data transmission.

[0038] The charging circuit of a lithium-ion battery pack containing 16 single-string batteries connected in series is specifically described, such as Figure 2 As shown in

[0039] There are two groups of battery type selection relays, namely, battery type selection relay K18 and battery type selection relay K19. There are four groups of charging current selection relays, namely, charging current selection relay K20, charging current selection relay K21, charging current selection relay K22 and charging current selection relay K23. The charging relays are K1, K2, K3, ..., K16, K17.

[0040] Battery type selection relay K18 and battery type selection relay K19 are connected in parallel to the live wire of the AC circuit breaker, charging current selection relay K20 and charging current selection relay K21 are connected in parallel to battery type selection relay K18, charging current selection relay K22 and charging current selection relay K23 are connected in parallel to battery type selection relay K19, charging current selection relay K20 is connected to a 3.6V3A lithium iron phosphate charger, charging current selection relay K21 is connected to a 3.6V5A lithium iron phosphate charger, charging current selection relay K22 is connected to a 4.2V3A ternary lithium charger, and charging current selection relay K23 is connected to a 4.2V5A ternary lithium charger.

[0041] The positive pole wiring of the DC output end of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are intersected and connected, and then 16 positive charging lines are led out and respectively connected in series with the charging relays K1, K2, K3,...K16 and the positive poles of the 16 single-string batteries, and the negative pole wiring of the DC output end of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are intersected and connected, and then 16 negative charging lines are led out and respectively connected to the charging relays K2, K3, K4,...K17 and the negative poles of the 16 single-string batteries.

[0042] The neutral line of the AC circuit breaker is connected to the AC input neutral line interface of the 4.2V5A ternary lithium charger, the AC output neutral line interface of the 4.2V5A ternary lithium charger is connected to the AC input neutral line interface of the 4.2V3A ternary lithium charger through a wire, the AC output neutral line interface of the 4.2V3A ternary lithium charger is connected to the AC input neutral line interface of the 3.6V5A lithium iron phosphate charger through a wire, and the AC output neutral line interface of the 3.6V5A lithium iron phosphate charger is connected to the AC input neutral line interface of the 3.6V3A lithium iron phosphate charger through a wire.

[0043] The method of equalizing charging is explained. Figure 3 This is a flowchart of the single string automatic equalization charging process of the ion battery pack, including the following steps:

[0044] 1) Start the charging circuit through the human-computer interactive display screen, select the battery type to be charged as lithium iron phosphate battery or ternary lithium battery, select the charging current according to the battery type, 3A or 5A, and transmit the selected battery type and charging current control signal to the PLC controller;

[0045] 2) The PLC controller sends a closing signal to the battery type selection relay K18 or the battery type selection relay K19 according to the battery type and charging current selected on the human-computer interaction display screen, sends a closing signal to one of the charging current selection relays K20, K21, K22 and K23; and sends a closing signal to two adjacent charging relays among the charging relays K1, K2, K3, ..., K16, K17;

[0046] 3) The PLC controller controls the two charging relays connected to the positive and negative poles of a single string of batteries in the lithium-ion battery pack to close, and the charging line of the single string of batteries is connected for charging;

[0047] 4) The charger constantly detects the voltage of a single battery string during charging. When the required charging voltage is reached and the charging current is reduced to the full current of a single battery string, the charger sends a full charge signal to the PLC controller.

[0048] 5) The PLC controller controls the charging relays connected to the positive and negative poles of a single string of batteries to disconnect, and then closes the two charging relays connected to the positive and negative poles of another single string of batteries to charge the single string of batteries;

[0049] 6) Repeat steps 3, 4 and 5 to fully charge all single-string batteries in all ion battery packs. The PLC controller sends a disconnect signal to the battery type selection relay, the charging current selection relay and the two charging relays used for the last charging, and the charging is completed.

[0050] The battery and charging current are selected through the human-machine interactive display screen, and the operation is started through the human-machine interactive display screen; a single-string automatic equalization charging execution circuit for 1-16 lithium-ion battery packs with different charging rates is designed, that is, the charging type is selected through the battery type selection relay, and the current is selected through the charging current selection relay, and then the built-in 4 different chargers are started to output to charge the single-string battery. When the single-string battery is fully charged, the charger will send a signal to the PLC, and the PLC will control the single-string charging relay to switch to the next string of batteries for charging until the end. The charging efficiency of a single-string battery is improved quickly.

Claims

1. An automatic equalizing charging circuit for a single string of batteries in a lithium-ion battery pack, characterized in that: It includes a PLC controller, a human-machine interactive display screen and a charging circuit, and the human-machine interactive display screen is connected to an interactive interface of the PLC controller; The charging circuit includes a connection plug connected to the AC mains, an AC circuit breaker, a battery type selection relay, a charging current selection relay, a charger and a charging relay. The live wire of the AC circuit breaker, the battery type selection relay, the charging current selection relay and the charger are connected in series. Two battery type selection relays are provided, corresponding to the lithium iron phosphate battery pack and the ternary lithium battery pack respectively. Each battery type selection relay is connected to two groups of charging current selection relays. The positive pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the positive pole of a single string of batteries in the lithium battery pack to be charged. The negative pole of the DC output terminal of the charger is connected in series with the charging relay and then connected to the negative pole of a single string of batteries in the lithium battery pack to be charged. The control wiring of the battery type selection relay, the charging current selection relay and the charging relay is connected to the PLC controller; The charger is provided with a full charge signal feedback output interface, which is connected to the PLC controller. After the charger detects that a single battery is fully charged, it sends out a full charge signal through the full charge signal feedback output interface. The PLC controller receives the signal and sends a signal to stop charging the battery.

2. The automatic equalization charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 1, characterized in that: The human-machine interactive display screen has display, touch input and output functions. The touch input is used to select the battery type and charging current, and the charging of a single-string battery is started through the human-machine interactive display screen.

3. The automatic equalization charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 1, characterized in that: The battery type selection relay is used to select the battery type of different material cells, and the charging current selection relay is used to select the current, thereby starting the built-in different chargers to output and charge the single string of batteries. When the single string of batteries in the lithium battery pack to be charged is fully charged, the PLC controller switches the charging relay to the next single string of batteries for charging.

4. The automatic equalization charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 1, characterized in that: The lithium-ion battery pack contains 16 single-string batteries connected in series, and the charging relays connected to the positive poles of the 16 single-string batteries are respectively charging relays K1, K2, K3, ... K16, and the negative pole of the last single-string battery is connected to the charging relay K17. There are four groups of chargers, namely 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger. The charging current selection relays correspond to the four groups of chargers, namely charging current selection relay K20, charging current selection relay K21, charging current selection relay K22 and charging current selection relay K23, and the two battery type selection relays are battery type selection relay K18 and battery type selection relay K19.

5. The automatic equalizing charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 4, characterized in that: Battery type selection relay K18 and battery type selection relay K19 are connected in parallel to the live wire of the AC circuit breaker, charging current selection relay K20 and charging current selection relay K21 are connected in parallel to battery type selection relay K18, charging current selection relay K22 and charging current selection relay K23 are connected in parallel to battery type selection relay K19, charging current selection relay K20 is connected to a 3.6V3A lithium iron phosphate charger, charging current selection relay K21 is connected to a 3.6V5A lithium iron phosphate charger, charging current selection relay K22 is connected to a 4.2V3A ternary lithium charger, and charging current selection relay K23 is connected to a 4.2V5A ternary lithium charger.

6. The automatic equalizing charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 5, characterized in that: The positive pole wiring of the DC output end of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are crossed and connected, and then 16 positive charging lines are led out and connected in series with the charging relays K1, K2, K3,...K16 and the positive poles of 16 single-string batteries respectively, and the negative pole wiring of the DC output end of the 3.6V3A lithium iron phosphate charger, 3.6V5A lithium iron phosphate charger, 4.2V3A ternary lithium charger and 4.2V5A ternary lithium charger are crossed and connected, and then 16 negative charging lines are led out and connected to the charging relays K2, K3, K4,...K17 and the negative poles of 16 single-string batteries respectively.

7. The automatic equalizing charging circuit for a single string of batteries in a lithium-ion battery pack according to claim 6, characterized in that: The neutral line of the AC circuit breaker is connected to the AC input neutral line interface of the 4.2V5A ternary lithium charger, the AC output neutral line interface of the 4.2V5A ternary lithium charger is connected to the AC input neutral line interface of the 4.2V3A ternary lithium charger through a wire, the AC output neutral line interface of the 4.2V3A ternary lithium charger is connected to the AC input neutral line interface of the 3.6V5A lithium iron phosphate charger through a wire, and the AC output neutral line interface of the 3.6V5A lithium iron phosphate charger is connected to the AC input neutral line interface of the 3.6V3A lithium iron phosphate charger through a wire.

8. A method for charging a single string of batteries in a lithium-ion battery pack according to claim 7, characterized in that: The following steps are included: 1) Start the charging circuit through the human-computer interactive display screen, select the battery type to be charged as lithium iron phosphate battery or ternary lithium battery, select the charging current according to the battery type, and transmit the selected battery type and charging current control signal to the PLC controller; 2) The PLC controller sends a closing signal to the battery type selection relay K18 or the battery type selection relay K19 according to the battery type and charging current selected on the human-machine interactive display screen, sends a closing signal to one of the charging current selection relays K20, K21, K22 and K23; and sends a closing signal to two adjacent charging relays among the charging relays K1, K2, K3, ..., K16, K17; 3) The PLC controller controls the two charging relays connected to the positive and negative poles of a single string of batteries in the lithium-ion battery pack to close, and the charging line of the single string of batteries is connected for charging; 4) The charger constantly detects the voltage of a single battery string during charging. When the required charging voltage is reached and the charging current is reduced to the full current of a single battery string, the charger sends a full charge signal to the PLC controller. 5) The PLC controller controls the charging relay connected to the positive and negative poles of a single battery string to disconnect, and then connects the charging relay connected to the positive and negative poles of another single battery string. The two connected charging relays are closed to charge the single string of batteries; 6) Repeat steps 3), 4) and 5) to fully charge all single-string batteries in all ion battery packs. The PLC controller sends a disconnect signal to the battery type selection relay, the charging current selection relay and the two charging relays used for the last charging, and the charging is completed.

9. The charging method according to claim 8, characterized in that: After the last single string of batteries is fully charged, there is a delay of 5 seconds, and the two charging relays connected to the positive and negative poles of the next single string of batteries are closed.

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