Full-automatic balanced discharging device for lithium ion battery

Abstract

The utility model relates to a full-automatic balanced discharging device for a lithium ion battery. The full-automatic balanced discharging device comprises an interface matcher, an interface protection circuit, a voltage sampling circuit, a main switch, a high-power load, a main controller, a multi-circuit state display lamp and a cooling fan group, the maintained battery pack is connected to the system through the interface matcher via the balance charging plug. And the main controller controls the voltage sampling circuit to compare the voltage of the maintained battery string with the safe voltage, and when the voltage is higher than the safe voltage, the main switch is switched on to discharge the battery string through the main discharge path until all the battery strings are discharged to the safe voltage. The beneficial effects of the utility model are that the single string of batteries in the lithium ion battery pack are discharged independently, thereby achieving the effect of overall balanced discharge and prolonging the service life of the batteries; the voltage of a single battery is automatically detected, and discharging is automatically stopped after the battery is discharged to a safe voltage; a high-power pure resistive load is used as a discharge element, and a fan is used for heat dissipation.

Description

Technical Field

[0001] This utility model patent belongs to lithium-ion battery pack maintenance equipment, which involves a fully automatic balanced discharge device for lithium-ion batteries. It can be used for offline maintenance of various multi-string power batteries, model aircraft batteries, and power supply batteries to extend the service life of lithium-ion battery packs. Background Art

[0002] Lithium-ion batteries are the mainstream type of batteries at present. They have the remarkable characteristics of high energy density, light weight, high discharge rate, and long service life. They are widely used in various occasions. In normal use, lithium-ion batteries should be avoided as much as possible from overcharging and over-discharging. Under normal circumstances, lithium-ion batteries can be used for a long time. However, when not in use for a long time, the voltage of a single string of batteries must be maintained at a safe voltage of about 3.85V. Any deviation from this voltage will seriously affect the service life of the battery.

[0003] In most cases, lithium-ion batteries are used in multiple strings in series. To discharge each string of batteries to a safe voltage, balanced discharge is required. The so-called balanced discharge means that in a series battery pack, each string of batteries must be discharged individually, rather than performing series discharge at the end of the battery string.

[0004] Balanced charging and discharging can greatly increase the overall service life of the battery pack. Because the electrical characteristics of each battery in each series of batteries in the battery pack cannot be exactly the same, during a long period of charging and discharging, the charging and discharging characteristics of a battery are prone to deterioration, affecting the power supply characteristics of the entire battery pack and making the entire battery pack unusable.

[0005] In order to store lithium batteries safely for a long time, the battery pack needs to be discharged to a safe voltage value. If the battery pack is discharged as a whole instead of balanced, on the one hand, the discharge termination voltage of a single battery in the battery string is difficult to control; on the other hand, the load power required for the overall discharge is large, otherwise the discharge time will be longer.

[0006] The fully automatic lithium-ion battery balancing discharge equipment can automatically detect the voltage of a single string of batteries, and balance discharge a single battery individually as needed. When the safe voltage is reached, the discharge will automatically stop and the status will be displayed using lights, so that all batteries in the multi-string battery are discharged to a safe voltage. Utility Model Content

[0007] The utility model provides a full-automatic balanced discharge device for lithium-ion batteries, which can balance discharge a single battery as required, thus avoiding many deficiencies caused by overall discharge.

[0008] The technical solution adopted by the utility model is:

[0009] A fully automatic balanced discharge device for lithium-ion batteries, comprising an interface matcher, an interface protection circuit, a main controller, a voltage sampling circuit, a high-power load and a multi-circuit status display lamp;

[0010] The fully automatic balanced discharge device utilizes the balanced charging lines between the lithium-ion battery packs connected in series to discharge, and the discharge channels are completely independent; the discharge of each lithium-ion battery is determined according to the voltage of the lithium-ion battery.

[0011] The voltage sampling circuit adopts an optical coupling method to electrically isolate the sampling of the front stage and the voltage access of the back stage, so that the lithium-ion batteries in series can sample each other completely independently. The voltage sampling circuit is connected to the lithium-ion battery pack through the interface matcher and the interface protection circuit;

[0012] The path of each lithium-ion battery is independently monitored and discharged, and the executive contacts of the high-power relay of the discharge path are a synchronous double-pole structure; the voltage at both ends of each lithium-ion battery is independently monitored, and the voltage sampling circuit is used for potential isolation; the single-path lead of each lithium-ion battery is connected to the balance charging line.

[0013] The sampled voltage of the lithium-ion battery through the voltage sampling circuit is sent to the main controller. In the multi-channel analog-to-digital conversion converter of the main controller, the sampled voltages of different channels are converted into analog-to-digital in a time-sharing manner. The single-chip microcomputer of the main controller completes the voltage sampling of all channels by controlling the selection signal of the converter, forms a digital sampled voltage signal, and sends it to the single-chip microcomputer of the main controller in a time-sharing manner to obtain the current voltage value of each lithium-ion battery. The voltage value will be compared with the safety voltage of 3.85V. When the voltage value is lower than the safety voltage, the red indicator light will be turned on to indicate that the voltage of the line is low and does not need to be discharged, but the battery pack needs to be charged. If the voltage value is higher than the safety voltage, the relay closure signal of the signal is sent out, and after passing through the corresponding relay drive circuit, the high-power relay is energized, and the battery string of the line starts to discharge. At the same time, the voltage of the line is continuously monitored. After a period of discharge, when the voltage value is equal to the safety voltage, a relay shutdown signal is sent, the high-power relay is disconnected, and the discharge ends.

[0014] The high-power load is an independent high-power air-cooled resistor, wherein the resistance value and the power value are determined according to the battery usage.

[0015] The multi-channel battery status display light is a red and green dual-color LED. When the voltage of the lithium-ion battery is lower than the safe voltage, the red indicator light is lit; during the discharge process, the green indicator light flashes; after the discharge is completed, the green indicator light is always on; and the indicator lights correspond to the corresponding lithium-ion batteries one by one.

[0016] The single lead of each lithium-ion battery is connected to the balanced charging line. The details are as follows: first, the two wires pass through an input protection circuit, which is composed of an anti-reverse connection circuit and an anti-overvoltage circuit; then the connected voltage signal is sent to the optocoupler circuit to isolate the primary and secondary potentials, and use the linear range of the optocoupler to obtain a voltage that changes linearly with the optocoupler light-emitting level voltage at the receiving level of the optocoupler; finally, the voltage is used in the sampling voltage formation circuit to obtain the battery string sampling voltage.

[0017] A high-air-volume cooling fan group consisting of a temperature acquisition probe, a fan driver and a cooling fan is set in the chassis. The temperature acquisition probe obtains the temperature inside the chassis, and the microcontroller controls the fan speed through the fan driver according to the temperature to control the temperature inside the chassis within an appropriate range.

[0018] The beneficial effects of the utility model are:

[0019] Discharge the single string of batteries in the lithium-ion battery pack separately to achieve the effect of overall balanced discharge and extend the battery life; automatically detect the voltage of a single battery, and stop discharging automatically after discharging to a safe voltage; use a high-power pure resistive load as a discharge element, and use a fan for heat dissipation; use optical couplers for inter-stage isolation sampling, and adjacent battery packs are completely independent and do not affect each other; use simple indicator lights to display the status of a single battery, which is stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the utility model;

[0021] Figure 2 This is a block diagram of the voltage sampling circuit of the utility model;

[0022] Figure 3 It is a schematic diagram of the main discharge path of the utility model;

[0023] Figure 4 This is a schematic diagram of the main controller of the utility model. DETAILED DESCRIPTION

[0024] The utility model is used for daily maintenance of lithium-ion battery packs. When discharge is required, after connecting to the discharge device, the lithium-ion battery pack will be automatically balanced and discharged as required, and each lithium-ion battery in the battery pack will be discharged to a safe storage voltage.

[0025] like Figure 1As shown, the utility model device includes interface matching, interface protection circuit, voltage sampling circuit, main switch, high-power load, main controller, multi-circuit status display lamp and cooling fan group. The maintained battery group is connected to the system through the balanced charging plug through the interface matching device. The main controller controls the voltage sampling circuit to compare the voltage of the maintained battery string with the safety voltage. When the voltage is higher than the safety voltage, the main switch is turned on to discharge the lithium-ion battery through the main discharge path until all lithium-ion batteries are discharged to the safety voltage.

[0026] like Figure 3 As shown, in order to achieve independent monitoring and discharge of each channel, the discharge channel needs to be isolated, and the main discharge channel is connected to the corresponding discharge channel. Taking 4 groups of lithium-ion batteries as an example, the lithium-ion batteries B1, B2, B3, and B4 in the battery pack are connected in series, and the 5 taps of the balance charging line are connected to the corresponding discharge channels according to the circuit diagram. K1-K4 are the execution contacts of the main channel high-power relay, which is a synchronous double-pole structure. If the lithium-ion battery B1 needs to be discharged, the two contacts of K1 are energized, and B1 is connected to the load R1 alone, and discharged alone, which will not affect other battery strings, nor will it be affected by other lithium-ion batteries.

[0027] In order to independently monitor the voltage across a single lithium-ion battery, the voltage sampling circuit must also be isolated. Figure 2 As shown in the figure, this figure shows one of the voltage sampling circuits. If the battery pack has N circuits, there will be N identical voltage sampling circuits in the circuit. The single lead of the lithium-ion battery is connected to the relevant part of the balance charging line, such as Figure 3 At both ends of B3, first, these two wires pass through an input protection circuit, which is composed of an anti-reverse connection circuit and an anti-overvoltage circuit. Once the wiring is wrong, resulting in reverse input connection and input overvoltage, the circuit will be protected to prevent the subsequent circuit from burning out; the connected voltage signal is sent to the optocoupler circuit to isolate the primary and secondary potentials, and use the linear range of the optocoupler to obtain a voltage that changes linearly with the optocoupler light-emitting level voltage at the receiving level of the optocoupler, and obtain the battery string sampling voltage in the sampling voltage formation circuit. The potential zero point of the sampling voltage is the system ground, so that the independent measurement voltage of all battery strings can be obtained, which is independent of the position of the lithium-ion battery in the series circuit, which is also the key to balanced discharge.

[0028] like Figure 4As shown, the sampled voltages of N lithium-ion batteries are sent to the main controller. In the multi-channel analog-to-digital conversion (A / D) converter of the main controller, the sampled voltages of different channels are converted to analog-to-digital (A / D) in time. The single-chip microcomputer (MCU) of the main controller can quickly complete the voltage sampling of all channels by controlling the selection signal of the converter, forming a digital sampled voltage signal, and sending it to the single-chip microcomputer (MCU) in time to obtain the current voltage value of each lithium-ion battery. The voltage value will be compared with the safety voltage (3.85V). When the voltage value is lower than the safety voltage, the red indicator light will be turned on, indicating that the voltage of the channel is low and does not need to be discharged, but the battery pack needs to be charged; if the voltage value is higher than the safety voltage, the relay pull-in signal of the signal is sent out, and the high-power relay is pulled in through the corresponding relay drive circuit, and the lithium-ion battery of the channel starts to discharge; at the same time, the voltage of the channel is continuously monitored. After a period of discharge, when the voltage value is equal to the safety voltage, the relay shutdown signal is sent, the high-power relay is disconnected, and the discharge ends.

[0029] The high-power load is an independent high-power air-cooled resistor. The resistance value and power value are determined according to the battery usage, but the value needs to be considered redundant. Discharging too quickly can easily damage the battery pack. Since the load will emit a lot of heat when working, a high-airflow cooling fan group consisting of a temperature acquisition probe, a fan drive and a cooling fan is set in the chassis. Figure 1 As shown, the temperature acquisition probe obtains the temperature inside the chassis, and the single-chip microcomputer (MCU) controls the fan speed according to the temperature to control the temperature inside the chassis within an appropriate range.

[0030] The multi-channel battery status display light is a red and green dual-color LED. When the lithium-ion battery voltage is lower than the safe voltage, the red indicator light is on; during the discharge process, the green indicator light flashes; after the discharge is completed, the green indicator light is always on. And the indicator lights correspond to the corresponding lithium-ion battery positions one by one.

Claims

1. A fully automatic balanced discharge device for lithium-ion batteries, characterized in that: The fully automatic balanced discharge device includes an interface matcher, an interface protection circuit, a main controller, a voltage sampling circuit, a high-power load and a multi-channel battery status display lamp; The fully automatic balanced discharge device uses the balanced charging lines between the lithium-ion battery packs connected in series to discharge, and the discharge channels are completely independent; the discharge of each lithium-ion battery is determined according to the voltage of the lithium-ion battery; The voltage sampling circuit adopts an optical coupling method to electrically isolate the sampling of the front stage and the voltage access of the back stage, so that the lithium-ion batteries connected in series can be sampled completely independently from each other. The voltage sampling circuit is connected to the lithium-ion battery pack through the interface matcher and the interface protection circuit. Each lithium-ion battery path is independently monitored and discharged, and the execution contacts of the high-power relay in the discharge path are synchronized double-pole structures; the voltages at both ends of each lithium-ion battery are independently monitored, and the voltage sampling circuit is used for potential isolation; the single-path lead of each lithium-ion battery is connected to the balance charging line; The sampled voltage of the lithium-ion battery through the voltage sampling circuit is sent to the main controller. In the multi-channel analog-to-digital converter of the main controller, the sampled voltages of different channels are converted into analog-to-digital in a time-sharing manner. The single-chip microcomputer of the main controller completes the voltage sampling of all channels by controlling the selection signal of the converter, forms a digital sampled voltage signal, and sends it to the single-chip microcomputer of the main controller in a time-sharing manner to obtain the current voltage value of each lithium-ion battery. The voltage value will be compared with the safety voltage of 3.85V. When the voltage value is lower than the safety voltage, the red indicator light will be turned on to indicate that the voltage is low and does not need to be discharged, but the battery pack needs to be charged. If the voltage value is higher than the safety voltage, the relay energizing signal of the signal is sent out, and after the corresponding relay drive circuit, the high-power relay is energized, and the battery string starts to discharge. At the same time, the voltage of the line is continuously monitored. After a period of discharge, when the voltage value is equal to the safety voltage, a relay shutdown signal is sent out, the high-power relay is disconnected, and the discharge ends. The high-power load is an independent high-power air-cooled resistor, wherein: the resistance value and the power value are determined according to the battery usage; The multi-channel battery status display light is a red and green dual-color LED. When the voltage of the lithium-ion battery is lower than the safe voltage, the red indicator light is lit; during the discharge process, the green indicator light flashes; after the discharge is completed, the green indicator light is always on; and the indicator lights correspond to the corresponding lithium-ion batteries one by one.

2. The fully automatic balanced discharge device for lithium-ion batteries according to claim 1, characterized in that: A high-air-volume cooling fan group consisting of a temperature acquisition probe, a fan driver and a cooling fan is set in the chassis. The temperature acquisition probe obtains the temperature inside the chassis, and the microcontroller controls the fan speed through the fan driver according to the temperature to control the temperature inside the chassis within an appropriate range.

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