CN107528353A - One kind series winding battery voltage balanced method and equalizing circuit - Google Patents

Abstract

The present invention provides a kind of series winding battery voltage balanced method and equalizing circuit, this method is in charging process if it find that the voltage for having any cell is higher by one threshold value of average voltage, then the battery is discharged by discharge circuit, its voltage is set to be reduced to average value, the circuit is to realize the equilibrium to cell in battery pack using a chip.Due to only carrying out equilibrium in battery charging process, other time does not discharge battery, overcomes the deficiency of current equalizing system.

Description

A voltage equalization method and equalization circuit of series-connected batteries

technical field

The invention relates to the field of use of power batteries, in particular to a battery balancing method and a balancing circuit when a large number of batteries are connected in series.

Background technique

With the intensification of environmental pollution, new energy technologies such as electric vehicles have received worldwide attention and rapid development, and battery energy storage has become a bottleneck in the development of electric vehicles. Due to the requirements of the driving range of electric vehicles and the limitation of low voltage and low capacity of the battery cells themselves, a large number of battery cells are required to be connected in series in the power battery pack to provide the required driving voltage and driving ability. However, due to existing manufacturing technology and inevitable differences in external environments such as temperature, the initial capacity, working voltage, and remaining capacity of a large number of cells cannot be completely consistent, resulting in overcharge and over discharge of individual cells during battery use. , affecting battery life and safety. Moreover, due to the existence of the "barrel effect" that affects the capacity of the entire battery pack, the positive feedback effect makes the "loss" of battery cells with small capacity more serious. A good battery balancing technology can greatly reduce the inconsistency between battery cells, thereby effectively avoiding the occurrence of overcharge or overdischarge of some battery cells in the battery pack, thereby maintaining the use characteristics of the battery pack. Therefore, battery balancing technology occupies an important position in the electric vehicle battery management system. Here, batteries include chemical batteries such as lead-acid batteries and lithium batteries that are commonly used at present, and physical batteries such as supercapacitors. Both chemical batteries and physical batteries need to be balanced when they are connected in series due to individual differences of single batteries.

Chinese Patent Publication No. CN 104113110 A discloses a battery balancing circuit, which includes:

The battery pack includes N battery cells connected in series, wherein the battery cells are divided into odd groups and even groups according to numbers, each battery cell has an anode and a cathode, and N is an integer greater than 1.

Inductors are used to store and release energy.

The balance control switch includes N+1 controllable switches, where N is the number of battery cells.

The controllable switch connects the anode and cathode of the battery cell to the inductor, wherein the controllable switches are divided into odd groups and even groups according to the number, the odd group of controllable switches are connected to one pole of the inductor, and the even group of controllable switches are connected to one pole of the inductor. on the other pole of the inductor.

The balance controller is used to detect and process the real-time voltage, current, SOC and other data of the battery cell, formulate a balance control strategy, and control the balance control switch to open and close.

The equalization circuit monitors the voltage or SOC of the battery cells in real time, and judges that the cells need to be balanced, so as to realize the energy transfer between the cells or between the cells and multiple cells.

However, since the circuit needs to be in the equalization process all the time, there is energy transfer between the batteries. During the energy transfer process, there is energy loss, which may even cause the product to heat up and affect the life of the product. At the same time, it is not suitable for integration. circuit.

Contents of the invention

The purpose of the present invention is to overcome the deficiency of each equalizing circuit in the current series battery pack, and provide a series battery voltage equalizing method and equalizing circuit, the method is only in the charging process of the battery, and the battery is not discharged at other times.

The technical solution adopted by the present invention to achieve its technical purpose is: a voltage equalization method for series-connected batteries. The circuit discharges the battery, reducing its voltage to an average value.

Since the battery is only balanced during the charging process of the battery, the battery is not discharged at other times, which overcomes the shortcomings of the current balancing system.

Further, the above method for equalizing the voltage of series-connected batteries includes the following steps:

Step 1. Measure the average voltage of each single cell in the battery pack connected in series in real time;

Step 2. Determine whether the battery pack is in the charging process, if it is in the charging process, turn to step 3, otherwise end the equalization process;

Step 3, real-time detection of the real-time voltage of the single battery;

Step 4. Subtract the real-time voltage value of the single battery from the average voltage value at this moment. If it is greater than the set threshold value, turn to step 5, otherwise end the equalization process;

Step 5, using the discharge circuit to discharge the two ends of the single battery.

Further, in the above method for equalizing the voltage of series-connected batteries: in step 1, a set of series resistors are connected at both ends of the series-connected battery packs, wherein the resistance of the series-connected resistors is the same as that of the single cells in the battery pack. The quantity is the same, and the resistance value of each resistor is the same; measuring the voltage across any resistor is the average voltage of each single battery in the battery pack.

Further, in the above-mentioned series battery voltage equalization method: in the step 2, the average voltage value of each single battery in the battery pack measured in the previous time is compared with the average voltage value of each single battery in the battery pack measured in the next time. Compared with the average voltage value of the whole battery, if the average voltage value of each single cell in the battery pack measured in the latter measurement is greater than the average voltage value of each single cell in the battery pack measured in the previous time, it is judged that the battery pack is being adjusted. Charge.

Further, the above-mentioned voltage equalization method for series-connected batteries: also includes the step of overvoltage protection for the single battery, in this step, by judging the voltage of the single battery detected in real time, if it is greater than the specified maximum voltage of the single battery, Then control the discharge circuit to discharge the single battery, and indicate.

The present invention also provides a series battery voltage equalization circuit, which includes a single battery processing module for performing equalization processing on each single battery in the series battery pack; the single battery processing module is set on an integrated circuit chip , including:

An average voltage detection circuit for real-time measurement of the average voltage of each single cell in the battery pack connected in series;

A charging state detection circuit for judging whether the battery pack is being charged;

A single battery voltage real-time detection circuit for real-time detection of the real-time voltage of the single battery;

comparison circuit;

"AND" logic gate circuit;

discharge circuit;

The input terminal of the charging state detection circuit is connected to the output terminal of the average voltage detection circuit, and when charging, the output of the charging state detection circuit is valid;

The input end of the comparison circuit is the output end of the single cell voltage real-time detection circuit and the output end of the average voltage detection circuit, and the signal at the output end of the single cell voltage real-time detection circuit is higher than the signal at the output end of the average voltage detection circuit When a set value is reached, the output of the comparison circuit is valid;

The two input terminals of the "AND" logic gate circuit are respectively connected to the output terminal of the described charging state detection circuit and the output terminal of the described comparison circuit, and when the output terminal of the "AND" logic gate circuit is valid driving the discharge circuit to work;

The discharge circuit is arranged at both ends of the single battery.

Further, in the above series battery voltage equalization circuit: the average voltage detection circuit includes a first voltage detection module, a group of voltage dividing resistors equal to the number of single cells in the series battery pack, and all the voltage dividing resistors The two ends of the series-connected battery packs with the same resistance value are connected in series, and the first voltage detection module detects the voltage at both ends of any voltage dividing resistor.

Further, in the above series battery voltage equalization circuit: the charging state detection circuit includes an operational amplifier U1, a resistor R1, a resistor R2, and a capacitor C; the output of the average voltage detection circuit is connected to the operational amplifier U1 through the resistor R1 The same-phase terminal, the output of the average voltage detection circuit is connected to the non-phase terminal of the operational amplifier U1 through the resistor R2, and the capacitor C is connected to the non-phase terminal of the operational amplifier U1 and the negative pole of the single battery.

Further, in the above series battery voltage equalization circuit: the discharge circuit includes a discharge transistor Q and a discharge current limiting resistor R4, the output of the "AND" logic gate circuit is connected to the base of the discharge transistor Q, and the discharge limiter One end of the current resistor R4 is connected to the emitter of the discharge transistor Q, the other end is connected to the negative pole of the single battery, and the collector of the discharge transistor Q is connected to the positive pole of the single battery.

Further, in the above series battery voltage equalization circuit: the output terminals of the average voltage detection circuit and the single battery voltage real-time detection circuit also include an output circuit for processing the output signal to improve the output load capacity.

The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a single battery processing module of the present invention.

FIG. 2 is a schematic diagram of a charging state detection circuit in Embodiment 1 of the present invention.

Fig. 3 is a schematic diagram of the discharge circuit in Embodiment 1 of the present invention.

Fig. 4 is a schematic diagram of the equalization circuit of the series battery group according to Embodiment 1 of the present invention.

detailed description

Embodiment, this embodiment is when charging the battery pack connected in series, each single cell is processed, so that the voltage of each single cell in the battery pack is balanced, and the single cell can be a lead-acid storage battery or a lithium battery that is more commonly used at present. Secondary batteries of chemical batteries such as batteries can also be physical batteries such as supercapacitors. In the future, single batteries refer to such physical batteries or chemical secondary batteries.

In this embodiment, it mainly embodies the use of a three-pin chip or a six-pin chip to balance the single batteries in a group of series-connected battery packs. During equalization, the balancing work is only done during the charging process of the series-connected battery packs. Therefore, it is necessary to detect the working state of the battery pack. If charging is in progress, the real-time voltage of each single battery is detected. If the voltage of a certain single battery is higher than the average voltage, the battery is discharged so that The voltage is lowered to meet the requirements. If it is a 2.7V supercapacitor battery, during the charging process, the voltage of the single battery is 40mV higher than the uneven voltage, and the discharge circuit can be driven to discharge the single battery. The specific steps of the method used by the three-pin chip or the six-pin chip are as follows:

Step 1. Measure the average voltage of each single cell in the series-connected battery pack in real time; at present, there are many means for measuring the average voltage, such as measuring the voltage of the entire battery pack and dividing it by the number of single cells to obtain the average voltage. This is used a lot in this field, especially when intelligent processors such as single-chip microcomputers are used in digital circuits. In this embodiment, it is also very good to adopt a method, which is to connect a group of series resistors at both ends of the battery pack in series, wherein the resistance number of the series resistor is consistent with the number of single cells in the battery pack, and the resistance values of each resistor are the same ; Measuring the voltage across any resistor is the average voltage of each single cell in the battery pack.

Step 2. Determine whether the battery pack is in the charging process. If it is in the charging process, turn to step 3, otherwise end the equalization process; this step is the key, only to judge the subsequent steps in the charging process, otherwise stop stop. There are many ways to judge whether the battery pack is in the charging process. For example, by detecting the voltage of the battery pack, if the real-time voltage at the back is higher than the previous voltage, it can be concluded that the voltage of the battery is rising, so it is charging. In the embodiment, because the obtained samples are obtained by measuring the voltage across the middle resistor of the above series resistors to obtain the average voltage, therefore, the average voltage is used to determine whether charging is in progress. By comparing the average voltage value of each single cell in the battery pack measured in the previous measurement with the average voltage value of each single cell in the battery pack measured in the next measurement, if each cell in the battery pack measured in the latter measurement If the average voltage value of the whole battery is greater than the average voltage value of each single battery in the battery pack measured last time, it is judged that the battery pack is being charged. Of course, there are many ways to judge whether it is charging, such as: the charging state detection circuit also includes a rising edge judgment circuit composed of other circuit structures such as AD detection, digital delay, etc., which can also realize whether charging is judged.

Step 3, detecting the real-time voltage of the single battery in real time.

Step 4, subtract the average voltage value at this moment from the real-time voltage value of the single battery, if it is greater than the set threshold value, then turn to step 5, otherwise end this equalization process; in this embodiment, the threshold value setting 40mV is enough, as long as the voltage of the single cell exceeds the average voltage of 40mV, the single cell is discharged.

In addition, in the charging process, if the charged voltage exceeds a threshold value, the charging needs to be stopped. For example, a 2.7V super capacitor will stop charging when it is charged to 2.7V. Therefore, in the charging process, it is also necessary to determine Whether the charging is complete, if the condition of charging completion is reached, the charging will be stopped immediately. Therefore, this embodiment also includes a step of overvoltage protection for the single battery. In this step, by judging the voltage of the single battery detected in real time, if If it is greater than the specified maximum voltage of the single battery, the discharge circuit is controlled to discharge the single battery and an indication is given.

In this embodiment, an integrated circuit chip can be used to realize the above functions. As shown in Figure 1, the chip has only six pins and has the following functional circuits in the chip. The chip is a single battery that processes a single battery processing circuit. Such an integrated circuit chip is provided for each single battery in the series-connected battery pack, and all the integrated circuit chips are connected as shown in Figure 4 to balance the entire series-connected battery pack.

An average voltage detection circuit for real-time measurement of the average voltage of each single cell in the series-connected battery pack; the average voltage detection circuit includes a first voltage detection module, a group of voltage dividing resistors equal to the number of single cells in the series-connected battery pack , in this embodiment, the voltage dividing resistors are arranged outside the chip, so that in practical application, these resistors with the same size and size can be selected locally to ensure the accuracy of the average voltage detection result. All voltage-dividing resistors with the same resistance value are connected in series at both ends of the series-connected battery pack, and the first voltage detection module detects the voltage at both ends of any voltage-dividing resistor, which is the average voltage. Here, the first voltage detection module is a module for detecting voltage, and only distinguishes other voltage detection modules in the future. As shown in Figure 1 and Figure 4, the voltage dividing resistor is a resistor outside the chip. Therefore, it is necessary to set two more pins for the chip, such as pins 1 and 2 shown in Figure 1. In practice chip design In this case, the voltage dividing resistor can also be integrated into the integrated circuit chip. In this way, the pins of the chip can be reduced. In the chip, the average voltage can be obtained by measuring the voltage on the voltage dividing resistor. Since the voltage divider resistors are set in the integrated circuit chip, if the balance chip of each single battery in the series battery pack is not in a batch during practical use, it is not easy to ensure that the resistance value of each voltage divider resistor is accurate. Equally, this may result in inaccurate average voltage detection.

A charge state detection circuit for judging whether the battery pack is being charged; the input end of the charge state detection circuit is connected to the output end of the average voltage detection circuit, and the output of the charge state detection circuit is valid when charging. This circuit has many forms at present, and present embodiment adopts the circuit of schematic diagram as shown in Figure 2, and charging state detection circuit comprises operational amplifier U1, resistance R1, resistance R2, electric capacity C; Average voltage detection circuit output is connected operation through resistance R1 The non-inverting end of the amplifier U1 and the output of the average voltage detection circuit are connected to the out-of-phase end of the operational amplifier U1 through the resistor R2, and the capacitor C is connected to the out-of-phase end of the operational amplifier U1 and the negative pole of the single battery. In addition, there may also be a discharge resistor R3 in this circuit to discharge the non-inverting terminal of the operational amplifier U1. This circuit is very simple. It only delays the analog signal of the average input voltage and compares it with the later one. If the later one is higher than the previous one, it will output a valid signal, but it needs a capacitor C, which is outside the integrated circuit chip. A capacitor C makes the chip have a pin 3. If other circuits are used, this capacitor C is not needed. For example, in the actual use process, the rising edge judgment circuit composed of other circuit structures such as AD detection and digital delay is used. , It is also possible to realize whether to charge or not, so that the capacitor C is not set too large. Therefore, in the end, the chip does not need pins 1, 2, and 3.

A single battery voltage real-time detection circuit for real-time detection of the real-time voltage of the single battery; this circuit can detect the voltage at both ends of the single battery in the same way as the first voltage detection module above. There are many technologies for detecting the voltage at both ends of a single battery, and there are also many technologies suitable for integrated circuit design. In this embodiment, a voltage detection module suitable for integrated circuits is used.

Comparison circuit and "AND" logic gate circuit, discharge circuit.

The discharge circuit is a CCS circuit that discharges both ends of the single battery. As shown in Figure 3, the discharge circuit includes a discharge transistor Q and a discharge current limiting resistor R4. The output of the "AND" logic gate circuit is connected to the base of the discharge transistor Q. One end of the current limiting resistor R4 is connected to the emitter of the discharge transistor Q, the other end is connected to the negative pole of the single battery, and the collector of the discharge transistor Q is connected to the positive pole of the single battery. In practical use, the discharge circuit is a discharge circuit with a minimum length of time. Once the discharge circuit is started, it will maintain a minimum set discharge time.

The input end of the comparison circuit is the output end of the single battery voltage real-time detection circuit and the output end of the average voltage detection circuit, and the signal at the output end of the single battery voltage real-time detection circuit is higher than the signal at the output end of the average voltage detection circuit. value, the comparison circuit output is valid.

The two input terminals of the "AND" logic gate circuit are respectively connected to the output terminal of the described charging state detection circuit and the output terminal of the described comparison circuit, and when the output terminal of the "AND" logic gate circuit is valid, it drives the The discharge circuit works.

In addition, the output terminals of the average voltage detection circuit and the single battery voltage real-time detection circuit also include an output circuit for processing the output signal to improve the output load capacity.

As shown in Figure 4, it is an equalization circuit for a series-connected battery pack composed of n batteries, which is processed by a chip processed by a single battery. n resistors of the same resistance value are connected in series, where n is any integer greater than 1. The 1st and 2nd pins of the chip processed by each single battery are connected between a resistor, the 3rd pin is connected to the negative pole of the single battery through a capacitor, and the 4th and 5th pins are connected across the single battery. At both ends, the 6th pin of each chip is connected in parallel to output TP3 and connected to indicating devices such as display lamps.

Claims (10)

1. A voltage equalization method for series-connected batteries, characterized in that: if the method finds that the voltage of any single battery is higher than a threshold value of the average voltage during the charging process, the battery is discharged through a discharge circuit, so that Its voltage drops to the average value. 2. The voltage equalization method for series battery cells according to claim 1, comprising the following steps: Step 1. Measure the average voltage of each single cell in the battery pack connected in series in real time; Step 2. Determine whether the battery pack is in the charging process, if it is in the charging process, turn to step 3, otherwise repeat steps 1 and 2; Step 3, real-time detection of the real-time voltage of the single battery; Step 4. Subtract the real-time voltage value of the single battery from the average voltage value at this moment. If it is greater than the set threshold value, turn to step 5, otherwise end the equalization process; Step 5. Discharge the single battery. 3. The voltage equalization method for series-connected batteries according to claim 2, characterized in that: in the step 1, a group of series resistors are connected at both ends of the series-connected battery packs, wherein the resistance value of the series-connected resistors is The number of single cells in the battery pack is the same, and the resistance value of each resistor is the same; measuring the voltage across any resistor is the average voltage of each single cell in the battery pack. 4. The voltage equalization method for series-connected batteries according to claim 2, characterized in that: in the step 2, the average voltage value of each single cell in the battery pack measured in the previous measurement is compared with the average voltage value of the subsequent measurement Compared with the average voltage value of each single cell in the battery pack, if the average voltage value of each single cell in the battery pack measured in the latter measurement is greater than the average voltage value of each single cell in the battery pack measured in the previous measurement , and this state is continuous, it is judged that the battery pack is being charged. 5. The voltage equalization method for series-connected batteries according to claim 2, characterized in that: it also includes the step of overvoltage protection for the single battery, in this step, by judging the voltage of the single battery detected in real time, if it is greater than the specified If the highest voltage of the single battery is reached, the discharge circuit is controlled to discharge the single battery and indicated. 6. A series battery voltage equalization circuit, including a single battery processing module that performs equalization processing on each single battery in the series battery pack; it is characterized in that: the single battery processing module is arranged in an integrated circuit chip, including: An average voltage detection circuit for real-time measurement of the average voltage of each single cell in the battery pack connected in series; A charging state detection circuit for judging whether the battery pack is being charged; A single battery voltage real-time detection circuit for real-time detection of the real-time voltage of the single battery; comparison circuit; "AND" logic gate circuit; discharge circuit; The input terminal of the charging state detection circuit is connected to the output terminal of the average voltage detection circuit, and when charging, the output of the charging state detection circuit is valid; The input end of the comparison circuit is the output end of the single cell voltage real-time detection circuit and the output end of the average voltage detection circuit, and the signal at the output end of the single cell voltage real-time detection circuit is higher than the signal at the output end of the average voltage detection circuit When a set value is reached, the output of the comparison circuit is valid; The two input terminals of the "AND" logic gate circuit are respectively connected to the output terminal of the described charging state detection circuit and the output terminal of the described comparison circuit, and when the output terminal of the "AND" logic gate circuit is valid driving the discharge circuit to work; The discharge circuit uses two pins of the integrated circuit chip to connect with both ends of the single battery. 7. The voltage equalization circuit of series-connected batteries according to claim 6, characterized in that: said average voltage detection circuit comprises a first voltage detection module disposed in the integrated circuit chip, a set of voltage detection modules disposed outside the integrated circuit chip The voltage-dividing resistors equal to the number of single cells in the series-connected battery pack, and all the voltage-dividing resistors have the same resistance value are connected in series at both ends of the series-connected battery pack. The first voltage detection module uses two integrated circuit chips. The pins are respectively connected to both ends of any voltage dividing resistor. 8. The voltage equalization circuit of series-connected batteries according to claim 6, wherein the charging state detection circuit comprises an operational amplifier U1 in an integrated circuit chip, a resistor R1, a resistor R2, and a capacitor C outside the integrated circuit; The output of the average voltage detection circuit is connected to the non-phase end of the operational amplifier U1 through the resistance R1, the output of the average voltage detection circuit is connected to the out-of-phase end of the operational amplifier U1 through the resistance R2, and the out-of-phase end of the operational amplifier U1 is used The pins of the integrated circuit chip are connected to one end of the capacitor C, and the other end of the capacitor C is connected to the negative pole of the single battery. 9. The series battery voltage equalization circuit according to claim 6, characterized in that: the discharge circuit includes a discharge transistor Q and a discharge current limiting resistor R4, and the output of the "AND" logic gate circuit is connected to the discharge transistor The base of Q, one end of the discharge current-limiting resistor R4 is connected to the emitter of the discharge transistor Q, the other end is connected to the negative pole of the single battery through the pin of the integrated circuit chip, and the collector of the discharge transistor Q is connected to the single electrode through the pin of the integrated circuit positive terminal of the battery. 10. The series battery voltage equalization circuit according to any one of claims 6 to 9, characterized in that: the output terminals of the average voltage detection circuit and the single battery voltage real-time detection circuit also include a pair of output signals An output circuit that performs processing to increase the output load capacity.