CN102680846B - Methods for judging and protecting reliability of connection among battery units, and protection device - Google Patents

Abstract

The invention relates to a connection reliability judgment, a protection method and a protection device between battery units. For at least two battery units connected in series, measure the terminal voltage of each battery unit; compare the terminal voltages of all adjacent two battery units, if If the difference between the terminal voltages of any pair of adjacent battery cells exceeds the set voltage and lasts longer than the set time, it is judged that the connection between the battery cells in series is faulty; otherwise, it is judged that the connection is normal. The judgment method relied on by this judgment method is simple and easy to implement, does not require a lot of electric quantity, and the criterion is highly reliable, and the required judgment time is relatively short.

Description

Connection reliability judgment, protection method and protection device between battery cells

technical field

The invention relates to a power battery pack, especially a method for judging and protecting the connection reliability between battery units, and a protection device for preventing power battery packs and series battery boxes from connecting failures.

Background technique

The power battery pack, especially the power battery pack of an electric vehicle is composed of several power battery boxes connected in series, and each power battery box is equipped with a number of single batteries connected in series, and the pole connection points between the power battery boxes are in the electric vehicle During operation, the connection point of the battery box is prone to increase in connection resistance, causing overheating and burning of the connection point. The conditions that cause the resistance of the connection point to increase abnormally are: the pole connection point of the electric vehicle motor is in poor contact before starting; the connection point is loose during the operation of the electric vehicle; the connection point pole and the contact parts are oxidized.

Electric vehicle power battery box is the key core equipment, once a failure occurs, it is directly related to the safe operation of the vehicle. However, in the prior art, the means for judging the fault are relatively complicated, the reliability is low, and the judging time is relatively long. Therefore, according to the characteristics and requirements of the electric vehicle power battery box circuit, a corresponding protection design scheme must be proposed.

Contents of the invention

The purpose of the present invention is to provide a method for judging and protecting the reliability of the connection between battery cells, which can easily and reliably judge the occurrence of connection faults between battery cells for further protection, thereby solving the problem of complicated and difficult fault judgment methods in the prior art. The problem of low reliability and long judgment time. On the basis of the above method, the present invention also proposes a protection device against connection failure of the electric vehicle power battery box and a protection device against connection failure of the power battery pack.

In order to achieve the above object, the judging method scheme of the present invention is: a judging method for connection reliability between battery cells, the steps are as follows: for at least two battery cells connected in series, measure the terminal voltage of each battery cell; compare all The terminal voltage of adjacent battery cells, if the difference between the terminal voltages of any pair of adjacent battery cells exceeds the set voltage and lasts longer than the set time, it is judged that the connection between the battery cells in series is faulty, otherwise, Then it is judged that the connection is normal.

The battery unit is a single battery or a battery box.

The protection method scheme of the present invention: a protection method for connection faults between battery units, for at least two battery units in series, measure the terminal voltage of each battery unit; compare the terminal voltages of all adjacent battery units; if there is If the difference between the terminal voltages of any pair of adjacent battery cells exceeds the set voltage and lasts longer than the set time, it is judged that the connection between the battery cells in series is faulty, otherwise, it is judged that the connection is normal; when the connection fails, For protection, cut off the power supply output of the battery cells connected in series.

The battery unit is a single battery or a battery box.

The following analyzes the protection method of the present invention starting from the battery pack.

The equivalent circuit of battery n in the battery pack is shown in Figure 2: where E _n , R _eqn are the internal potential and internal resistance of battery n; R _2n-1 , R _2n are the contact resistances of the two poles of battery n; U′ _n is the terminal voltage of battery n, U _n is the battery terminal voltage measured by the logic unit; when the battery poles are in good contact, the contact resistance R _2n-1 , R _2n can be ignored, and U′ _n ≈ U _n .

When the battery pole is not in good contact, R _2n increases to R _f , as shown in Figure 3: the contact resistance R _2n-1 can be ignored, and there is U _n ≈ U′ _n + U _f . U _f is the arc voltage drop. Theoretically, if the on-site conditions permit and U′ _n and U _n can be actually measured, the arc voltage drop U _f can be calculated to identify the poor contact of the pole. In practice, it is difficult to measure U′ _n due to limited conditions. Therefore, the present invention adopts the method of measuring the voltage of adjacent batteries to equivalently solve U′ _n , so as to obtain the arc voltage U _f . The specific implementation method is as shown in Figure 4: Assume that the contact resistance of the 1# battery is R ₂ and the pole contact is poor, resulting in an arc resistance of R _f and an arc voltage of U _f ; under normal circumstances, the characteristics of the two batteries are very close, That is, the battery terminal voltages are approximately equal, and there is U′ ₁ ≈ U′ ₂ . The 2# battery poles are in good contact with U′ ₂ ≈U ₂ , so the arc voltage U _f ≈U ₁ -U′ ₁ ≈U ₁ -U ₂ .

When the arc voltage U _f is greater than the fixed value U _set and the duration is greater than the fixed value t _set , it means that there is a fault in the power battery pack.

The above derivation points out: measure the terminal voltage of the two batteries, and find the terminal voltage difference, if the terminal voltage difference is small, it means that the characteristics of the two adjacent batteries are the same (both normal or both have poor contact), if the terminal voltage difference Larger, it can be concluded that two adjacent batteries exhibit different characteristics, and at least one of the batteries has a problem of poor contact, that is, a fault occurs in the power battery pack. The judgment method relied on by this judgment method is simple and easy to implement, does not require a lot of electrical quantity, and the criterion is highly reliable, and the required judgment time is relatively short.

The object of the above derivation is the contact problem between single cells with the same performance and the poles of the single cells. By extension, it can also be a battery unit composed of the same number of single cells connected in series (the single The contact resistance between bulk batteries is neglected) and the contact problem between adjacent battery cells; it can also be extended to the contact problem of the connection point between the battery box and the battery box in the field of electric vehicles-the electric vehicle power supply is composed of several power batteries The boxes are connected in series, and each power battery box is equipped with a number of single cells in series (the contact resistance between the single cells in the battery box can be ignored), and the pole connection points between the power battery boxes are connected when the electric vehicle is started. Before and during operation, the connection point is prone to loosening, the connection point pole and the contact part of the components are oxidized, which will lead to the increase of the connection point junction resistance, the connection point will be burned, and the power supply will be affected.

According to the method of the present invention, the present invention also provides a protection device against connection faults of power battery packs, the protection device includes a logic unit for measuring the terminal voltage of each single battery, and measures the two voltages of adjacent single batteries. Each logic unit is connected by communication; each logic unit drives and controls a corresponding switch contact, and all the switch contacts are connected in series in the control circuit of the power circuit power switch, and the power circuit power switch is used to switch the power supply output of the power battery pack; Each logic unit compares the terminal voltage difference between the corresponding single battery and the adjacent single battery. If the terminal voltage difference exceeds the set voltage and lasts longer than the set time, it is judged that there is a failure in the connection of the power battery pack, and vice versa. , then it is judged that the connection is normal; if it is judged that the connection is faulty, the logic unit will drive and control the corresponding switch contact to open, and if the connection is judged to be normal, the logic unit will drive and control the corresponding switch contact to close.

The adjacent battery boxes are connected through optical fiber communication.

The present invention also provides a protection device for preventing connection failures of electric vehicle power battery boxes, the protection device includes a logic unit for measuring the terminal voltage of each battery box, and measures the communication connection between two logic units of adjacent battery boxes; Each logic unit drives and controls a corresponding switch contact, and all the switch contacts are connected in series in the control circuit of the power circuit power switch, and the power circuit power switch is used to switch the power supply output of the series battery box; The terminal voltage difference between the battery box and the adjacent battery box, if the terminal voltage difference exceeds the set voltage and lasts longer than the set time, it is judged that the connection between the battery boxes in series is faulty, otherwise, it is judged that the connection is normal; If it is judged that the connection is faulty, the logic unit will drive and control the corresponding switch contact to open, and if the connection is judged to be normal, the logic unit will drive and control the corresponding switch contact to close.

The adjacent battery boxes are connected through optical fiber communication.

In the protection device, each logic unit only needs to compare the criterion and control its corresponding switch contact, and the control is simple. Due to the redundant design, the reliability of the protection action is high. The protection device of the invention can effectively prevent problems caused by hardware damage, and solves the problem that hardware failures in harsh environments affect the reliable operation of protection.

Description of drawings

Fig. 1 is the circuit principle diagram of protection device of the present invention;

Fig. 2 is the equivalent circuit diagram of battery n in the battery pack;

Fig. 3 is an equivalent circuit diagram when the n-pole of the battery is in poor contact;

Fig. 4 is the equivalent circuit diagram of 1# battery and 2# battery;

Fig. 5 is a schematic circuit diagram of an embodiment of a battery box protection device.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Judgment method embodiment

As shown in Figure 1, the power battery box of an electric vehicle, from battery box 1, battery box 2 to battery box n, has the same number and type of single cells installed in each battery box. Measure the terminal voltage of each battery box; compare the terminal voltages of all two adjacent battery boxes, if the difference between the terminal voltages of any pair of adjacent battery boxes exceeds the set voltage and lasts longer than the set time, then It is judged that the connection between the battery units in series is faulty, otherwise, it is judged that the connection is normal. The theoretical basis of the judgment is analyzed in detail in the content of the invention. The set voltage is the above-mentioned fixed value U _set , and the set time is the above-mentioned fixed value t _set .

Usually, the connection between the single cells in the battery box is very reliable, and the contact resistance is negligible, so the above embodiments are concerned with the connection between the battery boxes. As other implementations, the above method can also be applied to each single battery in the power battery pack to investigate the connection reliability between each single battery and judge the connection reliability of the entire power battery pack.

Embodiment of protection method

On the basis of the above judgment method, according to the judgment result, when the connection fails, the protection will be carried out, and the power supply output of the series battery box (power battery pack) will be cut off.

Example of battery box protection device

As shown in Figure 1, the protection device includes a logic unit for measuring the terminal voltage of each battery box, and the two logic units for measuring adjacent battery boxes are connected through optical fiber communication; each logic unit drives and controls a corresponding switch contact, all The switch contacts of the power circuit are connected in series in the control circuit of the power switch of the power circuit, and the power switch of the power circuit is used for switching on and off the power supply output of the series battery box; each logic unit compares the terminal voltage difference between the corresponding battery box and the adjacent battery box , if the terminal voltage difference exceeds the set voltage and the duration is longer than the set time, it will be judged that the connection between the battery boxes in series is faulty, otherwise, it will be judged that the connection is normal; if the connection is faulty, the logic unit will drive and control the corresponding switch If the contact is disconnected, it is judged that the connection is normal, and the logic unit drives and controls the corresponding switch contact to close.

The protection device shown in Figure 5 provides protection for the electric vehicle power battery pack composed of two battery boxes connected in series. Battery box 1 and battery box 2 correspond to logic unit 1 and logic unit 2 respectively. The logic unit 1 measures the terminal voltage of the battery box 1, receives the terminal voltage of the battery box 2 collected by the logic unit 2, compares it, and drives and controls the corresponding switch contact action according to the comparison result; at the same time, the logic unit 2 measures the terminal voltage of the battery box 2 Voltage, receive the terminal voltage of the battery box 1 collected by the logic unit 1, compare it, and drive and control the corresponding switch contact action according to the comparison result; as shown in Figure 5, when any switch contact is disconnected, the power circuit power switch is disconnected , the power battery pack cannot output.

As other implementation manners, communication methods such as cables may also be used between logic units, but the effect is not as reliable as optical fiber communication.

Embodiment of single battery protection device

It is sufficient to replace the battery box in the embodiment of the battery box protection device with a single battery, so details are not repeated here.

Claims (4)

1. the determination methods of coupling reliability between battery unit, it is characterized in that, step is as follows: at least two battery units of series connection, measure the terminal voltage of each battery unit; The terminal voltage of more all adjacent cell, if have the difference of arbitrary terminal voltage to adjacent cell to exceed setting voltage and the duration is greater than setting-up time, then judge that the connection between the battery unit of connecting is broken down, otherwise, then judge to connect normal; Described battery unit is cell or battery case; Connected by pole between described adjacent cell; E _n, R _eqnfor built-in potential, the interior resistance of battery n; R _2n-1, R _2nfor two pole contact resistances of battery n; U _n' be the terminal voltage of battery n, U _nfor the battery terminal voltage that logical block measures; When battery electrode column contact is good, contact resistance R _2n-1, R _2nignore, have U _n' ≈ U _n; When battery electrode column loose contact, R _2nbe increased to R _f, contact resistance R _2n-1ignore, have U _n≈ U _n'+U _f, U _ffor arc light pressure drop.

2. connect a guard method for fault between battery unit, it is characterized in that, at least two battery units of series connection, measure the terminal voltage of each battery unit; The terminal voltage of more all adjacent cell; If have the difference of arbitrary terminal voltage to adjacent cell to exceed setting voltage and the duration is greater than setting-up time, then judge that the connection between the battery unit of connecting is broken down, otherwise, then judge to connect normal; When connection is broken down, protect, the power supply cutting off series-connected cell unit exports; Described battery unit is cell or battery case; Connected by pole between described adjacent cell; E _n, R _eqnfor built-in potential, the interior resistance of battery n; R _2n-1, R _2nfor two pole contact resistances of battery n; U _n' be the terminal voltage of battery n, U _nfor the battery terminal voltage that logical block measures; When battery electrode column contact is good, contact resistance R _2n-1, R _2nignore, have U _n' ≈ U _n; When battery electrode column loose contact, R _2nbe increased to R _f, contact resistance R _2n-1ignore, have U _n≈ U _n'+U _f, U _ffor arc light pressure drop.

3. anti-power battery pack connects a protective device for fault, and it is characterized in that, described protective device comprises the logical block for measuring each cell terminal voltage, and two logical block communications of measuring neighboring unit cell connect; The make and break contact that each logical block drived control one is corresponding, all make and break contacts are connected in the control loop of power loop power switch, and described power loop power switch exports for the power supply of break-make power battery pack; Terminal voltage between the more corresponding cell of each logical block and neighboring unit cell is poor, if terminal voltage difference exceedes setting voltage and the duration is greater than setting-up time, then judges to connect in power battery pack to break down, otherwise, then judge to connect normal; Judge that connection is broken down, the logical block make and break contact that then drived control is corresponding disconnects, and judge to connect normally, the logical block make and break contact that then drived control is corresponding closes; Connected by optical-fibre communications between described adjacent cell case; Connected by pole between described adjacent cell; E _n, R _eqnfor built-in potential, the interior resistance of battery n; R _2n-1, R _2nfor two pole contact resistances of battery n; U _n' be the terminal voltage of battery n, U _nfor the battery terminal voltage that logical block measures; When battery electrode column contact is good, contact resistance R _2n-1, R _2nignore, have U _n' ≈ U _n; When battery electrode column loose contact, R _2nbe increased to R _f, contact resistance R _2n-1ignore, have U _n≈ U _n'+U _f, U _ffor arc light pressure drop.

4. anti-power battery box of electric vehicle connects a protective device for fault, and it is characterized in that, described protective device comprises the logical block for measuring each battery case terminal voltage, and two logical block communications of measuring adjacent cell case connect; The make and break contact that each logical block drived control one is corresponding, all make and break contacts are connected in the control loop of power loop power switch, and described power loop power switch exports for the power supply of break-make series-connected cell case; Terminal voltage between the more corresponding battery case of each logical block and adjacent cell case is poor, if terminal voltage difference exceedes setting voltage and the duration is greater than setting-up time, then judges to connect between the battery case of connecting to break down, otherwise, then judge to connect normally; Judge that connection is broken down, the logical block make and break contact that then drived control is corresponding disconnects, and judge to connect normally, the logical block make and break contact that then drived control is corresponding closes; Connected by optical-fibre communications between described adjacent cell case; Connected by pole between described adjacent cell; E _n, R _eqnfor built-in potential, the interior resistance of battery n; R _2n-1, R _2nfor two pole contact resistances of battery n; U _n' be the terminal voltage of battery n, U _nfor the battery terminal voltage that logical block measures; When battery electrode column contact is good, contact resistance R _2n-1, R _2nignore, have U _n' ≈ U _n; When battery electrode column loose contact, R _2nbe increased to R _f, contact resistance R _2n-1ignore, have U _n≈ U _n'+U _f, U _ffor arc light pressure drop.