CN107139742B - Electric power balance method of vehicle power battery - Google Patents

Abstract

The invention discloses a kind of Vehicular dynamic battery monomer electric quantity balancing methods, wherein power battery monomer electricity can be made to be maintained at SOC after method of the invention is applied to battery management system_AVEWithin the scope of ± η.According to power battery attribute of performance, in the first half stage of vehicle life cycle, 2 < η of η 1, at this time equilibrium can make power battery monomer electricity be maintained at SOC_AVEIn 1 range of ± η, electricity consumed by battery management system equilibrium is the electricity of power battery Redundancy Design, and equilibrium does not influence demand of the vehicle to battery capacity.In the second half section of vehicle life cycle, 2 > η of η 1, at this time equilibrium can make power battery monomer electricity be maintained at SOC_AVEIn 2 range of ± η, equalization function guarantees that battery cell electricity deviation is no more than consistent characteristic itself, it can prevent Individual cells monomer from the phenomenon that accelerated ageing, under-voltage, zero-pressure occur, power battery can be made both to have met demand of the vehicle to energy and in turn ensure the consistent characteristic of itself, to make balanced purpose definitely.

Description

Electric power balance method of vehicle power battery

technical field

The invention belongs to the field of new energy vehicle power batteries, and relates to a method for balancing the power of a vehicle power battery cell.

Background technique

As an energy storage unit of a new energy vehicle, the performance of the power battery directly affects the performance of the vehicle. Because the actual operating environment of new energy vehicles is complex and changeable, in order to ensure that the power battery can work efficiently, reliably and safely, an effective battery management system is necessary. Especially for lithium-ion batteries with strong activity (poor safety), the significance and necessity of the battery management system are more prominent.

One of the core tasks of the battery management system is to balance the power of the battery cells inside the power battery. Because the internal environmental status of the battery cannot be guaranteed to be consistent, it is difficult to ensure the same power of the battery cells inside the battery, which requires the battery management system to control the battery. The state of charge of the cells is balanced. In practice, the inconsistency of the battery power will accelerate the attenuation of the battery assembly capacity, reduce the energy utilization efficiency of the vehicle, and affect the performance of the vehicle.

At present, domestic and foreign automobile manufacturers, battery manufacturers and scientific research institutions have proposed battery cell power balance methods which can be roughly divided into two categories. After judging the inconsistent state of battery cell power, the battery cell is charged and discharged to achieve the purpose of balancing the battery cell power. Due to the low reliability and cost of the parallel charging and discharging circuit, this method is suitable for vehicle use. The practical significance of battery cell power balance is small; second, it focuses on parallel dischargeable circuits at the positive and negative terminals of the battery cell. After judging the inconsistent state of the battery cell power, in order to meet the capacity requirements of the vehicle Due to the simplicity of the parallel discharge circuit, high reliability and low cost, this method is more suitable for vehicle power battery cell power balance.

To sum up, the use of parallel discharge circuits at both ends of the battery cells to balance the power of the battery cells has the advantages of simple and reliable circuit, low cost, high feasibility, and is an effective way to balance the power of the vehicle power battery cells.

SUMMARY OF THE INVENTION

The purpose of the present invention is a method for balancing the electric power of the power battery cells for vehicles, which clarifies the goal of balancing the electric power of the power battery cells, so that the battery management system can balance the electric power of the power battery cells more efficiently.

The present invention solves the technical problem by adopting the following technical solutions: a method for balancing the power of a vehicle power battery cell, which includes:

S10. The demand for battery capacity of the vehicle is specified as C1;

S20. The total capacity of the battery assembly is specified as C2;

S30. The percentage of capacity of the battery that cannot be used on the vehicle is specified as £;

S40 , taking the SOC of the battery cell as a condition for judging whether to start cell balancing, specifying that the SOC of the battery cell is SOC _CELL , and the average SOC of the battery cells in the entire power battery pack is SOC _AVE ;

S50. Judge the power consistency of all cells in the entire power battery pack. When the SOC _CELL value of a certain cell exceeds a certain value η of the average SOC _AVE of the battery cells, that is, when SOC _CELL -SOC _AVE ≥ η , the battery management system will control the parallel discharge circuit to discharge the battery cell.

Optionally, the calculation formula of the n value is as follows:

η=MAX(η1, η2); η1=1-C1/C2-￡;

Among them, η1 is the balanced capacity value of the battery assembly; η2 is the consistency deviation of the battery cells.

Optionally, the consistency deviation η2 is:

η2=(SOC _MAX -SOC _MIN )/2;

Among them, SOC _MAX is the maximum value of the SOC of the battery cell, and SOC _MIN is the minimum value of the SOC of the battery cell.

Optionally, in the step S50, at the initial stage of vehicle startup and at the end of vehicle external charging, the power consistency of all cells in the entire power battery pack is judged; The equalization time is required, and the equalization circuit is controlled to perform equalization operation on the battery cells with inconsistent power according to the calculated equalization time.

The present invention has the following beneficial effects: after the method of the present invention is applied to the battery management system, the power of the single power battery can be kept within the range of SOC _AVE ±η. According to the performance attributes of the power battery, in the first half of the vehicle life cycle, η2<η1, at this time the balance can keep the power battery cell power within the range of SOC _AVE ±η1, and the power consumed by the battery management system balance is the power battery redundancy The designed power balance does not affect the vehicle's demand for battery power. In the second half of the vehicle life cycle, η2>η1, at this time the balance can keep the power of the power battery cells within the range of SOC _AVE ±η2, the battery management system has rarely turned on the balance function, unless the battery cells are consistent The balance deviates from its own property η2, and the equalization function ensures that the deviation of the battery cell power does not exceed its own consistent characteristics, which can prevent the phenomenon of accelerated aging, undervoltage and zero voltage of individual battery cells. After the battery management system applies the balancing method of the patent of the present invention, the power battery can not only meet the energy demand of the vehicle, but also ensure its own consistent characteristics, so that the purpose of balancing is more clear.

Description of drawings

1 is a schematic diagram of an equalization circuit using discharge equalization according to the present invention;

Figure 2 is a schematic diagram of a balanced target;

Figure 3 is a schematic diagram of a dynamic balance target;

The markings in the figure are as follows: 101-battery unit; 102-parallel discharge resistance at both ends of the battery; 103-microcontroller.

Detailed ways

The technical solutions of the present invention will be further elaborated below with reference to the embodiments and the accompanying drawings.

Example 1

Based on the consistency of the battery cells in the vehicle life cycle and the capacity characteristics of the battery in the vehicle life cycle, this embodiment provides a power balance method for vehicle power battery cells, which is applied to a new energy vehicle. The balancing function of the management system adopts a balancing circuit of discharge balancing, takes the SOC of the battery cell as the judgment basis, and the balancing target applies the dynamic balancing target described in this embodiment.

As shown in FIG. 1 , in the equalization circuit of this embodiment, each battery cell is connected in parallel with a discharge resistor, and the switch of the parallel circuit is controlled by the pin of the microcontroller to be turned on and off. When the microcontroller determines the battery cell that needs to be balanced, it directly controls the switch connected in parallel with the battery cell to close, and the battery cell is discharged and balanced. When the balance is completed, the microcontroller controls the switch to turn off and stop. balanced.

The method includes the following steps:

S10. Specify the vehicle's demand for battery capacity as C1

In the entire life cycle of new energy vehicles, in order to meet the needs of users, vehicles have certain capacity requirements for power batteries. As the mileage of the vehicle increases, the capacity demand of the vehicle for the power battery can be a fixed value or a variable value. This patent specifies that the vehicle's demand for the battery capacity is C1.

S20. The total capacity of the battery assembly is specified as C2

During the use of the power battery, with the increase of the mileage of the vehicle and the passage of time, the capacity of the power battery itself will attenuate. This patent stipulates that the total capacity of the battery assembly is C2.

S30. The percentage of capacity of the battery that cannot be used in the vehicle is specified as £

At present, the new energy vehicle will not exhaust the power in the battery during the use of the power battery. For example, the battery power of the hybrid vehicle is generally used in the range of 30%-70%, so that the battery will have 60% of the power that will not be used. By the way, this patent specifies the percentage of capacity that the battery is not usable in the vehicle as £.

S40. The SOC of the battery cell is used as a condition for judging whether to start cell balance, and the SOC of the battery cell is defined as SOC _CELL , and the average SOC of the battery cells in the entire power battery pack is SOC _AVE

S50. Judge the power consistency of all cells in the entire power battery pack. When the SOC _CELL value of a certain cell exceeds a certain value η of the average SOC _AVE of the battery cells, that is, when SOC _CELL -SOC _AVE ≥ η , the battery management system will control the parallel discharge circuit to discharge the battery cell.

Among them, the calculation formula of η value is as follows:

η=MAX(η1, η2); η1=1-C1/C2-￡;

Among them, η1 is the balanced capacity value of the battery assembly; η2 is the consistency deviation of the battery cell, which is a variable that changes with the increase of mileage, and MAX is a function of the larger value of η1 and η2.

In this embodiment, the consistency deviation η2 is defined as:

η2=(SOC _MAX −SOC _MIN )/2.

If η2<η1, then η=η1, in this case, the battery energy can meet the vehicle demand.

If η2>η1, then η=η2, in this case, the battery has no excess energy balance, and the balance is only to prevent the battery cell from exceeding its own consistent characteristics.

If η2=η1, then η=η2=η1, in this case, the battery energy can meet the vehicle demand.

At the initial stage of vehicle startup and at the end of external charging of the vehicle, the consistency of battery power is judged, and the time required for balancing is calculated after the battery cells are judged to be inconsistent in power. The microcontroller controls the balancing circuit according to the calculated balancing time. The battery cells perform equalization operations.

The method of this embodiment clarifies the goal of balancing the power of the power battery cells, so that the battery management system can more efficiently balance the power of the power battery cells.

The sequence of the above embodiments is only for convenience of description, and does not represent the advantages or disadvantages of the embodiments.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be The technical solutions described in the foregoing embodiments are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (2)

1. a kind of Vehicular dynamic battery monomer electric quantity balancing method characterized by comprising

The demand of S10, regulation vehicle to battery capacity is C1；

S20, regulation battery assembly total capacity value are C2；

S30, regulation battery volume percent unusable on vehicle are ￡；

S40, using the SOC of battery cell as judge whether start electric quantity balancing condition, it is specified that the SOC of battery cell is SOC_CELL, the average SOC of battery cell is SOC in entire power battery pack_AVE；

S50, the judgement of electricity consistency is carried out to monomers all in entire power battery pack, as the SOC of some monomer_CELLValue exceeds The average SOC of battery cell_AVEWhen a certain numerical value η, i.e. SOC_CELL-SOC_AVEWhen >=η, battery management system will control parallel discharge Circuit discharges to the battery cell；

Wherein, the calculation formula of η value is as follows:

η=MAX (η 1, η 2)；η 1=1-C1/C2- ￡；

Wherein, η 1 by battery assembly energy equalization volume value；η 2 is the consistent sexual deviation of battery cell；

Wherein, consistent sexual deviation η 2 are as follows:

η 2=(SOC_MAX–SOC_MIN)/2；

Wherein, SOC_MAXFor the maximum value of battery cell SOC, SOC_MINFor the minimum value of battery cell SOC.

2. Vehicular dynamic battery monomer electric quantity balancing method according to claim 1, which is characterized in that in the step In S50, at vehicle launch initial stage and vehicle external charge latter stage, it is consistent that electricity is carried out to monomers all in entire power battery pack Property judgement；And after judgement obtains the inconsistent battery cell of electricity, calculate and need the balanced time, and controls parallel discharge electricity Road carries out equalization operation according to the time for balance the being calculated battery cell inconsistent to electricity.