CN107139742A - Vehicular dynamic battery monomer electric quantity balancing method - Google Patents

Abstract

The invention discloses a method for balancing the power of a single power battery for a vehicle. After the method of the invention is applied to a battery management system, the power of a 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, equalization can keep the power of the single power battery within the range of SOC _AVE ± η1, and the power consumed by the battery management system for balance is 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 equalization can keep the power of the power battery within the range of SOC _AVE ± η2. The equalization function ensures that the deviation of the power of the single battery does not exceed its own consistent characteristics, which can prevent individual batteries from Accelerated aging, under-voltage, and zero-voltage phenomena of the single cell can make the power battery not only meet the energy demand of the vehicle but also ensure its own consistent characteristics, thus making the purpose of equalization more clear.

Description

Electricity balance method for vehicle power battery cells

technical field

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

Background technique

As an energy storage unit of new energy vehicles, 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 even 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 environment of the battery cannot be guaranteed to be consistent, it is difficult to ensure that the power of the battery cells inside the battery is consistent. This requires the battery management system to balance the power of the battery. The power state of the monomer is balanced. In practice, the inconsistency of the battery capacity will accelerate the attenuation of the capacity of the battery assembly, reduce the energy utilization efficiency of the vehicle, and affect the performance of the vehicle.

At present, the battery cell power balance methods proposed by domestic and foreign automobile manufacturers, battery manufacturers and scientific research institutions can be roughly divided into two categories. First, it focuses on parallel connection of chargeable and dischargeable circuits at the positive and negative ends of the battery cell. After judging the inconsistency of the electric quantity of the battery cell, charge and discharge the battery cell to achieve the purpose of balancing the electric quantity of the battery cell. Due to the low reliability and cost of the parallel charge and discharge circuit, this method is not suitable for vehicles. The practical significance of battery cell power balance is small; second, it focuses on connecting the dischargeable circuit in parallel at the positive and negative ends of the battery cell. After judging the inconsistent state of the battery cell power, in order to meet the capacity demand of the vehicle And performance requirements, discharge operation on the battery cells to achieve the purpose of balancing the power of the battery cells. Due to the simple parallel discharge circuit, high reliability and low cost, this method is more suitable for the power balance of the vehicle power battery cells.

To sum up, using a parallel discharge circuit at both ends of the battery cell to balance the battery cell has the advantages of simple and reliable circuit, low cost, and high feasibility. It is an effective way to balance the charge of the vehicle power battery cell.

Contents of the invention

The object of the present invention is a method for balancing the power of a single power battery for a vehicle, which clarifies the target of power balance of a single power battery, so that the battery management system can balance the power of a single power battery more efficiently.

The present invention adopts the following technical solution to solve the technical problem: a method for balancing the power of a vehicle power battery unit, which includes:

S10. It is stipulated that the vehicle's demand for battery capacity is C1;

S20, specifying that the total capacity of the battery assembly is C2;

S30. It is stipulated that the percentage of capacity of the battery that cannot be used in the vehicle is £;

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

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

Optionally, wherein, 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 cells.

Optionally, wherein, the consistency deviation η2 is:

η2=( _SOCMAX - _SOCMIN )/2;

Wherein, 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 external charging of the vehicle, the power consistency of all cells in the entire power battery pack is judged; A time for equalization is needed, and the equalization circuit is controlled to perform equalization operations on 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 electric quantity 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, equalization can keep the power of the single power battery within the range of SOC _AVE ± η1, and the power consumed by the battery management system for balance is power battery redundancy The designed power balance does not affect the vehicle's demand for battery power. In the second half of the vehicle's life cycle, η2>η1, at this time, equalization can keep the battery power of the power battery within the range of SOC _AVE ± η2, and the battery management system has rarely turned on the equalization function, unless the battery cells are consistent. Sexuality deviates from its own property η2, and the equalization function ensures that the deviation of the battery's single power does not exceed its own consistent characteristics, which can prevent individual battery cells from accelerated aging, undervoltage, and zero voltage. After the battery management system applies the equalization 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 equalization is more clear.

Description of drawings

Fig. 1 is a schematic diagram of an equalization circuit adopting discharge equalization of the present invention;

Fig. 2 is a schematic diagram of an equilibrium target;

Fig. 3 is a schematic diagram of a dynamic equilibrium target;

The marks in the figure are: 101-battery monomer; 102-discharge resistors connected in parallel at both ends of the battery; 103-microcontroller.

detailed description

The technical solutions of the present invention will be further described below in conjunction with the embodiments and the accompanying drawings.

Example 1

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

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

The method comprises the steps of:

S10. It is stipulated that the vehicle's demand for battery capacity is C1

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

S20. It is stipulated that the total capacity of the battery assembly is C2

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

S30. It is stipulated that the percentage of the capacity of the battery that cannot be used on the vehicle is ￡

At present, new energy vehicles will not run out of power in the power battery during the use of the power battery. For example, the use range of the battery power of a hybrid vehicle is generally 30%-70%, so that 60% of the battery power will not be used. It is understood that this patent stipulates that the percentage of capacity of the battery that cannot be used on the vehicle is ￡.

S40. Use the SOC of the battery cell as the condition for judging whether to start power balancing, specify 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. Judging the power consistency of all cells in the entire power battery pack, when the SOC _CELL value of a cell exceeds a certain value η of the average SOC _AVE of the battery cell, that is, SOC _CELL -SOC _AVE ≥ η , the battery management system will control the parallel discharge circuit to discharge the battery cell.

Wherein, the calculating 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 taking the larger value of η1 and η2.

In this embodiment, 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 needs of the vehicle.

If η2>η1, then η=η2, in this case, the battery has no redundant 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 start-up and the end of external charging of the vehicle, the consistency state of the battery power is judged, and the time required for equalization is calculated after judging the inconsistent battery cells, and the microcontroller controls the equalization circuit according to the calculated equalization time. The battery cells perform a balancing operation.

The method of this embodiment clarifies the target of power balance of the single power battery, so that the battery management system can balance the power of the single power battery more efficiently.

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, rather than 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 Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; 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 various embodiments of the present invention.

Claims (4)

1. a kind of Vehicular dynamic battery monomer electric quantity balancing method, it is characterised in that including：

S10, regulation vehicle are C1 to the demand of battery capacity；

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 the condition for judging whether to start electric quantity balancing, the SOC of regulation battery cell is SOC_CELL, the average SOC of battery cell is SOC in whole electrokinetic cell bag_AVE；

S50, electricity uniformity is carried out to all monomers in whole electrokinetic cell bag judge, as the SOC of some monomer_CELLValue Beyond the average SOC of battery cell_AVEDuring a certain numerical value η, i.e. SOC_CELL-SOC_AVEDuring >=η, battery management system will control in parallel Discharge circuit discharges the battery cell.

2. Vehicular dynamic battery monomer electric quantity balancing method according to claim 1, it is characterised in that

Wherein, the calculation formula of η values 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.

3. Vehicular dynamic battery monomer electric quantity balancing method according to claim 2, it is characterised in that

Wherein, consistent sexual deviation η 2 is：

η 2=(SOC_MAX–SOC_MIN)/2；

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

4. Vehicular dynamic battery monomer electric quantity balancing method according to claim 3, it is characterised in that in the step In S50, at vehicle launch initial stage and vehicle external charge latter stage, electricity is carried out to all monomers in whole electrokinetic cell bag consistent Property is judged；And after judging to draw the inconsistent battery cell of electricity, the time in a balanced way that needs is calculated, and control balanced electricity Road carries out equalization operation according to the time for balance calculated the battery cell inconsistent to electricity.