阅读说明：本技术 一种动力电池系统及低温充电优化加热策略的充电方法 (Power battery system and charging method for low-temperature charging optimized heating strategy ) 是由 李倩 何帅强 孙光忠 宋小梅 于 2019-09-23 设计创作，主要内容包括：本发明涉及电动汽车充电技术领域,公开了一种动力电池系统及低温充电优化加热策略的充电方法,动力电池系统在低温条件下充电时,利用加热系统来升温,当温度达到允许小电流充电时,加热和充电同时进行,加热系统产生的热量加上动力电池系统自身的反应热、焦耳热提高动力电池系统温度,使动力电池系统温度快速上升,且快速处于额定持续大电流充电的过程,缩短低温条件下的充电时间。停止加热的温度点确认为动力电池放热量与加热系统产生热量的平衡点,不会出现加热系统停止后温度持续下降导致反复启动加热系统的问题,达到了低温条件下充电时间短、避免出现反复启动加热系统的效果。(The invention relates to the technical field of electric vehicle charging, and discloses a power battery system and a charging method for a low-temperature charging optimization heating strategy. The heating stopping temperature point is determined as the balance point of the heat release of the power battery and the heat generated by the heating system, the problem that the heating system is repeatedly started due to the fact that the temperature continuously drops after the heating system stops cannot occur, and the effects that the charging time is short and the heating system is repeatedly started under the low-temperature condition are achieved.)

1. A power battery system, characterized in that: including charging circuit, heating circuit, battery management system, charging circuit is equipped with total negative relay, charging relay, heating circuit is equipped with heating system, and heating system includes heating relay, heater, heating circuit with total negative relay, the parallelly connected setting of charging relay, total negative relay charging relay heating relay all with battery management system links to each other, but battery management system gathers the interior battery temperature of power battery system.

2. A power cell system according to claim 1, wherein: the heater is PTC hot plate or adds the hotting mask, charge the return circuit with all be equipped with current sensor on the heating circuit, current sensor with battery management system links to each other.

3. A charging method for optimizing a heating strategy in low-temperature charging is characterized by comprising the following steps: comprises the following steps

Connecting a charging gun of a charging pile with a power battery system, confirming a signal, successfully shaking hands of a battery management system and the charging pile, and detecting the lowest temperature T of a battery in the power battery system by the battery management system;

step two, the lowest temperature T of the battery is less than T₀When the battery is in a heating mode and charging is not allowed, the power battery system sends a request voltage U₁Requesting a current I₁Heating; when T > T₁Then, entering the third step;

step three, the lowest temperature T of the battery₀≤T＜T₂Meanwhile, heating and charging are carried out simultaneously, and the power battery sends a request voltage U₂Requesting a current I₂(ii) a When the lowest temperature T of the battery is more than T₃When the charging is finished, stopping heating and entering a normal charging mode; t is₃The balance temperature point is the discharge heat of the power battery and the heat generated by the heating system;

step four, the lowest temperature T of the battery is more than or equal to T₂The battery management system sends a request voltage U₃Request current I₃And entering a normal charging mode.

4. The charging method of a low temperature charging optimized heating strategy of claim 3, wherein: request voltage U₁For heating the system rated voltage, request voltage I₁Power P/U of heating system₁(ii) a Request voltage U₂Request voltage U₃For charging voltage of power battery system, request current I₂＝I₁+ charging current, request current I₃The charging current of the power battery system is obtained.

5. A cryogenic temperature according to claim 4The charging method of the charging optimization heating strategy is characterized in that: when the battery in the power battery system is a ternary battery, the request voltage U is₁The required voltage U is 3.65V of the battery system string number₂The number of battery system strings is 4.2V; when the battery in the power battery system is a lithium iron battery, the power battery system requests a voltage U₁The requested voltage was 3.65V by battery system string number.

6. The charging method of the low-temperature charging optimized heating strategy of claim 4, wherein: t is₀In the range of-5 to 0 ℃ and T₁The range of (B) is 5-10 ℃.

7. The charging method of the low-temperature charging optimized heating strategy of claim 4, wherein: t is₂The range of (A) is 10-15 ℃.

8. The charging method of the low-temperature charging optimized heating strategy of claim 4, wherein: heat generated by heating system

9. The charging method of a low temperature charging optimized heating strategy according to claim 4 or 8, characterized in that: t is₃The range of (A) is 16-20 ℃.

10. The charging method of the low-temperature charging optimized heating strategy of claim 4, wherein: and step five, charging according to the charging power table and the terminal charging strategy until a charging cutoff condition is reached, and finishing charging.

Technical Field

The invention relates to the technical field of electric automobile charging, in particular to a power battery system and a charging method for a low-temperature charging optimized heating strategy.

Background

With the global demand and attention on energy and environmental protection problems, new energy automobiles come into operation, because the automobiles meet the requirements of social sustainable development. In addition, the policy of our country for new energy vehicles encourages and subsidizes, electric vehicles in China are also increasingly popularized, and various vehicle types such as commercial vehicles and passenger vehicles are widely applied.

The lithium ion battery is used as a power source of a new energy automobile, belongs to an important component of the new energy automobile, and the performance of the lithium ion battery directly influences the use of the electric automobile. Among all environmental factors, the temperature has the greatest influence on the charge and discharge performance of the lithium battery, and the electrochemical reactions of the anode, the cathode and the electrolyte are all related to the environmental temperature. Under the condition of low temperature, the activity of the anode and cathode materials is reduced, the conductivity of the electrolyte is also reduced, the charging capability is reduced, and only small current charging or no charging is allowed; the discharge capacity is reduced, the internal resistance of the low-temperature discharge battery is increased, the available capacity is reduced, and the cycle life of the battery is influenced. When the lithium cell was less than 0 ℃ in the temperature, most lithium cells were not allowed to charge, in order to solve the low temperature problem of charging, power battery can increase design heating system, opens heating circuit earlier in the low temperature charging stage, utilizes PTC hot plate or heating film heating to improve battery system temperature, waits to open again after the temperature rise to charge. However, the unreasonable heating strategy in the low-temperature charging process can cause repeated opening of the heating loop or too long low-temperature charging time, which leads to poor experience of consumers and great complaints of users.

Therefore, the applicant provides a charging method for optimizing a heating strategy for charging under a low-temperature condition, and the charging method is mainly used for solving the problems that the charging time of the electric automobile is too long and a heating system is repeatedly started under the low-temperature condition.

Disclosure of Invention

The invention aims to provide a power battery system and a charging method of a low-temperature charging optimization strategy, which have the technical effect of avoiding repeatedly starting a heating system under the low-temperature condition of the power battery system.

The invention provides a power battery system which comprises a charging loop, a heating loop and a battery management system, wherein the charging loop is provided with a total negative relay and a charging relay, the heating loop is provided with a heating system, the heating system comprises a heating relay and a heater, the heating loop is connected with the total negative relay and the charging relay in parallel, the total negative relay, the charging relay and the heating relay are all connected with the battery management system, and the battery management system can acquire the temperature of a battery in the power battery system.

By adopting the technical scheme, the Battery management system, namely a Battery Management System (BMS) is an indispensable part of the power Battery system, and has the function of monitoring and controlling the charging and discharging processes of the Battery according to the use environment, so that the energy stored in the Battery is utilized to the maximum extent on the premise of ensuring the safety of the Battery. The battery management system is mainly used for battery temperature acquisition, voltage monitoring, charge state estimation, communication with a charger, safety protection and the like.

The relay is an automatic switch element with an isolation function, and the battery management system drives the control coil through a high side or a low side to drive the load loop to be attracted or disconnected.

The invention is further provided with: the heater is PTC hot plate or adds the hotting mask, charge the return circuit with all be equipped with current sensor on the heating circuit, current sensor with battery management system links to each other.

By adopting the technical scheme, the current sensor is a detection device, can sense the information of the current of the detected loop, and can output the sensed information through electric signals or other required forms of information so as to meet the requirements of information transmission, processing, storage, display, recording, control and the like. The battery management system acquires current information in a battery charging and heating loop through a current sensor.

The fuse is an electric appliance which fuses a melt by heat generated by itself to open a circuit when a current exceeds a predetermined value. The fuse is mainly used for overload and short-circuit protection, and the fuse can be arranged on the charging loop and the heating loop.

The PTC heating plate or the heating film is self-heated after power supply to raise the resistance value to enter a jump zone, the surface temperature of the heating plate or the heating film is kept at a constant value, the temperature is only related to the Curie temperature and the applied voltage of the heating plate or the heating film and is basically unrelated to the ambient temperature, the battery core is heated to raise the temperature of the battery, and the battery is in the proper temperature to carry out large-current charging.

The invention provides a charging method of a low-temperature charging optimization strategy, which comprises the following steps of firstly, connecting a charging gun of a charging pile with a power battery system, confirming a signal, successfully shaking hands of a battery management system and the charging pile, and detecting the lowest temperature T of a battery in the power battery system by the battery management system; step two, the lowest temperature T of the battery is less than T₀When the battery is in a heating mode and charging is not allowed, the power battery system sends a request voltage U₁Requesting a current I₁Heating; when T > T₁Then, entering the third step; step three, the lowest temperature T of the battery₀≤T＜T₂Meanwhile, heating and charging are carried out simultaneously, and the power battery sends a request voltage U₂Requesting a current I₂(ii) a When the lowest temperature T of the battery is more than T₃When the charging is finished, stopping heating and entering a normal charging mode; t is₃The balance temperature point is the discharge heat of the power battery and the heat generated by the heating system; step four, the lowest temperature T of the battery is more than or equal to T₂The battery management system sends a request voltage U₃Request current I₃And entering a normal charging mode.

The invention is further provided with: request voltage U₁For heating the system rated voltage, request voltage I₁Power P/U of heating system₁(ii) a Request voltage U₂Request voltage U₃For charging voltage of power battery system, request current I₂＝I₁+ charging current, request current I₃The charging current of the power battery system is obtained.

The invention is further provided with: power batteryWhen the battery in the system is a ternary battery, the voltage U is requested₁The required voltage U is 3.65V of the battery system string number₂The number of battery system strings is 4.2V; when the battery in the power battery system is a lithium iron battery, the power battery system requests a voltage U₁The requested voltage was 3.65V by battery system string number.

By adopting the technical scheme: the ternary battery refers to a ternary polymer lithium battery.

The invention is further provided with: t is₀In the range of-5 to 0 ℃ and T₁The range of (B) is 5-10 ℃.

By adopting the technical scheme, namely T is more than or equal to-5 DEG C₀≤0℃，5℃≤T₁≤10℃

The invention is further provided with: t is₂The range of (A) is 10-15 ℃.

By adopting the technical scheme, the temperature T is more than or equal to 10 DEG C₂≤15℃。

The invention is further provided with: heat generated by heating system

In the formula

The heat generated by the battery heating system in unit time is expressed in unit J/S; c is the equivalent specific heat capacity of the lithium battery, and the unit J/(kg DEG C); m is the mass of the battery system and is Kg; dT/dT is the rate of change of temperature with time; discharge heat of power battery system

In the formulaIs the battery heating power, unit W; i is the charging current of the battery system, the discharging is positive, the charging is negative, and the unit A is; e is the battery system terminal voltage, unit V; e₀For open circuit of battery systemPressure, unit V; t is the temperature of the battery system in unit ℃; dE0/dT is the temperature coefficient; when in use

When the temperature is higher than the set temperature, the balance temperature point of the discharge heat of the power battery and the heat generated by the heating system is reached, and the battery temperature of the power battery system is T₃。

Through adopting above-mentioned technical scheme, the battery in the power battery system adopts the lithium cell, and the heat production mainly includes joule heat and reaction heat, adopts above-mentioned scheme to calculate.

The invention is further provided with: t is₃The range of (A) is 16-20 ℃.

By adopting the technical scheme, the temperature T is more than or equal to 16 DEG C₃≤20℃。

The invention is further provided with: and step five, charging according to the charging power table and the terminal charging strategy until a charging cutoff condition is reached, and finishing charging.

The invention has the beneficial effects that: when the power battery system is charged under the low-temperature condition, the heating system is utilized to raise the temperature, when the temperature reaches the temperature which allows the low-current charging, the heating and the charging are carried out simultaneously, the heat generated by the heating system and the reaction heat and the Joule heat of the power battery system improve the temperature of the power battery system, so that the temperature of the power battery system is quickly increased, the power battery system is quickly in the rated continuous high-current charging process, and the charging time under the low-temperature condition is shortened. The heating stopping temperature point is determined as the balance point of the heat release of the power battery and the heat generated by the heating system, the problem that the heating system is repeatedly started due to the fact that the temperature continuously drops after the heating system stops cannot occur, and the effects that the charging time is short and the heating system is repeatedly started under the low-temperature condition are achieved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is an electrical schematic of the power battery system of the present invention.

FIG. 2 is a control flow diagram of the low temperature charge optimization strategy of the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.