Lithium battery charging and heating control method for reverse three wheels

Abstract

The invention discloses a lithium battery charging and heating control method for reverse three wheels, which comprises the following steps: (1) firstly, heating a battery pack, and if a three-stage fault is triggered, carrying out a high-voltage process; (2) if the third-level fault is not triggered, obtaining the temperature of each unit of the battery in the battery pack; (3) if it is detected that the temperature in the battery is smaller than or equal to 17 DEG C and smaller than or equal to 28 DEG C, the charging condition is met, a main negative relay and a charging relay are closed in sequence, and charging request voltage: 3.65 V * string number and current are sent; (3A) when it is detected that the actual charging current is larger than 0.5 A (lasting for 3S), a heating relay is closed, a charging-while-heating stage is entered, and a charging-while-heating request is sent; and (4) if the temperature Tmin in the battery is detected to be greater than or equal to 20 DEG C or Tmax is detected to be greater than or equal to 30 DEG C, entering a charging only stage, directly disconnecting the heating relay, and sending a charging only request. The battery pack preheating strategy based on heating target temperature optimization is adopted, and the performance and the endurance mileage of the battery in the low-temperature environment are improved.

Description

Technical Field

[0001] The invention relates to the technical field of three-wheel batteries, and in particular to a charging and heating control method for a lithium battery used in a reverse three-wheel vehicle. Background Art

[0002] With the technological development of reverse three-wheelers and the expansion of the domestic market, when reverse three-wheelers are used in the Northeast region, low temperatures often occur in winter. When reverse three-wheel electric vehicles are parked in low temperature environments in winter, the power battery temperature will reach a low temperature state of the ambient temperature in a short time. The charging and discharging capabilities of lithium power batteries will be limited or even reduced to 0 in low temperature states. Lithium power batteries used in low temperature environments for a long time will lead to a decrease in battery capacity.

[0003] In order to optimize the low-temperature charging and discharging performance of the power battery of the reverse three-wheeler, it is necessary to increase the temperature of the power battery, so a power battery pack heating function is set in a low-temperature environment.

[0004] At present, the above technologies mainly have the following disadvantages:

[0005] 1. When the reverse tricycle is in a short-distance driving with a high SOC (state of charge), if the battery temperature is directly heated once it falls below the set threshold, a large amount of electric energy will be consumed without further increasing the battery capacity. As a result, after the battery is heated, the vehicle's endurance cannot be effectively improved, and may even be more seriously attenuated.

[0006] 2. Charging the power battery requires that the temperature of the power battery is within an appropriate temperature range. If the temperature of the power battery is too low, the power battery needs to be heated before charging. However, in the prior art, the charging operation of the power battery is directly connected to a DC power supply and heated by an additional heating component, resulting in large energy loss and high charging costs.

[0007] In order to improve the cruising range of electric vehicles in low temperature environments, a battery pack preheating strategy based on heating target temperature optimization can be adopted. First, the maximum discharge energy of the battery at different temperatures is determined through experimental tests; secondly, based on the energy retention rate of the battery at different temperatures and considering the impact of temperature on battery life, a nonlinear multi-objective constraint equation is established and solved to obtain the optimal heating target temperature of the battery under different ambient temperatures and different SOC states; finally, the heating strategy is verified based on the vehicle physical model calibrated with measured data. For lithium batteries of reverse three-wheeled vehicles, a similar method can be used to determine the optimal heating target temperature based on their actual use, thereby improving the performance and cruising range of the battery in low temperature environments. Summary of the invention

[0008] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a lithium battery charging and heating control method for a reverse tricycle, which adopts a battery pack preheating strategy based on heating target temperature optimization to improve the performance and cruising range of the battery in low temperature environments.

[0009] In order to achieve the above object, the present invention is implemented by the following technical solution: a lithium battery charging and heating control method for a reverse tricycle, comprising the following steps:

[0010] 1. First, heat the battery pack. If a level 3 fault is triggered, perform the high-voltage process.

[0011] 2. If the level 3 fault is not triggered, obtain the temperature of each battery unit in the battery pack;

[0012] 3. If the temperature inside the battery is detected to be Tmin≤17℃ and Tmax≤28℃ (the above values ​​will be adjusted in different products), the charging conditions are met, the main load and charging relay are closed in sequence, and a charging request voltage is sent: 3.65V*number of strings, current: 3A, and the actual charging current is detected to be >0.5A (for 3S), the heating relay is closed, and the charging and heating stage is entered, and a charging and heating request is sent;

[0013] 4. If the temperature inside the battery is detected to be Tmin ≥ 20℃ or Tmax ≥ 30℃ (the above values ​​will be adjusted in different products), it will enter the charging-only stage, directly disconnect the heating relay, and send a charging-only request.

[0014] The lower high voltage process in step 1 is: disconnect the heating relay, the charging relay, and the main negative relay in sequence.

[0015] When the heating relay is closed, the charging request is the heating current and the table value (when Tmin<0℃, the charging table value is 0, and only the heating current value is available at this time)

[0016] When the heating relay is not closed, the charging request is a table lookup value.

[0017] The present invention has the following beneficial effects:

[0018] 1. Improve charging and discharging efficiency: Low temperature will increase the internal resistance of the battery, thereby reducing the charging and discharging efficiency. Heating the battery pack can reduce the internal resistance of the battery and make the current flow more smoothly inside the battery. For example, the charging time may be doubled or even more at low temperatures, but by heating the battery pack, the charging time can be shortened and the charging efficiency can be improved.

[0019] 2. Enhance battery power output: At low temperatures, the power output capacity of the battery will be greatly limited. For example, the acceleration performance of electric vehicles may be significantly reduced at low temperatures, and the climbing ability will also be weakened. Heating the battery pack can increase the power output of the battery, so that the vehicle can still maintain good power performance in low temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments;

[0021] Figure 1 It is a control flow chart of the present invention. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0023] Reference Figure 1 , this specific implementation adopts the following technical solution: A lithium battery charging and heating control method for a reverse tricycle, comprising the following steps:

[0024] 1. First, heat the battery pack. If a level 3 fault is triggered, perform the high-voltage process.

[0025] 2. If the level 3 fault is not triggered, obtain the temperature of each battery unit in the battery pack;

[0026] 3. If the temperature inside the battery is detected to be Tmin≤17℃ and Tmax≤28℃, the charging conditions are met, and the main load and charging relay are closed in sequence, and a charging request voltage is sent: 3.65V*number of strings, current: 3A, and the actual charging current is detected to be >0.5A (for 3S), and the heating relay is closed to enter the charging and heating stage, and a charging and heating request is sent;

[0027] 4. If the temperature inside the battery is detected to be Tmin ≥ 20°C or Tmax ≥ 30°C, the charging-only stage is entered, the heating relay is directly disconnected, and a charging-only request is sent.

[0028] The specific description of charging heat in this specific implementation method is as follows:

[0029] 1. Charging heating on and off temperature

[0030] Opening temperature: Tmin≤17℃ and Tmax≤28℃;

[0031] Shutdown temperature: Tmin ≥ 20°C or Tmax ≥ 30°C;

[0032] 2. Heating film specifications

[0033] Specifications: Voltage: 3.65V*number of strings, current: 3A.

[0034] 3. Charging and heating process

[0035] ① During the charging process, it is detected that Tmin≤17℃ and Tmax≤28℃, and the charging conditions are met. The main load and charging relay are closed in sequence, and a charging request voltage: 3.65V*number of strings, current: 3A. The actual charging current is detected to be greater than 0.5A (lasting 3S). The heating relay is closed and the charging and heating stage is entered. A charging and heating request is sent, voltage: 3.65*S; current: charging current + heating current.

[0036] ② If Tmin≥20℃ or Tmax≥30℃ is detected, the charging-only stage is entered, the heating relay is directly disconnected, and a charging-only request is sent. Voltage: 3.65*S Current: charging current.

[0037] ③ During the heating process, a charging level 3 fault is triggered. It is necessary to follow the charging high voltage process and execute the high voltage reduction, disconnecting the heating relay, charging relay, and main negative relay in sequence.

[0038] ④Note:

[0039] When the heating relay is closed, the charging request is the heating current and the table value (when Tmin<0℃, the charging table value is 0, and only the heating current value is available at this time);

[0040] When the heating relay is not closed, the charge request is the table lookup value.

[0041] 4. Charging heating failure

[0042] ① No current during charging for 5 minutes: If the charging relay is closed and there is no current output for 5 minutes, handle the charging level 3 fault, prohibit charging and heating, and restart to recover.

[0043] ② Abnormal heating temperature rise: The heating relay is closed for more than 6 hours, Tmin<0℃, and a heating fault is reported. It is handled according to the charging level 3 fault, charging and heating are prohibited, and the battery is restarted to recover.

[0044] ③ Abnormal charging and heating current: During the charging and heating process, if the discharge current is detected to be greater than 2A and lasts for 10 minutes, the abnormal charging and heating current fault will be reported and handled according to the charging level 3 fault. Charging and heating are prohibited and the system will be restarted to recover.

[0045] Heating the battery pack is an important part of the battery thermal management system. Under different working environments, the battery temperature can be kept within a safe range through reasonable heating and cooling strategies. For example, in the cold winter, heating the battery pack can ensure that the battery is at a suitable temperature when starting, avoiding performance degradation and safety issues caused by low temperature. In the hot summer, the thermal management system can prevent the battery from overheating through cooling measures.

[0046] A good thermal management system can improve the safety and reliability of the battery and extend the battery life. At the same time, it can also improve the consistency of the battery pack, reduce the performance differences caused by temperature differences, and improve the stability of the entire system.

[0047] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A lithium battery charging and heating control method for a reverse tricycle, characterized in that: The following steps are involved: (1) First, heat the battery pack. If a level 3 fault is triggered, the high-voltage process is performed. (2) If the level 3 fault is not triggered, obtain the temperature of each battery unit in the battery pack; (3) If the temperature inside the battery is detected to be Tmin≤17℃ and Tmax≤28℃, the charging conditions are met, the main load and charging relay are closed in sequence, and a charging request voltage is sent: 3.65V*number of strings, current: 3A, and the actual charging current is detected to be greater than 0.5A (for 3S), the heating relay is closed, and the charging and heating stage is entered, and a charging and heating request is sent; (4) If the temperature inside the battery is detected to be Tmin ≥ 20°C or Tmax ≥ 30°C, the charging-only stage is entered, the heating relay is directly disconnected, and a charging-only request is sent.

2. A lithium battery charging and heating control method for a reverse tricycle according to claim 1, characterized in that: The lower high voltage process in step (1) is: disconnecting the heating relay, the charging relay, and the main negative relay in sequence.

3. The method for controlling charging and heating of a lithium battery for a reverse tricycle according to claim 1, characterized in that: When the heating relay is closed, the charging request is the heating current and the table lookup value. When Tmin<0℃, the charging table lookup value is 0, and at this time there is only the heating current value.

4. The method for controlling charging and heating of a lithium battery for a reverse tricycle according to claim 1, characterized in that: When the heating relay is not closed, the charging request is a table lookup value.

Images