CN-121989724-A - Low-temperature slow charging control method for pure electric vehicle

CN121989724ACN 121989724 ACN121989724 ACN 121989724ACN-121989724-A

Abstract

The invention relates to the technical field of electric automobiles and discloses a low-temperature slow charge control method of a pure electric automobile, which comprises the following steps that a battery management system acquires the current state of charge and the current temperature of a battery in response to a low-temperature slow charge starting signal; and receiving the maximum allowable discharge power limit value by the whole vehicle controller, and limiting the initial running power of the battery heating device based on the maximum allowable discharge power limit value so that the power extracted from the battery by the battery heating device does not exceed the maximum allowable discharge power limit value. The invention can cooperatively manage the power flow among the whole vehicle controller, the battery management system, the vehicle-mounted charger and the heater, and can strictly avoid the over-current and over-discharge faults of the battery while ensuring the low-temperature heating requirement.

Inventors

CHEN LIBO
WANG DINGJIANG
WANG BEI
CHENG DONG
LIU YIWEI
LI ZUOHUI
ZHOU XINGCHI

Assignees

重庆长安跨越车辆有限公司

Dates

Publication Date: 20260508
Application Date: 20260330

Claims (8)

1. The low-temperature slow charging control method for the pure electric vehicle is characterized by being applied to a vehicle comprising a battery management system, a whole vehicle controller, a vehicle-mounted charger and a battery heating device, and comprising the following steps of: responding to a low-temperature slow charge starting signal, and acquiring the current state of charge and the current temperature of the battery by a battery management system; If the current state of charge is lower than a preset charge threshold and the current temperature is lower than a preset temperature threshold, the battery management system sends a maximum allowable discharge power limit value to the whole vehicle controller; and receiving the maximum allowable discharge power limit value by the vehicle controller, and limiting the initial operation power of the battery heating device based on the maximum allowable discharge power limit value so that the power extracted from the battery by the battery heating device does not exceed the maximum allowable discharge power limit value.
2. The method for controlling low-temperature slow charging of a pure electric vehicle according to claim 1, wherein the whole vehicle controller obtains the actual output power of the vehicle-mounted charger and the current charging request power sent by the battery management system in real time during the operation of the battery heating device.
3. The method for low-temperature slow charge control of a battery electric vehicle of claim 2, wherein after establishing a stable slow charge connection, the battery management system calculates a heating power required to heat the battery to a target temperature; The battery management system compensates the heating power into the charging request power, and generates and sends a charging requirement containing the compensated charging request power to the whole vehicle controller; And the whole vehicle controller controls the vehicle-mounted charger to output corresponding charging power based on the charging demand.
4. The method for low-temperature slow charge control of a battery electric vehicle of claim 3, further comprising the step of the vehicle controller performing power comparison and limiting: When the current running power of the battery heating device is larger than the actual output power of the vehicle-mounted charger, the vehicle controller compares the current charging request power with the actual output power, and generates a heating power limiting instruction by taking the smaller value of the current charging request power and the actual output power as a reference; And the whole vehicle controller downwards regulates the running power of the battery heating device according to the heating power limiting instruction, so that the running power after the downwards regulation is not more than the actual output power.
5. The method for low-temperature slow charge control of a battery electric vehicle according to claim 4, wherein when the temperature of the battery core is lower than a preset low-temperature threshold value and the current running power of the battery heating device is higher than the rated output power or the real-time output power of the vehicle-mounted charger, the whole vehicle controller is triggered to execute the power comparison and limitation steps.
6. The method for low-temperature slow charge control of a battery electric vehicle according to claim 4, wherein the step of down-regulating the operating power of the battery heating device comprises: And the whole vehicle controller sends a power reduction instruction to the battery heating device until the real-time running power of the battery heating device is smaller than or equal to the actual output power of the vehicle-mounted charger, so as to ensure that the battery is in a non-discharge state or the discharge power is not out of limit in the charging process.
7. The method for low-temperature slow charge control of a battery electric vehicle according to claim 1, wherein the battery management system periodically broadcasts the maximum allowable discharge power limit to the vehicle controller via a preset controller area network identifier.
8. The method for low-temperature slow charge control of a battery electric vehicle according to claim 1, further comprising, after the step of limiting the initial operating power of the battery heating device: And after confirming that the vehicle-mounted charger starts to stably output the charging power, the vehicle-mounted controller releases the power limit on the battery heating device and takes over the request and compensation of the heating power by the battery management system.

Description

Low-temperature slow charging control method for pure electric vehicle Technical Field The invention relates to the technical field of electric automobiles, in particular to a low-temperature slow charging control method for a pure electric automobile. Background In the popularization and application process of the pure electric vehicle, the charging problem in the low-temperature environment is always a key technical problem for restricting user experience and vehicle reliability. Under the low temperature condition, the viscosity of the electrolyte in the lithium ion battery is increased, the ionic conductivity is reduced, the internal resistance of the battery core is obviously increased, and the lithium ions are difficult to insert and extract. This change in physicochemical properties is directly manifested as a substantial decay in the chargeable and dischargeable capabilities of the battery. If the battery is directly charged with high power at this time, lithium dendrites are easily formed on the surface of the negative electrode, and the internal short circuit is caused by puncturing the diaphragm, so that serious safety accidents are caused. Therefore, the battery is preheated in a low-temperature environment, so that the temperature of the battery is raised to a proper working range, and the battery is a necessary premise for ensuring the charging safety and efficiency. The main technical scheme in the industry at present is to adopt a vehicle-mounted high-pressure air heating or water heating heater, namely a WPTC, drive a PTC element to heat by high-voltage electricity, and heat a battery pack by cooling liquid circulation or air convection. However, WPTC is a high-voltage electric load whose rated power is generally high, up to 3kW to 7kW or even more, and the electric power required when it is instantaneously put into operation needs to be supplied from the power cell itself. In the case of a battery having a low SOC and a low temperature, the discharge capacity of the battery itself has been severely limited, and the maximum discharge current limit that can be sustained is far lower than that in the normal temperature state. At this time, the high-power heater is suddenly connected, the power taking power of the high-power heater easily instantaneously breaks through the discharge current protection threshold set by the battery management system, and directly triggers the overcurrent fault protection mechanism of the BMS, so that the charging process is forcibly interrupted, and even the electric core structure inside the battery is possibly damaged, which is the first technical obstacle to be solved urgently. In addition, in a typical scenario of charging with a household ac slow charging pile, the charging power is typically limited to around 3.3 kW. Under such relatively fixed boundary conditions of power supply, the power distribution contradiction of the entire system is further exacerbated if the battery is in a low temperature low SOC state. When WPTC is started to heat, its operating power tends to occupy a significant portion of the output power of the vehicle-mounted charger, and may even completely exceed the full power available from the OBC. In this case, if the control strategy fails to sense and respond to the actual output capability of the OBC and the real-time requirements of the BMS, the WPTC is caused to continuously draw power from the battery side to make up for the shortage of the OBC power. The unexpected battery discharging behavior is very easy to cause deep overdischarge of the battery core under the fragile state of low temperature and low SOC of the battery, and further causes irreversible damage to the service life and safety of the battery. In view of the foregoing, it is often difficult to combine the reliability of charging start, the duration of heating process and the battery safety margin at the same time in the existing control strategy, and there is a need for an intelligent control method capable of coordinating the power relationship among the battery, the charger and the heater from the system level. Disclosure of Invention The invention aims to provide a low-temperature slow charging control method for a pure electric vehicle, which can cooperatively manage power flows among a whole vehicle controller, a battery management system, a vehicle-mounted charger and a heater, and can strictly avoid battery overcurrent and overdischarge faults while guaranteeing low-temperature heating requirements. The basic scheme provided by the invention is that the low-temperature slow charge control method of the pure electric vehicle is applied to a vehicle comprising a battery management system, a whole vehicle controller, a vehicle-mounted charger and a battery heating device, and comprises the following steps of: responding to a low-temperature slow charge starting signal, and acquiring the current state of charge and the current temperature of the battery by a ba