CN-121973675-A - Low-temperature charging management method and system for pure electric vehicle

CN121973675ACN 121973675 ACN121973675 ACN 121973675ACN-121973675-A

Abstract

The invention relates to the technical field of electric automobiles and discloses a low-temperature charging management method and a system for a pure electric automobile, wherein the method comprises the following steps that in response to the vehicle entering a low-temperature charging mode, a BMS judges that the battery temperature is lower than a first preset temperature threshold, and a VCU acquires the maximum allowable discharging power of a power battery sent by the BMS; and after the water heater PTC enters a stable heating stage, the BMS calculates the running consumption power of the water heater PTC in real time and compensates the running consumption power into the charging current required by the charging pile so as to maintain the charging power of the power battery pack. The invention can furthest improve the overall efficiency of low-temperature quick charge and the service life of the battery cell on the premise of ensuring safety.

Inventors

HE SHAN
WANG BEI
LI RENJIE
CHENG DONG
LIU YIWEI
LI ZUOHUI
ZHOU XINGCHI

Assignees

重庆长安跨越车辆有限公司

Dates

Publication Date: 20260505
Application Date: 20260327

Claims (10)

1. The low-temperature charging management method for the pure electric vehicle comprises a battery management system BMS, a whole vehicle controller VCU and a water heater PTC for heating a power battery pack, and is characterized by comprising the following steps of: Responding to the vehicle entering a low-temperature charging mode, judging that the battery temperature is lower than a first preset temperature threshold value by the BMS, and acquiring the maximum allowable discharging power of the power battery sent by the BMS by the VCU; In the initial stage of starting the water heater PTC to heat the power battery pack, the VCU limits the actual running power of the water heater PTC according to the maximum allowable discharging power of the power battery so as not to exceed the maximum allowable discharging power of the power battery; After the water heater PTC enters the stable heating stage, the BMS calculates the operation consumption power of the water heater PTC in real time and compensates the operation consumption power into the charging current requested to the charging pile to maintain the charging power of the power battery pack.
2. The low-temperature charge management method for a pure electric vehicle according to claim 1, further comprising the steps of: After the water heater PTC finishes heating the power battery pack, the BMS acquires the temperatures of a plurality of battery cores in the power battery pack and calculates the maximum temperature difference; When the maximum temperature difference exceeds a second preset temperature threshold, the VCU starts a circulating water pump to drive cooling liquid to circulate in the power battery pack until the maximum temperature difference is reduced below a third preset temperature threshold so as to balance the temperature of the battery cells.
3. The low-temperature charge management method for a pure electric vehicle according to claim 1, wherein the BMS determines that the battery temperature is lower than a first preset temperature threshold, and issues a heating request to the VCU when the battery state of charge SOC is lower than a preset SOC threshold.
4. The low-temperature charge management method for a pure electric vehicle according to claim 1, wherein the VCU periodically receives a message containing a maximum allowable power discharge current or power of the power battery from the BMS through a controller area network CAN bus, and determines the maximum allowable power discharge of the power battery based on the message.
5. The low-temperature charge management method for a pure electric vehicle according to claim 1, wherein the VCU adopts a closed-loop control manner to dynamically adjust the power of the PTC of the water heater so that its actual operating power is always lower than or equal to the maximum allowable discharge power of the power battery.
6. The low-temperature charge management method for a pure electric vehicle according to claim 1, wherein when the BMS calculates the operation consumption power of the water heater PTC in real time, it comprises the following operations: The BMS acquires a charging current value requested by the BMS to the charging pile, detects the charging current value actually output by the charging pile, calculates a difference value between the requested current value and the actual current value, and determines the running consumption power of the PTC of the water heater according to the difference value and the current power battery pack voltage.
7. The low-temperature charge management method for a pure electric vehicle according to claim 6, wherein the compensating the operation consumption power into the charging current requested to the charging pile comprises the operations of: and the BMS stacks the basic request current for charging the power battery and the compensation current corresponding to the PTC operation consumption power of the water heater, and generates and sends the final charging request current to the charging pile.
8. The low temperature charge management method for a pure electric vehicle according to claim 1, wherein, in the charging process, when the BMS detects that the battery temperature rises to a preset exit temperature higher than the first preset temperature threshold, it stops sending a heating request to the VCU and exits the stable heating stage.
9. The low-temperature charge management method for a pure electric vehicle according to claim 1, further comprising, between the initial stage and the steady heating stage: The BMS judges whether the charging current has reached a steady state, and confirms that the steady heating phase has been entered when the actual charging current is stabilized around the charging current value requested by the BMS.
10. The low-temperature charge management system for a pure electric vehicle according to any one of claims 1 to 9, characterized by being configured to perform the low-temperature charge management method for a pure electric vehicle, comprising: the battery management system BMS is used for acquiring state parameters of the power battery pack, wherein the state parameters at least comprise battery temperature, battery state of charge (SOC), maximum allowable battery discharge power and actual charging current, and generating and sending a heating request signal, a temperature equalization request signal and a charging current request to the direct current charging pile according to the state parameters; The vehicle control unit VCU is in communication connection with the BMS and is respectively in control connection with a water heater PTC for heating a power battery pack and a circulating water pump for driving cooling liquid to circulate, and is used for receiving a heating request signal sent by the BMS and the maximum allowable discharge power of the battery, and limiting the actual running power of the water heater PTC according to the maximum allowable discharge power of the battery in the initial stage of starting the water heater PTC so as not to exceed the maximum allowable discharge power of the battery; The BMS is also used for calculating the running consumption power of the water heater PTC in real time according to a basic charging current request value sent to the charging pile and a detected actual charging current value after the water heater PTC enters a stable heating stage, and compensating the running consumption power to a final charging current request sent to the charging pile; The VCU is also used for responding to the temperature equalization request signal and starting the circulating water pump to drive cooling liquid to circulate in the power battery pack so as to balance the temperature of the battery cells.

Description

Low-temperature charging management method and system for pure electric vehicle Technical Field The invention relates to the technical field of electric vehicles, in particular to a low-temperature charging management method and system for a pure electric vehicle. Background The chemical characteristics of the power battery determine that the lithium ion activity of the power battery is obviously reduced in a low-temperature environment, so that the internal resistance of the battery is increased, the available capacity is attenuated, and the charge and discharge power of the power battery is severely limited. The method not only affects the daily use performance of the pure electric vehicle, but also brings great inconvenience to users in a charging scene of rapidly supplementing electric energy. Therefore, the safe and efficient high-power direct current quick charging is realized in a low-temperature environment, and the electric vehicle has become one of key technical bottlenecks for improving the user experience in winter and promoting the electric vehicle to be further popularized. In order to solve the problem of low-temperature charging, the current mainstream technical scheme is to equip a vehicle with a battery heating system, wherein water heating PTC (WPTC) is widely adopted due to high heating efficiency and good safety. The basic working principle is that in the initial stage of charging, the WPTC is powered by a power battery to generate heat and preheat a battery pack through cooling liquid circulation, and after the temperature of the battery rises to a proper interval, the battery pack is charged with high power. Although the scheme can solve the feasibility problem of low-temperature charging, in practical application, the scheme exposes new technical contradiction especially under the extreme working condition of low state of charge (SOC) of the battery. In particular, when the vehicle starts a fast charge in a low temperature environment and the battery SOC is low, the high power required to start the WPTC will be provided entirely by the battery itself. At this moment, the charging has not been started or is only in a trickle state, and the battery needs to output a large current to maintain the operation of the heater, and is in a state of lack of electricity, so that the discharging capability of the battery is limited. At this time, if the power requirement of the WPTC exceeds the maximum discharge power allowed by the Battery Management System (BMS), the discharge overcurrent protection mechanism of the BMS is triggered, resulting in heating interruption and even charging failure, and the battery life and system safety may be affected in serious cases. In addition, because WPTC heating is generally concentrated in a specific area of a cooling liquid flow channel, uneven heating of an electric core inside a battery pack is easily caused, and if intervention is not performed after the heating is finished, the consistency of battery cells is further deteriorated due to excessive temperature difference, and performance decay is accelerated. Meanwhile, during the whole heating period, a part of the charging current is consumed by the WPTC, so that the current actually used for battery charging is far lower than the request value of the charging pile, resulting in a significantly prolonged charging time, contrary to the "quick charging" experience pursued by the user. In summary, in the prior art, during the low-temperature quick charging process, the starting safety, the heating temperature uniformity and the charging timeliness are difficult to be compatible. Disclosure of Invention The invention aims to provide a low-temperature charging management method and system for a pure electric vehicle, which can coordinate energy flow among a battery, a heater and a charging pile from a system level, and furthest improve the overall efficiency of low-temperature quick charging and the service life of a battery core on the premise of ensuring safety. To achieve the above object, the present invention provides the following basic scheme. Scheme one The low-temperature charging management method for the pure electric vehicle comprises a battery management system BMS, a whole vehicle controller VCU and a water heater PTC for heating a power battery pack, and comprises the following steps of: Responding to the vehicle entering a low-temperature charging mode, judging that the battery temperature is lower than a first preset temperature threshold value by the BMS, and acquiring the maximum allowable discharging power of the power battery sent by the BMS by the VCU; In the initial stage of starting the water heater PTC to heat the power battery pack, the VCU limits the actual running power of the water heater PTC according to the maximum allowable discharging power of the power battery so as not to exceed the maximum allowable discharging power of the power battery; After the water heater PTC enters