GB2604419A

GB2604419A - Method for charging a traction battery of an electric vehicle by means of a charging column and charging system

Info

Publication number: GB2604419A
Application number: GB2114248.4A
Authority: GB
Inventors: Metzger Christian; Lang Maximilian; Neu Matthias
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 2020-10-05
Filing date: 2021-10-05
Publication date: 2022-09-07
Anticipated expiration: 2041-10-05
Also published as: GB2604419B; GB202114248D0

Abstract

A method of charging a traction battery 1 of an electric vehicle (EV) by means of a charging column/station 2 as part of a charging system 10. The traction battery can be charged at two different charging voltage levels at least. After the EV has been connected to the charging column, data is exchanged between a battery management system (BMS) 3 of the EV and the charging column in order to negotiate a charging voltage. A maximum permissible total charging voltage is communicated to the charging station by the BMS by means of at least one battery handshake message (BHM) 4. The communicated maximum permissible total charging voltage is lower than a highest charging voltage level of the traction battery by a defined amount. An insulation test 5 may be carried out and a first battery charging parameter (BCP) 6 message of the BMS may be evaluated. A message of charger maximum output capacity (CML) 7 may be transmitted by the charging station to the BMS for evaluation. The message CML may be repeatedly transmitted until the BMS no longer transmits the message BCP, whereupon the message BRO 8 is received by the charging station. The signal value maximum voltage last received in BCP message 16 may be stored and used for the current charging process as a limit.

Description

Method for charging a traction battery of an electric vehicle by means of a charging column and charging system The present invention relates to a method for charging a traction battery of an electric vehicle by means of a charging column. In this case, the traction battery can be charged at at least two different charging voltage levels.

In order to make possible electric vehicles with high ranges and at the same time a low weight owing to low cable cross sections, the traction batteries of said electric vehicles are increasingly being operated with electric currents at a DC voltage level of 800 V. However, electric currents at a DC voltage level of 400 V are usually provided for charging stations.

In the prior art, electric vehicles with a power electronics system have therefore become known, which make it possible to charge vehicles at a voltage level of 800 V at a charging station at a lower voltage level of 400 V, for example. However, such a power electronics system reduces the efficiency of the charging process and potentially also limits the performance.

It is therefore proposed to provide charging stations that can also handle accordingly higher voltage levels. However, this entails significant problems since some of the standards to be taken into account for charging stations do not permit voltage levels or a switchover between two different voltage levels within the context of the charging process at all.

For example, charging columns in accordance with the GB/T charging standard provide, in accordance with the standard, only a charging voltage level of 400 V. In this case, the GB/T standards 18487.1-2015 and 27930-2015 for DC charging of electric vehicles make provision for vehicles to operate only at a fixed voltage level of 400 V, for example, and for no automatic switchover between two voltage levels during a charging process to be possible or allowed. When an electric vehicle then requests a higher charging voltage, the charging column moves to an error mode and charging is no longer possible. A further problem is that a first insulation test, for example at the voltage level 400 V, and a subsequent charging at the voltage level 800 V (and an insulation monitoring procedure adapted thereto) is not normatively covered by these standards.

The present invention seeks to improve the interoperability of charging stations, in particular in accordance with the GB/T standard, and electric vehicles that support a plurality of voltage levels. In this case, a safe and at the same time uncomplicated switchover of the charging parameters during the charging process, in particular taking into account relevant norms, and, for example, the GB/T standard for charging stations is preferably intended to be possible.

This can be achieved by a method having the features of claim 1. A charging system according to an aspect of the invention is the subject matter of claim 13. Preferred developments of the invention are the subject matter of the dependent claims. Further advantages and features of the present invention will emerge from the general description and from the description of the exemplary embodiment.

The method according to an aspect of the invention is used for charging a traction battery of an electric vehicle by means of a charging column. In this case, the traction battery can be charged at at least two different charging voltage levels. After the electric vehicle has been connected to the charging column, in particular using at least one charging cable, data is exchanged between a battery management system of the electric vehicle and the charging column in order to negotiate a charging voltage. For this purpose, a maximum permissible total charging voltage is communicated to the charging station by the battery management system by means of at least one battery handshake message (BHM). In this case, said communicated maximum permissible total charging voltage is lower than a highest charging voltage level of the traction battery by a defined amount.

The method according to aspects the invention affords numerous advantages. A considerable advantage is afforded by the battery handshake message at the charging voltage level of the traction battery that has been decreased in a targeted manner. This prevents, for example, error messages arising when a vehicle at a voltage level of 800 V registers at a charging station according to the GB/T standard.

As a result, a switchover of the voltage level on the part of the charging column is also reliably possible, as result of which the overall charging process is made possible in the first place or significantly improved. This is because, without such a switchover, the maximum charging power of the charging station is usually not exhausted or technically limited, since the GB/T standard permits only uncooled charging cables, which often have a maximum current-carrying capability of 250 A. This method affords a particular advantage when the charging voltage level is higher than the voltage for the insulation test.

It is advantageous and preferred that the communicated maximum permissible total charging voltage is reduced to a value that corresponds to the lower or lowest charging voltage level of the traction battery. In particular, the permissible total charging voltage is reduced to one of 400 V. Other total charging voltages are also possible. As a result, the charging process at charging columns in accordance with the GB/T standard is significantly improved.

It is also possible and advantageous that the communicated maximum permissible total charging voltage is reduced to a value that is stored in the battery management system for the respectively (currently) connected charging station. In particular, the communicated maximum permissible total charging voltage is 400 V +/-10% or +/20%. In particular, the value to which the communicated maximum permissible total charging voltage is reduced is selected depending on a standard of the charging column. It is also possible and advantageous that the value to which the communicated maximum permissible total charging voltage is reduced corresponds to a (maximum) voltage level, predetermined by the charging column, for an insulation test and preferably for a first or initial insulation test.

At least one measurement variable is preferably stipulated for an insulation test for the upcoming charging process. In particular, a minimum of the communicated maximum permissible total charging voltage and of an insulation strength of the charging column stored in the charging column is determined for this purpose. In particular the insulation strength of the charging column and of the components thereof is determined by way of previous configuration. The insulation test for the upcoming charging process is then preferably carried out by the charging column taking into account this previously stipulated measurement variable.

A (first) battery charging parameter (BCP) message about a maximum voltage of the traction battery is preferably transmitted by the battery management system to the charging station. In this case, a value for the maximum voltage is preferably communicated to the charging station, said value being lower than an actual maximum voltage of the traction battery by a defined amount. In this case, a value that corresponds to the value of the lower charging voltage level of the traction battery is preferably communicated. To this end, the actual maximum voltage of the traction battery is preferably reduced by the same amount as is also provided for the reduction of the maximum permissible total charging voltage. It is possible that for this purpose the same value as for the communicated maximum permissible total charging voltage is communicated to the charging column. In particular, said message is evaluated by the charging station.

In particular, at least one message about a chargers maximum output capacity (CML) is transmitted to the battery management system by the charging station. In particular, said message is evaluated by the battery management system.

At least one further battery charging parameter (BCP) message about a maximum voltage of the traction battery is transmitted to the charging station by the battery management system. In this case, a value for the maximum voltage is preferably communicated to the charging station, said value corresponding to the (actual) maximum voltage of the traction battery when this is lower than or equal to the chargers maximum output capacity (CML) communicated by the charging station It is also possible and preferred that, in this case, a value for the maximum voltage is communicated to the charging station, said value corresponding to a lower charging voltage level of the traction battery when the (actual) maximum voltage of the traction battery is greater than the chargers maximum output capacity (CML) communicated by the charging station. In particular, said message is evaluated by the charging station.

In particular, the battery management system can repeatedly transmit further battery charging parameter (BCP) messages to the charging station in order to negotiate a charging voltage. In particular, the charging station responds in each case with a communication of the chargers maximum output capacity (CML) to the battery management system. In particular, the chargers maximum output capacity (CML) is at least 800 V and preferably at least 900 V and, for example, 950 V +/-10%.

It is possible and preferred that messages about a chargers maximum output capacity (CML) are repeatedly transmitted by the charging station to the battery management system, in particular until the battery management system no longer transmits further battery charging parameter (BCP) messages and/or until at least one message that the battery management system is battery charging ready (BRO) is received by the charging station.

In particular, the last received value for the maximum voltage of the traction battery from the battery charging parameter (BCP) message transmitted by the battery management system is stored by the charging station and used as a limit for the charging voltage for the present charging process. This stored value corresponds, in particular, to the negotiated charging voltage. In particular, a charging voltage of the charging voltage level of 800 V is negotiated.

The charging process is preferably not interrupted by the charging station during and/or after the procedure of the previously described steps. An interruption is possible, in particular, when a normatively required or stored time-out time is exceeded.

In all of the configurations, it is preferred that the charging voltage negotiated for the current charging process is used by the charging station for at least one (continuous) insulation monitoring procedure during the charging process and/or for at least one further insulation test. In particular, an insulation monitoring procedure takes place during the charging process. In particular, the insulation monitoring process is adapted to the charging voltage used.

In one advantageous configuration of the previously described method or in another method according to the invention for charging a traction battery of an electric vehicle by means of a charging column, provision is made for a (first) battery charging parameter (BCP) message about a maximum voltage of the traction battery to be transmitted to the charging station by the battery management system. In this case, a value for the maximum voltage is preferably communicated to the charging station, said value corresponding to a lower charging voltage level of the traction battery and/or to a charging voltage level of 400 V when a chargers maximum output capacity (CML) communicated previously by the charging station is lower than the voltage taken into account for an insulation test.

This method affords a particular advantage when the charging voltage level is designed to be lower than the voltage for the insulation test. This method according to the invention is also preferably at least partly designed as has been described previously.

In one configuration, at least one further battery charging parameter (BCP) message about a maximum voltage of the traction battery is transmitted by the battery management system to the charging station in order to negotiate a charging voltage that is higher than the maximum voltage communicated in the previously transmitted (first) battery charging parameter (BCP) message, but lower than or equal to the chargers maximum output capacity (CML) communicated previously by the charging station.

The charging system according to aspects of the invention is suited and designed to be operated according to the method according to aspects of the invention or one of the configurations.

In particular, the charging system comprises at least one battery management system for a traction battery of an electric vehicle that can be charged at at least two different charging voltage levels. In particular, the charging system comprises at least one charging column that can be coupled to the battery management system. In particular, the battery management system is coupled to the charging column by the connection of a charging cable of the charging column to the electric vehicle as intended.

In accordance with aspects of the invention, a charging voltage level is understood to mean, in particular, a voltage range in which the traction battery can be charged. For example, the charging voltage during charging can deviate from the voltage level +110% or +/-20% for technical reasons. In accordance with the invention, a voltage level is understood to mean, in particular, a voltage range in which the traction battery is in operation as intended. For example, a battery having a voltage level of 800 V thus has between approximately 750 and approximately 850 V depending on the state of charge of the battery. In particular, the traction battery can be charged at at least two different charging voltage levels.

Within the context of the present invention, a lower charging voltage level of the traction battery is understood to mean, in particular, a charging voltage level other than the highest charging voltage level and preferably the lowest charging voltage level. In the event that more than two and, for example, three or more charging voltage levels are provided for the traction battery, the lower charging voltage level of the traction battery is understood to mean, in particular, such a charging voltage level that is at 400 V and/or that does not exceed a charging voltage standard provided for the respective charging column.

In particular, at least one and, in particular, the lower (lowest) charging voltage level is at 400 V and at least one other charging voltage level is at 800 V. Other voltage levels are also possible. It is possible that the charging voltage for the charging process deviates by up to 10% or 20% from the provided charging voltage level.

In particular, the battery management system and the charging column send the messages cyclically and preferably independently of one another. In particular, a transmitted message is evaluated by the respective receiver. In particular, the data exchange is initiated using the battery handshake message (BHM). In all of the configurations, it is particularly preferred that the data exchange takes place in accordance with J1939.

Further advantages and features of the present invention will emerge from the exemplary embodiments, which will be discussed below with reference to the appended figures.

B

In the figure: figure 1 shows a highly schematic illustration of a charging system according to an embodiment of the invention.

Figure 1 shows a charging system 10 according to an embodiment of the invention, which is operated in accordance with the method according to an embodiment of the invention. The charging system 10 is used to charge a traction battery 1 of an electric vehicle, which is not shown in more detail here. An on-board electrical system having a voltage level of, for example, 800 V can be supplied with electrical energy using the traction battery 1. The traction battery 1 can be charged in this case at two charging voltage levels and, for example, at 400 V and 800 V. The actual charging voltage is then produced according to the state of charge or overall state of the traction battery 1 between 350 V and 450 V or between approximately 700 V and 900 V. A charging column 2 is provided with a charging cable, which is not shown in any more detail here, in order to charge the traction battery 1. In order to make safe and reliable charging possible, the charging column 2 and a battery management system 3 of the motor vehicle communicate with one another continuously during the charging process. In this case, in particular, corresponding processing of a J1939 communication between the charging column 2 and the battery management system 3 takes place. In particular, the insulation of the electrical components is also monitored over the entire charging process.

An exemplary procedure of the method according to the invention is described in the following text with reference to figure 1 for a case in which a charging voltage level is higher than a voltage for an insulation test 5: Evaluation of the battery handshake message BHM 4 of the battery management system 3, said message containing the signal maximum allowable total charging voltage, for example 400 V. The charging column 2 knows, owing to previous configuration, which insulation strengths all of the connected components of the charging column 2 have.

The minimum of this signal, that is to say maximum allowable total charging voltage and the set insulation strength, is determined and stipulated as measurement variable for this charging process.

Based on the earlier evaluation, the charging column 2 will carry out an insulation test 5 using said measurement variable.

Evaluation of the first battery charging parameter BCP message 6 of the battery management system 3, said message containing the signal maximum voltage, for example 400 V. Transmission of the message CML 7 by the charging station 2, said message containing the signal maximum output voltage, for example 950 V. Evaluation and acceptance of the subsequent further battery charging parameter BCP message 16 of the battery management system 3, said message containing the signal maximum voltage, for example 800 V. Repeated transmission of the message CML 7 of the charging station 2, said message containing the signal maximum output voltage, for example 950 V. This takes place until the battery management system 3 no longer transmits the message BCP 16 and the message BRO 8 is received by the charging station 2.

The signal value maximum voltage last received in the battery charging parameter BCP message 16 of the battery management system 3 is stored and further used for the current charging process as a limit, for example 800 V. During or after the procedure of the described steps, the charging process is not interrupted or terminated by the charging station 2, unless the normatively required time-out time is exceeded.

An exemplary procedure of the method according to the invention is described in the following text for a case in which the charging voltage level is lower than the voltage for the insulation test 5: Evaluation of the battery handshake message BHM 4 of the battery management system 3, said message containing the signal maximum allowable total charging voltage, for example 800 V. The charging column 2 knows, owing to previous configuration, which insulation strengths all of the connected components of the charging column 2 have.

Evaluation of the first battery charging parameter BCP message 6 of the battery management system 3, said message containing the signal maximum voltage, for example 800 V. Transmission of the message CML 7 by the charging station 2, said message containing the signal maximum output voltage, for example 500 V. Evaluation and acceptance of the subsequent further battery charging parameter BCP message 16 of the battery management system 3, said message containing the signal maximum voltage, for example 400 V. Repeated transmission of the message CML 7 of the charging station 2, said message containing the signal maximum output voltage, for example 500 V. This takes place until the battery management system 3 no longer transmits the message BCP 16 and/or the message BRO 8 is received by the charging station 2.

The signal value maximum voltage last received in the battery charging parameter BCP message 16 of the battery management system 3 is stored and further used for the current charging process as a limit, for example 500 V. During or after the procedure of the described steps, the charging process is not interrupted or terminated by the charging station 2, unless the normatively required time-out time is exceeded.

Embodiments of the invention presented here offer a significant increase in the interoperability of charging stations 2 with vehicles whose traction batteries 1 support a plurality of voltage levels. At the same time, optimization of the charging process on the part of the charging station 2 with respect to charging power and efficiency is made possible.

Claims

Patent claims 1. A method for charging a traction battery of an electric vehicle by means of a charging column, wherein the traction battery can be charged at at least two different charging voltage levels and wherein, after the electric vehicle has been connected to the charging column, data is exchanged between a battery management system of the electric vehicle and the charging column in order to negotiate a charging voltage and wherein for this purpose a maximum permissible total charging voltage is communicated to the charging station by the battery management system by means of at least one battery handshake message (BHM) and wherein said communicated maximum permissible total charging voltage is lower than a highest charging voltage level of the traction battery by a defined amount.
2. The method as claimed in the preceding claim, wherein the communicated maximum permissible total charging voltage is reduced to a value that corresponds to the lower charging voltage level.
3. The method as claimed in either of the preceding claims, wherein the communicated maximum permissible total charging voltage is reduced to a value that is stored in the battery management system for the respectively connected charging station and/or wherein the communicated maximum permissible total charging voltage is 400 volts +/-10%.
The method as claimed in any one of the preceding claims, wherein a measurement variable for an insulation test is stipulated for the upcoming charging process and wherein for this purpose a minimum of the communicated maximum permissible total charging voltage and of an insulation strength of the charging column stored in the charging column is determined and wherein the insulation test for the upcoming charging process is carried out by the charging column taking into account the previously stipulated measurement variable.
The method as claimed in any one of the preceding claims, wherein a battery charging parameter (BCP) message about a maximum voltage of the traction battery is transmitted by the battery management system to the charging station and wherein, in this case, a value for the maximum voltage is communicated to the charging station, said value being lower than an actual maximum voltage of the traction battery by a defined amount and preferably corresponding to the value of the lower charging voltage level of the traction battery.
The method as claimed in any one of the preceding claims, wherein a message about a chargers maximum output capacity (CML) is transmitted by the charging station to the battery management system and wherein said message is evaluated by the battery management system.
The method as claimed in any one of the preceding claims, wherein at least one further battery charging parameter (BCP) message about a maximum voltage of the traction battery is transmitted by the battery management system to the charging station and wherein, in this case, a value for the maximum voltage is communicated to the charging station, said value corresponding to the maximum voltage of the traction battery when this is lower than or equal to the chargers maximum output capacity (CML) communicated by the charging station or wherein, in this case, a value for the maximum voltage is communicated to the charging station, said value corresponding to a lower charging voltage level of the traction battery when the maximum voltage of the traction battery is greater than the chargers maximum output capacity (CML) communicated by the charging station.
8. The method as claimed in any one of the preceding claims, wherein messages about a chargers maximum output capacity (CML) are repeatedly transmitted by the charging station to the battery management system until the battery management system no longer transmits further battery charging parameter (BCP) messages and/or until a message that the battery management system is battery charging ready (BRO) is received by the charging station.
9. The method as claimed in any one of the preceding claims, wherein the last received value for the maximum voltage of the traction battery from the battery charging parameter (BCP) message transmitted by the battery management system is stored by the charging station and used as a limit for the charging voltage for the current charging process.
The method as claimed in the preceding claim, wherein the charging voltage negotiated for the current charging process is used by the charging station for at least one insulation monitoring procedure during the charging process.
11 The method in particular as claimed in any one of the preceding claims, wherein a battery charging parameter (BCE') message about a maximum voltage of the traction battery is transmitted by the battery management system to the charging station and wherein, in this case, a value for the maximum voltage is communicated to the charging station, said value corresponding to a lower charging voltage level of the traction battery when a chargers maximum output capacity (CML) communicated previously by the charging station is lower than the voltage taken into account for an insulation test.
12 The method as claimed in the preceding claim, wherein at least one further battery charging parameter (BCP) message about a maximum voltage of the traction battery is transmitted by the battery management system to the charging station in order to negotiate a charging voltage that is higher than the maximum voltage communicated in the previously transmitted battery charging parameter (BCP) message, but lower than or equal to the chargers maximum output capacity (CML) communicated previously by the charging station.
13. A charging system, suited and designed to be operated in accordance with the method as claimed in any one of the preceding claims.