Method of controlling the charging current of a high-voltage battery of an electric vehicle without active cooling of said high-voltage battery

Abstract

A method (10) of controlling the charging current of a high-voltage battery of an electric vehicle during a charging phase in the absence of active cooling of the high-voltage battery is described. An external temperature (TAmb) relative to the high-voltage battery is sensed (102), via a first temperature sensor of the vehicle. An internal temperature (TBatt_Cell_Max) of the high-voltage battery is sensed (102), via at least a second temperature sensor of the vehicle. A first limit value (IBatt_Lim_NoClgRaw) of the charging current is determined (102), based on the external temperature (TAmb) and the internal temperature (TBatt_Cell_Max). A control signal (BatteryClgNotAvl) indicative of whether a cooling system of the high-voltage battery of the vehicle is activatable or not is received (104). In response to the control signal (BatteryClgNotAvl) indicating that the cooling system is not activatable, a charging current (IBatt_Lim_NoClg) equal to or less than the first limit value (IBatt_Lim_NoClgRaw) is injected into the high-voltage battery.

Description

[0001] Method of controlling the charging current of a high-voltage battery of an electric vehicle without active cooling of said high-voltage battery

[0002] TEXT OF THE DESCRIPTION

[0003] Field of the invention

[0004] The present invention relates to electric vehicles equipped with a high-voltage battery, for example an 800 V battery, which supplies energy primarily to the electric powertrain assembly (for this reason also called traction battery), and which can be recharged by connection to an external charging infrastructure (so-called charging stations). Such vehicles may include battery electric vehicles (BEV) or hybrid electric vehicles (HEV).

[0005] The invention was developed with reference to controlling the charging current input to the battery during the charging phase, by a vehicle control unit, particularly in the condition wherein the vehicle cooling system is not able to cool the high-voltage battery.

[0006] Prior art

[0007] In modern electric vehicles, which include a high-voltage battery (e.g., 800 V - also indicated as "HV battery" in the present description, from high voltage) dedicated primarily to powering the powertrain assembly and other relevant electrical loads (e.g., the air conditioning system of the passenger compartment, the heating and / or cooling system of the battery pack, etc.), one or more vehicle control units (e.g., the battery management system or "BMS" control unit, and / or the vehicle dynamic control module or "VDCM" control unit) manage the battery charging process, determining for example the optimal value of the charging current that has to be absorbed by the vehicle (i.e. , delivered by the charging station), also as a function of one or more operational parameters of the vehicle itself.

[0008] Some documents of possible interest in this technical field are CN 209016229 U and US 6,903,534 B2.

[0009] In particular, in the known solutions, if the vehicle is in a condition wherein it is not possible to cool down the traction battery, charging of the battery (or more generally of the vehicle) is prevented (i.e., the maximum value of the charging current drawn from the charging station is set to zero). This type of control is implemented for safety reasons, since during the charging phase the battery tends to heat up, and the inability to activate its cooling represents a potential danger to the safety and integrity of the battery itself.

[0010] For example, cooling of the battery may be prevented due to faults or malfunctions of the cooling system. Under these conditions, in conventional vehicles, charging of the high-voltage battery is completely prevented, causing inconvenience to the user, who cannot recharge the vehicle until the cooling system is repaired.

[0011] Therefore, there is a need in the art to develop a method for controlling the charging current of a high-voltage battery of an electric vehicle (i.e., controlling the current input to the battery), to be implemented when it is not possible to simultaneously activate cooling of the high-voltage battery for any reason (e.g., due to faults and / or malfunctions of the cooling system).

[0012] Object of the invention

[0013] The object of the invention is to solve the technical problem mentioned above. In particular, the object of the invention is that of providing a method for determining the (upper) limit value of the charging current to be used during the charging phase of an electric vehicle (and consequently controlling, limiting, the charging current input to the battery), even when the battery cooling system cannot be activated, for example due to faults and / or malfunctions.

[0014] Summary of the invention

[0015] The object of the invention is achieved by a method having the features forming the subject of the claims that follow, which form an integral part of the technical teaching provided herein in relation to the invention.

[0016] The method can be implemented by one or more electronic control units of a vehicle, for example by the battery management system (BMS) control unit and / or by the vehicle dynamic control module (VDCM) control unit. Brief description of the figures

[0017] The invention will now be described with reference to the accompanying figures, provided by way of non-limiting example only, in which:

[0018] Figure 1 is a block diagram illustrating the steps of a method for controlling the charging current of the high-voltage battery of an electric vehicle, in a condition wherein the battery cooling system cannot be activated, according to one or more embodiments of the present description;

[0019] Figure 2 is a diagram qualitatively exemplifying the trend of the limit value of the charging current, in a condition wherein the battery cooling system cannot be activated, as a function of the ambient temperature and the maximum temperature detected among the battery cells, according to one or more embodiments of the present description;

[0020] Figure 3 is a block diagram illustrating a step of selecting the limit value of the charging current in the method according to one or more embodiments of the present description; and

[0021] Figure 4 is a block diagram summarizing the steps of a method for controlling the charging current of the high-voltage battery of an electric vehicle, in a condition wherein the battery cooling system cannot be activated, according to one or more embodiments of the present description.

[0022] Detailed description

[0023] As anticipated, the invention is applicable to electric vehicles equipped with a high-voltage battery that can be recharged via an external charging infrastructure (charging station), and relates to a method for determining the (upper) limit value of the charging current to be used during the vehicle charging phase (and consequently controlling the charging current absorbed by the vehicle and injected into the battery), even when the battery cooling system cannot be activated (e.g., due to faults or malfunctions of the cooling system itself).

[0024] In particular, the method described herein allows determining a limit value for the charging current that can be supplied as input to the high- voltage battery, allowing the battery to be charged without thereby reaching a critical (too high) battery temperature, even if the battery cooling system is not active (and / or cannot be activated). Substantially, the method described herein is based on the fact that, even when the battery cooling system cannot be activated, the battery can still exchange heat (in particular, release heat) with the external environment and the parts of the vehicle surrounding the battery itself. This "natural" cooling power, due to the simple conduction of heat from the battery to the outside, is significantly lower than the cooling power obtainable by using the cooling system, but can still be exploited to cool the battery while it is being recharged in a very "derated" mode, i.e., at a slow rate, with a low (limited) charging current compared to normal charging conditions, trying to limit as much as possible the thermal dissipation (i.e., heat production) during the charging phase due to the Joule effect in the battery.

[0025] As illustrated in the block diagram of Figure 1 , method 10 may substantially comprise two steps indicated by references 102 and 104. In step 102, further described below, the external ambient temperature TAmb and the temperature TBatt_ceii_Max, which is the highest among the temperatures detected for all the individual cells that make up the traction battery (hereinafter, also referred to simply as "battery temperature" for brevity), are detected - by means of suitable temperature sensors of the vehicle. The external temperature TAmb may be detected, depending on the embodiments, at different points: for example, it can be detected outside the vehicle body, or in an internal region of the vehicle but external to the battery pack. Also in step 102, based on these two detected temperatures, a first limit value (or "raw" value) lBatt_Lim_NocigRaw of the charging current is then determined. In step 104, further described below, the raw current limit value I Batt_Lim_NocigRaw is received and a binary signal (or flag) BatteryCIgNotAvl is received, which indicates whether the battery cooling function is available or not (i.e., whether the cooling system can be activated or not); based on these signals, the final limit value lBatt_Lim_Nocig of the charging current to be used in the current vehicle operating conditions is determined. The actual charging current (injected into the battery) is then controlled (e.g., by the BMS control unit and / or the VDCM control unit) as a function of the final limit value I Batt_Lim_Nocig (i.e., maintained at a value equal to or less than the limit I Batt_Lim_NoClg) .

[0026] The operation of block 102 for determining the "raw" limit value I Batt_Lim_NocigRaw of the charging current will now be described with reference to Figure 2. Figure 2 qualitatively illustrates the trend of the current limit value I Batt_Lim_NocigRaw determined as a function of TBatt_ceii_Max for different values of specifically for four different values TAmbi, TAmb2, TAmb3, TAmb4. Generally, the limit value of the charging current lBatt_Lim_NocigRaw decreases (e.g., linearly, as exemplified in Figure 2) as the battery temperature TBatt_ceii_Max increases, until it becomes zero when the battery temperature TBatt_ceii_Max reaches a critical threshold value Ter (possibly, minus a certain safety margin). Furthermore, generally the limit value of the charging current I Batt_Lim_NocigRaw decreases as the ambient temperature TAmb increases, since a higher ambient temperature impedes more significantly heat dissipation from the battery to the outside: thus, in the example of Figure 2, one could have TAmbi<TAmb2<TAmb3<TAmb4. Therefore, in step 102, the method (e.g., implemented by the vehicle's BMS control unit and / or VDCM control unit) comprises detecting the two temperatures TAmb and TBatt_ceii_Max, and determining the "raw" limit value of the charging current lBatt_Lim_NocigRaw according to the dependency laws illustrated in Figure 2, which can be implemented using one or more stored characteristic maps (e.g., implemented by analytical functions, piecewise functions, or look-up tables). This substantially allows balancing the thermal power developed due to the Joule effect during battery charging with the "natural" cooling thermal power of the battery, i.e., that due to the normal conduction of heat from the battery to the rest of the vehicle and to the external environment, present even if the battery cooling system is not active. Therefore, at the output of block 102, the method substantially provides a limit value for the charging current I Batt_Lim_NocigRaw that allows recharging the traction battery without increasing its temperature beyond the critical threshold Ter by exploiting only the "natural" heat dissipation from the battery to the outside, without any intervention of the cooling system.

[0027] Obviously, it will be understood that the BMS control unit and / or the VDCM control unit can simultaneously determine other limit values for the charging current also based on other algorithms (e.g., charging performance optimization algorithms, safety algorithms, etc.), as a function of other parameters and / or operating conditions. Therefore, the limit value I Batt_Lim_NocigRaw calculated in this way must be interpreted not as a current value that must necessarily be absorbed during charging, but as a further limit value to be considered in the charging phase control process.

[0028] The operation of block 104 for determining the final limit value I Batt_Lim_Nocig of the charging current will now be described with reference to Figure 3. Substantially, block 104 operates as a selector that receives at a first input the raw limit value lBatt_Lim_NocigRaw calculated by block 102 and at a second input an unlimited current value lBatt_No_umited, and is controlled by the binary signal BatteryCIgNotAvl which indicates whether the battery cooling function is available or not. In particular, the signal BatteryCIgNotAvl comes from a vehicle control unit (e.g., external to the BMS). The signal BatteryCIgNotAvl is asserted (e.g., set to 1 ) when the cooling system is not able to cool the battery, and is de-asserted (e.g., set to 0) when the cooling system is able to cool the battery. If the signal BatteryCIgNotAvl is asserted and thus indicates that the cooling function cannot be activated, the final limit value lBatt_Lim_Nocig of the charging current is set equal to the raw value I Batt_Lim_NocigRaw calculated by block 102. If instead the signal BatteryCIgNotAvl is de-asserted and thus indicates that the cooling function can be activated, the final limit value lBatt_Lim_Nocig of the charging current is set equal to the unlimited value lBatt_No_umited. The unlimited current value I Batt_No_Limited is a constant and high value, possibly stored in the BMS control unit and / or the VDCM control unit (thus, not received from outside), so that the charging current is not limited without reason when the cooling system is able to cool the battery, as expected under normal vehicle operating conditions.

[0029] Therefore, as can be inferred from the preceding description, the method 10 described herein for determining the limit value of the charging current to be used when the battery cooling system cannot be activated substantially articulates into two steps, as also exemplified in the block diagram of Figure 4: in step 102, a raw current limit value lBatt_um_NocigRaw is determined as a function of the ambient temperature TAmb and the maximum temperature detected among all the battery cells TBatt_ceii_Max, using one or more correlation maps (e.g., calibratable); and in step 104, the final current limit value lBatt_Lim_Nocig is set equal to the raw value lBatt_Lim_NocigRaw if the cooling system indeed cannot be activated, or the final current limit value lBatt_um_Nocig is set to an unlimited value I Batt_No_Limited if the cooling system can be activated.

[0030] The method described herein for determining (and therefore controlling, limiting) the value of the charging current when the battery cooling system cannot be activated advantageously allows the vehicle user to recharge the battery under any condition (albeit with a limited charging current, and therefore a longer charging time than normal), preventing the user from being unable to recharge the vehicle because a fault or malfunction of the cooling system of the battery pack has occurred.

[0031] It will be noted that in the text of the present description, reference has been made several times to the limit value of the charging current "input to the battery" or "injected into the battery", since the method described herein relates to controlling (within the determined limit value) the current that can be absorbed by the battery, which however does not necessarily coincide with the current delivered by the charging infrastructure (i.e. , by the charging station). In fact, in addition, the method described herein advantageously allows using a portion of the energy drawn from the charging infrastructure (i.e., from the charging station), during the "slow" charging phase, to power other electrical loads of the vehicle (e.g., the passenger compartment air conditioning and / or heating system) without drawing energy from the battery. It follows that the current delivered by the charging station can be higher than the current supplied as input to the battery for recharging it, since a portion of the current is used "in real time" to power other electrical loads of the vehicle.

[0032] Naturally, the construction details and embodiments may be widely varied from what has been described and illustrated without thereby departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A method (10) of controlling the charging current of a high- voltage battery of an electric vehicle during a charging phase without active cooling of said high-voltage battery, said method (10) comprising:- sensing (102), via a first temperature sensor of said vehicle, a temperature external (TAmb) to said high-voltage battery;- sensing (102), via at least one second temperature sensor of said vehicle, an internal temperature (TBatt_ceii_Max) of said high-voltage battery;- determining (102), based on said external temperature (TAmb) and said internal temperature (TBatt_ceii_Max), a first limit value (lBatt_um_NocigRaw) of the charging current;- receiving (104) a control signal (BatteryCIgNotAvl) indicative of whether a cooling system of said high-voltage battery of the vehicle is activatable or not; and- in response to said control signal (BatteryCIgNotAvl) being indicative of the cooling system not being activatable, injecting a charging current (lBatt_Lim_Nocig) equal to or less than said first limit value (lBatt_Lim_NocigRaw) in said high-voltage battery.

2. The nethod (10) of claim 1 , wherein the step of determining (102) said first limit value (lBatt_Lim_NocigRaw) of the charging current comprises decreasing said first limit value (lBatt_Lim_NocigRaw) as said internal temperature ( TBatt_ceii_Max) increases.

3. The method (10) of claim 1 or claim 2, wherein the step of determining (102) said first limit value (lBatt_Lim_NocigRaw) of the charging current comprises zeroing said first limit value (lBatt_Lim_NocigRaw) if said internal temperature (TBatt_ceii_Max) is higher than a certain critical threshold value (Ter).

4. The method (10) of any of the previous claims, wherein the step of determining (102) said first limit value (lBatt_Lim_NocigRaw) of the charging current comprises decreasing said first limit value (lBatt_Lim_NocigRaw) as said external temperature (TAmb) increases.

5. The method (10) of any of the preceding claims, comprising, in response to said control signal (BatteryCIgNotAvl) being indicative of the cooling system being activatable, injecting a charging current (lBatt_Lim_Nocig)not limited by said first limit value (iBattjjmj cigRaw) in said high-voltage battery.

6. The method (10) of any of the previous claims, comprising sinking, from a charging infrastructure external to the vehicle, a current higher than the current injected in said high-voltage battery of the vehicle, and using the current difference between the current sunk from the charging infrastructure and the current injected in said high-voltage battery to supply one or more electrical loads of said vehicle other than said high-voltage battery.

7. The method (10) of any of the previous claims, wherein the step of sensing (102) said internal temperature ( TBatt_ceii_Max) of said high- voltage battery comprises:- sensing a plurality of internal temperature values at different points of said high-voltage battery; and- selecting, as the internal temperature ( TBatt_ceii_Max) of said high- voltage battery, the highest value in said plurality of internal temperature values.

8. The method (10) of claim 7, wherein the step of sensing a plurality of internal temperature values comprises sensing a temperature value for each battery cell in said high-voltage battery.

9. The method (10) of any of the previous claims, wherein said external temperature ( TAmb) relative to said high-voltage battery is a temperature of the environment external to the vehicle.

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