CN112009309B - Equalization circuit, design method thereof and battery management system - Google Patents
Equalization circuit, design method thereof and battery management system Download PDFInfo
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- CN112009309B CN112009309B CN201910393465.0A CN201910393465A CN112009309B CN 112009309 B CN112009309 B CN 112009309B CN 201910393465 A CN201910393465 A CN 201910393465A CN 112009309 B CN112009309 B CN 112009309B
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- 238000012360 testing method Methods 0.000 claims description 46
- 230000017525 heat dissipation Effects 0.000 claims description 14
- 238000013021 overheating Methods 0.000 description 5
- 230000005669 field effect Effects 0.000 description 4
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
- B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
- B60L3/0046—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to electric energy storage systems, e.g. batteries or capacitors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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Abstract
The invention provides an equalizing circuit, a design method thereof and a battery management system, wherein the equalizing circuit comprises: the control sub-circuit comprises a control end, a first end and a second end, wherein the control end is used for accessing a control signal, and the control signal is used for controlling the conduction state between the first end and the second end; the first series branch comprises a first equalizing resistor and a first thermistor which are connected in series, and the first series branch is connected in series between a first end and a signal input end of a first battery monomer in the battery module; the second series branch comprises a second equalizing resistor and a second thermistor which are connected in series, and the second series branch is connected in series between the second end and the signal input end of a second battery monomer in the battery module. Therefore, if the temperature of the equalizing resistor is increased due to the increase of the current of the series branch, the resistance value of the thermistor is rapidly increased along with the temperature increase, so that the current in the series branch is reduced, the temperature of the equalizing resistor is also reduced, and the thermal protection of the battery module is realized.
Description
Technical Field
The invention relates to the technical field of control, in particular to an equalization circuit, a design method thereof and a battery management system.
Background
Nowadays, automobiles are very popular, especially electric automobiles, and therefore, the safety of use of the battery module is related to the safety of use of the automobiles. Among the equalizer circuit of current battery module, the realization of balanced function is realized through the break-make that the inside integrated control component of simulation front end control was realized, consequently when overvoltage or other reasons appear in the control element and cause the breakdown, can lead to great electric current to flow through the temperature rise that the equalizing resistance leads to equalizing resistance, equalizing resistance continuously generates heat and can lead to the battery to fire burning at your circuit board after reaching the certain degree, causes the influence to the safety of battery module car even.
Therefore, the equalization circuit of the conventional battery module has the technical problem of poor thermal protection performance.
Disclosure of Invention
The embodiment of the invention provides an equalizing circuit, a design method thereof and a battery management system, which aim to solve the technical problem that the equalizing circuit of the conventional battery module has poor thermal protection performance
In order to achieve the purpose, the invention provides the following specific scheme:
in a first aspect, an embodiment of the present invention provides an equalizing circuit, which is applied to thermal protection of a battery module, and includes:
the control sub-circuit comprises a control end, a first end and a second end, wherein the control end is used for accessing a control signal, and the control signal is used for controlling the conduction state between the first end and the second end;
the first series branch comprises a first equalizing resistor and a first thermistor which are connected in series, and the first series branch is connected in series between the first end and a signal input end of a first battery cell in the battery module;
and the second series branch comprises a second equalizing resistor (131) and a second thermistor which are mutually connected in series, and the second series branch is connected between the second end and the signal input end of a second battery cell in the battery module in series.
Optionally, the first thermistor and/or the second thermistor are thermistors with positive temperature coefficients.
Optionally, one end of the first balancing resistor is connected to the first end of the control sub-circuit, the other end of the first balancing resistor is connected to one end of the first thermistor, and the other end of the first thermistor is connected to the input end of the first battery cell;
one end of the second equalizing resistor is connected with the second end of the control sub-circuit, the other end of the second equalizing resistor is connected with one end of the second thermistor, and the other end of the second thermistor is connected with the input end of the second battery cell.
Optionally, the control sub-circuit includes a control transistor, a control electrode of the control transistor is used for accessing the control signal, a first electrode of the control transistor is connected to one end of the first balancing resistor, and a second electrode of the control transistor is connected to one end of the second balancing resistor.
Optionally, the first battery cell and the second battery cell are two adjacent battery cells in the battery module.
Optionally, the equalizing circuit further includes a bias resistor connected in series between the control electrode and the second electrode of the control transistor.
In a second aspect, an embodiment of the present invention provides a method for designing an equalization circuit, which is applied to a battery module, as set forth in any one of the first aspects, where the method includes:
a thermistor is tested in series on the equalizing resistor of the equalizing circuit of the battery module;
determining a first mapping relation of the temperature of the equalizing resistor along with the change of the environment temperature;
determining a second mapping relation of the temperature of the test thermistor along with the temperature change of the equalizing resistor;
selecting a target type of test thermistor as a target thermistor according to the first mapping relation and the second mapping relation;
and connecting the target thermistor and the equalizing resistor in series.
Optionally, the target thermistor includes a first thermistor and a second thermistor; the equalization circuit includes:
the control sub-circuit comprises a control end, a first end and a second end, wherein the control end is used for accessing a control signal, and the control signal is used for controlling the conduction state between the first end and the second end;
the first series branch comprises a first equalizing resistor, the first equalizing resistor is connected with the first thermistor in series, and the first series branch is connected between the first end and a signal input end of a first battery cell in the battery module in series;
and the second series branch comprises a second equalizing resistor, the second equalizing resistor is connected with a second thermistor in series, and the second series branch is connected between the second end and the signal input end of a second battery monomer in the battery module in series.
Optionally, the test thermistor is a thermistor with a positive temperature coefficient of which the resistance value is 0 ohm at normal temperature.
Optionally, the step of determining the first mapping relationship of the temperature of the balancing resistor changing with the ambient temperature includes:
determining a first mapping relation of the temperature of the equalizing resistor changing along with the ambient temperature according to the maximum equalizing current of the battery monomer in the battery module, the ambient temperature and the resistance parameter of the equalizing resistor, wherein the resistance parameter of the equalizing resistor comprises at least one of resistance, power, heat dissipation coefficient and surface area.
Optionally, the step of determining a first mapping relationship of the temperature of the balancing resistor changing along with the ambient temperature according to the maximum balancing current of the battery cell in the battery module, the ambient temperature, and the resistance parameter of the balancing resistor includes:
calculating the resistance value and the power of the balancing resistor according to the maximum balancing current of the single battery of the battery module;
and determining the first mapping relation according to the resistance value, the power, the heat dissipation coefficient and the surface area of the equalizing resistor.
Optionally, the first mapping relationship includes at least one of:
optionally, the first mapping relationship is: the temperature of the equalizing resistance is ambient temperature + K power/(heat dissipation coefficient surface area), wherein K is a coefficient of variation.
Optionally, the step of determining a second mapping relationship of the temperature of the test thermistor with the temperature change of the balancing resistor includes:
assembling the test thermistor and the equalizing resistor on a circuit board according to a preset layout;
and adjusting the temperature of the equalizing resistor for multiple times, measuring temperature change data of the thermistor, and obtaining a second mapping relation of the temperature of the test thermistor along with the temperature change of the equalizing resistor.
Optionally, the step of selecting the test thermistor of the target model as the target thermistor according to the first mapping relationship and the second mapping relationship includes:
determining a first temperature range of the equalizing resistor, which needs thermal protection, according to the first mapping relation and a preset safe temperature range of the battery module;
determining a second temperature range of the thermistor needing thermal protection according to the first temperature range and the second mapping relation;
and determining the test thermistor with the working temperature range matched with the second temperature range as the target thermistor.
In a third aspect, an embodiment of the present invention provides a battery management system, which is characterized by including a battery module and the equalizing circuit according to any one of the first aspect.
In the embodiment of the invention, the equalizing circuit for thermal protection of the battery module comprises a control sub-circuit and two series branches, wherein a first end and a second end of the control sub-circuit are respectively connected to two single batteries of the battery module through the two series branches, and in addition, a control end of the control sub-circuit is connected to a control signal capable of controlling the conduction state between the first end and the second end. The two series branches comprise a balance resistor and a thermistor which are connected in series. Like this, if the signal of telecommunication of battery module access is too big, the electric current increase of series branch leads to the equalizing resistance to heat up, before reaching the safe temperature range of predetermineeing of battery module, thermistor's resistance increases along with the temperature risees rapidly, and then makes the electric current in the series branch reduce, and the temperature of equalizing resistance also reduces along with it to avoid battery module overheated burning, realized the thermal protection to battery module.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of an equalizing circuit according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of a method for designing an equalizing circuit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an equalizing circuit according to an embodiment of the present invention. As shown in fig. 1, an equalizing circuit applied to thermal protection of a battery module includes:
the control sub-circuit 110, the control sub-circuit 110 includes a control terminal 111, a first terminal 112, and a second terminal 113, the control terminal 111 is configured to access a control signal, where the control signal is configured to control a conducting state between the first terminal 112 and the second terminal 113;
a first series branch 120, wherein the first series branch 120 includes a first equalizing resistor 121 and a first thermistor 122 connected in series, and the first series branch 120 is connected in series between the first end 112 and a signal input end of a first battery cell 210 in the battery module 200;
a second series branch 130, wherein the second series branch 130 includes a second equalizing resistor 131 and a second thermistor 132 connected in series, and the second series branch 130 is connected in series between the second end 113 and a signal input end of a second battery cell 220 in the battery module 200.
In this embodiment, the equalizing circuit includes a control sub-circuit 110, a first series branch 120 and a second series branch 130, and both the first series branch 120 and the second series branch 130 are connected to the control sub-circuit 110. Specifically, the control sub-circuit 110 includes a control terminal 111, a first terminal 112 and a second terminal 113, and the control sub-circuit 110 is externally connected with a control signal, which can control a conduction state between the first terminal 112 and the second terminal 113. For example, when the control terminal 111 is switched on with a low-level control signal, the first terminal 112 and the second terminal 113 are connected, and when the control terminal 111 is switched on with a high-level control signal, the first terminal 112 and the second terminal 113 are disconnected.
Specifically, the first equalizing resistor 121 and the first thermistor 122 are connected in series between the connection of the first end 112 of the control sub-circuit and the signal input terminal of the first battery cell 210 in the battery module 200, and the second equalizing resistor 131 and the second thermistor 132 are connected in series between the connection of the second end 113 of the control sub-circuit and the signal input terminal of the second battery cell 220 in the battery module 200.
The first battery cell 210 and the second battery cell 220 are different battery cells in the battery module 200. In consideration of the signal flow direction between the battery cells in the battery module 200, the first battery cell 210 and the second battery cell 220 are preferably two adjacent battery cells in the battery module 200, so as to implement electrical signal detection and thermal protection between the adjacent battery cells.
Further, the first thermistor 122 and/or the second thermistor 132 are thermistors with positive temperature coefficients.
The thermistor includes a Positive Temperature Coefficient thermistor (PTC) and a Negative Temperature Coefficient thermistor (NTC), both of which are semiconductor resistors having Temperature sensitivity. When the temperature of the positive temperature coefficient thermistor is lower than a preset sensitive temperature range, the resistance value of the thermistor is very small or close to zero so as to reduce the influence of the thermistor on a circuit where the thermistor is located, and once the temperature of the thermistor reaches the preset sensitive temperature range, the resistance value of the thermistor is increased in a step mode along with the increase of the temperature, and the higher the temperature is, the larger the resistance value is. On the contrary, when the temperature of the thermistor is lower than the preset sensitive temperature range, the resistance value of the thermistor is very large to control the on-off state of the circuit, and once the temperature of the thermistor reaches the preset sensitive temperature range, the resistance value of the thermistor can be rapidly reduced along with the increase of the temperature, and the higher the temperature is, the smaller the resistance value is.
In the present embodiment, when applied to the thermal protection of the battery module 200, the thermistor is preferably a positive temperature coefficient thermistor. As a result, when the current of the battery module 200 receiving the electric signal is excessively large, the temperature of the balancing resistor increases. When the temperature value of the equalizing resistor is increased to a certain temperature value, the resistance value of the thermistor connected with the equalizing resistor in series is rapidly increased, so that the current in the circuit is reduced, the temperature is reduced, the battery module 200 is protected from being burnt due to overheating, and the thermal protection performance of the equalizing circuit is improved.
In one specific embodiment, one end of the first equalizing resistor 121 is connected to the first end 112 of the control sub-circuit, the other end of the first equalizing resistor 121 is connected to one end of the first thermistor 122, and the other end of the first thermistor 122 is connected to the input end of the first battery cell 210;
one end of the second balancing resistor 131 is connected to the second end 113 of the control sub-circuit, the other end of the second balancing resistor 131 is connected to one end of the second thermistor 132, and the other end of the second thermistor 132 is connected to the input end of the second battery cell 220.
When the circuit board is assembled, the equalizing resistors can be arranged to be connected with the corresponding thermistors in series, and the spacing distance is 1 mm to 3 mm, so that the thermistors can accurately sense the temperature of the equalizing resistors, and the current of the equalizing circuit is adjusted according to the temperature sensitivity.
Of course, the order of assembling the corresponding equalizing resistors and thermistors may be changed, for example, the first thermistor 122 is connected to the first end 112 of the control sub-circuit, the first equalizing resistor 121 is connected in series between the first thermistor 122 and the signal input end of the first battery cell 210, the second thermistor 132 is connected to the second end 113 of the control sub-circuit, and the second equalizing resistor is connected in series between the second thermistor 132 and the signal input end of the second battery cell 220.
The balancing resistor provided by the embodiment of the invention comprises the control sub-circuit and two series branches, wherein the first end and the second end of the control sub-circuit are respectively connected to the two single batteries of the battery module through the two series branches, and in addition, the control end of the control sub-circuit is connected to a control signal capable of controlling the conduction state between the first end and the second end. The two series branches comprise a balance resistor and a thermistor which are connected in series. Like this, if the signal of telecommunication of battery module access is too big, the electric current increase of series branch leads to the equalizing resistance to heat up, before reaching the safe temperature range of predetermineeing of battery module, thermistor's resistance increases along with the temperature risees rapidly, and then makes the electric current in the series branch reduce, and the temperature of equalizing resistance also reduces along with it to avoid battery module overheated burning, realized the thermal protection to battery module.
On the basis of the above embodiment, the control sub-circuit 110 includes a control transistor, a control electrode of the control transistor is used for accessing the control signal, a first electrode of the control transistor is connected with one end of the first equalizing resistor 121, and a second electrode of the control transistor is connected with one end of the second equalizing resistor 131.
In this embodiment, the control sub-circuit 110 includes a control transistor, i.e., a solid semiconductor device capable of performing a switching function, which is used as a variable current switch to control the on/off of the control sub-circuit by using a control signal, and the on/off speed is fast. Specifically, the control transistor includes a control electrode for receiving a control signal, a first electrode connected in series with the first equalizing resistor 121 or the first thermistor 122 in the first series branch 120, and a second electrode connected in series with the second equalizing resistor 131 or the second thermistor 132 in the second series branch 130.
The control transistor may be a field effect transistor, a thin film transistor, or a triode. If the control transistor is a field effect transistor or a thin film transistor, the control electrode of the control transistor corresponds to the grid electrode of the field effect transistor or the thin film transistor, and the first electrode and the second electrode respectively correspond to the source electrode and the drain electrode of the field effect transistor or the thin film transistor. Further, if the control transistor is an N-type transistor, the control transistor is turned on when the control signal is at a high level, i.e., the source and the drain are turned on. On the contrary, if the control transistor is a P-type transistor, when the control signal is at a low level, the control transistor is turned on, i.e., the source and the drain are turned on. In addition, if the control transistor is a triode, the control electrode corresponds to the base electrode of the triode, and the first electrode and the second electrode correspond to the collector electrode and the emitter electrode of the triode respectively.
In one embodiment, as shown in fig. 1, the equalizing circuit further comprises a bias resistor 140, and the bias resistor 140 is connected in series between the control electrode and the second electrode of the control transistor.
In this embodiment, a bias resistor 140 is connected in series between the control electrode and the second electrode of the control transistor, and one of the purposes is to control the transistor to provide a bias voltage. In addition, because the resistance between the control electrode and the second electrode is very large, very high voltage is generated at two ends of the equivalent capacitor between the gate and the second electrode due to very little electric quantity, and the addition of the bias resistor 140 can timely discharge the possibly existing very little electric quantity, so as to prevent two ends of the equivalent capacitor between the gate and the second electrode from being mistakenly broken down, and protect the control transistor.
In another embodiment, as shown in fig. 1, a parasitic diode is further present in the control transistor, and the parasitic diode is connected between the first pole and the second pole of the control transistor, and can play a role of free-wheeling to prevent avalanche breakdown of the control transistor.
When the equalization circuit provided by the embodiment of the present invention is applied to the management system of the battery module 200, under a normal condition, when the control sub-circuit 110 is controlled to be turned on by the control signal, the first thermistor 122 and the second thermistor 132 operate at a normal temperature, and the heating value thereof does not cause the increase of the resistance value. When the control sub-circuit 110 breaks down due to an overvoltage, the second pole of the control sub-circuit 110 is shorted to ground, the first pole and the second pole break down, resulting in an increase in current through the first equalizing resistor 121 and the second equalizing resistor 131, and thus in a temperature rise. When the temperature rises to the preset temperature value, the resistance values of the first thermistor 122 and the second thermistor 132 increase along with the temperature rise, so that the current limiting effect is achieved, and the battery module 200 is prevented from burning due to overhigh temperature rise of the equilibrium temperature.
Referring to fig. 2, fig. 2 is a schematic flow chart of a method for designing an equalization circuit according to an embodiment of the present invention, which is used for designing an equalization circuit applied to a battery module, where the equalization circuit may be the equalization circuit in the embodiment shown in fig. 1. As shown in fig. 2, the method mainly comprises the following steps:
and step 205, connecting the target thermistor and the equalizing resistor in series.
In the method for designing the equalizing circuit provided by the embodiment, the designed equalizing circuit is used for a thermal protection scheme of the battery module. The main design idea is to connect a thermistor in series with a balancing resistor of a commonly used balancing circuit, and to realize current-limiting thermal protection of the balancing circuit by utilizing the characteristic that the resistance value of the thermistor increases along with the rise of temperature within a certain temperature range.
Specifically, the battery module has the safe temperature range of predetermineeing, if the ambient temperature that the battery module was located does not exceed the safe temperature range of predetermineeing, then the battery module is in safe state, can not overheated burning. If the environmental temperature exceeds the preset safe temperature range, the battery module is in a dangerous state, and the danger of overheating combustion is possibly generated. When the temperature of the battery module rises, the ambient temperature also rises, and the temperature of the equalizing resistor in the equalizing circuit where the battery module is located also rises. In specific applications, the actual temperature of the battery module is usually higher than the temperature of the balancing resistor.
The thermistor has an operating temperature range, which is a temperature threshold of the thermistor when the resistance value of the thermistor increases, and a change relationship that the resistance value of the thermistor increases with the increase of the temperature. The thermistor is connected in series with the equalizing resistor when being assembled, and a small distance exists between the thermistor and the equalizing resistor, and the distance enables the temperature of the thermistor to change along with the temperature of the equalizing resistor, so that the temperature change of the thermistor is directly related to the temperature change of the equalizing resistor. Generally, the temperature variation trend of the thermistor along with the temperature of the equalizing resistor is only related to the assembly distance between the thermistor and the equalizing resistor, and is not directly related to the specific model of the thermistor.
When the design is specific, at least one test thermistor is selected to be connected in series with the equalizing resistor of the equalizing circuit. Optionally, the test thermistor comprises a first thermistor and a second thermistor; as shown in fig. 1, the equalization circuit may include:
the control sub-circuit 110, the control sub-circuit 110 includes a control terminal 110, a first terminal 112 and a second terminal 113, the control terminal 110 is configured to access a control signal, wherein the control signal is configured to control a conducting state between the first terminal 112 and the second terminal 113;
a first series branch 120, wherein the first series branch 120 includes a first equalizing resistor 121, the first equalizing resistor 121 is connected in series with the first thermistor 122, and the first series branch 120 is connected in series between the first end 112 and a signal input end of a first battery cell 210 in the battery module 200;
a second series branch 130, wherein the second series branch 130 includes a second equalizing resistor 131, the second equalizing resistor 131 is connected in series with a second thermistor 132, and the second series branch 130 is connected in series between the second end 113 and a signal input end of a second battery cell 220 in the battery module 200.
In addition, the test thermistor can be a thermistor with a positive temperature coefficient, the resistance value range of the test thermistor at normal temperature is [0, N ] ohm, and N is a first threshold value.
The resistance value of the test thermistor at normal temperature is defined to be greater than or equal to 0 ohm and less than or equal to the first threshold value, preferably equal to 0 ohm. Here, 0 ohm may mean that the thermistor has no resistance at normal temperature. However, considering that the resistance value of the thermistor at normal temperature is difficult to reach 0 ohm absolutely because of some tolerance in the resistor manufacturing process, a specific value of the first threshold may be limited to a milliohm level, for example, 30 milliohm, so as to limit the resistance value of the selected thermistor at normal temperature to approach zero infinitely. For example, the types of the thermistors are PRG21BC0R2MM1RA and PRG21BC0R6MM1RA, the thermistors are made of ceramics, and the performance is stable.
The thermistor with the resistance value close to or equal to 0 ohm at the normal temperature is adopted, the influence of the thermistor on the equalizing circuit is small when the thermistor is tested at the normal temperature, and the resistance protection circuit is increased only when the temperature reaches a certain temperature range, so that the equalizing runaway is avoided. Of course, the test thermistor may also be a thermistor with other positive temperature coefficients with smaller resistance at normal temperature, and is not limited. During specific design, the first mapping relation is determined according to the condition that the temperature of the equalizing resistor changes along with the ambient temperature, the second mapping relation is determined according to the condition that the temperature of the testing thermistor changes along with the temperature of the equalizing resistor, and then the selection type of the thermistor is determined according to the first mapping relation, the second mapping relation and the preset safe temperature clothing range of the battery module, namely the testing thermistor meeting the requirements is selected as a target thermistor and is connected in series with the equalizing resistor of the equalizing circuit.
It should be noted that the test thermistors are in a one-to-one correspondence with the determined target thermistors. For example, the equalization circuit includes: a first thermistor, i.e. a first test thermistor, in series with a first equalization resistor, and a second thermistor, i.e. a second test thermistor, in series with a second equalization resistor. Then, in contrast, the target thermistor determined after the test also includes: the first target thermistor is determined by the first test thermistor and the first series branch, and the second target thermistor is determined by the second test thermistor and the second series branch, the first target thermistor replaces the first test thermistor to be connected with the first equalizing resistor in series, and the second target thermistor replaces the second test thermistor to be connected with the second equalizing resistor in series.
In one embodiment, the step of selecting the target type of test thermistor as the target thermistor according to the first mapping relationship and the second mapping relationship in step 204 may include:
determining a first temperature range of the equalizing resistor, which needs thermal protection, according to the first mapping relation and a preset safe temperature range of the battery module;
determining a second temperature range of the thermistor needing thermal protection according to the first temperature range and the second mapping relation;
and determining the test thermistor with the working temperature range matched with the second temperature range as the target thermistor.
In the present embodiment, the scheme for determining the target thermistor is further defined. After the layout of the thermistor and the equalizing resistor on the circuit board is determined, firstly, the corresponding relationship between the temperature change of the thermistor and the temperature change of the equalizing resistor is determined through a temperature change test, namely, the change curve or the functional relationship of the temperature of the thermistor along with the temperature change of the equalizing resistor in a preset distance range.
Optionally, the step of determining the second mapping relationship of the temperature of the test thermistor varying with the temperature of the balancing resistor in step 203 may include:
assembling the test thermistor and the equalizing resistor on a circuit board according to a preset layout;
and adjusting the temperature of the equalizing resistor for multiple times, measuring temperature change data of the thermistor, and obtaining a second mapping relation of the temperature of the test thermistor along with the temperature change of the equalizing resistor.
The temperature change curves of the thermistors of different models are basically consistent, are related to the temperature of the equalizing resistor and the distance between the equalizing resistor and the thermistor, and are basically unrelated to the models of the thermistors, so that the temperature change curve tests of the thermistors of multiple models are not needed. In order to select a thermistor with a high matching degree or a high sensitivity, the distance between the equalizing resistor and the thermistor can be appropriately adjusted.
According to the preset safe temperature range of the battery module and the first mapping relation between the temperature of the equalizing resistor and the environment temperature, the temperature range of the equalizing resistor when the battery module needs to be thermally protected can be determined, and the temperature range is defined as a first temperature range, namely, after the equalizing resistor reaches the first temperature range, the current-limiting protection of the thermistor is needed.
Therefore, according to the first temperature range of the balancing resistor and the second mapping relation of the temperature of the thermistor along with the temperature change of the balancing resistor, the temperature range corresponding to the thermistor when the balancing resistor needs to be thermally protected can be determined and defined as the second temperature range. When the thermistor reaches the second temperature range, the current of the whole circuit needs to be limited by increasing the resistor, so that the equalizing circuit is thermally protected. Therefore, the thermistor with the working temperature range matched with the second temperature range can be found out to be used as the target thermistor to be connected. Of course, considering that the working temperature ranges of different thermistors are relatively close to each other, the thermistor with the resistance value increased greatly can be selected as far as possible, so that the current in the circuit is reduced as far as possible, and the safety of the battery module is protected.
Optionally, the step of determining the first mapping relationship of the temperature of the equalizing resistance varying with the ambient temperature in step 202 may include:
and determining a first mapping relation of the temperature of the equalizing resistor along with the change of the ambient temperature according to the maximum equalizing current of the battery monomer in the battery module, the ambient temperature and the resistance parameter of the equalizing resistor.
Further, the step of determining a first mapping relationship of the temperature of the balancing resistor changing along with the ambient temperature according to the maximum balancing current of the battery cell in the battery module, the ambient temperature and the resistance parameter of the balancing resistor includes:
calculating the resistance value and the power of the balancing resistor according to the maximum balancing current of the single battery of the battery module;
and determining the first mapping relation according to the environment temperature, the resistance value of the equalizing resistor, the power, the heat dissipation coefficient and the surface area.
In this embodiment, when the first mapping relationship is determined, the electrical parameters of the battery module according to the first mapping relationship at least include: the maximum equalizing current of the battery monomer, the ambient temperature and the resistance parameter of the equalizing resistance. Specifically, the resistance parameters of the equalizing resistor include resistance, power, heat dissipation coefficient and surface area. The resistance value and the power of the balancing resistor can be calculated according to the maximum balancing current and the working voltage of the single battery. Specifically, the formula for calculating the resistance value may be: r ═ Vmax/ImaxThe formula for calculating power may be: p ═ Imax*ImaxR. Wherein R represents the resistance of the equalizing resistor, P represents the power, and VmaxIndicating the maximum operating power of the battery cellPressure, ImaxRepresenting the maximum equalization current of the battery cell.
In a specific embodiment, as shown in table 1, the first mapping relationship includes at least one of the following:
TABLE 1
In the present embodiment, the first mapping relationship is explained by a specific numerical example. Namely:
for example, when the maximum equalizing current of the battery cell is 75mA, the maximum working voltage V of the battery cellmaxWhen the voltage is 4.2V, the power of the equalizing resistor is 0.315W; at this time, if the ambient temperature is 25 ℃, the coefficient of variation is 0.95, the coefficient of heat dissipation is 25, and the surface area of the equilibrium resistance is 8.00E-04 (i.e., 0.0008 square meter), the temperature of the equilibrium resistance is 39.96 ℃.
For example, when the maximum equalizing current of the battery cell is 100mA, the maximum working voltage V of the battery cellmaxWhen the voltage is 4.2V, the power of the balance resistor is 0.42W; at this time, if the ambient temperature is 40 ℃, the coefficient of variation is 0.95, the coefficient of heat dissipation is 25, and the surface area of the equilibrium resistance is 8.00E-04 (i.e., 0.0008 square meter), the temperature of the equilibrium resistance is 59.95 ℃.
For example, when the maximum equalizing current of the battery cell is 150mA, the maximum working voltage V of the battery cellmaxWhen the voltage is 4.2V, the power of the balance resistor is 0.63W; at this time, when the ambient temperature was 25 ℃, the coefficient of variation was 0.95, the heat dissipation coefficient was 25, and the surface area of the equalizing resistor was 1.60E-03, the temperature of the equalizing resistor was 39.96 ℃.
For other possible examples of the first mapping relationship, reference may be made to table 1 above, which is not described again. From the data sets in table 1 above, it can be seen that the temperature of the equalizing resistor changes with the change of the heat dissipation coefficient when the parameters such as the ambient temperature and the surface area of the equalizing resistor are determined. Of course, the data set corresponding to the first mapping relationship may also include other situations, and is not limited.
In another embodiment, the first mapping relationship is: the temperature of the equalization resistor is ambient temperature + K power/(heat dissipation coefficient surface area). And K is a variation coefficient, generally K can be 0.5-1.5, the value of the specific variation coefficient K can be determined according to the actual situation, and the temperature of the equalizing resistor can be determined when parameters such as power, heat dissipation coefficient and surface area of the equalizing resistor are determined according to the mapping relation without limitation. For example, when the power of a single battery is 0.315W, if the heat dissipation coefficient of the balancing resistor is 7.5, the variation coefficient K is 0.95, the surface area of the balancing resistor is 0.0008 square meter, and the ambient temperature is 40 ℃, the temperature of the balancing resistor is 40+0.95 × 0.315/(25 × 0.0008) ═ 54.96 ℃.
Of course, the formula corresponding to the mapping relationship of the balance resistance may have other situations, and is not limited.
And determining a test thermistor according to the steps, and arranging the test thermistor and the balance resistor on the flexible circuit board, wherein the distance between the test thermistor and the balance resistor is preferably set to be 1 mm. The temperature of the equalizing resistor and the temperature of the thermistor under different environmental temperatures can be obtained through multiple tests, a second mapping relation is obtained, the type of the thermistor matched with the working temperature range is selected, and the type of the thermistor is connected in the equalizing circuit in series. Therefore, under the normal balancing working condition, the resistance value of the target thermistor is kept unchanged, when the temperature of the balancing resistor is increased to a preset temperature value, the resistance value of the target thermistor is increased, and the current in the balancing circuit is reduced, so that the battery module is protected from being burnt or damaged due to overheating.
The design method of the equalization circuit provided by the embodiment of the invention is used for determining the required target thermistor in the equalization circuit according to the specific parameters of the equalization module in the battery module, so that when the electric signal accessed by the battery module is too large, the current of the series branch increases to cause the temperature rise of the equalization resistor, before the preset safe temperature range of the battery module is reached, the resistance value of the thermistor rapidly increases along with the temperature rise, the current in the series branch is further reduced, and the temperature of the equalization resistor is also reduced along with the current rise, so that the battery module is prevented from being burnt due to overheating, and the thermal protection of the battery module is realized. For a specific implementation process of the circuit design method provided in the embodiment of the present invention, reference may be made to the specific implementation process of the equalization circuit provided in the above embodiment, and details are not repeated here.
In addition, an embodiment of the present invention provides a battery management system, which is characterized by including a battery module and an equalizing circuit provided as the above embodiment shown in fig. 1.
According to the battery management system provided by the embodiment of the invention, the equalizing circuit is adopted to carry out thermal protection on the battery module, so that when an electric signal accessed by the battery module is overlarge, the current of the series branch of the equalizing circuit is increased to cause the temperature rise of the equalizing resistor, before the preset safe temperature range of the battery module is reached, the resistance value of the thermistor is rapidly increased along with the temperature rise, the current in the series branch is further reduced, the temperature of the equalizing resistor is also reduced along with the temperature rise, the battery module is prevented from being burnt due to overheating, and the thermal protection of the battery module is realized. For a specific implementation process of the battery management system provided in the embodiment of the present invention, reference may be made to the specific implementation process of the equalization circuit provided in the above embodiment, and details are not repeated here.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal (such as a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present invention.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (14)
1. A design method of an equalization circuit is applied to thermal protection in a battery module, and the equalization circuit comprises the following steps: the control sub-circuit (110), the control sub-circuit (110) comprising a control terminal (111), a first terminal (112) and a second terminal (113), the control terminal (111) being configured to access a control signal, wherein the control signal is configured to control a conducting state between the first terminal (112) and the second terminal (113);
a first series branch (120), wherein the first series branch (120) comprises a first equalizing resistor (121) and a first thermistor (122) which are connected in series with each other, and the first series branch (120) is connected in series between the first end (112) and a signal input end of a first battery cell (210) in the battery module (200);
a second series branch (130), the second series branch (130) comprising a second balancing resistor (131) and a second thermistor (132) connected in series with each other, the second series branch (130) being connected in series between the second end (113) and a signal input terminal of a second battery cell (220) in the battery module (200);
the design method of the equalization circuit comprises the following steps:
a thermistor is tested in series on the equalizing resistor of the equalizing circuit of the battery module;
determining a first mapping relation of the temperature of the equalizing resistor along with the change of the environment temperature;
determining a second mapping relation of the temperature of the test thermistor along with the temperature change of the equalizing resistor;
selecting a target type of test thermistor as a target thermistor according to the first mapping relation and the second mapping relation;
and connecting the target thermistor and the equalizing resistor in series.
2. The method according to claim 1, characterized in that the first thermistor (122) and/or the second thermistor (132) are thermistors with a positive temperature coefficient.
3. The method according to claim 1 or claim 2, characterized in that one end of the first equalizing resistor (121) is connected to a first end (112) of the control sub-circuit, the other end of the first equalizing resistor (121) is connected to one end of the first thermistor (122), the other end of the first thermistor (122) is connected to an input of the first battery cell (210);
one end of the second equalizing resistor (131) is connected with the second end (113) of the control sub-circuit, the other end of the second equalizing resistor (131) is connected with one end of the second thermistor (132), and the other end of the second thermistor (132) is connected with the input end of the second battery cell (220).
4. A method according to claim 3, characterized in that the control sub-circuit comprises a control transistor, the control transistor having a control electrode for switching in the control signal, the control transistor having a first electrode connected to one end of the first equalizing resistor (121) and a second electrode connected to one end of the second equalizing resistor (131).
5. The method of claim 3, wherein the first battery cell (210) and the second battery cell (220) are two adjacent battery cells in the battery module (200).
6. The method of claim 4, wherein the equalization circuit further comprises a bias resistor connected in series between the control electrode and the second electrode of the control transistor.
7. The method of claim 1, wherein the test thermistor is a positive temperature coefficient thermistor, and the resistance value of the test thermistor at room temperature is in the range of [0, N ] ohms, and N is in the milliohm range.
8. The method of claim 1, wherein the step of determining a first mapping of the temperature of the balancing resistor as a function of ambient temperature comprises:
and determining a first mapping relation of the temperature of the equalizing resistor along with the change of the ambient temperature according to the maximum equalizing current of the battery monomer in the battery module, the ambient temperature and the resistance parameter of the equalizing resistor.
9. The method according to claim 8, wherein the step of determining the first mapping relationship of the temperature of the balancing resistor varying with the ambient temperature according to the maximum balancing current of the battery cells in the battery module, the ambient temperature and the resistance parameter of the balancing resistor comprises:
calculating the resistance value and the power of the balancing resistor according to the maximum balancing current of the single battery of the battery module;
and determining the first mapping relation according to the environment temperature, the resistance value of the equalizing resistor, the power, the heat dissipation coefficient and the surface area.
10. The method of claim 9, wherein the first mapping relationship comprises at least one of:
11. the method of claim 9, wherein the first mapping relationship is: the temperature of the equalizing resistance is ambient temperature + K power/(heat dissipation coefficient surface area), wherein K is a coefficient of variation.
12. The method of claim 1, wherein said step of determining a second mapping of the temperature of said test thermistor as a function of the temperature of said balancing resistor comprises:
assembling the test thermistor and the equalizing resistor on a circuit board according to a preset layout;
and adjusting the temperature of the equalizing resistor for multiple times, measuring temperature change data of the thermistor, and obtaining a second mapping relation of the temperature of the test thermistor along with the temperature change of the equalizing resistor.
13. The method of claim 1, wherein the step of selecting the target type of test thermistor as the target thermistor according to the first mapping relationship and the second mapping relationship comprises:
determining a first temperature range of the equalizing resistor, which needs thermal protection, according to the first mapping relation and a preset safe temperature range of the battery module;
determining a second temperature range of the thermistor needing thermal protection according to the first temperature range and the second mapping relation;
and determining the test thermistor with the working temperature range matched with the second temperature range as the target thermistor.
14. A battery management system, characterized by comprising a battery module and an equalizing circuit, wherein the equalizing circuit is designed according to the design method of any one of claims 1 to 5.
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| CN114002482B (en) * | 2021-12-24 | 2022-03-18 | 深圳市永联科技股份有限公司 | Equipment current detection method and electronic equipment |
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