CN108983109B  Current estimation chip for battery, estimation method and residual electric quantity metering system  Google Patents
Current estimation chip for battery, estimation method and residual electric quantity metering system Download PDFInfo
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 CN108983109B CN108983109B CN201810912125.XA CN201810912125A CN108983109B CN 108983109 B CN108983109 B CN 108983109B CN 201810912125 A CN201810912125 A CN 201810912125A CN 108983109 B CN108983109 B CN 108983109B
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 WHXSMMKQMYFTQSUHFFFAOYSAN lithium Chemical compound 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[Li] WHXSMMKQMYFTQSUHFFFAOYSAN 0.000 description 1
 229910052744 lithium Inorganic materials 0.000 description 1
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Classifications

 G—PHYSICS
 G01—MEASURING; TESTING
 G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
 G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
 G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
 G01R31/3644—Constructional arrangements
 G01R31/3648—Constructional arrangements comprising digital calculation means, e.g. for performing an algorithm
Abstract
The invention relates to a current estimation chip for a battery, an estimation method and a remaining capacity metering system for a battery. The current estimation chip includes: the device comprises a temperature compensation module, a battery state judgment module and a calculation module; the temperature compensation module is used for receiving temperature information of the battery and compensating the internal resistance rdc of the battery according to the temperature information of the battery; the battery state judging module is used for receiving the battery voltage vbat and judging the state of the battery according to the change condition of the battery voltage vbat; the calculation module is used for estimating the current of the battery according to the battery voltage vbat, the battery state and the battery internal resistance rdc. The current estimation chip and the estimation method can realize accurate estimation of the battery current without using a current sampling resistor, can still accurately estimate the battery current even under the occasions of large current, low temperature and the like, and have low hardware system cost.
Description
Technical Field
The invention relates to the technical field of chips, in particular to a current estimation chip for a battery. The invention also relates to a current estimation method for a battery and a residual charge metering system for a battery.
Background
At present, with the popularization of electronic products such as intelligent wearing and intelligent terminals, accurate display of the remaining battery capacity becomes an important performance index of related products. If the remaining battery capacity cannot be accurately displayed, on one hand, user experience is affected, for example, problems that the used battery capacity changes unevenly, the battery capacity is shut down if more batteries exist, and charging is not full occur; on the other hand, the limit of battery power utilization is also affected.
Whether the display of the residual battery capacity is accurate depends on whether the measurement of the residual battery capacity is accurate or not; and whether the measurement of the residual electric quantity of the battery is accurate depends on whether the measurement of the current of the battery is accurate or not to a great extent.
In the prior art, in order to obtain the remaining capacity of the battery, the following two methods are generally adopted:
1. the method comprises the steps of collecting current information of a battery in real time by using a highprecision current sampling resistor, and obtaining the residual electric quantity of the battery through a series of calculations by using an impedance tracking algorithm and by using battery voltage and current information. Because the acquired current information is accurate, the acquired residual electric quantity of the battery is accurate. However, due to the use of high precision current sampling resistors, material costs, the cost of the IC itself, the production cost of the calibration current information, and the like are high.
2. The current sampling resistor is not used, only the information such as the voltage, the temperature and the like of the battery is sampled, the current of the battery is obtained through calculation, and then the residual electric quantity of the battery is obtained through calculation. However, due to the algorithm, the current metering method cannot accurately determine the states of the battery, such as different states of static state, charging state, discharging state, and the like, and does not consider the influence of temperature on the battery current, and the like, which results in inaccurate calculated battery current, and further cannot ensure accurate calculation result of the remaining power, and the user may find that the power change is abnormal when using the battery, and experience is poor.
Disclosure of Invention
Based on the above situation, a primary object of the present invention is to provide a current estimation chip and an estimation method for a battery, which can accurately estimate a battery current without using a current sampling resistor, so as to measure a remaining battery capacity with low cost and high accuracy. Another object of the present invention is to provide a remaining capacity metering system for a battery.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
according to a first aspect of the present invention, a current estimation chip for a battery includes: a temperature compensation module, a battery state judgment module and a calculation module, wherein,
the temperature compensation module is used for receiving the temperature information of the battery and compensating the internal resistance rdc of the battery according to the temperature information of the battery;
the battery state judging module is used for receiving the battery voltage vbat and judging the state of the battery according to the change condition of the battery voltage vbat;
the calculation module is used for estimating the current of the battery according to the battery voltage vbat, the battery state and the battery internal resistance rdc.
Preferably, the temperature compensation module compensates the internal resistance rdc of the battery by using a predetermined temperature compensation coefficient kt in a manner that: rdc ktr_{base}Wherein r is_{base}Is the internal resistance of the battery at a predetermined reference temperature.
Preferably, the battery state determination module includes:
an initial state judgment unit for judging an initial absolute percentage remaining capacity PCT of the battery;
and the state processing unit is used for judging the current state of the battery.
Preferably, the battery state determination module periodically receives the battery voltage vbat, and the state processing unit determines the battery voltage change rate dv/dt and a voltage change amplitude generated at the same voltage change rate dv/dt according to voltage data of a plurality of past cycles, and determines the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
Preferably, the calculation module comprises:
a current estimation unit for periodically estimating battery current ibat according to the battery voltage vbat and the battery internal resistance rdc^{*}And according to the battery state, estimating the battery current ibat^{*}Is determined at battery current ibat^{*}If the current is the real current, the estimation result is reserved, otherwise, the estimation result is discarded;
a current correction unit for correcting the estimated battery current ibat according to a predetermined current update coefficient^{*}And correcting to obtain an estimated value of the battery current.
Preferably, the current estimation unit estimates the battery current by:
wherein OCV is the opencircuit voltage of the battery, and kt is the temperature compensation coefficient.
Preferably, the current correction unit corrects the battery current in a manner that:
ibat^{*}←C1×ibat^{*}+C2；
where C1 and C2 are predetermined current update coefficients.
Preferably, the temperature compensation module, the battery state judgment module and the calculation module are integrated into one microprocessor.
Preferably, the device further comprises a storage module for storing the calculation result and the intermediate quantity and the initial quantity in the calculation process.
Preferably, the temperature compensation module, the battery state judgment module and the calculation module are all digital circuits.
Preferably, the battery state judgment module further comprises an IC sampling circuit, configured to collect battery voltage vbat and temperature information of the battery, and transmit a collection result to the battery state judgment module and the temperature compensation module.
According to a second aspect of the present invention, a current estimation method for a battery, which performs estimation using the aforementioned current estimation chip, comprises the steps of:
s200, the battery state judging module receives the battery voltage vbat and judges the state of the battery according to the change condition of the battery voltage vbat;
s300, the temperature compensation module receives the temperature information of the battery and compensates the internal resistance rdc of the battery according to the temperature information of the battery;
and S400, estimating the current of the battery by the calculation module according to the battery voltage vbat, the battery state and the battery internal resistance rdc.
Preferably, in the step S200, the battery state determination module periodically receives the battery voltage vbat, determines the battery voltage change rate dv/dt and a voltage change amplitude Δ vbat _ jump generated at the same voltage change rate dv/dt according to voltage data of a plurality of past cycles, and determines the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
Preferably, in step S300, the temperature compensation module compensates the internal resistance rdc of the battery by using a predetermined temperature compensation coefficient kt, and the compensation method is as follows: rdc ktr_{base}Wherein r is_{base}Is the internal resistance of the battery at a predetermined reference temperature.
Preferably, the calculation module comprises a current estimation unit and a current correction unit;
the step S400 includes the substeps of:
s410, the current estimation unit periodically estimates the battery current ibat according to the battery voltage vbat and the battery internal resistance rdc^{*}And according to the battery state, estimating the battery current ibat^{*}Is determined at battery current ibat^{*}If the current is the real current, retaining the estimated result, and executing the substep S420, otherwise, discarding the estimated result;
s420, the current correction unit performs correction on the estimated battery current ibat according to a predetermined current update coefficient^{*}And correcting to obtain an estimated value of the battery current.
Preferably, the current estimation chip further includes an IC sampling circuit;
the step S200 further includes the steps of:
s100, the IC sampling circuit collects battery voltage vbat and battery temperature information and transmits a collection result to the battery state judgment module and the temperature compensation module.
According to a third aspect of the present invention, a remaining capacity metering system for a battery includes:
the current estimation chip is used for estimating the current of the battery; and
and the residual electric quantity metering chip is used for calculating the residual electric quantity of the battery according to the estimated battery current.
Preferably, the remaining power metering chip includes:
an electric quantity increment calculation unit for calculating an electric quantity increment of the battery according to the estimated battery current;
and the residual capacity calculating unit is used for calculating the relative percentage residual capacity SOC of the battery according to the calculation result of the capacity increment calculating unit.
Preferably, the remaining power metering chip further includes:
and the aging compensation unit is used for estimating the change of the battery capacity Qmax, updating the battery capacity Qmax and transmitting the updating result to the electric quantity increment calculation unit for calculating the electric quantity increment of the battery.
Preferably, the system further comprises an upper computer, and the output end of the residual electricity quantity metering chip is connected with the upper computer so as to transmit the calculation result to the upper computer.
The current estimation chip and the estimation method for the battery do not need to use a current sampling resistor, but accurately estimate the current of the battery by measuring the voltage and the temperature of the battery, considering the influence of the temperature on the equivalent internal resistance of the battery and accurately judging the state of the battery, can accurately estimate the current of the battery even under the occasions of large current, low temperature and the like, and have low cost of a hardware system.
Drawings
Preferred embodiments of a current estimation chip, an estimation method, and a remaining capacity metering system according to the present invention will be described below with reference to the accompanying drawings. In the figure:
FIG. 1 is a schematic diagram of a current estimation chip according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of a remaining charge metering system according to a preferred embodiment of the present invention;
FIG. 3 is a hardware schematic diagram of a remaining charge metering system according to a preferred embodiment of the present invention;
FIG. 4 is a schematic diagram of the remaining charge metering chip shown in FIG. 2;
FIG. 5 is a flow chart of a current estimation method according to a preferred embodiment of the present invention;
fig. 6 is a flowchart of a remaining electric quantity measuring method according to a preferred embodiment of the present invention;
fig. 7 is a detailed process of the aging compensation step of fig. 6.
Detailed Description
Aiming at the problem that the metering cost of the residual battery capacity is high or the metering precision is insufficient due to inaccurate estimation of the battery current in the prior art, the invention provides a novel battery current estimation chip and an estimation method, which can realize highprecision current estimation with low cost, so that the metering of the residual battery capacity is more accurate and the metering cost is low. Based on the battery current estimation chip, the invention also provides a system and a method for measuring the residual electric quantity of the battery. It is to be readily understood that the battery according to the present invention is mainly referred to as a rechargeable battery.
The present invention relates in the context of a plurality of specific acronyms, whose meanings are as follows: OCV, i.e., open circuit voltage (open circuit voltage); PCT, absolute percentage remaining charge (percentage of battery Qmax); qmax, i.e., battery capacity (Maximum capacity of battery); SOC, i.e. the relative percentage of charge remaining (state of charge), refers to the relative percentage of charge remaining at a certain current, temperature and aging state. Because PCT refers to the amount of electricity that can be discharged when the battery is in an ideal state and the internal resistance rdc is 0; the SOC is a relative quantity, and is meaningful only when conditions such as current, temperature, aging degree, and discharge cutoff voltage vbat _ zero are determined, and therefore, in the system and method for measuring remaining battery power according to the present invention, the finally obtained remaining battery power is a relative percentage remaining battery power SOC.
A first aspect of the present invention provides a current estimation chip 100 for a battery, as shown in fig. 1, including: a temperature compensation module 200, a battery state judgment module 300, and a calculation module 400, wherein,
the temperature compensation module 200 is configured to receive temperature information of a battery, compensate an internal resistance rdc of the battery according to the temperature information of the battery, and transmit a compensation result to the battery state judgment module 300 or the calculation module 400;
the battery state judging module 300 is configured to receive the battery voltage vbat and judge the state of the battery according to a change of the battery voltage vbat;
the calculation module 400 is configured to estimate the current of the battery according to the battery voltage vbat, the battery state, and the battery internal resistance rdc.
The current estimation chip 100 of the present invention can judge the battery state and calculate the influence of the temperature on the equivalent internal resistance of the battery without using a current sampling resistor, only by inputting the battery voltage information and the temperature information, thereby realizing accurate estimation of the battery current based on the judgment result and the calculation result, and being capable of accurately estimating the battery current even under the occasions of large current, low temperature, etc., and having low system cost.
In specific implementation, a voltage acquisition module and/or a temperature acquisition module (not shown) may be disposed at an input end of the current estimation chip 100 of the present invention, the input end of the voltage acquisition module is electrically connected to a corresponding battery, so as to acquire a terminal voltage of the battery, convert the terminal voltage into a digital voltage signal, and output the digital voltage signal to an input end of the chip 100 (specifically, an input end of the battery state judgment module 300), and the temperature acquisition module acquires a temperature of the battery, converts the temperature into a digital temperature signal, and output the digital temperature signal to an input end of the chip 100 (specifically, an input end of the temperature compensation module 200).
Preferably, as shown in fig. 3, the IC sampling circuit 4 is disposed in the chip 100, the first resistors R1 and R2 are disposed outside the chip 100 for measuring the battery voltage, the third resistor R3 is disposed for measuring the temperature of the battery, the measured data are respectively transmitted to the voltage sampling terminal and the temperature sampling terminal of the IC sampling circuit 4, and the IC sampling circuit 4 converts the corresponding data into a digital voltage signal and a digital temperature signal and transmits the digital voltage signal and the digital temperature signal to the battery state judgment module 300 and the temperature compensation module 200. By way of example, the third resistor R3 may be a ntc resistor inside the battery, or a ntc resistor outside the battery, or other temperature sensing element, as long as the battery temperature can be sensed.
Alternatively, the current estimation chip 100 of the present invention can also obtain the voltage and temperature information of the battery from the corresponding BMS (i.e., battery management system) or PMU (i.e., power management unit) and directly use the information for calculation when in operation, and the object of the present invention can also be achieved.
Preferably, the battery state judging module 300 may include:
an initial state judgment unit for judging an initial absolute percentage remaining capacity PCT of the battery;
and the state processing unit is used for judging the current state of the battery, wherein the possible states of the battery comprise charging, discharging, stillness and the like.
The battery state determination module 300 is mainly used for comprehensively determining whether the battery is currently in a charging, discharging or static state according to the change rate of the voltage, the direction of the change rate, the amplitude of sudden change of the battery voltage and the like, and is significant in indicating the increase and decrease direction of the percentage of the remaining power from a qualitative point of view.
Preferably, the battery state determination module 300 receives the battery voltage in the static state as the opencircuit voltage OCV of the battery, and the initial state determination unit may determine the initial absolute percentage remaining capacity PCT of the battery according to a predetermined correspondence relationship (e.g., a predetermined OCVPCT curve or table) between the OCV and the PCT.
Preferably, the battery state determination module 300 receives the battery voltage vbat periodically, and the state processing unit determines the voltage change rate dv/dt and the voltage change amplitude generated at the same voltage change rate dv/dt of the battery according to the voltage data of a plurality of past periods, and determines the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
For example, the IC sampling circuit 4 collects the battery voltage vbat and updates the battery voltage vbat again every fixed cycle (e.g., 1 second, 2 seconds, etc.); on this basis, the battery state determination module 300 (specifically, the state processing unit) determines the voltage change rate dv/dt according to the current battery voltage vbat and the count values of the past several cycles, for example:
here, vbat4 is the current battery voltage, vbat3, vbat2 and vbat1 are the voltage count values of the past three cycles, respectively, and Δ t3, Δ t2 and Δ t1 are the corresponding time intervals, respectively.
Subsequently, the state processing unit rejoins the previously stored and periodically updated dv/dt value, which may be labeled, for example, (dv/dt)_{old}Calculating the voltage change amplitude generated under the same dv/dt:
where t0 denotes the time at which the dv/dt value starts, and tend denotes the time at which the dv/dt value ends.
Thus, the state processing unit can process the state according to dv/dt, (dv/dt)_{old}And Δ vbat _ jump judging the state of the battery: the discharge rate of the battery can be judged according to dv/dt, according to (dv/dt)_{old}The discharge rate at a moment on the battery can be determined, and the sudden change of the voltage, i.e., the voltage change amplitude Δ vbat _ jump, can be combined to determine whether the battery is in a discharged or charged or stationary state. For example dv/dt>(dv/dt)_{old}>0, and Δ vbat _ jump>Rdc _ x I, which is the current internal resistance of the battery, represents that the battery is currently in a charging state and the current is I.
Preferably, the temperature compensation module 200 compensates the internal resistance rdc of the battery by using a predetermined temperature compensation coefficient kt, in a manner that:
rdc＝kt*r_{base} (3)
wherein r is_{base}Is the internal resistance of the battery at a predetermined reference temperature (typically, normal temperature, e.g., 25 ℃).
The significance of the temperature compensation module 200 for compensating the internal resistance of the battery is that the corresponding metering system and metering method can adapt to the lowtemperature occasions, and the relative percentage remaining capacity can still be accurately calculated at low temperature.
Specifically, r_{base}The voltage difference of charge and discharge at the preset reference temperature is divided by the discharge current. The temperature compensation coefficient kt may be obtained in advance through a test, for example, the temperature compensation coefficient kt at each temperature is obtained by performing a test on a plurality of different temperatures, and is stored in a list form, and when the temperature compensation module 200 performs temperature compensation, the applicable temperature compensation coefficient kt may be determined according to a current battery temperature lookup table.
The temperature compensation module 200 may generate the temperature compensation coefficient kt (for example, obtained by table lookup) after the IC sampling circuit 4 outputs the battery temperature temp (or after the battery temperature temp is obtained through other ways), so as to compensate the equivalent internal resistance of the battery.
Preferably, the calculation module 400 may include:
a current estimation unit for periodically estimating the battery current ibat according to the battery voltage vbat and the battery internal resistance rdc^{*}And according to the battery state, estimating the battery current ibat^{*}Is determined at battery current ibat^{*}In the case of true current, the estimate is retained, e.g. by battery current ibat^{*}Transmitting the current to a current correction unit, otherwise, discarding the estimation result;
a current correction unit for correcting the estimated battery current ibat according to a predetermined current update coefficient^{*}And correcting to obtain an estimated value of the battery current.
Preferably, the current estimation unit estimates the battery current by:
wherein OCV is the opencircuit voltage of the battery, kt is the temperature compensation coefficient, r_{base}Is the internal resistance of the battery at a predetermined reference temperature.
Assuming that the battery is in a charged state, the battery voltage vbat increases, and therefore the charging current derived from the above equation should be positive. Given that the battery is in a discharged state, vbat will decrease, and hence the charging current derived from the above equation should be negative. Therefore, in conjunction with the battery state determined by the battery state determination module 300, it can be determined whether the estimated battery current is a real current or a false current. That is, if the charge/discharge state of the battery does not match the sign of the battery current, the estimated battery current is false, so that the estimated result can be discarded without being transmitted to the current correction unit, and the current will not be used to perform the subsequent current correction process.
However, since the equivalent internal resistance of the battery varies with the temperature and the discharge capacity, the accuracy of the battery current ibat can not be ensured by simply measuring rdc at various discharge currents and temperatures. Therefore, preferably, the present invention modifies the battery current ibat by the current modification unit in a dynamic tracking manner such that ibat gradually converges to the true ibat as follows:
ibat^{*}←C1×ibat^{*}+C2 (5)
wherein C1 and C2 are predetermined current update coefficients, which are determined, for example, by: multiple sets of charge and discharge data are measured in advance for the battery, for example, the battery is charged and discharged by using a fuel gauge which is not calibrated by C1 and C2, and the detection is carried out by using a precise coulometer, and the following values under different discharge currents and charge currents are taken (assuming that 6 sets are taken): (Δ C1 ), (Δ C2, Δ C2), (Δ C3 ), (Δ C4, Δ C4), (Δ C5 ) and (Δ C6, Δ C6), where Δ Ci (i ═ 1 to 6) is a fuel gauge measurement value and Δ Ci (i ═ 1 to 6) is a true value of coulometer measurement, the measurement value is compared with the true value, and then linear interpolation is performed, so that fitted C1 and C2 can be obtained.
By setting a suitable number of iterations (e.g. 210, preferably 25), it is ensured that the estimated battery current converges to a true current value.
Preferably, the temperature compensation module 200, the battery state judgment module 300 and the calculation module 400 are all microprocessors, and more preferably, these modules may be integrated into one microprocessor (e.g., the microprocessor 5 in fig. 3).
Preferably, as shown in fig. 3, the current estimation chip 100 of the present invention may further include memory modules connected to the microprocessor 5, such as general memory modules RAM 8 and ROM 7, for storing calculation results, intermediate and initial quantities during calculation, preset information (e.g., OCVPCT curve, temperature compensation coefficient list), and the like.
Alternatively, any one of the temperature compensation module 200, the battery state judgment module 200 and the calculation module 400 may also be a digital circuit.
On the basis of the above work, a second aspect of the present invention provides a remaining capacity metering system for a battery, as shown in fig. 2 to 3, comprising:
the current estimation chip 100 provided in the foregoing of the present invention is used for estimating the current of the battery; and
and a remaining capacity metering chip 500 for calculating a remaining capacity of the battery based on the estimated battery current.
Since the current estimation chip 100 of the present invention can estimate the battery current with low cost and accuracy, the remaining capacity measurement system of the present invention can calculate the remaining capacity of the battery with low cost and accuracy, so that the remaining capacity of the battery can be displayed more accurately.
Preferably, as shown in fig. 4, the remaining charge metering chip 500 includes:
a power increment calculation unit 600 for calculating a power increment of the battery based on the estimated battery current, for example, periodically;
a remaining capacity calculation unit (i.e., SOC calculation unit) 700 for calculating a relative percentage remaining capacity SOC of the battery, for example, periodically, based on the calculation result of the capacity increment calculation unit.
Preferably, the manner of calculating the power increment by the power increment calculating unit 600 is as follows:
where t0 represents the start of a cycle.
The following describes a process of the remaining power calculating unit 700 calculating the relative percentage remaining power SOC of the battery:
as the battery capacity changes, the relative percentage remaining capacity PCT of the battery also changes, where the amount of change is denoted as Δ PCT (t), and represents the increment of the change in the battery capacity percentage at the current time:
in the formula, Qmax is the battery capacity.
Therefore, the absolute percentage remaining power pct (t) of the battery at the current moment can be calculated, and the calculation formula is as follows:
pct(t)＝pct(t_{0})+Δpct(t) (8)
in the formula, pct (t)_{0}) Is the absolute percentage remaining capacity of the battery at the beginning of a cycle.
The present invention proposes the concept of residual capacity as a relative percentage of the residual capacity at a given cutoff voltage vbat _ zero, at a certain current and temperature. Because, the point at which the SOC is 0 is an amount related to the battery voltage.
vbat_zero+i_{load}*rdc(temp)＝OCV_{soc＝0} (9)
Rdc (temp) here is obtained from formula (3) and is the internal resistance at a certain temperature; i.e. i_{load}Is the load current.
When the SOC is 0, the corresponding battery voltage is the cutoff voltage, the value of which is related to the temperature temp, the load current i_{load}And (4) correlating. At this time, OCV_{soc＝0}The corresponding pct cannot be 0 but a dynamically changing value, pct x, where x is the footer of pct, representing pct at different states. This is distinguished from pct (t) in that pct x represents pct when SOC is 0, and pct is under a specific condition. According to the basic knowledge of lithium batteries, there is a specific onetoone correspondence between the open circuit voltage OCV and pct, which can be expressed as pct ═ f (OCV):
pctx＝f(OCV_{soc＝0}) (10)
therefore, SOC is a dynamic relative quantity calculated as:
where pcty is a pct value (y is also a subscript of pct) corresponding to OCV when the battery is fully charged, represents pct when SOC is 100, and is pct under specific conditions, and is denoted as pcty f (OCV)_{soc＝100})。
Then, remaining power calculating section 700 can obtain final output value SOC from equation (11).
The invention provides a concept of aging compensation and simultaneously provides a method for realizing aging compensation, because the capacity Qmax of the battery is reduced after the battery is charged and discharged circularly.
As shown in fig. 4, the remaining capacity measuring chip 500 of the present invention preferably further includes an aging compensation unit 800 for estimating a change in the battery capacity Qmax, updating the battery capacity Qmax, and transmitting the updated result to the increased capacity calculation unit 600 for calculating the increased capacity of the battery so as to more accurately calculate the relative percentage remaining capacity SOC of the battery.
Preferably, the aging compensation unit 800 updates the battery capacity Qmax in a manner that:
Qmax_{new}←kq×Qmax^{*}+(1kq)×Qmax_{old} (13)
wherein Qmax_{new}Is the updated battery capacity;
Qmax^{*}is the estimated current battery capacity;
Qmax_{old}is the battery capacity before updating;
kq is a predetermined aging compensation coefficient, denoted Qmax^{*}Account for Qmax_{new}The specific gravity of (a) can be determined by experiments;
pct (ta) and pct (tb) are absolute percentage remaining capacities of the battery in a stationary state twice before and after the battery;
and deltac is the increment of the electric quantity of the battery from the previous static state to the current static state.
That is, when the battery is in a state of satisfying the standstill condition, that is, when the voltage change Rate does not exceed Δ Rate, the battery may be considered to be in a standstill state, and the aging compensation unit 800 may perform aging compensation at this time. In the abovedescribed stationary condition, Δ Rate represents the voltage change Rate of the battery per second in μ V/s, and its value is, for example, a certain value of 100 or less. When performing the aging compensation, the aging compensation unit 800 may obtain the PCT (tb) of the current static state of the battery through a predetermined OCVPCT curve, and then may estimate the value of the battery capacity and the degree of aging based on the last static state PCT (ta) and the increment of the amount of electricity accumulated during the period between the two static states.
The aging compensation unit 800 calculates the updated battery capacity Qmax_{new}Then, it is transmitted to the electricity amount increase calculation unit 600, and the electricity amount increase calculation unit 600 transmits Qmax_{new}The calculation is carried out in the formula (7), so that the aging degree of the battery can be fully considered in the subsequent calculation, and the calculation of the residual electric quantity of the battery is more accurate.
Preferably, as shown in fig. 3, when the system for measuring remaining battery power in accordance with the preferred embodiment of the present invention is actually operated, the IC sampling circuit 4 inside the current estimation chip 100, the external first resistor R1 and the external second resistor R2 may jointly form a voltage acquisition module, the first resistor R1 and the second resistor R2 are connected in series and then connected to two ends of the battery 1, and a common end of the first resistor R1 and the second resistor R2 is connected to a voltage sampling end of the IC sampling circuit 4. Meanwhile, the IC sampling circuit 4 inside the current estimation chip 100 and the external third resistor R3 may jointly form a temperature acquisition module, one end of the third resistor R3 is connected to the negative electrode of the battery 1, and the other end is connected to the temperature sampling end of the IC sampling circuit 4.
In a specific application, as shown in fig. 3, the output end of the remaining power metering chip 500 may be further connected to the upper computer 6, so as to transmit the calculation result to the upper computer 6. Preferably, the upper computer 6 includes, but is not limited to, a mobile phone, a notebook computer, a tablet computer, a controller of an intelligent wearable device, an aircraft controller, a robot controller, an intelligent household appliance, an onvehicle multimedia device, or intelligent hardware, and the like.
As shown in fig. 3, the battery 1 is electrically connected to the load 2, and the positive electrode of the charger 3 is connected to the positive electrode of the battery 1. In the working process of the battery 1, under different occasions including the charging process of the battery 1, the power utilization process of the load 2, the static state of the battery 1 and the like, the IC sampling circuit 4 collects the terminal voltage of the battery 1 through the first resistor R1 and the second resistor R2, collects the temperature of the battery 1 through the third resistor R3, transmits the collection result to the microprocessor 5, and carries out microprocessingThe battery state judgment module 300, the temperature compensation module 200, the calculation module 400 and the like in the device 5 perform a series of operations to estimate the battery current and transmit the battery current to the remaining power metering chip 500, and then the relative percentage remaining power SOC and the updated battery capacity Qmax of the battery are obtained through a series of transportation of the remaining power metering chip 500_{new}And the obtained result can be transmitted to the upper computer 6, and the upper computer 6 displays the remaining capacity of the battery or informs the user in other modes.
Another aspect of the present invention provides a current estimation method for a battery, which is estimated, for example, by the current estimation chip 100 provided in the foregoing of the present invention, as shown in fig. 5, the method including the steps of:
s200, the battery state judging module 300 receives the battery voltage vbat and judges the state of the battery according to the change condition of the battery voltage vbat;
s300, the temperature compensation module 200 receives the temperature information of the battery and compensates the internal resistance rdc of the battery according to the temperature information of the battery;
s400, the calculating module 400 estimates the current of the battery according to the battery voltage vbat, the battery state and the battery internal resistance rdc.
The sequence of step S200 and step S300 may be interchanged or performed simultaneously.
The current estimation method can realize accurate estimation of the battery current by judging the battery state and calculating the influence of the temperature on the equivalent internal resistance of the battery under the condition of not using the current sampling resistor, and further based on the judgment result and the calculation result, can still accurately estimate the battery current even under the occasions of large current, low temperature and the like, and can effectively reduce the hardware cost.
In step S200, the battery voltage vbat received by the battery state determination module 300 may be from a voltage acquisition module outside the current estimation chip 100, or may be from, for example, BMS or PMU, or may be from the IC sampling circuit 4 inside the current estimation chip 100. Similarly, in step S300, the temperature information received by the temperature compensation module 200 may be from a temperature acquisition module outside the current estimation chip 100, or may be from, for example, a BMS or a PMU, or may be from the IC sampling circuit 4 inside the current estimation chip 100.
Preferably, when the current estimation chip 100 of the present invention includes the IC sampling circuit 4 (see fig. 3), as shown in fig. 5, the method further includes, before step S200, the steps of:
s100, the IC sampling circuit 4 collects the battery voltage vbat and the temperature information temp of the battery, and transmits the collected result to the battery state determining module 300 and the temperature compensating module 200.
Preferably, in the step S200, the battery state determination module 300 receives the battery voltage in the stationary state, and takes the battery voltage as the open circuit voltage OCV of the battery; then, an initial absolute percentage remaining capacity PCT of the battery may be determined according to a predetermined correspondence relationship between OCV and PCT (e.g., OCVPCT curve).
Preferably, in the step S200, the battery state determination module 300 periodically receives the battery voltage vbat, determines the voltage change rate dv/dt of the battery and the voltage change amplitude Δ vbat _ jump generated at the same voltage change rate dv/dt according to voltage data of a plurality of past cycles, and determines the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
That is, the IC sampling circuit 4 may continuously continue to collect the battery voltage vbat after the battery voltage vbat is collected for the first time, for example, the battery voltage vbat is updated again at regular intervals (e.g., 1 second, 2 seconds, etc.); on the basis of the voltage change rate dv/dt, the battery state determination module 300 may determine the voltage change rate dv/dt according to the current battery voltage vbat and the counting values of the past several cycles, for example, according to the aforementioned formula (1).
Preferably, in step S200, the voltage variation amplitude Δ vbat _ jump is calculated by equation (2):
where t0 indicates the time at which dv/dt starts, and tend indicates the time at which dv/dt ends.
That is, after calculating the rate of change of voltage dv/dt, the battery state determination module 300 may also reunite previously stored and periodically updated dv/dt values, such as may be labeled (dv/dt)_{old}The amplitude of the voltage change generated at the same dv/dt is calculated by equation (2).
Thus, in step S200, the battery state determination module 300 can determine the state of the battery based on dv/dt, (dv/dt)_{old}And Δ vbat _ jump judging the state of the battery: the discharge rate of the battery can be judged according to dv/dt, according to (dv/dt)_{old}The discharge rate at a moment on the battery can be determined, and the sudden change of the voltage, i.e., the voltage change amplitude Δ vbat _ jump, can be combined to determine whether the battery is in a discharged or charged or stationary state. For example dv/dt>(dv/dt)_{old}>0, and Δ vbat _ jump>Rdc _ x I, which is the current internal resistance of the battery, represents that the battery is currently in a charging state and the current is I.
Preferably, in the step S300, the temperature compensation module 200 compensates the internal resistance rdc of the battery by using a predetermined temperature compensation coefficient kt, and the compensation manner is as shown in formula (3):
rdc＝kt*r_{base}；
wherein r is_{base}Is the internal resistance of the battery at a predetermined reference temperature (typically, normal temperature, e.g., 25 ℃).
Specifically, as previously described, r_{base}The voltage difference of charge and discharge at the preset reference temperature is divided by the discharge current. The temperature compensation coefficient kt may be obtained in advance through a test, for example, a test is performed on a plurality of different temperatures to obtain the temperature compensation coefficient kt at each temperature, and the temperature compensation coefficient kt is stored in a list form, and when the temperature compensation module 200 performs temperature compensation in step S300, the applicable temperature compensation coefficient kt may be determined according to a current battery temperature lookup table.
Preferably, in the step S300, the temperature compensation module 200 first obtains current temperature information of the battery, and then determines the corresponding temperature compensation coefficient kt according to the temperature information table. Specifically, for example, the battery temperature may be collected by the IC sampling circuit 4 and the third resistor R3, or the battery temperature may be obtained by other means (for example, directly obtained from the corresponding BMS or PMU), so that the applicable temperature compensation coefficient kt may be determined.
Preferably, as shown in fig. 6, the step S400 includes the substeps of:
s410, estimating current: the current estimation unit periodically estimates battery current ibat according to battery voltage vbat and battery internal resistance rdc^{*}And judging the estimated battery current ibat according to the battery state^{*}The authenticity of (1), at the battery current ibat^{*}If the current is the real current, retaining the estimated result, and executing the substep S420, otherwise, discarding the estimated result;
s420, correction current: the current correction unit performs correction on the estimated battery current ibat according to a predetermined current update coefficient^{*}And correcting to obtain the corrected battery current.
Preferably, as shown in fig. 6, in step S400, the substep S420 further includes the substeps of:
and S430, judging whether the correction times reach the preset times, if so, finishing the correction, outputting an estimation result, and otherwise, returning to the substep S410. Here, the predetermined number of times is, for example, 2 to 10 times, preferably 2 to 5 times, for example, 3 times or 4 times, etc.
That is, before the predetermined number of corrections is reached, substeps S410 and substep S420 may be iteratively performed to iteratively track the battery current to approximate its true value.
Preferably, in said substep S410, it is according to equation (4), i.e.Estimate battery current ibat^{*}Where OCV is the open circuit voltage of the battery, kt is the temperature compensation coefficient, r_{base}Is the internal resistance of the battery at a predetermined reference temperature.
Subsequently, the estimated battery current ibat may be determined according to the battery state determined in step S200^{*}Whether or not it is a true current, e.g. such asIf the battery is in a charging state, the battery current ibat^{*}Should be positive, if the battery is in a discharged state, then the battery current ibat^{*}Should be negative, so if the chargedischarge state of the battery and the battery current ibat^{*}If the signs do not match, the predicted battery current ibat is indicated^{*}Is false, the result of this estimation can be discarded without performing the substep S420, and the false current will not be used to perform the subsequent current correction process.
Preferably, in the substep S420, according to equation (5), i.e. ibat^{*}←C1×ibat^{*}+ C2, for the estimated battery current ibat^{*}The correction is made, where C1 and C2 are predetermined current update coefficients.
Through the correction, an accurate battery current estimation value can be obtained.
Still another aspect of the present invention provides a method for measuring a remaining amount of battery, which is performed by the system for measuring a remaining amount of battery provided in the foregoing aspect of the present invention, for example, and includes the steps of:
s000, estimating the battery current by the current estimation chip 100; step S000 includes, for example, the aforementioned steps S100S400;
and S500, calculating the residual capacity of the battery by the residual capacity metering chip 500 according to the estimated battery current.
Specifically, as shown in fig. 6, the step S500 may further include the steps of:
s600, calculating the electric quantity increment: the incremental charge calculation unit 600 periodically calculates the estimated battery current (i.e. the corrected battery current ibat)^{*}) Calculating the electric quantity increment delta C of the battery;
s700, calculating SOC: the remaining power calculating unit 700 periodically calculates a relative percentage remaining power SOC of the battery according to the calculated power increment Δ C of the battery.
Preferably, in step S600, the electric quantity increment calculation unit 600 is according to equation (6), that isAnd calculating the increment of the electric quantity deltaC of the battery, wherein t0 represents the starting time of one period.
Preferably, in step S700, the remaining power calculating unit 700 sequentially performs the following calculations:
(1) calculating the percentage change increment delta pct (t) of the electric quantity of the battery at the current moment, wherein the calculation formula is formula (7), namelyWherein Qmax is the battery capacity;
(2) calculating the absolute percentage remaining power pct (t) of the battery at the current moment, wherein the calculation formula is formula (8), namely pct (t)_{0}) + Δ pct (t), where pct (t)_{0}) Absolute percentage remaining capacity of the battery at the start of a cycle;
(3) calculating the relative percentage remaining charge SOC of the battery according to the formula (11), that isWhere, pctx is the absolute percentage remaining capacity when the SOC of the battery is 0, and is denoted as pctx ═ f (OCV)_{soc＝0}) (ii) a pcty is the absolute percentage remaining capacity at which the SOC of the battery is 100, and is denoted as pcty f (OCV)_{soc＝100})。
Preferably, as shown in fig. 6, before the step S700, a step of:
s800, aging compensation: the aging compensation unit 800 estimates a change in the battery capacity Qmax, and updates the battery capacity Qmax to perform aging compensation on the battery capacity Qmax.
The method for measuring the residual electric quantity of the battery fully considers the condition that the capacity of the battery is reduced after the battery is charged and discharged circularly, and updates the capacity of the battery through the aging compensation step, so that the accuracy of measuring the residual electric quantity of the battery can be further improved.
Preferably, as shown in fig. 7, the step S800 includes the substeps of:
s810, judging whether the battery meets the static condition at present, if so, determining the absolute percentage residual capacity PCT of the battery under the current static condition, otherwise, continuing to wait until the static condition is met;
s820, taking absolute percentage remaining electric quantity pct (ta) and pct (tb) when the battery is in a static state twice before and after, and calculating electric quantity increment delta C of the battery from the previous static state to the current static state;
s830, estimating the current battery capacity Qmax^{*}The calculation formula is formula (12), i.e.
S840, updating the battery capacity Qmax in the manner of equation (13):
Qmax_{new}←kq×Qmax^{*}+(1kq)×Qmax_{old}；
wherein Qmax_{new}For updated battery capacity, Qmax_{old}Kq is a predetermined aging compensation coefficient for the battery capacity before update.
Preferably, in the substep S810, if the voltage change Rate per second of the battery does not exceed Δ Rate, the battery is considered to be in a static state, wherein Δ Rate ≦ 100 μ V. That is, in the abovedescribed stationary condition, Δ Rate represents the voltage change Rate of the battery per second in μ V/s, and its value is, for example, a certain value of 100 or less.
When the battery is in a stationary state, that is, when the voltage change Rate does not exceed Δ Rate, it may be considered that the battery is in a stationary state, and the aging compensation may be performed by the aging compensation unit 800. When performing the aging compensation, the aging compensation unit 800 may obtain the PCT (tb) of the current static state of the battery through a predetermined OCVPCT curve, and then may estimate the value of the battery capacity and the degree of aging based on the last static state PCT (ta) and the increment of the amount of electricity accumulated during the period between the two static states.
After determination of the updated battery capacity Qmax_{new}Then, the aging degree of the battery can be fully considered in the subsequent calculation by substituting the formula (7) in the step S700, so that the calculation of the remaining capacity of the battery is more accurate.
Fig. 6 shows a complete flow of a preferred embodiment of the battery remaining charge measuring method of the present invention, including the steps of:
a: the system is powered on and reset;
b: initializing a state;
c: detecting a voltage and a temperature (step S100);
d: judging whether the information has errors, such as whether the voltage and/or the temperature are obviously abnormal, if so, informing the upper computer to reset, otherwise, continuously executing the subsequent steps (such as step S200);
e: judging the battery state (step S200);
f: performing temperature compensation rdc (step S300);
g: estimating the current (step S410);
h: correcting the current (step S420);
i: judging whether the correction times reach (step S430), if not, returning to continue to execute the step S410, if so, continuing to execute the subsequent steps (step S600);
j: calculating the increment of the electric quantity (step S600);
k: judging whether a static condition is reached, if so, executing aging compensation (step S800), otherwise, continuing to execute the subsequent steps (step S700);
l: calculating the SOC (step S700);
m: and reporting the calculation result to an upper computer.
The steps CI are performed by the current estimation chip 100, and the steps JM are performed by the remaining charge measurement chip 500.
The current estimation chip, the estimation method, the residual electric quantity metering system and the metering method are verified by experiments, and the precision of metering the residual electric quantity of the battery is obviously higher than that of the scheme of not adopting a current sampling resistor in the prior art.
The current estimation chip and the residual electricity metering system can be applied to various occasions, including but not limited to various digitalanalog hybrid ICs, PMUs, BMS and other systems.
Those skilled in the art will readily appreciate that the abovedescribed preferred embodiments may be freely combined, superimposed, without conflict.
It will be understood that the embodiments described above are illustrative only and not restrictive, and that various obvious and equivalent modifications and substitutions for details described herein may be made by those skilled in the art without departing from the basic principles of the invention.
Claims (8)
1. A current estimation chip for a battery, comprising: a temperature compensation module, a battery state judgment module and a calculation module, wherein,
the temperature compensation module is used for receiving the temperature information of the battery and compensating the internal resistance rdc of the battery according to the temperature information of the battery, so that the estimated current ibat is estimated^{*}Adjusting the estimated current ibat^{*}The estimated current ibat is the ratio of the difference between the battery voltage vbat and the battery opencircuit voltage OCV to the internal battery resistance rdc when the battery is in a charging state^{*}Is a positive value, and estimates the current ibat when the battery is in a discharge state^{*}Negative, ibat at rest^{*}Is 0;
the battery state judging module is used for receiving the battery voltage vbat and judging the state of the battery according to the change condition of the battery voltage vbat;
the calculation module is used for estimating the current of the battery according to the battery voltage vbat, the battery state and the battery internal resistance rdc, wherein the calculation module comprises:
a current estimation unit for periodically estimating battery current ibat^{*}And according to the battery state, estimating the battery current ibat^{*}Is judged, and the calculated battery estimated current ibat is used^{*}When the symbol and the chargedischarge state of the battery accord with the correct corresponding relation, the estimation result is retained, otherwise, the estimation result is abandoned;
a current correction unit for estimating the current ibat of the reserved battery^{*}And correcting to obtain an estimated value of the battery current, wherein the battery current ibat is corrected in a dynamic tracking manner in such a way that ibat gradually increasesConverge to the true ibat:
ibat^{*}←C1×ibat^{*}+C2
wherein, C1 and C2 are predetermined current update coefficients, which are determined by: and measuring a plurality of groups of charging and discharging data of the battery in advance, comparing the measured values with the real values, and obtaining fitted C1 and C2 by linear interpolation.
2. The current estimation chip of claim 1, wherein the temperature compensation module compensates the internal resistance rdc of the battery by using a predetermined temperature compensation coefficient kt by: rdc ktr_{base}Wherein r is_{base}Is the internal resistance of the battery at a predetermined reference temperature.
3. The current estimation chip of claim 1, wherein the battery state determination module comprises:
an initial state judgment unit for judging an initial absolute percentage remaining capacity PCT of the battery;
and the state processing unit is used for judging the current state of the battery.
4. The current estimation chip of claim 3, wherein the battery state judgment module periodically receives the battery voltage vbat, and the state processing unit determines a battery voltage change rate dv/dt and a voltage change amplitude generated at the same voltage change rate dv/dt according to voltage data of a plurality of past cycles, and judges the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
5. A current estimation method for a battery, characterized in that estimation is performed using the current estimation chip according to one of claims 1 to 4, comprising the steps of:
s200, the battery state judging module receives the battery voltage vbat and judges the state of the battery according to the change condition of the battery voltage vbat;
s300, the temperature compensation module receives the temperature information of the battery and compensates the internal resistance rdc of the battery according to the temperature information of the battery;
s400, estimating the current of the battery by the calculating module according to the battery voltage vbat, the battery state and the battery internal resistance rdc, wherein the calculating module comprises a current estimating unit and a current correcting unit;
the step S400 includes the substeps of:
s410, the current estimation unit periodically estimates the battery current ibat^{*}And according to the battery state, estimating the battery current ibat^{*}Is judged, and the calculated battery estimated current ibat is used^{*}When the symbol and the chargedischarge state of the battery accord with the correct corresponding relation, retaining the estimation result, and executing the substep S420, otherwise, abandoning the estimation result;
s420, estimating current ibat of the reserved battery by the current correction unit^{*}And correcting to obtain an estimated value of the battery current, wherein the battery current ibat is corrected in a dynamic tracking manner as follows, so that ibat gradually converges to the real ibat:
ibat^{*}←C1×ibat^{*}+C2
wherein, C1 and C2 are predetermined current update coefficients, which are determined by: and measuring a plurality of groups of charging and discharging data of the battery in advance, comparing the measured values with the real values, and obtaining fitted C1 and C2 by linear interpolation.
6. The current estimation method according to claim 5, wherein in step S200, the battery state determination module periodically receives the battery voltage vbat, determines a battery voltage change rate dv/dt and a voltage change amplitude Δ vbat _ jump generated at the same voltage change rate dv/dt according to voltage data of a plurality of past cycles, and determines the current state of the battery according to the voltage change rate dv/dt and the voltage change amplitude.
7. The current estimation method according to claim 5 or 6,
the current estimation chip also comprises an IC sampling circuit;
the step S200 further includes the steps of:
s100, the IC sampling circuit collects battery voltage vbat and battery temperature information and transmits a collection result to the battery state judgment module and the temperature compensation module.
8. A remaining capacity metering system for a battery, comprising:
the current estimation chip according to one of claims 1 to 4, for estimating the current of a battery; and
the remaining capacity metering chip includes:
an electric quantity increment calculation unit for calculating an electric quantity increment of the battery according to the estimated battery current;
and the residual capacity calculating unit is used for calculating the relative percentage residual capacity SOC of the battery according to the calculation result of the capacity increment calculating unit.
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