JP3733663B2 - Electric vehicle battery capacity meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacity meter for a battery for an electric vehicle. In particular, even when the battery controller limits the output of the battery so that the inside of the battery does not exceed the limit temperature, it gives the driver dissatisfaction and discomfort. The present invention relates to a capacity meter for a battery for an electric vehicle that displays so as not to appear.
[0002]
[Prior art]
Conventionally, in an electric vehicle using a secondary battery, for example, a capacity meter of a battery for an electric vehicle is generally used as a means for notifying a driver of a dischargeable capacity (remaining capacity) of the secondary battery. It is.
In this capacity meter, for example, LED segments are arranged in a row in a “he” shape, the remaining capacity is full at the right end of the “he” character, the empty state is at the left end, and the LED segment is lit The remaining capacity is displayed (see FIG. 6).
As the characteristics of the secondary battery, the dischargeable capacity decreases when the battery temperature decreases (for example, below freezing point), but only the decrease in the dischargeable capacity at a low temperature is corrected and displayed on the capacity meter.
[0003]
[Problems to be solved by the invention]
However, for example, in a lithium ion secondary battery, when the internal temperature of the battery becomes higher than a certain limit temperature, the internal pressure increases, the electrolytic solution decomposes, etc., and the battery becomes unstable. It must be used and controlled so that its limit temperature is not exceeded.
As an example of such control, a case is assumed in which a high-load traveling that is not assumed at the time of designing an electric vehicle is performed in a state where the depth of discharge is deep during midsummer day. In this case, since the battery temperature rises rapidly, the battery controller limits the output of the battery so that the inside of the battery does not exceed the limit temperature.
[0004]
As a result, even though the battery capacity still remains and the capacity meter has not instructed empty (that is, a display indicating that the vehicle can normally run), the vehicle controller is in a driving state in which only the non-noro operation can be performed due to the output limitation of the battery controller. There is a problem that the driver is dissatisfied and uncomfortable. This is not preferable from the viewpoint of the merchantability of electric vehicles.
The present invention has been made in view of the above-described problems, and prevents the driver from being dissatisfied or uncomfortable even when a high load is performed in a state where the outside air temperature is high and the depth of discharge is deep. An object of the present invention is to provide a capacity meter for a battery for an electric vehicle that improves the merchantability of the vehicle.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is a secondary battery, a capacity meter that displays a remaining capacity of the secondary battery, a temperature detection unit that detects a temperature of the secondary battery, and the second battery. In an electric vehicle including a battery controller that obtains a remaining capacity that can be discharged by a secondary battery and limits the output of the secondary battery at a predetermined temperature, until the battery controller starts limiting the output of the secondary battery A first remaining capacity calculating means for obtaining a remaining capacity (first remaining capacity) that can be discharged by the secondary battery, a first remaining capacity obtained by the first remaining capacity calculating means, and the second obtained by the battery controller. comparison means for the next cell is compared with the dischargeable residual capacity (second remaining capacity), the comparison result of said comparing means, when the first remaining capacity is smaller than the second remaining capacity, the first residue the capacitor capacitance as the correction value Characterized in that a correction display means for displaying.
[0006]
According to the first aspect of the present invention, the first remaining capacity calculating means calculates the remaining capacity (first remaining capacity) that the secondary battery can discharge before the battery controller starts limiting the output of the secondary battery. Ask. The comparison means compares the first remaining capacity obtained by the first remaining capacity calculation means with the remaining capacity (second remaining capacity) that can be discharged by the secondary battery obtained by the battery controller. The correction display means displays the first remaining capacity as a correction value on the capacity meter when the comparison result of the comparing means is smaller than the second remaining capacity.
[0007]
According to a second aspect of the present invention, the first remaining capacity calculating means includes an average output calculating means for obtaining an average output of the secondary battery, and a current secondary battery temperature detected by the temperature detecting means. And a temperature rise time calculating means for calculating a time spent to rise to the secondary battery temperature at which the output restriction is started.
According to the second aspect of the present invention, the average output calculating means constituting the first remaining amount calculating means obtains the average output of the secondary battery, and the temperature rise time calculating means is the current detected by the temperature detecting means. The time spent for the secondary battery temperature to rise to the secondary battery temperature at which the output restriction starts is calculated.
[0008]
According to a third aspect of the present invention, the average output calculating means samples the battery having the highest battery temperature increase (temperature increase rate) per unit time by the temperature detecting means, thereby calculating the depth of discharge (DOD). It is a means for obtaining by performing a quadratic regression calculation as a parameter.
According to the third aspect of the invention, the average output calculating means samples the battery having the highest battery temperature rise (temperature increase rate) per unit time by the temperature detecting means, and uses the depth of discharge (DOD) as a parameter. Obtained by quadratic regression calculation.
[0009]
【The invention's effect】
According to the invention described in each claim, when the battery temperature is suddenly increased and the actual capacity remains, it is predicted that the output is limited and it becomes almost impossible to travel. Because it can predict the remaining capacity until the output limit is applied in response to the cooling state, and correct the capacity meter instruction,
It becomes possible for the driver to know the remaining travelable distance in a form that more closely matches. Therefore, the merchantability of the electric vehicle can be improved without causing dissatisfaction or discomfort to the driver.
In addition, since the remaining capacity can be predicted using only a very simple parameter such as the temperature rise rate, there is an effect that it is not necessary to newly add a dedicated detection means or control device.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiment.
FIG. 1 is a block diagram of this embodiment.
As shown in FIG. 1, the lithium ion secondary battery is configured as an assembled battery 1 by a plurality of modules 2, and each module 2 is provided with a temperature detection means 3 for detecting the surface temperature of the battery.
[0011]
The assembled battery 1 is housed in a battery case 5 and has a configuration in which cooling air is supplied to the battery by a cooling fan 6 as battery cooling means. In addition, as a cooling means, the structure which provides a cooling water channel | path and flows water with a pump may be sufficient.
A signal related to the temperature detected by the temperature detecting means 3 is input to the battery controller 4 and used for various battery controls.
[0012]
The battery controller 4 constantly monitors the voltage, current, temperature, etc. of the battery, calculates the battery output that can be output at that time, sends a signal to the motor controller 8 that controls the motor 7, and further supplies the fan 6 that cools the battery. In addition to performing control, all other control related to the battery is performed. That is, the battery controller 4 also performs control of the flowchart of FIG.
[0013]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG.
[0014]
Among the plurality of modules 2, the control means of the present embodiment has the highest battery surface temperature (hereinafter sometimes referred to as Tb) of 20 ° C. or more, and the depth of discharge (hereinafter referred to as DOD). It is applied only when it is 50% or more (see FIG. 3).
[0015]
In FIG. 2, first, the battery surface temperature detecting means 3 detects the battery surface temperature Tb at every appropriate sampling time τsam, and the highest Tb among Tb detected simultaneously at a certain time is defined as [Tbmax, n]. (Step S1).
The highest battery surface temperature detected one time before this maximum value is taken as [Tbmax, n-1], and the rate of temperature increase (ΔT / Δτ) n is obtained by the following equation, and the appropriate number of times (K times) It is repeatedly stored in a memory (not shown) in the battery controller 4 (step S2).
[0016]
[Expression 1]
(ΔT / Δτ) n = (Tbmax, n−Tbmax, n−1) / τsam
Then, as shown in FIG. 3, the K temperature increase rates (ΔT / Δτ) n stored in the memory are assumed to be a horizontal axis DOD and a vertical axis ΔT / Δτ, and second order regression is performed. The coefficient of the quadratic equation is obtained.
[0017]
Here, in the lithium ion battery, the temperature increase rate ΔT / Δτ can be approximated by the following quadratic expression using DOD as a parameter in a region where DOD is 50% or more (FIG. 3 is a graph obtained by experiment, The portion where the DOD is 50% or more can be approximated to a quadratic curve).
[0018]
[Expression 2]
ΔT / Δτ = A × B × [(DOD) ² + C × (DOD) + D]
A: Coefficient determined by battery output B: Coefficient C determined by action of battery cooling means, D: Coefficients C, D determined by battery heat generation characteristics are constants determined in advance from battery characteristics, A corresponds to battery output, B is uniquely determined corresponding to the action of the battery cooling means (for example, cooling air speed), and is given as a table as shown in FIG.
[0019]
The DOD is uniquely given to the open circuit voltage in advance from the battery characteristics, and the voltage and current sampled over an appropriate current range by the battery voltage detecting means and the battery current detecting means (not shown). The horizontal axis represents current and the vertical axis represents voltage, which is calculated from the open-circuit voltage given as an intercept of the voltage axis that has been linearly regressed (the slope at this time is the internal resistance; see FIG. 5A).
[0020]
That is, the coefficient of the quadratic equation obtained by quadratic regression of (ΔT / Δτ) n at a certain DOD sampled when cooling air is flowing at a certain wind speed is compared with the number in the given table. Then, an average output at time τsam × K is obtained (step S3). Hereinafter, this average output is referred to as Pave. The difference between the battery temperature Tlim at which the output limit starts to be applied and the current Tbmax, assuming that the vehicle continues to travel in Pave thereafter, ΔTlim = Tlim−Tbmax
The time τlim spent for temperature rise is calculated backward from the quadratic expression of DOD with respect to ΔT / Δτ obtained (step S4).
[0021]
Then, the remaining capacity Cr (to be described next) always calculated by the battery controller 4 is compared with the remaining capacity Pave × τlim until the output limit starts to be applied depending on the battery temperature. If Pave × τlim is smaller than Cr, Cr Instead of Pave × τlim as the remaining capacity, the capacity meter instruction is corrected (step S5; yes). Here, how to determine the remaining capacity Cr is, for example, calculated based on the battery open voltage and internal resistance (FIG. 5A) determined during the DOD calculation in the lithium ion secondary battery, and can be output in that state. The fact that the discharge power amount is uniquely given to the power (FIG. 5B) is used. Then, the discharge amount is calculated by weighting the discharge power amount obtained from the power integration and the discharge power amount obtained from the calculated outputable power by various parameters, and the remaining capacity subtracted from the full capacity in the fully charged state is obtained.
[0022]
However, in the case where the capacity meter 10 as shown in FIG. 6 is mounted, for example, if the actual remaining capacity is left for 3 segments (indicated by 3), the Pave × τlim is equivalent to 1 segment. If there is only one remaining, the driver will not feel uneasy about sudden changes in the capacity meter by repeatedly reducing it by 1 segment and reducing it by 1 segment at the next Pave calculation. Control is performed as follows (step S6).
[0023]
In addition, when the capacity meter 10 has a remaining capacity of 4 segments or more remaining, the outside air temperature is abnormally high and the load is extremely high, and the calculated Pave × τlim is close to zero. When the calculation result is obtained (step S7, step S8), the capacity meter correction is not performed, and the driver is informed that the output is limited by the turtle-shaped warning light 9 meaning non-noro travel (step S9). Control is made so as not to cause a sudden change in the capacity meter that is inappropriate in terms of merchantability.
[0024]
In addition, due to the output restriction due to the battery temperature, the remaining capacity is instructed to be empty while the actual battery capacity remains (step S10), and then the battery temperature drops from the output restriction area due to running or stopping at an extremely low load. In the case of detachment, the remaining capacity in calculation is returned to Cr, but the capacity meter instruction is controlled so as not to return until IGNoff (turns off the switch for enabling the electric vehicle to run) or is charged.
[0025]
For example, when considering a situation where the outside air temperature is 35 ° C. or higher and the Hakone turnpike is continuously climbing up at 50 to 60 km / h, the battery has such a performance that the battery temperature rises by about 20 ° C. from full capacity to empty. And cooling means, due to output restrictions due to battery temperature, as shown in FIGS. 7 and 8 (A), the conventional capacity meter indicating control leaves about 2% of the DOD at about 70%. You can only run. FIG. 7 is a view showing an example of the battery temperature rise when the vehicle continuously climbs uphill in midsummer.
[0026]
However, in the capacity meter correction control according to the present embodiment, as shown in FIG. 8B, the display is reduced from the actual remaining capacity by correcting the remaining capacity based on the rate of temperature increase after DOD 50% (FIG. 8 ( P of A) is compared with Q of FIG. 8B), and when the output is limited (DOD 70%), it becomes empty E (see Q1). In this way, the driver can sensuously know the remaining mileage, and it is possible to prevent in advance a situation in which the vehicle is still unable to travel even though the capacity remains It becomes.
[0027]
If [remaining capacity Cr> remaining capacity Pave × τlim] is not satisfied in step S5 (step S5; NO), if Cr = 0 (step S11; YES), the process ends. If Cr = 0 is not satisfied (step S5; NO) Step S11; NO), it returns to step S1.
[Brief description of the drawings]
FIG. 1 is a block diagram of an exemplary embodiment of the present invention.
FIG. 2 is a flowchart of the embodiment.
FIG. 3 shows a sampled ΔT using the fact that the relationship between ΔT / Δτ and DOD at a DOD of 50% or higher and a battery temperature of 20 ° C. or higher can be approximated by a quadratic equation in the lithium ion secondary battery used in the embodiment. It is the graph which showed the process which calculates | requires the coefficient of a quadratic equation from / Δτ by quadratic regression.
FIG. 4 is a table used in the embodiment, showing a coefficient table corresponding to an output given from battery characteristics and a coefficient table given from battery cooling means characteristics;
FIG. 5 is an explanatory diagram showing an example of calculation of the remaining capacity of the secondary battery in the same embodiment example;
FIG. 6 is a diagram showing a capacity meter in the same embodiment example;
FIG. 7 is a diagram showing an example of a rise in battery temperature when continuously climbing in midsummer in the embodiment.
FIG. 8 is a diagram showing a comparison of capacitance meter correction control according to a conventional example and the present embodiment.
[Explanation of symbols]
1 Battery assembly 2 Module 3 Battery temperature detection means 4 Battery controller 5 Battery case 6 Cooling fan 7 Motor 8 Motor controller 9 Output limit warning light

Claims (3)

A secondary battery, a capacity meter for displaying the remaining capacity of the secondary battery, temperature detecting means for detecting the temperature of the secondary battery, and obtaining a remaining capacity that can be discharged by the secondary battery, and at a predetermined temperature In an electric vehicle comprising a battery controller that limits the output of a secondary battery,
First remaining capacity calculating means for obtaining a remaining capacity (first remaining capacity) that can be discharged by the secondary battery before the battery controller starts limiting the output of the secondary battery ;
Comparing means for comparing the first remaining capacity obtained by the first remaining capacity calculating means and the remaining capacity (second remaining capacity) that can be discharged by the secondary battery obtained by the battery controller;
And a correction display means for displaying the first remaining capacity as a correction value on the capacity meter when the comparison result of the comparing means is smaller than the second remaining capacity. Electric vehicle battery capacity meter. The first remaining capacity calculating means includes
Average output calculating means for obtaining an average output of the secondary battery;
2. A time calculating means for calculating a time spent for the current secondary battery temperature detected by the temperature detecting means to rise to a secondary battery temperature at which the output restriction is started. The capacity meter of the battery for electric vehicles as described. The average output calculation means is a means for obtaining by performing a second regression calculation using a discharge depth (DOD) as a parameter by sampling a battery having the highest battery temperature increase (temperature increase rate) per unit time by the temperature detection means. The capacity meter for a battery for an electric vehicle according to claim 2, wherein:

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