Secondary battery residual capacity meter

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a residual capacity meter for measuring the remaining capacity of an assembled battery mounted on an electric vehicle such as an electric vehicle.

【0002】

[Conventional technology]

Pure electric vehicles and hybrid electric vehicles are equipped with an assembled battery in which a large number of battery units of secondary batteries are connected in series. The remaining capacity meter of the assembled battery is used as a substitute for the fuel meter not only to grasp the mileage and the required charging time, but also to prevent deterioration of the assembled battery due to over-discharging or over-charging. That is, since the assembled battery deteriorates due to over-discharging, the discharge is limited when the remaining capacity becomes a certain level or less. Similarly, since the assembled battery deteriorates due to overcharging, charging is restricted when the remaining capacity exceeds a certain level. Therefore, it is extremely important for an electric vehicle to accurately grasp the remaining capacity of the assembled battery.

【0003】

FIG. 3 is a block diagram showing an example of a conventional remaining capacity meter mounted on an electric vehicle. Hereinafter, description will be given based on this drawing.

【0004】

The conventional remaining capacity meter 80 includes a voltage measuring unit 86 for measuring the total output voltage V of the assembled battery 84 in which a large number of secondary battery battery units 821,822, ..., 82n are connected in series, and the assembled battery 84. The current measuring unit 88 that measures the discharge current Id or the charging current Ic, the temperature measuring unit 90 that measures the temperature T of the assembled battery 84, and the total output voltage V measured by the voltage measuring unit 86 are combined with the current measuring unit 88. It is equipped with a residual capacity estimation unit 92 that estimates the remaining capacity C of the assembled battery 84 by correcting it using the discharge current Id or charge current Ic measured in the above and the temperature T measured by the temperature measurement unit 90. Is.

【0005】

The voltage measuring unit 86 includes a conducting wire 861,862 connected to the positive electrode and the negative electrode of the assembled battery 84, respectively, and a voltage measuring circuit 863 that converts the voltage between the conducting wires 861,862 into a voltage signal. The current measuring unit 88 includes a current sensor 881 that detects the current flowing in and out of the assembled battery 84, and a current measuring circuit 882 that converts the current detected by the current sensor 881 into a voltage signal. The temperature measuring unit 90 includes a temperature sensor 901 that detects the temperature of the assembled battery 84, and a temperature measuring circuit 902 that converts the temperature detected by the temperature sensor 901 into a voltage signal. The current sensor 881 is, for example, a current detection coil. The temperature sensor 901 is, for example, a thermistor. The voltage measurement circuit 863, the current measurement circuit 882, and the temperature measurement circuit 902 include, for example, an amplifier, an A / D converter, and the like. The remaining capacity estimation unit 92 includes, for example, a microprocessor and its computer program.

【0006】

The assembled battery 84 is connected to either the control circuit 961 or the charger 962 via the changeover switch 94. The control circuit 961 energizes and controls the traveling motor 982. The charger 962 generates a DC voltage for charging from the commercial power supply 982.

【0007】

Next, the operation of the remaining capacity meter 80 will be described.

【0008】

The total output voltage V when the assembled battery 84 is open corresponds to the remaining capacity C. Therefore, the remaining capacity C can be indirectly measured by measuring the total output voltage V. However, the total output voltage V at the time of discharging or charging the assembled battery 84 becomes lower as the discharge current Id or the charging current Ic becomes larger due to the internal resistance of the assembled battery 84 or the like. Further, the higher the temperature T of the assembled battery 84, the higher the total output voltage V because the chemical reaction is activated. Therefore, the relationship between the total output voltage V, the charging current Ic, the discharge current Id, and the temperature T and the remaining capacity C is investigated in advance, and these data are mapped to the remaining capacity estimation unit 92. As a result, the remaining capacity C can be known by correcting the total output voltage V using the charge current Ic, the discharge current Id, and the temperature T.

【0009】

When the remaining capacity C becomes equal to or lower than the lower limit value during traveling, the remaining capacity meter 80 stops the traveling motor 982 via, for example, the control circuit 961. Further, when the remaining capacity C becomes equal to or higher than the upper limit value during charging, the remaining capacity meter 80 terminates charging via the charger 981. In this way, deterioration of the assembled battery 84 due to over-discharging or over-charging is prevented.

【0010】

[Problems to be Solved by the Invention]

However, the conventional remaining capacity meter 80 has the following problems.

【0011】

The large number of battery units 821 to 82n constituting the assembled battery 84 have variations in charge / discharge characteristics and the degree of deterioration. On the other hand, in the conventional remaining capacity meter 80, charging / discharging is stopped based on the remaining capacity C obtained by the total output voltage V of the assembled battery 84. As a result, some of the battery units 821 to 82n were over-discharged or over-charged, and their deterioration was accelerated.

【0012】

[Purpose of Invention]

Therefore, an object of the present invention is to provide a secondary battery remaining capacity meter capable of reliably preventing over-discharging and over-charging of the assembled battery by accurately grasping the remaining capacity of the assembled battery.

【0013】

[Means for solving problems]

The remaining capacity meter according to the present invention measures the remaining capacity of the assembled battery, and includes a voltage measuring unit, a current measuring unit, a temperature measuring unit, and a remaining capacity estimating unit. The assembled battery is formed by connecting a large number of battery units of secondary batteries in series.

【0014】

The remaining capacity meter according to claim 1 has the following configuration. The voltage measuring unit measures the output voltage for each battery unit. The current measuring unit measures the discharge current of the assembled battery. The temperature measuring unit measures the temperature for each battery unit. The remaining capacity estimation unit corrects the output voltage measured by the voltage measuring unit using the discharge current measured by the current measuring unit and the temperature measured by the temperature measuring unit, thereby correcting the remaining capacity of each battery unit. Is calculated, and the remaining capacity of the assembled battery is estimated based on the minimum remaining capacity of these. Further, the remaining capacity estimation unit has a function of limiting discharge when the minimum remaining capacity reaches the lower limit value (claim 2).

【0015】

Many battery units that make up an assembled battery vary in charge / discharge characteristics and the degree of deterioration. Therefore, the output voltage and temperature of each battery unit are measured, and the output voltage is corrected by the temperature and discharge current to obtain the remaining capacity of each battery unit. Then, the remaining capacity of the assembled battery is estimated based on the minimum remaining capacity. That is, the remaining capacity of the assembled battery at this time corresponds to the battery unit having the smallest remaining capacity. Therefore, there is no possibility that the battery unit having the smallest remaining capacity will be over-discharged.

【0016】

In addition, the assembled battery mounted on an electric vehicle has a structure in which a large number of battery units are stacked vertically and horizontally and has a large amount of electricity, so that heat tends to be trapped inside. Therefore, the battery unit on the inner side becomes considerably hotter than the battery unit on the outer side. Therefore, in the remaining capacity meter according to the present invention, the remaining capacity of each battery unit is accurately estimated by measuring the temperature of each battery unit and correcting the output voltage of each battery unit based on the temperature. ..

【0017】

The remaining capacity meter according to claim 3 has the following configuration. The voltage measuring unit measures the output voltage for each battery unit. The current measuring unit measures the charging current of the assembled battery. The temperature measuring unit measures the temperature for each battery unit. The remaining capacity estimation unit corrects the output voltage measured by the voltage measuring unit using the charging current measured by the current measuring unit and the temperature measured by the temperature measuring unit, thereby correcting the remaining capacity of each battery unit. Is calculated, and the remaining capacity of the assembled battery is estimated based on the maximum remaining capacity of these. Further, the remaining capacity estimation unit has a function of limiting charging when the maximum remaining capacity reaches the upper limit value (claim 4).

【0018】

Many battery units that make up an assembled battery vary in charge / discharge characteristics and the degree of deterioration. Therefore, the output voltage and temperature of each battery unit are measured, and the output voltage is corrected by the temperature and charging current to obtain the remaining capacity of each battery unit. Then, the remaining capacity of the assembled battery is estimated based on the maximum remaining capacity. That is, the remaining capacity of the assembled battery at this time corresponds to the battery unit having the largest remaining capacity. Therefore, there is no possibility that the battery unit having the largest remaining capacity will be overcharged.

【0019】

The voltage measuring unit may measure the output voltage for each of a plurality of battery units (claim 5). The temperature measuring unit may measure the temperature for each of a plurality of battery units (claim 6). In these cases, the configurations of the voltage measuring unit and the temperature measuring unit are simplified.

【0020】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing an embodiment of a remaining capacity meter according to the present invention. Hereinafter, description will be given based on this drawing. However, the same parts as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

【0021】

The remaining capacity meter 10 of the present embodiment measures the remaining capacity C of the assembled battery 84, and includes a voltage measuring unit 12, a current measuring unit 88, a temperature measuring unit 14, and a remaining capacity estimating unit 16. The assembled battery 84 is formed by connecting a large number of secondary battery unit 821,822, ..., 82n in series. The battery units 821 to 82n are lead batteries.

【0022】

The voltage measuring unit 12 measures the output voltages V1, V2, ..., Vn for each battery unit 821 to 82n. The current measuring unit 88 measures the discharge current Id or the charge current Ic of the assembled battery 84. The temperature measuring unit 14 measures the temperatures T1, T2, ..., Tn for each of the battery units 821 to 82n. The remaining capacity estimation unit 16 uses the output voltage V1 to Vn measured by the voltage measurement unit 12 as the discharge current Id or charge current Ic measured by the current measurement unit 88 and the temperature T1 to Tn measured by the temperature measurement unit 14. By making corrections using and, the remaining capacities C1 to Cn for each battery unit 821 to 82n are obtained.

【0023】

In addition, the remaining capacity estimation unit 16 has the following functions. The remaining capacity C of the assembled battery 84 is estimated based on the minimum remaining capacity Cmin of the remaining capacities C1 to Cn during discharge (that is, during running). When the remaining capacity Cmin reaches the lower limit Cl, the discharge is limited via the control circuit 961. For example, stop the discharge. At the time of charging, the remaining capacity Cmax of the assembled battery 84 is estimated based on the maximum remaining capacity Cmax of the remaining capacities C1 to Cn. When the remaining capacity Cmax reaches the upper limit Ch, charging is restricted via the charger 981. For example, stop charging.

【0024】

The voltage measuring unit 12 is a voltage between the conducting wires 121, 122, ..., 12n, 12 (n + 1) and the conducting wires 121 to 12 (n + 1) connected to the positive electrode and the negative electrode of each battery unit 821 to 82n, respectively. Is provided with a voltage measuring circuit 13 that converts the voltage into a voltage signal. The temperature measuring unit 14 includes a temperature sensor 141, 142, ..., 14n that detects the temperature of each battery unit 821 to 82n, and a temperature measuring circuit 15 that converts the temperature detected by the temperature sensors 141 to 14n into a voltage signal. It has. The temperature sensors 141 to 14n are, for example, thermistors. The voltage measurement circuit 13 and the temperature measurement circuit 15 include, for example, an amplifier, an A / D converter, and the like. The remaining capacity estimation unit 16 includes, for example, a microprocessor and its computer program.

【0025】

The n battery units 821 to 82n constituting the assembled battery 84 have variations in charge / discharge characteristics and the degree of deterioration. Therefore, the output voltages V1 to Vn and the temperatures T1 to Tn of each battery unit 821 to 82n are measured, the output voltages V1 to Vn are corrected by the temperature T1 to Tn and the discharge current Id or the charging current Ic, and each battery is used. Find the remaining capacities C1 to Cn of units 821 to 82n. Then, at the time of discharging (that is, during running), the remaining capacity C of the assembled battery 84 is estimated based on the minimum remaining capacity Cmin among the remaining capacities C1 to Cn. For example, let (remaining capacity Cmin) × n be the remaining capacity C of the assembled battery 84. That is, the remaining capacity C of the assembled battery 84 at this time corresponds to the battery unit 82 min having the smallest remaining capacity. Therefore, there is no possibility that the battery unit 82 min, which has the smallest remaining capacity, will be over-discharged.

【0026】

On the other hand, at the time of charging, the remaining capacity C of the assembled battery 84 is estimated based on the maximum remaining capacity Cmax of the remaining capacities C1 to Cn. For example, let (remaining capacity Cmax) × n be the remaining capacity C of the assembled battery 84. That is, the remaining capacity C of the assembled battery 84 at this time corresponds to the battery unit 82max having the largest remaining capacity. Therefore, there is no possibility that the battery unit 82max having the largest remaining capacity will be overcharged. Since the battery units 821 to 82n are connected in series, the discharge current Id and the charge current Ic are the same for all the battery units 821 to 82n.

【0027】

In addition, the assembled battery 84 mounted on an electric vehicle has a structure in which a large number of battery units 821 to 82n are stacked vertically and horizontally and has a large amount of electricity, so that heat tends to be trapped inside. Therefore, the battery unit on the inner side becomes considerably hotter than the battery unit on the outer side. Therefore, in the remaining capacity meter 10, the temperatures T1 to Tn are measured for each battery unit 821 to 82n, and the output voltages V1 to Vn of each battery unit 821 to 82n are corrected based on the temperature T1 to Tn. The remaining capacities C1 to Cn of the battery units 821 to 82n are accurately estimated.

【0028】

FIG. 2 is a flowchart showing the operation of the remaining capacity meter 10. Hereinafter, a description will be given based on FIGS. 1 and 2.

【0029】

In this description, the output voltage is simply referred to as "voltage" and the discharge current or charge current is simply referred to as "current". First, k = 1 is set (step 100), and the voltage Vk and the current Ik of the battery unit 82k are simultaneously measured via the voltage measuring unit 12 and the current measuring unit 88 (step 101). Subsequently, the voltage Vk is corrected by the current Ik, and this is set as the voltage Vk'at a constant current (including 0) (step 102). Subsequently, the temperature Tk of the battery unit 82k is measured via the temperature measuring unit 14 (step 103). Subsequently, the voltage Vk'is corrected by the temperature Tk, and this is set as the voltage Vk at a constant current and a constant temperature (step 104). Then, the voltage is based on the relationship between the pre-mapped voltage and the remaining capacity. Convert Vk to the remaining capacity Ck (step 105). The above steps 101 to 105 are repeated until k> n (steps 106 and 107).

【0030】

Subsequently, the minimum remaining capacity Cmin or the maximum remaining capacity Cmax is extracted from the remaining capacities C1 to Ck (step 108). Subsequently, the remaining capacity C of the assembled battery 84 is estimated based on the minimum remaining capacity Cmin or the maximum remaining capacity Cmax (step 109). For example, the remaining capacity C is obtained by multiplying the minimum remaining capacity Cmin or the maximum remaining capacity Cmax by the number n of the battery units 821 to 82n.

【0031】

Next, another embodiment of the remaining capacity meter 10 will be described.

【0032】

The voltage measuring unit 12 may measure the output voltage for each m (1 <m <n) battery units 821, .... In this case, the number of conductors 121, ... May be 1 / m, and the number of data processed by the voltage measuring circuit 13 is also 1 / m, so that the voltage measuring unit 12 is simplified. The output voltage measured by the voltage measuring unit 12 is the output voltage of m battery units 821, ... Connected in series.

【0033】

The temperature measuring unit 14 may measure the temperature for each m (1 <m <n) battery units 821, .... In this case, the number of temperature sensors 141, ... May be 1 / m, and the number of data processed by the temperature measuring circuit 15 is also 1 / m, so that the temperature measuring unit 14 is simplified. The temperature of each battery unit 821, ... Is measured by the temperature sensor 141, ... At the closest position, with all m having the same value.

【0034】

At this time, the temperature measuring unit 14 may measure the temperature of only the main battery units 821, .... For example, the temperature sensor 141, ... Is densely arranged on the inner battery unit 821, ... With a large temperature change, and the temperature sensor 141, ... Is placed on the outer battery unit 821, ... with a small temperature change. Arrange .. sparsely.

【0035】

Further, the temperature measuring unit 14 may measure the temperature of the battery units 821, ... with a number of temperature sensors 141, ... Less than the number n of the battery units 821, .... The temperature distribution of the battery units 821, ... Housed in a case having a fixed shape becomes constant according to the operating state. The operating state includes battery current, outside air temperature, vehicle speed, and the like. The temperature of each battery unit 821, ... is obtained by inputting the measured temperature into the map that is changed by these operating conditions.

【0036】

Needless to say, the present invention is not limited to the above embodiment. For example, the battery unit is not limited to a lead battery, and may be a lithium ion battery, a nickel hydrogen battery, or the like. When the present invention is applied to a hybrid electric vehicle, the charger portion becomes a generator.

【0037】

[Effect of the invention]

According to the remaining capacity meter according to the present invention, the output voltage and temperature of each battery unit are measured, the output voltage is corrected by the temperature and the discharge current, and the remaining capacity of each battery unit is obtained. By estimating the remaining capacity of the assembled battery based on the minimum remaining capacity, the remaining capacity of the assembled battery corresponds to the battery unit having the minimum remaining capacity, so that over-discharging of the battery unit having the minimum remaining capacity can be prevented (claim 1, 2).

【0038】

According to the remaining capacity meter according to the present invention, the output voltage and temperature of each battery unit are measured, the output voltage is corrected by the temperature and the charging current, and the remaining capacity of each battery unit is obtained. By estimating the remaining capacity of the assembled battery based on the maximum remaining capacity, the remaining capacity of the assembled battery corresponds to the battery unit having the maximum remaining capacity, so that overcharging of the battery unit having the maximum remaining capacity can be prevented (claim 3, Four).

【0039】

Further, by measuring the output voltage for each of a plurality of battery units, the voltage measuring unit can be simplified (claim 5). Further, by measuring the temperature for each of a plurality of battery units, the temperature measuring unit can be simplified (claim 6).

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows one Embodiment of the residual capacity meter which concerns on this invention.

[Figure 2]

It is a flowchart which shows the operation of the remaining capacity meter of FIG.

[Fig. 3]

It is a block diagram which shows an example of the conventional residual capacity meter.

[Explanation of symbols]

10 Remaining capacity meter 12 Voltage measuring unit 14 Temperature measuring unit 16 Remaining capacity estimation unit 821 ~ 82n Battery unit 84 sets of batteries 88 Current measuring unit Remaining capacity of C group batteries C1 ~ Cn Remaining capacity of each battery unit Ch Remaining capacity upper limit Lower limit of Cl remaining capacity Cmax maximum remaining capacity Cmin minimum remaining capacity Ic charging current Id discharge current T1 ~ Tn Temperature of each battery unit V1 ~ Vn Output voltage of each battery unit