JP2000040528A - Battery for hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery satisfying input-output requirements of a hybrid vehicle. SOLUTION: An open voltage of a battery is determined based on the maximum input and the maximum output required for a hybrid vehicle, and the capacity ratio of the positive electrode to the negative electrode of the battery is so selected as to set the open voltage at a predetermined value of SOC or in a predetermined range of SOC. Thereby, the maximum input and the maximum output required for a hybrid vehicle can be satisfied by a small number of batteries.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an engine and / or an engine.
Alternatively, the present invention relates to a battery used in a hybrid vehicle using a motor as a driving source.

[0002]

2. Description of the Related Art In an electric vehicle (EV),
The cruising range is determined by the amount of energy stored in the battery. There is a limit on the cruising distance with the current energy amount of the battery, and in order to further extend the cruising distance, a large number of batteries are required, which increases the cost and hinders the spread of electric vehicles.

[0003] Therefore, a hybrid system using an engine and / or a motor as a driving drive source is adopted. The engine runs at a high speed and a high load, and the engine is assisted by a battery and a motor as needed. By driving with a motor, the cruising range is extended and the battery usage is reduced, realizing a low-cost and highly fuel-efficient system.

Incidentally, parameters indicating the input / output performance of a battery include an energy density [Wh / kg] and a power density (output density) [W / kg]. In an electric vehicle, a high energy density is required to extend the cruising range, but the required power density is satisfied because a large number of batteries are used. On the other hand, in a hybrid vehicle, a high power density is required to satisfy the required input / output with a small amount of battery, but the energy density is not so important because the cruising distance can be increased in a driving mode using an engine.

[0005] In a hybrid vehicle, there is a demand for further weight reduction and cost reduction due to an increase in the load on the engine in comparison with an electric vehicle. Therefore, an output requirement for driving a motor with a small amount of battery and energy regeneration are required. Batteries with power densities that meet high input requirements.

Research and development have been conducted on conventional batteries for electric vehicles with the aim of improving energy density, and little attention has been paid to input / output characteristics, particularly input characteristics. In electric vehicles, a large number of batteries are used, so conventional batteries can sufficiently satisfy the input requirements, and it is not necessary to improve the input characteristics. Input characteristics that satisfy input requirements are important.

An object of the present invention is to provide a battery that satisfies the input / output requirements of a hybrid vehicle.

[0008]

(1) The invention of claim 1 is applied to a battery used in a hybrid vehicle using an engine and / or a motor as a driving source.
Then, the open-circuit voltage of the battery is determined based on the maximum input and the maximum output of the battery required as a hybrid vehicle, and the capacity ratio between the positive electrode and the negative electrode of the battery is selected so that the open-circuit voltage becomes a predetermined value of the SOC. By doing so, the above object is achieved. (2) The battery for a hybrid vehicle according to claim 2 is:
The capacity ratio of the positive electrode and the negative electrode is selected so that the open circuit voltage is obtained within a predetermined range of the SOC.

[0009]

(1) According to the first aspect of the present invention, the open-circuit voltage of the battery is determined based on the maximum input and the maximum output of the battery required as a hybrid vehicle.
Since the capacity ratio of the positive electrode and the negative electrode is selected so that the open circuit voltage can be obtained with respect to the predetermined value of OC, the SOC of the hybrid vehicle is required at a predetermined value of SOC required for the hybrid vehicle with a small amount of battery. Maximum input and output can be satisfied. (2) According to the second aspect of the present invention, the capacity ratio of the positive electrode and the negative electrode is selected so that the open circuit voltage is obtained within a predetermined range of the SOC. In a predetermined range of the SOC, the maximum input and the maximum output required for the hybrid vehicle can be satisfied.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a hybrid vehicle battery that satisfies the required input / output of a hybrid vehicle with a small amount will be described.

First, the input and output of the battery will be considered. FIG. 1 shows a characteristic example of the open circuit voltage Vo [v] with respect to the state of charge SOC [%] of the lithium ion battery. In the figure, the upper limit voltage Vu and the lower limit voltage Vl are allowable voltages at which the solvent of the battery is decomposed or the active material is damaged when the open voltage Vo exceeds those voltages. R is the internal resistance of the battery. Strictly speaking, the internal resistance Rin at the time of charging is different from the internal resistance Rout at the time of discharging. However, in the present embodiment, the difference is not a problematic level. = Rout = R The lithium ion battery has a characteristic that the open-circuit voltage Vo decreases as the SOC decreases. Assuming that the open-circuit voltage Vo is about 3.75 V as shown in the drawing, the SOC is about 35%.

The maximum charging current ic of the battery is:

Vu = Vo + ic * R, ic = (Vu-Vo) / R The maximum input Win of the battery is obtained by multiplying the maximum charging current ic by the upper limit voltage Vu.

## EQU2 ## Win = ic * Vu = Vu * (Vu-Vo) / R

Similarly, the maximum discharge current id of the battery
Is

Vl = Vo-id * R, id = (Vo-Vl) / R The maximum output Wout of the battery is obtained by multiplying the maximum discharge current id by the lower limit voltage Vl.

Wout = id * Vl = Vl * (Vo-Vl) / R

The maximum input Win and the maximum output Wou of the battery
The ratio Win / Wout of t is

## EQU5 ## Win / Wout = (Vu / Vl) * ｛(Vu−Vo)
/ (Vo-Vl)}. In Equation 5, the upper limit voltage Vu and the lower limit voltage Vl are important values that determine the life of the battery, and cannot be arbitrarily changed because they are values determined by the electrolyte, electrode material, and the like. Win
/ Wout changes. That is, as is clear from FIG. 1, the output Wout increases and the input Win decreases as the open-circuit voltage Vo increases, and the output o decreases as the open-circuit voltage Vo decreases.
ut decreases and the input Win increases.

Normally, in a hybrid vehicle, a reference value or a reference range of the SOC is set based on braking / driving conditions so that the driving request and the braking request of the vehicle can be accepted at any time. The charge / discharge is controlled so as to be always near the reference value or always within the reference range. For example, if the SOC reference value is 50
If it is set to%, the discharge amount and the charge amount become equal, and the drive request by the motor and the regenerative braking request can always be accepted to the same amount.

Therefore, as a battery for a hybrid vehicle, the input and output according to the driving demand and the braking demand of the vehicle must be satisfied in the SOC reference value or reference range. For example, if the SOC reference value is 50% or the reference range is 30 to 70%, and the input / output according to the braking / driving request is 20/30 kw, the SOC 50%
Or 30-70% must allow 20kw input and 30kw output.

Therefore, in this embodiment, the above equation 5
The open circuit voltage Vo of the battery is calculated backward from the input / output ratio Win / Wout required as a battery for a hybrid vehicle, and a battery having the open circuit voltage Vo at the SOC reference value or reference range is produced.
Then, the input / output requirements of the hybrid vehicle can be satisfied with the minimum battery in the reference SOC or the reference SOC range.

FIG. 2 shows that lithium manganate (LiMn
2O4) is a diagram showing the open-circuit voltage Vo with respect to the SOC of the lithium-ion battery using hard carbon for the negative electrode, showing a change in characteristics when the capacity ratio between the positive electrode and the negative electrode is changed. In the figure, the solid line shows the characteristics when the ratio of the amount of electricity [Ah] between the positive electrode and the negative electrode, that is, the capacity ratio is 1: 1, and the dashed line shows the characteristics when the capacity ratio is 1: 1.4. Current lithium-ion batteries are usually 1/1 to 1/1.
The capacity ratio is in the range of 4. The broken line shows the characteristics when the capacitance ratio is 1: 1.8. As is apparent from FIG. 2, by selecting the capacity ratio between the positive electrode and the negative electrode,
The characteristics of the open circuit voltage Vo with respect to OC can be arbitrarily changed.

For example, as a hybrid vehicle, SOC
If a 50% battery with a maximum output of 30 kw and a maximum input of 20 kw is required, the input / output ratio Win / Wout is 0.67.
From equation (5), the open circuit voltage Vo becomes approximately 3.75 V.
Therefore, from FIG. 2, when SOC = 50% and open circuit voltage Vo =
It is sufficient to select a capacity ratio of 1 / 1.5 to 1 / 1.6 that results in 3.75v.

In this manner, the open voltage Vo of the battery is determined based on the maximum input Win and the maximum output Wout of the battery required as a hybrid vehicle, and the open voltage Vo is obtained in a predetermined SOC or a predetermined range. Since the capacity ratio of the positive and negative electrodes of the battery is selected, a small amount of the battery can be used in a predetermined value or a predetermined range of the SOC required as a hybrid vehicle.
The maximum input and output required for a hybrid vehicle can be satisfied.

In the above-described embodiment, a lithium-ion battery has been described as an example. However, the type of the battery is not limited to the above-described embodiment. For example, a nickel-metal hydride battery, a lithium-polymer battery, or the like may be used. The present invention can be applied to other types of batteries.

In the above-described embodiment, the SOC
Although the description has been given by taking as an example a lithium ion battery using a positive / negative electrode material in which the open-circuit voltage Vo decreases as the voltage decreases, the positive / negative electrode material of the battery is not limited to the above embodiment, and other types of materials may be used. The present invention can be applied to the used battery.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between input and output with respect to SOC and open circuit voltage of a battery.

FIG. 2 is a diagram illustrating an example of a characteristic of an open circuit voltage with respect to an SOC of a battery.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Horie Nissan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Takeshi Iwai 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Nissan Motor Co., Ltd. ( 72) Inventor Takaaki Abe 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Inventor Yasuhiko Osawa 2 Takaracho 2 in Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. F-term (reference) 5H029 AJ02 AK03 AL07 HJ18 HJ19 in Takaracho 2 Kanagawa-ku, Yokohama-shi

Claims (2)

[Claims] A battery used in a hybrid vehicle that uses an engine and / or a motor as a driving source for driving the battery, wherein an open-circuit voltage of the battery is determined based on a ratio of a maximum input to a maximum output of the battery required as the hybrid vehicle. Wherein the capacity ratio between the positive electrode and the negative electrode of the battery is selected so that the open voltage is obtained with respect to the predetermined value. 2. The hybrid vehicle battery according to claim 1, wherein a capacity ratio between the positive and negative electrodes is selected so that the open circuit voltage is obtained within a predetermined range of SOC.