JP2536257B2 - Determining the life of stationary lead-acid batteries - Google Patents

Description

Description: [Industrial application] The present invention relates to a method for determining the life of a stationary lead storage battery.

[Prior Art] As a method for determining the life of a stationary lead storage battery,
A method of actually measuring the discharge capacity of the battery and a method of measuring the specific gravity of the electrolytic solution have been used. The former method of actually measuring the discharge capacity is not practical in that the load for discharge is large and it requires time and labor for the measurement.Therefore, the latter method of measuring the electrolytic solution specific gravity is the most general. Has been done.

[Problems to be Solved by the Invention] However, in the cathode absorption type stationary sealed lead-acid battery,
Since it is a closed type, there is a problem that it is difficult to measure the specific gravity of the electrolyte.

In view of the above problems, an object of the present invention is to propose a method for determining the life of a stationary lead storage battery without actually measuring the discharge capacity or measuring the electrolytic solution specific gravity.

[Means for Solving the Problem] In order to solve the above problems, in the life determining method for a stationary lead storage battery according to the present invention, the internal impedance of the lead storage battery whose life is to be determined is measured at a plurality of different angular frequencies. To do. Then, the inductance component (L) of the poles, straps, grids, etc., electrolytic solution resistance (Rs), electric double layer capacitance (C)
d), the charge transfer resistance (θ), the Warburg impedance (W), and the Warburg coefficient (σ) are used to apply the angular frequency to the complex impedance equation of the impedance equivalent circuit of Equation (1) below. By changing the value of each element, the value of each element that minimizes the difference between the combined impedance calculated by calculation and the internal impedance measured at each angular frequency is determined.

Then, the life of the battery is determined by comparing at least one of the determined electrolytic solution resistance (Rs), electric double layer capacity (Cd), charge transfer resistance (θ) and Warburg coefficient (σ) with the initial value. To do.

[Operation] When the life determining method of the present invention is used, the amount and surface area of the effective reaction active material, and the diffusion of the electrolytic solution into the active material are determined from the change over time in the calculated values of the respective elements of the complex impedance equation of the equivalent circuit. It is possible to appropriately estimate detailed information about the battery status such as the status. As a result, the life can be easily and accurately determined without actually measuring the discharge capacity of the battery, and even for a battery such as a stationary sealed lead storage battery in which it is difficult to measure the specific gravity of the electrolyte.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

The internal impedance of a stationary lead storage battery is represented by the impedance of an impedance equivalent circuit as shown in FIG. In the figure, L is the inductance component of the poles, straps, lattices, etc., Rs is the pure resistance component mainly consisting of the resistance of the electrolytic solution, that is, the electrolytic solution resistance, Cd is the electric double layer capacitance at the interface between the active material and the electrolytic solution, and θ Is the charge transfer resistance associated with the transfer of charges between the active material and the electrolytic solution, that is, the transfer reaction, and W is the Warburg impedance associated with the diffusion of the electrolytic solution.

The combined impedance Z of this equivalent circuit is represented by the following equation (1) as a function of the angular frequency ω, where σ is the Warburg coefficient of the Warburg impedance W.

Fig. 2 shows each element of the above formula (Rs, L, Cd, θ, σ, σ, so that the difference between the measured value of the internal impedance of the stationary lead-acid battery and the value calculated by the above formula and the measured value is minimized. W) is also shown together with the locus of impedance calculated and
It is generally called a Cole-Cole plot.

The measured battery had a capacity of 200 Ah, and the measurement frequency range was 0.1 Hz to 1 KHZ, and 21 points were measured within this range. As shown in the figure, when the frequency is about 1 to 100 Hz, the measured value and the calculated value of the equivalent circuit are in good agreement, and it can be seen that the expression of the equivalent circuit is appropriate.

Each element such as the electrolyte resistance Rs, the electric double layer capacity Cd, the charge transfer resistance θ, and the Warburg coefficient σ that constitute the equivalent circuit, when the battery reaches the end of its life, will change due to the causes shown in the following table. Conceivable.

Therefore, by applying several different angular frequencies to the impedance of the equivalent circuit and changing the value of each element, the difference between the synthetic impedance obtained by calculation and the internal impedance (measured value) measured at each angular frequency is minimized. Determine the value of the element. Then, by comparing the calculated value of each element with the initial value, the life of the battery can be determined easily and accurately.

FIG. 3 shows an outline of the internal impedance measuring means of the battery. Reference numeral 1 is a battery to be measured, 3 is an impedance characteristic detector, and 2 is a potentiostat connected between the two. The potentiostat has a potentio mode for measuring a current when a certain potential is applied and a galvanostat mode for measuring a potential when a certain current is applied. In this embodiment, the potentiostat is used in a galvanostat mode, and a frequency analyzer 3 supplies an alternating current of several kinds of different frequencies with a constant amplitude to the battery 1 via the potentiostat 2.
Connect the current monitor output and voltage monitor output (terminals that output the current applied to the sample and the generated voltage) to the input of the frequency characteristic analyzer 3 and change the measured values of the current monitor output and the voltage monitor output to the frequency. The corresponding internal impedance of the battery 1 is obtained.

Next, as a specific example, a 200 Ah stationary sealed lead-acid battery is subjected to an accelerated life test at high temperature, and a 1 to 100 Hz
FIGS. 4 to 7 show changes with time of each element calculated using the respective measured values of the internal impedance measured at one frequency. The Marquardt method, which is a kind of nonlinear least squares method, is used to calculate each element. Specifically, give an appropriate initial value to each element of the equivalent circuit, and change the value of each element of the equivalent circuit so that the difference between the impedance at each frequency calculated by this element and the impedance of the measured value is minimized. Then, when the difference becomes a certain value or less, the method of using this value as the solution is used. Since this calculation method and calculation formula are known to those skilled in the art, details thereof will be omitted. Note that this calculation can be easily performed using a computer.

FIG. 4 shows the transition of the electrolytic solution resistance Rs, FIG. 5 shows the transition of the electric double layer capacitance Cd, FIG. 6 shows the transition of the charge transfer resistance θ, and FIG.
The figure shows the transition of the Warburg coefficient σ. FIG. 8 also shows the transition of the actually measured discharge capacity.

As shown in FIG. 4, it is estimated that the electrolytic resistance solution Rs is increased from around 150 days and the specific gravity of the electrolytic solution is decreased, and as shown in FIG. 5, the electric double layer capacity Cd is gradually increased. It is presumed that the reaction area of the effective active material is decreased. Further, as shown in FIG. 6, the charge transfer resistance θ was estimated from around 200 days, and as shown in FIG. 7, the Warburg coefficient σ was increased from around 200 days. It is presumed that the diffusion of the electrolytic solution into the active material is deteriorated due to the lead conversion.

On the other hand, as shown in Fig. 8, the measured value of the discharge capacity is also 20
The capacity has drastically decreased from around 0 days, and it has reached the end of its life in 230 days. From the above, it is possible to determine the life of the battery by comparing the calculated value of any or all of the elements of the equivalent circuit described above with their respective initial values.

[Effects of the Invention] As described above, according to the present invention, the internal impedance of the lead storage battery is measured at various different angular frequencies, and the inductance component (L) of the poles, straps, grids, etc., the electrolyte resistance. (Rs), electric double layer capacitance (Cd), charge transfer resistance (θ), Warburg impedance (W), and Warburg coefficient (σ) The value of each element that minimizes the difference between the calculated synthetic impedance and the internal impedance measured at each angular frequency while changing the value of each element is determined, and the calculated value of each determined element is set to the initial value. Since the life of the battery is determined by comparing with, it is possible to measure the specific gravity of the electrolyte without measuring the discharge capacity of the battery and for the sealed lead acid battery for stationary use. It is possible to perform lifetime determination to an appropriate probability also Te easily 且 flame battery. Further, from the change in the calculated value of each element of the equivalent circuit, the amount and surface area of the effective reaction active material,
In addition, there is an advantage that necessary information regarding a detailed battery state such as a diffusion state of the electrolytic solution with respect to the active material can be appropriately estimated.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an impedance equivalent circuit of a stationary lead-acid battery, FIG. 2 is a characteristic curve diagram showing loci of measured impedance values and calculated impedances of the stationary lead-acid battery, and FIG. It is explanatory drawing which shows the outline | summary of an internal impedance measuring means. FIG. 4 shows the change over time of the electrolyte resistance Rs, FIG. 5 shows the change over time of the electric double layer capacitance Cd, and FIG. 6 shows the change over time of the charge transfer resistance θ.
The figure shows the time-dependent change of the Warburg coefficient σ, and FIG. 8 is each characteristic curve diagram showing the time-dependent change of the battery discharge capacity. L: Inductance component, Rs: Electrolyte resistance, Cd:
Electric double layer capacitance, θ ... Charge transfer resistance, W ... Warburg impedance.

Claims (1)

(57) [Claims] 1. An internal impedance of a lead-acid battery whose life is to be determined is measured at a plurality of different angular frequencies, and an inductance component (L) of a pole, a strap, a grid, etc., an electrolytic solution resistance (Rs), an electric double layer. The angular frequency is applied to the complex impedance equation of the following impedance equivalent circuit expressed by using the elements of capacitance (Cd), charge transfer resistance (θ), Warburg impedance (W) and Warburg coefficient (σ). Determine the value of each element where the difference between the synthetic impedance obtained by calculation while changing the value of each element and the internal impedance measured at each angular frequency is the minimum, Determined electrolyte resistance (Rs), electric double layer capacity (C
d), charge transfer resistance (θ) and Warburg coefficient (σ)
The method for determining the life of a stationary lead-acid battery is characterized in that the life of the battery is determined by comparing at least one of the values with the initial value.