Test Method for Residual Capacity of YUASA Battery

Test Method for Residual Capacity of Lead-acid yuasa Batteries
1) The traditional test method nbsp; the traditional capacity test method is to connect the battery to the load to discharge, according to a certain constant discharge rate, after the termination voltage, stop discharging, calculate the product of discharge time and discharge current, and get the capacity. Battery. Although this method can more accurately obtain the retention capacity of lead-acid batteries, it takes a long time in the measurement process, has a high labor cost, and has a high energy consumption. It has a certain risk to online batteries. At the same time, the batteries discharged frequently accelerate the aging of batteries and shorten the service life of batteries, so it is not suitable for many occasions.
For example, if the battery is discharged at 10A current and the discharging time is 10H, the capacity of the battery is 10*10=100AH.
For 200AH/12V batteries, if the discharge rate is 20 hours, the discharge current is 10A (0.05C), the discharge voltage is 10.5V, and the batteries can discharge continuously for 20 hours.
2) Ampere Time Integral Method
In this method, the discharge voltage and discharge time are put into the termination voltage to estimate the capacity of lead batteries. The formula is expressed as follows:

3) Curve Approximation Line Method
This method divides the curve into equal parts, divides it into small segments, then regards each segment as a straight line, and then connects these lines end to end.
Usually, the more segments the curve has, the more straight segments it has. The closer the curve fitted by these straight segments is to the actual curve, the closer the result is to the actual value.
Of course, there are some ways to choose the endpoints of these straight segments. When the number of segments is determined, the endpoint of the line can be selected. The choice of the end point can be determined by the second derivative of the curve (in the case of the existence of the second derivative) or by visual observation.
The relationship between the open-circuit voltage at both ends of the battery and the capacity of the battery is non-linear, as shown in Figure 1.
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Fig. 1 The relationship between open-circuit voltage and battery capacity
Through a lot of experiments, we can get the capacity relationship corresponding to each open-circuit voltage, and then use the fitting method to get the relationship curve. The relationship between output capacity and open-circuit voltage.
However, this method has its drawbacks. Firstly, the capacity of batteries varies with the change of ambient temperature, usage times and usage time, which leads to non-representative relationship. Secondly, it will take a long time to recover after the voltage at both ends of the battery is used. The inaccurate measurement will lead to the battery working for a long time.
However, this method can also be applied. For example, in our cell phone batteries, the remaining power is usually displayed on the cell phone screen. For example, at 2.11V, the battery capacity corresponding to the mobile phone is recorded at 100%, and when the voltage drops to 2.09V, the battery capacity corresponding to the mobile phone is recorded at 87%.
4) Internal resistance method
For lead-acid batteries, the smaller the battery capacity, the larger the internal resistance, there is a non-linear relationship between the two, as shown in Figure 2.

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The above formulas can be obtained by least square method. A large number of experimental data are used to obtain the values of a, B and m, and then the relationship between capacity and internal resistance is determined.
5) Density method
The electrolyte of lead-acid batteries is sulfuric acid. During charging, sulfuric acid is produced by chemical reaction inside lead-acid batteries, which increases the density of the solution, the active substance and the storage capacity. When discharged, sulfuric acid in the battery will participate in chemical reaction to form lead sulfate, which will reduce the density of the solution, reduce the active substances and release electricity.
From the above analysis, it can be seen that the capacity of lead-acid battery is proportional to the density of its electrolyte. The capacity can be determined indirectly by measuring the density of the electrolyte inside the battery, and the accuracy is still relatively high.
However, this method has some problems in practice. On the one hand, the current lead-acid batteries are sealed, so it is troublesome to open the battery cover after measurement. On the other hand, when a lead-acid battery is charged, water is decomposed from the positive electrode of the battery into oxygen and hydrogen, which undoubtedly increases the density of the electrolyte and leads to measurement errors. In addition, the density of the electrolyte can only be measured at rest. When an electric vehicle is running, the battery vibrates and it is not easy to measure the density of the battery electrolyte.
6) Neural Network Method
Neural network is an algorithm used in the field of modern artificial intelligence. It has the characteristics of self-learning, self-organization and distributed storage of information. It uses a structured parallel processing structure and does not require model prediction. It can directly obtain the input-output relationship of the system through input and output samples, and can arbitrarily approximate the non-linear and uncertain systems. We can use some excellent qualities of neural networks to predict the capacity of lead-acid batteries.
7) Kalman filtering method
The core of Kalman filtering method is its five recursive formulas, which make the best estimation in the sense of the minimum variance of the object of study.
In the Kalman formula, the discharge current, terminal voltage and ambient temperature of the battery should be included.
There are no detailed formulas here, you can refer to the relevant content of Kalman filtering.