The principle of automobile battery testing

Effect

The car battery tester is a professional measuring tool mainly for car batteries.

For the car, although the car battery does not account for a high proportion of the Cost, it plays a decisive role in the entire car. Therefore, understanding whether the car battery is still in good condition and replacing the obsolete battery in advance can effectively improve the service level of the enterprise and user satisfaction.

There are usually two methods for car battery testing: traditional testing and conductivity meter testing.

Detection method

Standards for traditional battery testing

In the 1990s, almost all the batteries used in cars in the world were lead-acid batteries. The biggest feature of lead-acid batteries was that the batteries were gradually aging as the batteries were used. When the battery capacity was reduced to 80% of its original rated capacity, The capacity of the battery may drop in a “diving” manner. At this time, although the battery may still provide a certain amount of energy, it may be scrapped at any time. In the international and domestic battery industry, 80% of the battery capacity is regarded as a critical point for lead-acid batteries. When the battery capacity is reduced to 80% of its original rated capacity, the battery needs to be replaced.

The traditional method to determine battery health

The traditional way to determine the health of a battery is to discharge. The current actual capacity of the battery is detected by discharging to determine the health of the battery. For car batteries, the International Battery Institute (BCI) stipulates that the battery should be discharged for 15 seconds (CCA) at 1/2 of the rated cold start current value at room temperature. If the battery voltage is above 9.6V, the battery has passed the discharge test. It Is a healthy battery.

Insufficient performance of traditional battery detection methods

The traditional method is to add an external load to detect battery performance:

1. The battery under test must be fully charged, at least 12.4V, but the fully charged voltage is not constant. Since the test principle is discharged, it will inevitably lead to changes in the measurement results;

2. For the same battery, continuous repeated measurement is not possible, and the test data may have reading errors. Because of the discharging process, the tested battery must be recharged after the test before it can be measured again;

3. A large amount of heat is emitted during the test, and continuous testing must be matched with a heat sink;

4. The test process requires the tester to be well-trained because the voltage value of the battery must be read at the moment of discharge for 15 seconds, which will affect the test conclusion.

Waste and impact caused by traditional insufficiency

It is precise because of the inadequacy of traditional battery detection methods that battery dealers, auto repair stations, and car dealers often return good batteries to manufacturers as bad batteries. According to the statistics of American car battery dealers INTERSTATE, the so-called return Among the bad batteries, 50% of the batteries are actually good. These batteries need to be recharged, not replaced. The good batteries are just due to erroneous judgments, meaninglessly going back and forth between the manufacturer and the dealer, causing each other in vain Cost Because many car repair outlets lack efficient testing tools, they fail to detect the weakened batteries in time before the car owners encounter problems, thus losing potential battery sales opportunities. The test methods such as the specific gravity indicator and terminal voltage used by traditional auxiliary reflect the charge status (SOC) of the battery, not the health status (SOJ). They cannot be used as an effective method to check whether the battery needs to be replaced.

Detection principle

The technical principle of conductivity meter

A large amount of experimental data shows that the conductance value has a very good linear relationship with the battery capacity. For the same battery, as the battery capacity decreases after use, the battery’s conductivity value will also decrease. Such a linear relationship is the basis for the conductivity meter to determine the battery’s health correctly. Because of this, the International Institute of Electrical and Electronics Engineers (IEEE) formally adopted the conductance test method as one of the testing standards for lead-acid testing batteries. On page 15 of the standard IEEE1118/1996 edition, it was clearly pointed out: An AC voltage of known frequency and amplitude is applied to both ends of the battery, and then the resulting current is measured. The AC conductance value is the ratio of the AC current component in phase with the AC voltage to the AC voltage. Obvious changes in conductivity (a decrease of more than 20%) mean changes in battery performance.

The working principle of the conductivity meter

As the battery is used, it will gradually age. The main reason for its aging is that the surface of the battery is sulfided and corroded, and the active material falls off, which can no longer carry out effective chemical reactions. This is the main reason that most batteries cannot continue to be used. The working principle of the conductivity meter is to determine the chemical reaction ability by measuring the ions on the electrode plate’s surface and infer the change of the battery capacity through the change of the electrode plate to determine the health of the battery. The test work performed by the conductivity meter is to compare the actual conductivity value measured by the battery with the standard conductivity value when the battery is in good condition. If the difference is large to a certain extent, it can be determined that the battery needs to be replaced. The practice has proved that the test result of the conductivity meter is consistent with the test result of the discharge value (CCA) with a value of 1/2. Compared with traditional discharge detection, the conductivity meter test method makes up for its shortcomings.

Development trend

For car batteries, the cold-start current is the most important indicator, and it is displayed in units of cold-start current in order to make it more intuitive and clear for users to use. When the customer uses it, input the rated CCA value according to the label of the battery, and then the meter will measure a conductance CCA value. The meter compares the difference between the two CCA values ​​to determine the health of the battery. Most countries in the world label batteries using cold start current, and it seems that the industry’s adoption of conductivity testing will become a trend.

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