Lithium battery capacity and internal resistance decryption

The relationship between internal resistance and a rated capacity of the battery and the relationship between internal resistance and electrically charged SOC of the same type of battery. More than a decade ago, people tried to use the changes in the internal resistance(or conductivity) of valve-controlled sealed lead-acid batteries to detect the capacity of the battery online and predict the battery life, but failed to do so; Recently, with the development of electric vehicle and electric vehicle industry, people have put forward higher and higher requirements for the high current discharge ability of power batteries, which requires that the internal resistance of batteries be reduced as much as possible. Therefore, this paper will further explore and clarify some commonly used battery internal resistance and capacity between the internal relationship.

The battery's charged SOC refers to the ratio of the capacity that the battery can release to its rated capacity. This data is important for post and telecommunications power systems and power batteries in use.

In 1992, David Feder published the test and statistical results of a valid-controlled sealed lead-acid battery(VRLA) using the Medtronic CelltronandMidtron electrical conductivity tester. Figure 1 shows 336 1000 Ah sealed lead-acid batteries discharged with 263A to 1. The distribution of 80V discharge time and battery conductivity(reciprocal of internal resistance). It can be seen that there is a linear correlation between them and the correlation coefficient R2 = 0.825.

It was thus suggested that for valve controlled sealed lead-acid batteries used online, the measured conductivity can be used to estimate their remaining capacity. Although more than a decade ago, I have repeatedly put forward a negative view of this view from the point of view of objective reality, and was later recognized by many peer experts. But today there are still some people who have not done any experiments to quote this outdated point without thinking, and therefore revisit the 'crux' of this point.

At present, valve-controlled sealed lead-acid batteries have gradually replaced open-type mobile electrolytic lead-acid batteries, and are widely used in post and telecommunications power supplies, UPS, and energy storage power systems. Power valve controlled sealed lead-acid batteries have not only been widely used in electric auxiliary vehicles but also recently to light electric vehicles. All these fields require on-line detection of battery charge state.

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