Battery voltage, current, and temperature are important operating parameters of the battery, but they do not reflect the internal state of the battery. As the most internationally recognized and most convenient performance parameter for the battery, the internal resistance can reflect the performance indicators such as the deterioration degree and capacity status of the battery, and these indicators cannot be reflected by operating parameters such as voltage, current and temperature.
The four main failure modes of the battery: (water loss, negative plate vulcanization, positive plate corrosion and thermal runaway directly affect the battery capacity, internal resistance increases) is the main reason for the increase in internal resistance of the battery.
As the capacity state of the battery decreases, the internal resistance of the battery increases. The larger the capacity of the battery, the smaller the internal resistance is reflected, and as the battery deteriorates, the internal resistance of the battery also increases significantly. Therefore, the internal resistance of the battery has a close relationship with its capacity: the increase in internal resistance of the battery is an important indicator of battery performance degradation.
The research results of the International Telecommunication Power Annual Conference show that if the internal resistance of the battery exceeds the normal value of 25%, the capacity has been reduced to about 80% of its nominal capacity. If the internal resistance of the battery exceeds 50% of the normal value, the battery capacity has been Reduce it to less than 80% of its nominal capacity and replace it in time.
The battery is used in series at most sites, and the performance status of the battery directly affects the performance state of the battery pack. At the same time, the backward battery in the battery pack will accelerate the degradation rate of other batteries connected in series. Therefore, the monitoring of the single battery is a necessary condition for ensuring the capacity status and service life of the battery pack.
By performing an internal resistance test on the battery cells in the battery pack, it is possible to accurately grasp the performance state of each of the battery cells in the battery pack. At the same time, it is of great significance to ensure the stability of the battery supply and extend the service life of the battery pack.
The capacity status of the battery will decrease as the usage time increases. According to the results of the International Electrochemical Conference on 25,000 communication batteries, the battery will enter an unstable period after 2 years of use. In other words, after 2 years of use, the battery pack will have a battery cell with a greatly reduced capacity.