Why do batteries need to be tested regularly?

Battery voltage, current and temperature are important working parameters of the battery, but they can not reflect the internal conditions of the battery. Internal resistance, as the most useful and fast functional parameter for storage battery, can reflect the deterioration degree and capacity of storage battery, which can not be reflected by voltage, current, temperature and other working parameters.
The four main failure modes of batteries (loss of water, vulcanization of negative plates, corrosion of positive plates and thermal runaway directly affect the capacity of batteries and increase of internal resistance) are the main reasons for the increase of internal resistance of batteries.
As the capacity of the battery decreases, the internal resistance of the battery increases. The larger the capacity of the battery, the smaller the internal resistance it reflects. With the increase of the deterioration of the battery, the internal resistance of the battery will also increase significantly. Therefore, the internal resistance of the battery is closely related to its capacity: the rise of the internal resistance of the battery is an important symbol of the deterioration of the battery function.
The research results of the International Telecommunication Power Supply Annual Conference show that if the internal resistance of the battery exceeds 25% of the normal value, the capacity has been reduced to about 80% of its nominal capacity, and if the internal resistance of the battery exceeds 50% of the normal value, the capacity of the battery has been reduced to less than 80% of its nominal capacity, which needs to be replaced in time.
Batteries are used in series in most fields. The function of single batteries directly affects the function of batteries. Together, the backward battery in the battery pack will speed up the degradation of other batteries in series with it. Therefore, the monitoring of single batteries is a necessary condition to ensure the capacity and service life of batteries.
By testing the internal resistance of the single battery in the battery group, the function of each single battery in the battery group can be accurately grasped. At the same time, it is of great significance to ensure the stability of battery power supply and extend the service life of battery packs.
The capacity of the battery will decrease with the increase of operation time.  According to the research results of 25,000 communication honorary batteries at the International Annual Conference on Electrochemistry, YUASA batteries will enter an unstable period after two years of operation. That is to say, after two years of operation, the storage battery unit will have a dramatic decline in capacity.