Principles of Battery Discharge and Maintenance Points in the Mid-to-Late Service Period

As a rechargeable energy storage device, the discharge process of a storage battery is the core link of energy conversion. Understanding the specific laws of discharge, the characteristics of each stage, and the key points of use and maintenance is crucial for extending the service life of the storage battery and ensuring its stable operation. During the discharge process, the terminal voltage, electrolyte density, and plate state of the storage battery will show obvious phased changes, and the differences in characteristics of different stages directly reflect the energy release state of the storage battery.

The discharge process of a storage battery can be roughly divided into three consecutive and distinct stages, each with clear laws regarding voltage changes, electrolyte reactions, and plate states. The first stage is the initial rapid drop stage. When the storage battery starts to discharge, the terminal voltage will drop rapidly from the initial 2.14V to 2.1V. The core change in this stage is that the sulfuric acid in the pores of the plates is quickly consumed, the electrolyte density decreases rapidly, and the concentration polarization phenomenon increases continuously, which in turn leads to a rapid drop in terminal voltage. This process reflects the rapid start and release of energy from the storage battery, with a relatively short duration but intense state changes.

After the initial stage, the discharge of the storage battery enters the second stage—the relatively stable stage, which is also the main stage of continuous energy release. At this time, the terminal voltage will drop slowly from 2.1V to 1.85V. Compared with the rapid changes in the first stage, the core feature of this stage is "dynamic balance": the sulfuric acid diffusing from the outside to the inside of the plate pores reaches a stable balance with the sulfuric acid consumed in the pores. Therefore, the rate of decrease in electrolyte density slows down, the growth of concentration polarization tends to be gentle, and the terminal voltage shows a slow and stable downward trend. This stage has a long duration and is a key period for the storage battery to actually play a power supply role, and its duration is directly related to the actual power supply capacity of the storage battery.

When the stable stage ends, the discharge of the storage battery enters the third stage—the final rapid drop stage, which means that the energy of the storage battery is about to be exhausted. At this time, the terminal voltage will drop rapidly from 1.85V to 1.75V. With the continuous consumption of sulfuric acid in the pores of the plates, the electrolyte density shows a straight-line downward trend, the concentration polarization increases sharply, and the plate reaction gradually stagnates. If the discharge continues, it may cause irreversible damage to the storage battery. Therefore, 1.75V is usually regarded as the termination voltage of battery discharge, and it is necessary to stop discharging and charge in time.

It is worth noting that even though lead-acid batteries have undergone strict selection and quality inspection at the factory to ensure the consistency of voltage and capacity, after a certain period of long-term use, the voltage inhomogeneity of each individual battery in the battery pack will gradually appear and increase. This inhomogeneity will lead to the coexistence of "undercharging" and "overcharging" during the charging process: conventional charging cannot perform targeted supplementary charging for undercharged batteries with lower voltage, nor can it limit the charging amount for batteries with higher voltage. In the long run, this will further aggravate the performance differences of each battery and shorten the overall service life of the battery pack.

Therefore, it is particularly important to do a good job in daily monitoring and maintenance in the mid-to-late service period of the battery pack. It is recommended to regularly or irregularly measure the open-circuit voltage of each individual battery, screen out the batteries with lower voltage through voltage detection, and perform separate supplementary charging on them to make the voltage and capacity of the battery consistent with other batteries in the battery pack, and try to reduce the performance gap between each battery. Through this targeted maintenance, the problem of voltage inhomogeneity of the battery pack can be effectively alleviated, the overall performance of the battery pack can be optimized, its service life can be extended, and the storage battery can continue to play a stable energy storage and power supply role in long-term use.

In short, the discharge process of a storage battery is a phased and regular energy conversion process. Mastering the voltage and electrolyte change characteristics of each stage can help us better judge the working state of the storage battery; while attaching importance to maintenance in the mid-to-late service period and timely adjusting the voltage consistency of each battery is the key to ensuring the long-term stable operation of the storage battery. Only by scientifically understanding its discharge principle and doing a good job in daily maintenance can we give full play to the energy storage value of the storage battery and avoid unnecessary losses and failures.