Alkaline batteries are widely used DC power sources in power plants and substations to supply power for the operation, control, signaling, protection, and emergency lighting of electrical equipment. They offer advantages such as high discharge rate, relatively simple charging and discharging maintenance, no need for a dedicated battery room, long service life (approximately 10-15 years), relatively low price, and low pollution. However, improper charging and discharging methods and battery quality issues can lead to a decrease in DC power capacity, causing difficulties in circuit breaker tripping and resetting. This article analyzes common related faults and provides corresponding solutions. 1. Large Voltage Dispersion Between Individual Cells The float charge voltage of alkaline batteries (mostly sintered type) is generally between 1.35V and 1.45V ± 0.05V. Voltage dispersion exceeding this range is considered large, and this phenomenon can be categorized into the following symptoms. 1.1 The large voltage dispersion of all individual cells is mainly caused by insufficient battery charging. The reasons are roughly as follows: 1) Insufficient initial charging; 2) Low float charge voltage; 3) Insufficient equalization charging; 4) Insufficient recovery charging after discharge. If low float charge voltage is found, it should be adjusted promptly. For insufficient initial charging, repeated charging and discharging can be used to bring the capacity to the specified value. 1.2 Extremely low voltage in a few cells: If an extremely low voltage is found during battery inspection, special attention should be paid to whether the polarity is reversed. If so, it should be removed from the circuit immediately; if not, it may be caused by a partial short circuit. A partial short circuit is a small short circuit formed between the anode and cathode plates of the battery. Low voltage caused by a partial short circuit can be restored by equalization charging. If it cannot be restored, the battery should be replaced. 1.3 As the battery's end date approaches, the dispersion increases. Due to the increasing years of use, the difference in self-discharge of alkaline batteries becomes increasingly significant. At this point, the voltage dispersion increases, so the number of battery measurements and equalization charging cycles should be increased to compensate for the differences in self-discharge. [b]2. Reduced Discharge Capacity[/b] During use, a decrease in battery discharge capacity is frequently observed. This is mainly caused by the following factors: 2.1 Insufficient Charging Insufficient charging manifests in the following ways: 1) Low float charge voltage and prolonged use. In one instance, a power station experienced a decrease in battery capacity after one year of operation. Investigation revealed that this was due to an inaccurate float charge voltage meter reading, resulting in a low float charge voltage over a long period. After restoring the battery's capacity through charging and discharging, it functioned normally. 2) Frequent charging and discharging, but insufficient charging during recovery, leading to reduced discharge capacity. Prolonged float charging can result in insufficient or uneven battery capacity due to significant electrochemical changes in the active materials. During activation charging and discharging, if the current is not properly controlled, capacity reduction can easily occur, especially during recharging after a charge-discharge cycle. 3) Lack of equalization charging. Equalization charging is a supplementary charge to the battery after an accident (no AC float charging). Failure to perform equalization charging will cause passivation of the plates and reduce battery capacity. In one substation, batteries were left in float charging mode after each power outage, leading to capacity reduction over time. Therefore, all users should pay attention to equalization charging and replenish charge promptly. After capacity reduction occurs, the cause should be identified and the fault eliminated. Simultaneously, the battery should undergo deep and repeated charge-discharge cycles to fully activate the chemical reaction. Ideally, the electrolyte should be replaced for better results. 2.2 Increased potassium carbonate content leads to capacity reduction. Besides insufficient charging, another reason is the increased potassium carbonate production due to the reaction of the electrolyte with carbon dioxide in the air or with electrolytic oxidation products of the battery components. When the potassium carbonate content in the electrolyte increases, the specific gravity of the electrolyte increases, the internal resistance of the battery increases, and the discharge voltage drop increases. This has an adverse effect during high-current discharge (such as when the oil switch trips, during charging and discharging). This also causes cadmium, the main component in the anode, to crystallize coarser during charging and discharging, reducing the effective surface area. Simultaneously, the reduction in hydroxide ions (OH⁻) can halt the discharge reaction. All of these factors contribute to lower plate voltage and insufficient battery capacity under high-current, high-rate discharge. Therefore, the electrolyte should be tested regularly. If testing methods are unavailable or the required electrolyte quantity is small, regular electrolyte replacement can solve these problems. In our external installations, we recommend that operating units replace the electrolyte every 2-3 years, combined with a deep charge-discharge cycle, which has proven effective. [b]3 Impure Distilled Water Electrolyte[/b] During installation, we also encountered battery malfunctions caused by impure distilled water in the electrolyte, resulting in reduced battery capacity, lower voltage, and leakage at the electrode rods. These issues were addressed appropriately based on their causes. Some malfunctions were also caused by problems with the charging and discharging devices. For example, at a power station in Altay, the automatic switching between equalization charging and float charging malfunctioned, which was not detected by the operators, resulting in prolonged operation in float charging mode and a significant reduction in capacity. During trip-close tests, remote closing was no longer possible. After electrolyte replacement and deep charge/discharge cycles, the capacity is restored. With proper maintenance and use, alkaline batteries can be used up to their designed lifespan. Operation and maintenance personnel should constantly observe various phenomena and promptly inspect and address any issues to ensure the DC system performs optimally.