(3) Research on the impact of imbalance on VRLA batteries has shown that the distribution of alloy composition and structure across different parts of the grid varies, leading to differences in electrochemical properties. This imbalance can cause variations in float voltage and charge/discharge voltage. Over time, as the battery undergoes multiple charge-discharge cycles, these voltage differences tend to increase, creating a feedback loop that worsens with each cycle. This phenomenon eventually leads to the formation of what is known as a "backward battery" or a failed battery. Currently, domestic standards limit the maximum float voltage difference within a battery to ≤50mV, while international standards are more stringent at ≤20mV. Therefore, it is crucial to monitor and minimize the voltage differences during float operation to ensure long-term performance and reliability.
(4) Thermal runaway is a critical issue in valve-regulated lead-acid (VRLA) batteries, especially due to their lean electrolyte design. The electrolyte is absorbed in the glass fiber mat, and when charging current increases, gas must be released through the safety valve, leading to water loss. This results in increased internal resistance, reduced capacity, and excessive heat generation during charge and discharge. If this heat is not dissipated quickly, it can trigger thermal runaway. Common causes include failure to reduce float voltage in time, improper sealing of the safety valve, or an excessively low opening pressure. In severe cases, thermal runaway may cause a sudden drop in battery voltage and a rapid rise in temperature, reaching up to 70–80°C. Therefore, thermal runaway must be taken seriously and monitored closely.
Based on the above analysis, proper maintenance of VRLA batteries is essential. Key practices include:
a. Installing air conditioning in the battery room to maintain a temperature between 22°C and 25°C, which extends battery life and maximizes capacity.
b. Ensuring that the float voltage does not exceed the manufacturer's recommended value, and adjusting it using a ±3mV/°C coefficient based on ambient temperature changes.
c. Using the lower limit of float voltage to mitigate the effects of imbalance during floating operation.
d. Performing equalization charging after deep discharge or when imbalance occurs, and doing so every three months. During equalization, pay attention to ambient temperature and reduce the equalization voltage by 3mV for every 1°C increase.
e. Using pulse charging techniques to potentially restore the performance of older or degraded batteries.
f. Keeping detailed records of individual battery voltages and internal resistances before commissioning, and comparing them periodically with original data to detect anomalies early.
g. Increasing testing frequency once the battery reaches half its service life, especially for 12V units. If resistance suddenly rises or voltage becomes unstable, treat it as a potential "backward battery."
h. Where possible, use single 2V VRLA batteries for UPS systems rated at 40kVA.
i. Regularly inspect the safety valve to check for signs of leakage or damage, ensuring it remains properly sealed.
j. During procurement, thoroughly understand the manufacturer’s production technology, quality control, and technical specifications. If necessary, conduct initial capacity tests to screen out inferior batteries.
In summary, effective communication and maintenance of VRLA batteries require understanding their unique characteristics and applying appropriate maintenance strategies. Through continuous learning, experience sharing, and improved practices, we can maximize battery performance and achieve the intended operational goals.
[2] Wang Qiuhong, Li Long. Pulse charging of lead-acid batteries [J]. Battery, 1995, (2): 38-40.
[3] CHEN Hongyu, WU Ling. Effect of Imbalance on VRLA Battery [J].
[4] Bao Weifang, Yan Zhigang, Zhu Yaozhen. Factors Affecting the Deep Cycle Life of VRLA Battery [DB/OL]. NUDE Battery Website (), Battery Technology Specialist.
[5] GNB Industrial Power Network Power FAQ [DB/OL].
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