(3) Research on the impact of imbalance on VRLA (Valve Regulated Lead-Acid) batteries reveals that the distribution of alloy composition and microstructure across different parts of the grid is not uniform. This unevenness leads to variations in electrochemical properties, which can result in differences in float voltage and charge/discharge voltages. Over repeated charge and discharge cycles, these voltage differences tend to increase, creating a cycle where the imbalance becomes more pronounced. This phenomenon ultimately leads to the formation of what is known as a "backward battery," or a failed battery. Currently, domestic standards allow a maximum float voltage difference of ≤50mV within a battery, while international standards are stricter, limiting it to ≤20mV. Therefore, it is crucial to monitor and minimize voltage differences during float operation to ensure long-term reliability and performance.
(4) Thermal runaway is a serious issue in valve-regulated batteries, especially those with a lean electrolyte design. In such batteries, the electrolyte is absorbed into the glass fiber mat. When charging current increases, gas is released through the safety valve, leading to water loss, increased internal resistance, and reduced capacity. The heat generated during charge and discharge can accumulate if not properly managed, eventually triggering 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 can cause a sudden drop in voltage and raise the battery housing temperature to 70–80°C. Therefore, this issue must be taken very seriously.
Based on the above analysis, proper maintenance of valve-regulated batteries is essential. Key measures include:
a. Installing air conditioning in the battery room to maintain temperatures 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 dynamically using a ±3mV/°C coefficient based on ambient temperature changes.
c. Using the lower limit of float voltage for floating power supply to mitigate imbalance effects.
d. Performing balanced charging after deep discharges or when the battery is unbalanced, and conducting periodic balancing every three months. During equalization, adjust the voltage according to ambient temperature—reducing it by 3mV for every 1°C increase.
e. Applying pulse charging to aging batteries to potentially restore some of their capacity.
f. Keeping detailed records of individual battery voltages and internal resistances before commissioning, and comparing them with data collected every six months. Any anomalies should be addressed immediately.
g. Increasing testing frequency once the battery reaches half its expected lifespan, particularly for 12V units. If resistance suddenly rises or voltage readings are unstable (especially with decimal fluctuations), treat it as a potential "backward battery."
h. Where possible, use 2V valve-regulated batteries for UPS systems rated at 40kVA.
i. Regularly inspecting the safety valves for signs of leakage or damage.
j. Carefully selecting and procuring batteries by understanding the manufacturer's technology, production methods, quality control, and technical specifications. If necessary, conduct initial capacity tests to screen out inferior units.
In summary, effective communication and maintenance of valve-regulated batteries require attention to their unique characteristics and varying maintenance needs. Through experience and continuous learning, maintenance practices can be improved to 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. Influence of Sulphation on VRLA Battery [J]. Power Technology, 2001, (5).
[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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