The main reasons for replacing batteries in a UPS power supply can be analysed from the following aspects:
**1. Termination of Battery Life**
- **Consideration of Float Life**: Under standard operating conditions and in a continuous float charging state, the period during which a UPS battery can deliver not less than 80% of its rated capacity is defined as its float life. Typically, the float life of a UPS battery is around 5 years. Beyond this period, the battery's performance gradually deteriorates, making it difficult to support the power requirements of the UPS system.
- **Limitation on Charge-Discharge Cycles**: The durability of a battery can also be gauged by the number of charge-discharge cycles it can undergo. The deeper the discharge, the fewer the cycles the battery can endure. For instance, with a 100% depth of discharge, the practical service life is approximately 100–200 cycles; at 50% depth of discharge, the cycle count can rise to 300–400; and at 30% depth of discharge, it may exceed 600 cycles. However, with frequent cycling, the battery's energy storage capacity steadily diminishes, eventually failing to meet the operational demands of the UPS system.
**2. Effects of External Environment**
- **Impact of Temperature on Batteries**: The performance of UPS batteries is significantly influenced by the temperature of their installation and usage environment. High temperatures can lead to overcharging, resulting in the release of gases and posing a threat to battery longevity. Conversely, low temperatures may cause undercharging, reducing battery activity and shortening its service life.
- **Accelerated Deterioration in Harsh Conditions**: In more demanding environments, such as those with frequent temperatures exceeding 35°C or a lack of regular manual maintenance, battery performance degrades at a faster rate. This necessitates more frequent battery replacements to ensure system stability.
**3. Self-Discharge and Ageing Issues of Batteries**
- **Capacity Loss Due to Self-Discharge**: During storage, transportation, and installation, batteries may experience capacity loss from self-discharge. Even when not in use, internal chemical reactions cause gradual discharge. Thus, for batteries left idle for extended periods, periodic recharging is essential.
- **Safety Hazards of Battery Ageing**: Over time, batteries inevitably age, showing signs like swelling, leakage, or acid seepage. These issues not only compromise performance and lifespan but also carry risks of fire or explosion. Therefore, upon detecting such ageing indicators, immediate replacement is necessary to ensure safety.
**4. Ensuring Stable Operation of the UPS System**
- **Core Function of the UPS System**: The primary role of a UPS system is to provide an uninterrupted power supply to connected loads during mains power anomalies or outages. If battery performance declines or fails, the UPS system cannot maintain reliable operation. Hence, regular battery replacement is critical to uphold continuous stability and ensure dependable power support for loads.
In summary, the key reasons for replacing batteries in a UPS power supply include the end of battery life, external environmental factors, self-discharge and ageing concerns, and the need to ensure system stability. To safeguard UPS operation and prolong battery life, users are advised to develop a suitable battery replacement schedule based on actual needs and environmental conditions, alongside conducting regular maintenance and upkeep.