2. Design life and effective service life of lead-acid batteries
According to data records, the application of lead-acid batteries in my country’s communications departments began in the 1930s, and it took decades from the earliest open lead-acid batteries to acid-proof lead-acid batteries in the 1960s. Since 1980s, valve-regulated sealed lead-acid battery (VRLA) has become a mainstream product as a replacement product and has been used all the time. As the energy storage component of AC UPS, valve-regulated sealed lead-acid battery (VRLA) is still the main and leading battery.
The service life of valve-regulated sealed lead-acid batteries is mainly divided into two types: cycle life and floating life:
· （1）Cycle life refers to every charge and discharge of the battery, which is called a charge and discharge cycle. The number of charge and discharge cycles that the battery can perform while maintaining a certain output capacity is called the cycle life of the battery;
· （2）Float charge life refers to the running time of the battery at the end of its usable life under the specified float charge voltage and ambient temperature. The end-of-life condition is set at less than 80% of the rated capacity at 10h rate.
From theoretical analysis, the design life of valve regulated sealed lead-acid batteries (VRLA) can fully reach 15-20 years, which is the basis for practical use. For example, in the communication industry standard YD/T799-2002 “Valve Regulated Sealed Lead Acid Batteries for Communication”, the service life of batteries is specified as follows: “The equivalent float charge life of 2V series batteries shall not be less than 8 years. The equivalent float charge life of batteries above 6V series shall not be less than 8 years. ”In the newly revised YD/T799-2010, the battery life has been further refined and standardized from the perspective of testing and inspection, as shown in Table 1.
In summary, and based on the analysis of actual usage, the current standard specifications for the lifespan of batteries are appropriate and feasible. The reason why the service life of valve regulated sealed lead-acid batteries (VRLA) currently used in UPS communication does not meet the requirements is not a problem of technical principles and production level.
3. Long delay batteries and high rate batteries
The batteries used in data centers can generally be divided into three categories based on discharge types: “instantaneous high current discharge” for oil generator sets, “long delay, low current discharge” for communication power systems, and “high rate discharge” for AC UPS systems.
In the power supply of traditional communication network equipment, the backup time of the communication power system is basically designed and configured according to several hours of the designed load. For example, 10h, 8h, and at least 3-5 hours. The battery pack is basically in a “long delay, low current” charging and discharging state, and the nominal capacity of the battery is also calibrated based on the capacity at a 10h discharge rate, such as 100Ah/12V, 200Ah/6V, 1000Ah/2V, etc., all of which can release electrical energy of 100Ah, 200Ah, and 1000Ah according to the discharge current at a 10h rate
For high-power AC UPS systems, 6V or 12V batteries are often used due to their high voltage. Due to various limitations such as battery capacity, number of parallel groups, and investment costs, its backup time is only 15 minutes. In other words, the discharge rate of the battery pack is much lower than the 10 hour rate, while the actual discharge current of the battery pack is much higher than the 10 hour rate discharge current. The discharge method of batteries has shifted to a “high rate” discharge method that falls between the traditional “long delay, low current” of backup batteries for communication and the “instantaneous high current discharge” of starter batteries. From the current technology and process structure of valve regulated sealed lead-acid batteries, communication backup batteries designed and produced according to “long delay, low current” cannot fully meet this application requirement.
Therefore, the selection of lead-acid batteries with 12V or 6V single cells is completely different for different usage scenarios. In traditional communication stations and base stations, traditional lead-acid batteries with low current and long delay should continue to be used for communication; For the battery pack used in the data center communication UPS system, a “high rate” battery pack suitable for high current discharge should be selected. The two should not be confused or abused.