1. Types of batteries commonly used in UpS
There are three types of batteries commonly used in UpS power supply: including open-type liquid lead-acid batteries, maintenance-free batteries, nickel-chromium batteries, factors that affect battery life, different types of batteries also have their own advantages and disadvantages. The batteries currently equipped by UpS manufacturers are generally maintenance-free batteries. The following are mainly maintenance-free batteries to analyze the characteristics of the three batteries:
1: Open-type liquid lead-acid battery
According to the structure, this type of battery can be divided into two types with a life span of 8-10 years and 15-20 years. Because this battery sulfuric acid electrolysis will produce corrosive gas, this battery must be installed in a ventilated room far away from precision electronic equipment, and the battery room should be laid with anti-corrosion tiles.Due to the evaporation, the specific gravity of the battery should be measured regularly, acid and water should be added. This battery can endure high temperature, high pressure and deep discharge. The battery room should be non-smoking and use open battery racks.
The battery cannot be transported after being charged, so the initial charge usually takes 55-90 hours after installation on site. The normal voltage of each cell is 2V, and the initial charging voltage is 2.6-2.7v.
2: Maintenance-free battery
Also known as valve-regulated sealed lead-acid batteries, the following principles must be followed in use and maintenance:
a: The allowable operating range of the sealed battery is 15 degrees -50 degrees, but using within 5 degrees -35 degrees can extend the battery life. Below minus 15 degrees, the chemical composition of the battery will change and cannot be charged. Use in the range of 20 degrees to 25 degrees will get the highest life. The battery will get a long life but lower capacity in low temperature operation, and will get a higher capacity but short life in high temperature operation.
b: The relationship between battery life and temperature can refer to the following rules. After the temperature exceeds 25 degrees Celsius, the battery life will be halved for every 8.3 degrees Celsius.
c: The design float voltage of maintenance-free battery is 2.3V/cell. The 12V battery is 13.8V. CSb company proposes 2.25-2.3V per section. In the case of 120 batteries in series, after the temperature is higher than 25 degrees Celsius, the float charge voltage should be reduced by 3MV for every degree of temperature increase. Similarly, for every degree of temperature increase, the voltage should be increased by 3MV to guard against insufficient charging. The final discharge voltage is 1.67V per cell at full load (30 minutes). In the case of a low discharge rate (low current discharge for a long time) to increase to 1.7V-1.8V per cell, ApCSYMMETRA can adjust the charging voltage according to the load.
d: If the battery is not recharged within 72 hours after the discharge is over. Sulfate will adhere to the pole plate to insulate and charge, and damage the battery.
e: When the battery is floating or evenly charged, the gas inside the battery is electrolyzed into water on the negative plate, so as to maintain the capacity of the battery without adding water. However, the corrosion of the battery plate will reduce the battery capacity.
f: The battery separator life is only 5-6 months when the ambient temperature is 30-40 degrees. Batteries stored for a long time must be recharged every 6 months. The battery must be stored in a dry and cool environment. The self-discharge rate of maintenance-free batteries in a 20 degree environment is 3-4% per month, and varies with temperature.
g: Maintenance-free batteries are equipped with safety valves. When the internal pressure of the battery rises to a certain level, the safety valve can automatically remove excess gas, and the safety valve will automatically recover when the internal pressure is restored.
h: The cycle life of the battery (lifetime of charging and discharging times) depends on the discharge rate, depth of discharge, and recovery charging method. The most important factor is the depth of discharge. When the discharge rate and time are pressed, the shallower the depth of discharge, the longer the battery cycle life. The maintenance-free battery has a cycle life of about 200 times under the condition of 100% deep discharge at 25 degrees.
i: When the battery reaches the end of its life, it shows capacity decay, internal short circuit, deformation of the outer shell, corrosion of the electrode plate, and drop in open circuit voltage.
j: IEEE means that the end of battery life is less than 80% of the nominal capacity AH. The nominal capacity has a nonlinear relationship with the actual backup time. A 20% reduction in capacity will reduce the backup time a lot. Some UpS manufacturers mean that the end of life of the battery is when the capacity drops to 50-60% of the nominal capacity.
k: It is absolutely forbidden to mix batteries of different capacities and different manufacturers, otherwise the battery life will be reduced.
l: If two sets of batteries are used in parallel, ensure that the battery is connected and the bus impedance is the same.
m: The maintenance-free battery means that there is no need to add liquid, but it is still necessary to regularly check the casing for cracks and electrolyte leakage.
3: Nickel-chromium battery
This type of battery is different from a lead-acid battery in that hydrogen and oxygen are present during electrolysis without corrosive gases, so it can be installed next to electronic equipment. In addition, water consumption is very small, and maintenance is generally not required. The normal life span is 20-25 years. Far more expensive than the aforementioned batteries. The initial installation cost is about three times that of lead-acid batteries. It will not affect battery life due to high ambient temperature, nor will it affect battery capacity due to low ambient temperature. Generally, the voltage of each cell is 1.2V, and UpS needs to design a higher charger voltage because of the use of this type of battery.
2. Advantages and disadvantages
1: Open-type lead-acid battery
Advantages: less investment, longer life than maintenance-free batteries, and lower temperature requirements.
Disadvantages: maintenance is more complicated, a dedicated battery room is required, corrosive gas is exhausted, the initial charge on the spot is 50-90 hours, and special maintenance is required.
2: Maintenance-free battery
Advantages: No need to add liquid and other maintenance, can be transported in a fully charged state, no need for maintenance.
Disadvantages: The battery will be damaged if it is not recharged in time, it is more sensitive to temperature, has a shorter life span, and is more expensive than lead-acid batteries.
3: Nickel-chromium battery
Advantages: low maintenance requirements, long life, insensitive to temperature, and no harmful gas emissions.
Disadvantages: The most expensive of the three batteries.
Three, UpS commonly used batteries
Nowadays, computer centers generally use maintenance-free batteries, which are more convenient to maintain, but the following tasks are also required:
1: Discharge once every three to four months to prevent plate oxidation.
2: The ambient temperature should be maintained at 20-25 degrees.
3: The connection should not be too tight or too loose, it needs to be checked frequently.
4: Check and replace in time after three years of use.
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