Common application knowledge of UPS power battery

1、 Types of commonly used UPS batteries

There are three types of batteries commonly used in UPS power applications: open type liquid lead-acid batteries, maintenance free batteries, and nickel chromium batteries. Factors that affect battery life also have their own advantages and disadvantages. The batteries provided by current UPS manufacturers are generally maintenance free batteries. The following mainly introduces the characteristics of three types of batteries to avoid maintenance:

1: Open type liquid lead-acid battery

This type of battery can be divided into two types based on its structure: 8-10 years and 15-20 years. Due to the corrosive gas generated by sulfuric acid electrolysis of this battery, it should be installed in a well ventilated room away from precision electronic equipment, and the battery room should be covered with anti-corrosion tiles.

Due to evaporation, open batteries require regular measurement of specific gravity and addition of acid and water. This battery can withstand high temperature, high voltage, and deep discharge. The battery room should be smoke-free and use open battery racks.

This battery cannot be transported after charging, so it usually takes 55-90 hours for initial charging after installation on site. The normal voltage for each section 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 should be followed in use and maintenance:

a: The allowable operating range for sealed batteries is 15-50 degrees, but using within 5-35 degrees can extend the battery life. The chemical composition of the battery will change below minus 15 degrees Celsius and cannot be charged. Using within the range of 20 to 25 degrees will result in a longer lifespan. Batteries will have a long lifespan but lower capacity when operating at low temperatures, and a higher capacity but shorter lifespan when operating at high temperatures.

b: The relationship between battery life and temperature can be referred to as follows: after the temperature exceeds 25 degrees Celsius, the battery life will be reduced by half for every 8.3 degrees Celsius increase.

c: The design float charge voltage of maintenance free batteries is 2.3V/cell. A 12V battery has a voltage of 13.8V. CSB recommends 2.25-2.3V per cell. When 120 cells are connected in series and the temperature exceeds 25 degrees Celsius, the float charge voltage should be reduced by 3MV for every degree of temperature increase. Similarly, to avoid insufficient charging, the voltage should be increased by 3MV for every degree of temperature increase. The discharge termination voltage is 1.67V per cell at full load (<30 minutes). At low discharge rates (low current long-term discharge), the voltage should be increased to 1.7v-1.8v per section, and the apcsymmetria can adjust the charging voltage according to the load.

d: If the battery is not recharged within 72 hours after discharge. Sulfate will adhere to the electrode plate for insulation charging, causing damage to the battery.

e: When the battery is float charged or evenly charged, the gas generated inside the battery is electrolyzed into water on the negative electrode plate, thereby maintaining the capacity of the battery without the need for external water. But the corrosion of battery plates will reduce the battery capacity.

f: The lifespan of the battery separator is only 5-6 months at an ambient temperature of 30-40 degrees Celsius. Batteries stored for a long time should be charged every 6 months. The battery should 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 eliminate excess gas. When the internal pressure is restored, the safety valve will automatically recover.

h: The cycle life (number of charge and discharge cycles) of a battery depends on the discharge rate, depth of discharge, and the method of restorative charging, with the factor being the depth of discharge. When the discharge rate and time are constant, the shallower the discharge depth, the longer the battery cycle life. The maintenance free battery has a cycle life of about 200 times under 25 degrees and 100 deep discharge conditions.

i: When the battery reaches its lifespan, it exhibits capacity decay, internal short circuit, shell deformation, plate corrosion, and reduced open circuit voltage.

j: IEEE defines the end of battery life as a capacity that is less than 80% of the nominal capacity AH. The relationship between nominal capacity and actual backup time is non-linear, and a 20% reduction in capacity will result in a significant decrease in backup time. Some UPS manufacturers define the end of battery life as a decrease in capacity to 50-60% of the nominal capacity.

k: It is prohibited to mix batteries of different capacities and manufacturers, otherwise it will reduce the battery life.

l: If two sets of batteries are used in parallel, the batteries should be connected and the busbar impedance should be the same.

m: Maintenance free batteries mean that there is no need to add liquid, but regular inspections of the casing for cracks and electrolyte leakage are also necessary.

3: Nickel chromium battery

This type of battery is different from lead-acid batteries, as it produces hydrogen and oxygen during electrolysis without producing corrosive gases, making it suitable for installation next to electronic devices. And the consumption of water is minimal, generally requiring no maintenance. The normal lifespan is 20-25 years. Far more expensive than the batteries mentioned earlier. 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 per cell is 1.2V, and UPS requires a higher charger voltage to be designed for the use of such batteries.

2、 Advantages and disadvantages:

1. Open type lead-acid battery:

Advantages: Less investment, longer lifespan of maintenance free batteries, and lower temperature requirements.

Disadvantages: Maintenance is complex and requires a dedicated battery room, with corrosive gases emitted. The initial charging time on site is 50-90 hours, and a dedicated person is needed for maintenance.

2: Maintenance free battery:

Advantages: No need for maintenance such as adding liquid, can be transported in a fully charged state, and does not require dedicated maintenance.

Disadvantages: Failure to recover charging in a timely manner can damage the battery, be sensitive to temperature, have a shorter lifespan, and are more expensive than lead-acid batteries.

3: Nickel chromium battery:

Advantages: Low maintenance requirements, long lifespan, insensitivity to temperature, and no harmful gas emissions.

Disadvantage: The three types of batteries are relatively expensive.

3、 UPS common batteries

Most computer centers nowadays use maintenance free batteries, which are easier to maintain, but the following tasks also need to be carried out:

1: Discharge once every three to four months to prevent electrode oxidation.

2: The ambient temperature should be maintained at 20-25 degrees Celsius.

3: The connection should not be too tight or too loose and should be checked regularly.

4: After three years of use, it is necessary to check and replace it in a timely manner.