There are three types of batteries commonly used in UpS power applications: including open-type liquid lead-acid batteries, maintenance-free batteries, nickel-chromium batteries, factors that affect battery life, and different types of batteries have their own advantages and disadvantages. The batteries provided by UpS manufacturers are generally maintenance-free batteries. The following describes the characteristics of the three types of batteries:

1: Open type liquid lead-acid battery
Such batteries can be divided into 8-10 years and 15-20 years of life according to their structure. Due to the corrosive gas generated by the electrolysis of sulfuric acid in this battery, such batteries must be installed in a room that is ventilated and away from precision electronic equipment, and the battery room should be covered with anti-corrosion tiles.

Due to evaporation, it is necessary to periodically measure the specific gravity of the open battery, add acid and water. This battery can endure high temperature, high pressure and deep discharge. The battery room should be non-smoking and use open battery racks.
This battery cannot be transported after charging, so it must be installed on site and charged. Initial charging generally takes 55-90 hours. 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 battery, the following principles must be followed during use and maintenance:
a: The allowable operating range of the sealed battery is 15°-50°, but use within 5°-35° can prolong the battery life. Below minus 15 degrees, the battery chemistry 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 long life but lower capacity at low temperature, and will get higher capacity but short life at high temperature.

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 higher.

c: The design float voltage of maintenance-free battery is 2.3V/cell. A 12V battery is 13.8V. CSB recommends 2.25-2.3V per cell. In the case of 120 batteries connected in series, after the temperature is higher than 25 degrees Celsius, the float voltage should be reduced by 3MV for each degree of temperature increase. Similarly, the voltage should be increased by 3MV for each degree of temperature increase in order to prevent insufficient charging. The discharge termination voltage is 1.67V per cell at full load (<30 minutes). In the case of low discharge rate (small current for a long time), it should be increased to 1.7V-1.8V per cell, and ApCSYMMETRA 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 plate to insulate and charge, and damage the battery.

e: When the battery is floating or equalizing, 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, corrosion of the battery plates will reduce the battery capacity.

f: The battery separator life is only 5-6 months when the ambient temperature is 30-40 degrees. Batteries that have been stored for a long time must be charged every 6 months. Batteries must be stored in a dry and cool environment. The self-discharge rate of the maintenance-free battery is 3-4% per month at 20 degrees and varies with temperature.

g: Maintenance-free batteries are equipped with safety valves. When the internal air 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 air pressure is restored.

h: The cycle life of the battery (the life of the number of charges and discharges) depends on the discharge rate, the depth of discharge, and the way of recovery charging, the most important factor of which is the depth of discharge. In terms of discharge rate and time, 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 100% deep discharge at 25 degrees.

i: When the battery reaches the end of its life, it shows capacity decay, internal short circuit, shell deformation, plate corrosion, and open circuit voltage reduction.

j: IEEE means that the end of battery life is less than 80% of the nominal capacity AH. There is a non-linear relationship between the nominal capacity and the actual backup time. If the capacity is reduced by 20%, the corresponding backup time will be greatly reduced. Some UpS manufacturers imply 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 manufacturers, otherwise the battery life will be reduced.

l: If two sets of batteries are used in parallel, ensure that the batteries are connected and the impedance of the bus bar is the same.

m: A maintenance-free battery means that it is not necessary to add liquid, but it is still necessary to regularly check the casing for cracks and electrolyte leakage.

3: Ni-Cr battery
Unlike lead-acid batteries, these batteries produce hydrogen and oxygen rather than corrosive gases during electrolysis, so they can be installed next to electronic equipment. And the consumption of water is very small, generally no maintenance is required. The normal lifespan is 20-25 years. Far more expensive than the aforementioned batteries. The initial installation costs about three times as much as 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 due to the application of such batteries. pros and cons:

1 Open lead-acid battery:

Advantages: less investment, longer life than maintenance-free batteries, and lower temperature requirements.

Disadvantages: maintenance is more complicated, special battery room is required, corrosive gas is discharged, and it must be initially charged on site for 50-90 hours, requiring special maintenance.

2: Maintenance-free battery:
Advantages: No maintenance such as adding liquid, can be transported in a fully charged state, and no maintenance is required.

Disadvantages: Failure to restore charging in time will damage the battery, it is more sensitive to temperature, has a shorter lifespan, and is more expensive than lead-acid batteries.

3: Ni-Cr battery:

Advantages: lower maintenance requirements, longer life, insensitive to temperature, no harmful gas emissions.
Cons: The most expensive of the three batteries.

UpS common battery
Most of the current computer centers generally use maintenance-free batteries, which are more convenient to maintain, but the following work is also required:
1: Discharge once every three to four months to prevent oxidation of the plates.
2: The ambient temperature should be kept at 20-25 degrees.
3: The connection should not be too tight or too loose, and should be checked frequently.
4: After three years of use, it needs to be checked and replaced in time.