How to Choose a Battery for an Uninterruptible Power Supply

Definition of Battery

An electronic device consisting of one or more electrochemical cells that convert stored chemical energy into a direct current voltage (VCD)

Characteristics of the Battery

1. Stored energy - Wh

2. The maximum current is the current that can be provided during discharge——A

3. The depth of discharge indicates the energy that the battery can withstand during discharge——%

Common types of batteries used in UPS

一．Lithium Battery

Composition:

positive electrode material, negative electrode material, electrolyte, separator and packaging material

Features:

1. Lithium batteries are smaller and lighter. The volume of the lithium battery is 2/3 of the volume of the lead-acid battery, and the weight is about 1/3 of the weight of the lead-acid battery. A lithium battery with the same volume has a higher capacity than a lead-acid battery.

2. Long life: The lithium iron phosphate battery pack has a longer service life under the same conditions, and the general life is basically about 4 to 5 years.

3. Excellent high-temperature performance: the heat peak of lithium iron phosphate battery can reach 350~500℃.

4. Fast charging: It can charge and discharge quickly at a high current of 2C, and the battery can be fully charged within 40 minutes by charging at 1.5C with a special charger.

5. Safe and reliable: Lithium iron phosphate has undergone strict safety tests and will not explode even in severe collisions.

6. Green and environmental protection: It complies with European RoHS regulations and is a green and environmentally friendly battery.

7. No memory effect: It can be used at any time, no need to fully discharge and then recharge.

8. Good performance: strong power, fast charging and fast discharging.

Precautions:

1. Operating ambient temperature
   It is necessary to give the battery a suitable temperature for normal operation and keep it. As far as the general battery is concerned, the temperature of its environment should be guaranteed to be between 20-25 degrees Celsius, and the lithium battery UPS can work normally at -20-60 degrees Celsius. No need for air conditioning, reducing equipment installation costs, maintenance costs, and electricity costs.

2. Regular inspections
   Regularly check the terminal voltage and internal resistance of each cell. During the operation of the lithium battery UPS power supply, it is impossible to rely on the internal charging circuit of the lithium battery UPS power supply to eliminate the above-mentioned imbalance caused by the characteristics of each unit battery changing with time, so this characteristic has already occurred. For a balanced battery pack, if offline equalization charging is not taken in time, its imbalance will become more and more serious.

3. Need to re-float charge under certain conditions
   The lithium battery UPS power supply has been shut down for more than 10 days. Before restarting, the UPS power supply should be started under the condition of no load to use the charging circuit in the machine to re-charge the lithium battery for more than 10-12 hours and then run with load. The UPS power supply is in the state of floating charge for a long time without discharging process, which is equivalent to being in the state of "storage and standby". If this state lasts for too long, the lithium battery will fail and be scrapped due to "excessive storage". It is mainly manifested as an increase in the internal resistance of the battery.

4. Need to reduce the depth of discharge
   The service life of lithium battery UPS is closely related to the depth it is discharged. The lighter the load carried by the lithium battery UPS power supply, the greater the ratio of the available capacity of the lithium battery to its rated capacity when the mains power supply is interrupted.
   When the lithium battery UPS power supply is interrupted by the mains power supply and the lithium battery is used to supply power to the inverter, most of the lithium battery UPS power supplies will sound a periodic alarm with an interval of about 4s to inform the user that it is now powered by the battery. energy. When the alarm sound becomes rapid, it means that the power supply is in deep discharge, and emergency treatment should be carried out immediately, and the lithium battery UPS power supply should be turned off. It's not forced, generally don't let the lithium battery UPS power supply work until the battery voltage is too low and it automatically shuts down.

5. Can use power supply peak charging

For users whose lithium battery UPS power supply has been in low-voltage mains or frequent power outages for a long time, in order to prevent premature damage to the battery due to long-term insufficient charging, the battery should be charged by making full use of the power supply peak (such as late at night) to ensure that the battery is in every hour. There is enough charging time after the first discharge. Generally, after the battery is deeply discharged, it takes at least 10-12 hours to recharge to 90% of the rated capacity.

二.VRLA=Valve Regulated Lead Battery

Name: valve-regulated lead-acid maintenance-free battery

Composition: Lead and Sulfuric Acid

Features:

1. Does not require forced ventilation

2. Can be installed in confined space

3. Can be installed in any direction (except downward)

4. No ongoing maintenance required

5. Maintenance-free, no need to add water and acid

6. Good sealing performance (no liquid leakage, no acid gas overflow)

7. Relatively small size

8. There is a one-way exhaust valve (also called safety valve) on the battery cover

The function of the valve is that when the gas inside the battery exceeds a certain value (usually represented by the air pressure value), that is, when the internal pressure of the battery rises to a certain value, the exhaust valve will automatically open to discharge the gas, and then automatically close the valve to prevent air from entering. inside the battery.

Type:

2V, 6V, 12V

Parameter metrics:

Battery electromotive force, open circuit voltage, termination voltage, working voltage, discharge current, capacity, battery internal resistance, storage performance, service life (float charge life, charge and discharge cycle life), etc.

三.NICD=Nickel Cadmium

Composition: Nickel hydroxide (NiOH) and metal cadmium (Cd) are used as chemicals for generating electricity

Features:

1. Nickel-cadmium batteries can be charged and discharged more than 500 times, which is very economical;

2. The internal resistance is small, and it can be discharged with a large current. When it is discharged, the voltage changes very little. As a DC power supply, it is a battery with excellent quality;

3. Because it is completely sealed, there will be no electrolyte leakage, and there is no need to replenish electrolyte;

4. Compared with other types of batteries, nickel-cadmium batteries can withstand overcharging or discharging, and the operation is simple and convenient;

5. The performance will not be degraded after being placed for a long time, and the original characteristics can be restored after being fully charged;

6. Can be used in a wide temperature range;

7. Because it is made of metal containers, it is mechanically strong;

8. Nickel-cadmium batteries are manufactured under very strict quality control and have very good quality and reliability

Precautions:

1. It can be stored in the temperature range of -30°C-50°C, but if it is stored for a long time, please store it below 35°C;

2. It is possible to save the state of charge or the state of discharge, but in comparison, the state of discharge can make the capacity recover earlier and be activated more easily;

3. When the battery is placed for a long time, it must be fully charged before use.