UPS Battery Configuration Guide

In short, the first thing is to confirm the power of the equipment that people want the UPS to carry, and then the power of the UPS can be confirmed. Generally speaking, the recommended load power is 30%~80% of the UPS power. If the load is too large, the UPS power supply may be overloaded when starting at the same time. If the load is too small, it will not only cause waste, but also be bad for the performance of the battery.

UPS Battery Configuration Guide

How UPS works
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At present, there are three common working methods in the market: backup, online interactive, and online double transformation (line pure online). The details are as follows:
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1 Backup UPS, without voltage regulator, there is a conversion time when the mains and battery are converted, generally used for personal computer protection, or when the performance requirements of the UPS power supply are not high, this type of UPS power segment is generally small ;
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2 Online interactive type, without voltage regulation, there is a conversion time when the mains and battery are converted, but there is a voltage regulation function, which is generally used in wiring rooms or micro computer rooms to protect servers and network equipment, etc. This type of UPS power section is generally in the Below 5kVA.
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3 On-line double conversion UPS, there is no conversion time when the mains and battery are converted, and the non-switching time is generally used to protect the server or network equipment and other equipment in the computer room. This type of UPS has power segments ranging from small to large, with a relatively large span of 1kVA ~1000kVA, which is more common in the market at present.
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The performances of the above UPS power sources are from high to low: online double conversion, online interactive, and backup. Price is generally proportional to performance. Does that mean we must choose an expensive UPS? the answer is negative. As our title, we have to choose the UPS that suits us. If it is used for personal computer, then you can choose a backup UPS. If it is used for server, it should be selected between online interactive and online double conversion, and the selection should be made according to the following conditions:
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1 Equipment requirements
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To see if the equipment needs high-precision power supply, you can check the logo on the nameplate of the load equipment or ask the equipment manufacturer. For high-precision power supply, you need to choose an online double-conversion UPS. The second is to look at the load type. Some loads are not allowed to have power supply flashes, such as: relay equipment or switching signal equipment. If this type of equipment is equipped with an online interactive UPS, it may be in the UPS market. When the electricity and the battery are switched, the load has a power failure or malfunction, so an online double conversion UPS should be selected for this type of equipment. If the device does not have the above two requirements, you can continue with the following steps.
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2 Local power grid
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If the quality of the local power grid is relatively good, that is to say, the voltage fluctuation is small at ordinary times, you can consider choosing an online interactive UPS at this time. However, if the quality of the local power grid is poor and the voltage fluctuation is large, it is recommended to use an online double-conversion UPS, because this type of UPS has better adaptability to the mains power than the online interactive type.
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3 Battery life after UPS is converted to battery
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If a longer time delay is required, you can consider choosing a dual-purpose machine or a UPS without built-in batteries. Both of these UPS power sources can be equipped with original batteries or third-party batteries to achieve longer time delays. Purpose.
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4 Installation method
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Generally speaking, there are two installation methods for UPS power supply, one is tower installation and the other is rack installation, which can be selected according to your computer room environment or site environment, and it should also be noted that not all UPS power supplies are Both installation methods are supported at the same time. In most cases, rack-mounted UPS can also be tower-mounted, but tower-type UPS may not be rack-mounted, because tower-type UPS may not be able to install rails. Therefore, after confirming the UPS power segment and working mode, be sure to confirm whether the UPS power supply can meet your installation requirements.
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Advantages and disadvantages of different types of UPS batteries
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There are three types of batteries in UPS applications: including open-type liquid lead-acid batteries, maintenance-free batteries, and nickel-chromium batteries. The batteries provided by UPS manufacturers are generally maintenance-free batteries. The following describes the characteristics of the three types of batteries:
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1 Open liquid lead-acid battery
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According to the structure, such batteries can be divided into 8-10 years and 15-20 years of life. Since the electrolysis of sulfuric acid produces corrosive gas, such batteries must be installed in a ventilated room away from sophisticated electronic equipment, and the battery room should be covered with anti-corrosion tiles.
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Due to evaporation, it is necessary to regularly 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.
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This battery cannot be transported after charging, so it must be charged after installation on site. The 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.
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2 Maintenance-free batteries
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Maintenance-free batteries, also known as valve-regulated sealed lead-acid batteries, must follow the following principles during use and maintenance:
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  1. The allowable operating range of sealed batteries is 15 degrees to 50 degrees, but use within 5 degrees to 35 degrees can prolong 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.
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    2 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.
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    3 The floating charge voltage of the maintenance-free battery is designed to be 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 avoid insufficient charging. Discharge termination voltage at full load (
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  2. If the battery is not recharged within 72 hours after the discharge is over. Sulfate will adhere to the plate to insulate and charge, and damage the battery.
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  3. When the battery is floating or equalizing, the gas generated 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.
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    6 The life of the battery separator 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.
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  4. 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. When the internal air pressure is restored, the safety valve will automatically recover.
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  5. The cycle life of a battery (charge and discharge times) depends on the discharge rate, the depth of discharge, and the way of recovery charging. The most important factor is the depth of discharge. At a certain 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.
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    9 When the battery reaches the end of its life, the capacity decays, the internal short circuit, the deformation of the casing, the corrosion of the plate, and the reduction of the open circuit voltage.
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    10 IEEE defines the end of battery life as a capacity 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 define the end of life of a battery as a capacity reduction of 50%-60% of its nominal capacity.
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    How to calculate the number of batteries in the UPS
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    1 Calculation method of battery
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    For example, a 40KVAUPS, the DC voltage is 384V, and each group has 32 12V batteries. If the backup time requires 2 hours, the calculated battery capacity is:
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    40000VA2H/(0.7384V)=297AH
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    So choose 3 groups of 100AH ​​batteries, a total of 96 cells.
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    The current of the battery pack is 40KVA/384V=104A, so choose 50mm2 cable for battery connection.
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    The total number of batteries = (power / DC voltage * hours) / each ampere hour * the number of blocks per group
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    Among them, the power is the power of the UPS, and the DC voltage is the voltage required by the UPS battery power supply. The DC voltage of the UPS with different powers is different. The number of blocks in each group is the minimum number of batteries required. Generally, when configuring batteries, the number of blocks in each group must be Integer multiples of , the common UPS DC voltage and the number of blocks in each group are as follows (each battery is calculated based on 12V):
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    For example, to configure a 5K 8-hour delay UPS with a power of 5000, a DC voltage of 96V, 8 batteries per group, and a 100AH ​​battery, the total number of batteries required is: (5000/96*8)/100 *8=32 blocks.

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