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| Basic Temperature Requirements for Matsushita Maintenance-Free Batteries in Use |
| Time：2019-07-19 Source： Views：1956 |
Battery is an important part of UPS system. Its quality is directly related to the reliability of the whole UPS system. No matter how advanced the UPS design and how complete the function is, once the battery fails, the best UPS can not provide discontinuous power supply. Never choose low-quality lead-acid batteries for the sake of low cost, which will affect the reliability of the whole UPS system and cause greater losses. Battery is the shortest part of uniform trouble-free time (MTBF) in the whole UPS system. If it can be used and maintained correctly, its service life can be prolonged, and vice versa, its service life will be greatly shortened. Therefore, we need to understand the basic principle of storage battery and the matters needing attention in its application.
Varieties of lead-acid batteries
Usually it can be divided into lead-acid batteries, lead-acid maintenance-free batteries and nickel-cadmium batteries. Considering load conditions, operating environment, service life and cost, UPS generally chooses valve-regulated lead-acid maintenance-free batteries. Its main characteristic is that oxygen is generated on the positive plate during charging, water is recovered on the negative plate by chemical reaction, and no water is added to maintain during the regular floating life, so it is also called maintenance-free lead-acid battery. Maintenance-free batteries are only compared with ordinary batteries. In the process of operation, the work of adding pure water or distilled water and adjusting the level of electrolyte is not exempted from all maintenance work. On the contrary, in order to complete the discontinuous power supply of UPS, we need to maintain and maintain lead-acid maintenance-free batteries more carefully.
Main factors affecting service life and matters needing attention
Here are the main factors affecting the service life of batteries and the matters needing attention in the operation process.
1
Environmental temperature has a great influence on the battery. If the ambient temperature is too high, the battery will be overcharged to produce gas. If the ambient temperature is too low, the battery will be short of charge, which will affect the service life of the battery. Therefore, the ambient temperature of the common request is about 25 C, and the floating charge voltage of UPS is also set according to this temperature. When applied in practice, the battery usually stops charging in the range of 5 ~35 ~C, and the capacity and service life of the battery will be greatly reduced if the temperature is lower than 5 ~35 ~C.
2
The discharge depth also has a great influence on the service life of batteries. The deeper the discharge depth of the battery, the less the number of cycles it uses. Therefore, deep discharge should be prevented in operation. Although UPS has battery low potential maintenance function, when a single battery discharges to about 10.5V, UPS will automatically shut down. However, if UPS is under the condition of light or no-load discharge, deep discharge of battery will also be formed.
3
In the process of storage, transportation and installation, the battery will lose its partial capacity due to self-discharge. Therefore, before the device is put into operation, the remaining capacity of the battery should be judged according to the open-circuit voltage of the battery, and then different methods should be adopted to stop the recharging of the battery. For spare batteries, recharging should be stopped every 3 months. The battery can be judged by measuring the open circuit voltage of the battery. Taking 12V battery as an example, if the open-circuit voltage is higher than 12.5V, it means that the battery has more than 80% energy storage. If the open-circuit voltage is lower than 12.5V, the recharging should be stopped immediately. If the open circuit voltage is less than 12V, it means that the battery can store less than 20% of the energy, and the battery is not usable.
4
Charging and discharging current of batteries is usually expressed in C. The practical value of C is related to the capacity of batteries. For example, a 100AH battery, C = 100A. The optimum charging current of Panasonic lead-acid maintenance-free battery is about 0.1C, and the charging current should not be greater than 0.3C. If the charging current is too large or too small, the service life of the battery will be affected. Discharge current is between 0.05C and 3C. UPS can meet this requirement in normal operation, but it is also necessary to avoid the occurrence of unexpected conditions, such as short circuit of batteries.
5
Charging voltage. Because UPS batteries belong to standby mode of operation, they are charged in the normal state of municipal power supply and discharge only when power failure occurs. In order to prolong the service life of batteries, UPS chargers are usually controlled by constant voltage and current limitation. When the batteries are overcharged, they turn to floating charging state. The floating charging voltage of each cell is set at about 13.6V. If the charging voltage is too high, the battery will be overcharged, and vice versa, the battery will be short of charge. Abnormal charging voltage may be caused by incorrect battery configuration or by faulty charger. Therefore, when installing batteries, we must pay attention to the correctness of the specifications and quantities of batteries. Batteries of different specifications and batches should not be mixed. External chargers should not use inferior chargers, and heat dissipation should be considered when installing them.
At present, in order to further improve battery life, advanced UPS adopts an ABM (Advanced Battery Management) three-stage intelligent battery management plan, namely, charging dividend initial charging, floating charging and rest three stages:
The first stage is constant current balanced charging, charging the battery capacity to 90%.
The second stage is floating charging, charging the battery capacity to 100%, and then stopping charging.
The third stage is natural discharge. In this stage, the battery application itself leaks electricity and discharges it continuously to the lower limit of the regular voltage, and then repeats the three stages mentioned above. This method changes the previous charging and overcharging, and still keeps the battery in a floating state of 24 hours a day, thus prolonging the life of the battery.
6
Maintenance-free batteries will not produce any gas in normal operation due to the use of absorption electrolyte system, but if users use improperly and form battery overcharge, gas will be generated. At this time, the internal pressure of batteries will increase, and the pressure valve on batteries will be opened, which will cause serious problems.
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