Common maintenance tips for UPS batteries

Engineers usually use multiple groups of cheap small-capacity batteries in parallel to achieve the larger battery capacity required by UPS. If multiple groups of batteries with poor performance uniformity are used in parallel, the battery groups with poor performance and low voltage will drag down the battery groups with good performance, causing the entire UPS battery system to fail prematurely. At present, performance uniformity is mainly measured based on battery voltage uniformity. There are many standard requirements in China. For example, the Ministry of Information Industry's YD/T 799--1996 standard requires that the floating charge voltage difference of the entire battery 2V unit at 25℃ is not greater than ±50mV, and the open circuit voltage difference is not greater than ±20mV; the Ministry of Electric Power's DL/T637--1997 standard requires that at 25℃, if the battery system uses 2V/cell battery, the difference between the highest and lowest open circuit voltages shall not exceed 30mV, 6V/cell battery shall not exceed 40mV, and 12V/cell battery shall not exceed 60mV. Generally, the number of parallel battery groups should not exceed 4. To prevent the premature failure of the entire battery system, when selecting batteries, requirements should be made in terms of performance uniformity. After determining the battery model, it is best to require the manufacturer to provide the same batch of battery products in a UPS system to reduce performance differences. For the same reason, batteries of different brands or different degrees of age are not recommended to be mixed due to large performance differences. Finally, it should be pointed out that even if the appropriate VRLA is selected, some necessary daily maintenance and management are still required to prevent premature battery failure.

1. UPS battery maintenance

With the continuous development of technology, the performance of UPS is getting better and better, the average trouble-free working time is getting longer and longer, and the reliability of the whole machine is getting higher and higher. It is particularly important to maintain the consumable batteries in UPS.

1.1 Initial charging of new batteries

After a new battery is installed, it is generally necessary to charge it for a longer period of time. The charging power supply should be charged according to the regulations in the instruction manual. After the battery pack is fully charged, it should be discharged and then charged again. The purpose is to extend the battery life and improve the battery activity and charging and discharging characteristics.

1.2 Regular charging and discharging

If the battery inside the UPS power supply is left idle for a long time or is in a floating charge state without being discharged for a long time, a large amount of lead sulfate in the battery will be adsorbed to the cathode surface of the battery, forming the so-called "sulfation" of the battery cathode plate. Since lead sulfate is an insulator, its formation will inevitably have a very bad effect on the charging and discharging of the battery, because the more sulfate formed on the cathode plate, the greater the internal resistance of the battery, and the worse the battery's charge and discharge performance, which will cause the battery to "age" and "activity" to decrease, greatly shortening the service life of the battery. Every 3 to 4 months, the UPS rectifier/charger should be turned off by artificially interrupting the mains power or by software/hardware control to discharge the battery in the UPS. For this battery discharge operation for "activating" the battery, its discharge time should be controlled at 1/3 to 1/4 of the normal discharge time.

1.3 Deep discharge is strictly prohibited

The service life of sealed maintenance-free batteries is closely related to the depth of discharge of the battery. The depth of discharge refers to the percentage of the ampere-hours discharged by the battery during the use of the battery by the user to its nominal capacity ampere-hours. Deep discharge will cause sulfation on the surface of the internal plates of the battery, resulting in an increase in the internal resistance of the battery. In severe cases, some batteries will experience "reverse polarity" and permanent damage to the battery. The depth of discharge of the battery seriously affects the service life of the battery. Do not let the battery be in a deep discharge state unless it is absolutely necessary.

1.4 Try to avoid overcurrent charging

Over-current charging can easily cause the positive and negative plates inside the battery to bend, causing the active materials on the surface of the plates to fall off, resulting in a decrease in the battery's available capacity. In severe cases, it can cause a short circuit and damage to the battery's internal plates.

1.5 Try to avoid over-voltage charging of batteries

Overvoltage charging often causes the water contained in the battery electrolyte to be electrolyzed and separated into hydrogen and oxygen and escape, thereby shortening the battery life.

1.6 Replace batteries with reduced activity or excessive internal resistance

(1) As the UPS power supply is used for a longer time, the charge and discharge characteristics of some batteries will gradually deteriorate, and the terminal voltage will drop significantly. The performance of such batteries can no longer be solved by the charging circuit inside the UPS power supply. Continuing to use them will pose a hidden danger and they should be replaced in time.

(2) If the internal resistance of the battery increases and the battery cannot be restored to its charging characteristics by charging with normal charging voltage, the battery should be replaced in time. The internal resistance of the battery is generally 10-30mΩ. If the internal resistance of the battery exceeds 200mΩ, it will not be enough to maintain the normal operation of the UPS. Batteries with large internal resistance must be replaced.

1.7 Avoid mixing old and new batteries or charging new and old batteries together

Since the internal resistance of new batteries is relatively small, while the internal resistance of old batteries has increased to varying degrees, when new and old batteries are mixed together for charging, the voltage division will be relatively large due to the large internal resistance of the old batteries, which can easily cause overvoltage charging. For new batteries, the internal resistance is smaller, the charging voltage is small but the current is relatively large, which can easily cause overcurrent. Therefore, mixing new and old batteries should be avoided during the charging and discharging process.

2 Battery usage environment

The service life of the battery is closely related to the ambient temperature. When the battery is at a low temperature, the zinc plate in the battery is easy to powderize, lose its storage performance, and cause permanent damage. When the temperature is too high, the capacity of the battery will also decrease, and serious damage will cause permanent damage. According to the technical specifications of the battery manufacturer, the best operating temperature of the battery is 20-25℃. Using it within this temperature range can extend the service life of the battery.