How to reduce the UPS power battery failure rate

- Nov 29, 2018-

Periodic inspection

Check the terminal voltage and internal resistance of each unit battery regularly. For the 12V unit battery, if it is found that the terminal voltage difference between each unit cell exceeds 0.4V or the internal resistance of the battery exceeds 80mΩ, the unit battery should be balancedly charged to restore the internal resistance of the battery. And eliminate the terminal voltage imbalance between each unit cell. When the charging is balanced, the charging voltage can be 13.5 to 13.8V. Most of the batteries that have been well-balanced and charged can restore their internal resistance to less than 30mΩ.

During the operation of the UPS power supply, the above imbalance caused by the characteristics of each unit battery changes with time is impossible to eliminate by relying on the internal charging circuit of the UPS power supply. Therefore, a battery having a significant imbalance in such characteristics has occurred. If the group does not take offline equalization processing in time, its imbalance will become more and more serious.


The UPS power supply is shut down for more than 10 days. Before restarting the power, the UPS power supply should be started under the condition of no load to re-charge the battery for 10~12h or more with the electric circuit of the charging sub-product inside the machine.

The UPS power supply is in a floating state for a long time without a discharge process, which is equivalent to being in a "storage standby" state. If this state lasts for a long time, the battery will be scrapped due to "storage for too long". It mainly shows that the internal resistance of the battery increases, and the internal resistance can reach several Ω in severe cases.

We found that at room temperature 20 ° C, after storage for 1 month, the capacity of the battery is about 97% of its rated value. If it is stored for 6 months, its usable capacity becomes 80% of the rated capacity. If the storage temperature rises, its usable capacity will also decrease.

Therefore, it is recommended that the user intentionally unplug the mains input every 20 °C months to allow the UPS to operate in a state where the battery supplies energy to the inverter. However, this operation is not suitable for a long time. When the load is about 30% of the rated output, it can be discharged for about 10 minutes.

Reduce deep discharge

His service life is closely related to the depth at which it is discharged. The lighter the load on the UPS power supply, the greater the ratio of the available capacity and its rated capacity when the mains supply is interrupted. In this case, when the UPS power supply is automatically shut down due to the low battery voltage, the battery is The depth of discharge is deeper.

ow does the actual process reduce the battery to be deeply discharged? The method is very simple: when the UPS power supply is interrupted by the mains supply and the battery is supplied to the inverter, most of the UPS power supply will ring once every 4s. A periodic alarm sounds to inform the user that the battery is now powered. When the alarm sounds suddenly, it indicates that the power supply is in deep discharge, and emergency treatment should be performed immediately to turn off the UPS power. It is not forced to do so, generally do not let the UPS power supply work until the battery voltage is too low and automatically shut down.

Use power supply peak charging

For users who have long-term UPS power supply with low-voltage power supply or frequent power failure, in order to prevent premature damage of the battery due to insufficient long-term charging, the battery should be fully charged (such as late-night time) to charge the battery to ensure that the battery is discharged every time. There is enough charging time after that. After the battery is deeply discharged, it takes at least 10 to 12 hours to recharge to 90% of the rated capacity. Pay attention to the choice of charger

Maintenance-free sealed batteries for UPS power supplies cannot be charged with a thyristor-type "quick charger". This is because the charger will cause the battery to be in a state of both "instantaneous overcurrent charging" and "instantaneous overvoltage charging." This state will greatly reduce the battery's usable capacity, which will cause the battery to be scrapped. When using the UPS power supply of the constant voltage cut-off charging circuit, be careful not to set the battery voltage too low to protect the operating point too low. Otherwise, it will easily generate overcurrent charging at the beginning of charging.

Of course, it is best to charge the charger with both constant current and constant voltage.

Guarantee power supply ambient temperature

The capacity available for the battery is closely related to the ambient temperature. Under normal circumstances, the performance parameters of the battery are calibrated at room temperature of 20 ° C. When the temperature is lower than 20 ° C, the available capacity of the storage will be reduced, and when the temperature is higher than 20 ° C, it is available. The capacity used will increase slightly. Different types of batteries from different manufacturers are affected by temperature. According to statistics, at -20 °C, the available capacity of the battery can only reach about 60% of the nominal capacity. It can be seen that the influence of temperature cannot be ignored.

Of course, to extend the life of the battery pack should not only pay attention to maintenance and use, but also should consider the load characteristics (resistance, inductance, capacitance) and size when selecting. Do not leave the battery in an excessively light load for a long time, so as to prevent the battery from being scrapped due to the UPS battery discharge current being too small.

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