Battery Replacement Life for UPS Power Supplies

The battery pack is an important part of the UPS system, and its cost is also high. Therefore, when the UPS system runs for a certain period of time and needs to be replaced in order to ensure the reliability of the UPS system, users will always ask what the standard for battery pack replacement is. Are there any relevant specifications and requirements?​​
There is no mandatory requirement for battery pack replacement, but relevant reference indicators are given for users’ reference. That’s the life of a lead-acid battery.

Battery Replacement Life for UPS Power Supplies

There are two indicators of the life of lead-acid batteries.

  1. Float life is the number of years that the battery can be used when the battery can discharge not less than 80% of the rated capacity under standard temperature and continuous float state.
  2. The number of 80% deep cycle charge and discharge is the number of times the full-capacity battery is fully charged after being discharged to 80% of the rated capacity, so that it can be recycled.

    The bottom line for both life metrics is 80% of the battery’s rated capacity. When the capacity is reduced by 20%, the battery will age faster and the reliability will be greatly reduced. The power supply time will also be doubled.

    Therefore, according to relevant specifications, when the rated capacity of the battery pack is lower than 80% of either of the two cases, it is recommended to replace the battery pack. Can’t be used without replacement. No, it’s just that the backup time is shortened and the system reliability is reduced, not necessarily a linear downward trend.

How to judge the capacity of the battery pack

There are two ways to judge the battery capacity: one is the battery internal resistance tester to test the current internal resistance of the battery. When the internal resistance of the battery increases to 1.5 times the internal resistance of the factory (personal experience), it means that the battery capacity has dropped below 80%. It is recommended to replace the battery pack. This method is somewhat biased, but it is the safest way to judge.

Secondly, the on-load measurement method, under the current load, uses the constant power method to calculate the battery backup time, and uses the battery capacity test function of the UPS to measure the battery backup time. When the two times are less than 80% of the calculation time, it is recommended to replace the battery. This method is highly accurate, but the risk is small, and relevant countermeasures need to be formulated.

Is it necessary to replace the battery pack when the capacity drops below 80%?

When the capacity of the battery pack drops below 80%, the customer needs to conduct a self-assessment on whether the battery pack needs to be replaced, how much the backup time of the UPS system has been shortened, and how the reliability of the system will affect the user’s business. Because there are too many industries and scenarios for UPS applications, and the standards and requirements are also different, there are no relevant rules.

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