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Why are the battery charge LEDs flashing on a Smart-UPS?

Battery Charge LED Bar Graph is flashing in unison.
Product line:
Smart-UPS, Smart-UPS Online

All Smart-UPS models with model numbers that begin with SU, SUA, SUM, SURT
All serial numbers

When operating on line, the runtime remaining (calculated by the Smart-UPS microprocessor) must be AT LEAST two minutes more than the low battery signal warning time.
If the UPS calculates the runtime remaining  as being less than 2 minutes more than the low battery signal time, the battery charge graph LEDs will flash


Option 1: Reset the low battery signal time to a lesser value. Take for example a Smart-UPS with 15 minutes of runtime at full charge, and with the low battery signal warning time set for 7 minutes. If runtime remaining is 8 minutes or less , then the battery bar graph LEDs will flash in unison. Try setting the low battery signal warning time to a lesser value through the Configuration menu and then the UPS Shutdown Parameters submenu of PowerChute plus. Two minutes is the lowest setting option available. Please keep in mind that when using PowerChute Business Edition server and console, the low battery signal time is set to 5 minutes and cannot be changed.

Option 2: Reduce the load or replace the battery. The firmware inside a Smart-UPS is designed to last for years, yet the batteries are consumable items. As the batteries age, they lose their ability to hold a charge and therefore available runtime will decrease over time. Once the runtime remaining is within 2 minutes of the low battery signal warning time, the battery charge LEDs will begin to flash and PowerChute software / SmartSlot accessories will report that the ""UPS batteries are discharged"", even if the battery is at 100% capacity. In the case of an older unit running with a heavy load, try reducing the attached load. If the unit is an XL (Extended Run) model, then try adding an additional battery pack. Typical battery life is 3 - 6 years. If you have an older UPS, try replacing the battery. XL battery packs and replacement battery cartridges are available for purchase on our website at

Option 3: Perform a Manual Runtime Calibration. This is a manual procedure and should not be confused with the runtime calibration performed through PowerChute software. The batteries inside of the Smart-UPS are controlled by a microprocessor within the UPS. Sometimes it is necessary to reset this microprocessor, especially after the installation of new batteries.
Note: Before beginning the calibration make sure the UPS has been online and charging for at leat 24 hours for just the UPS or 48 hours for a UPS with external batteries.
  1. Stop the PowerChute software from running and disconnect the serial cable.
  2. There must be at least a 30% load attached to the UPS during this procedure, and this load cannot fluctuate more than +/- 5%. This process will cause the UPS to shut off and cut power to its outlets, therefore, attach a non-critical load to the UPS and then force the UPS on battery by disconnecting it from utility power.
  3.  Allow the unit to run on battery until it turns off completely. Make sure a 30% load or greater is present!
  4.  Plug the UPS back into the wall outlet and allow it to recharge (it will recharge more quickly turned off and with no load present). Once the unit has recharged, the ""runtime remaining"" calculation should be more accurate. Remember that if the unit is an older model, then the runtime will not improve significantly.
Note: Should the previous steps not resolve the issue contact APC support at 800.890.4272 for further assistance.

An APC Smart-UPS has a microprocessor which calculates runtime primarily based on the load attached to the UPS and on its battery capacity. On the right side of the front display panel there is a vertical graph of five LEDs. Each LED is an indication of battery charge in increments of twenty percent: 20, 40, 60, 80, 100% (bottom to top). For example, if the battery charge is 95%, then only four of the five LEDs are illuminated. To ensure that an operating system receives a graceful shutdown when using PowerChute plus or a SmartSlot accessory, an alert is generated by the Smart-UPS indicating that the UPS has reached a low battery condition. The alert is audible (rapid beeping), visual (flashing battery LED or LEDs), and readable through the graphical interface of PowerChute software (or a native UPS shutdown program within a particular operating system.) In order to calculate this "low battery condition," all Smart-UPS products have a preconfigured low battery signal warning time of two minutes (this is the factory default setting). There are a total of four user-changeable settings: 2, 5, 7, or 10 minutes. If the low battery signal warning time is set for 2 minutes, then the alerts will activate simultaneously two minutes prior to shutdown. Similarly, if the total runtime for a particular UPS is 30 minutes with a low battery signal warning time set at 10 minutes, then the UPS will run on battery for 20 minutes before the low battery alert begins. Total runtime is primarily based on two factors, battery capacity and UPS load. UPS load and runtime on battery are inversely proportional: as load increases, battery runtime decreases and vice versa. When utility power is lost, the UPS begins discharging the battery in order to support the attached load. Once power returns, the Smart-UPS will automatically begin to recharge its battery.
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