APC SU1400XLT User Manual download pdf (Page 52)

4. Matrix-UPS and Smart-UPS recalculate the runtime-related parameters every time the UPS goes on

battery.

When doing a runtime calibration with "older" batteries, APC Technical Support recommend doing a

complete discharge and recharge first.

If you have "dumb" UPS (aka simple signalling) like a Back-UPS, then your only option is to do a manual

runtime calibration.

"Manual" Runtime Calibration

Most of the information in this section is taken from APC's website. Any non-APC additions have been

inserted in square brackets.

For a "smart" or "smart signalling" Back-UPS Pro or Smart-UPS:

Perform a Runtime Calibration. This is a manual procedure and should not be confused with the

runtime calibration performed through PowerChute plus [or apctest]. 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. Stop the PowerChute plus [or

apcupsd] software from running and disconnect the serial cable. There must be at least a 30% load

attached to the UPS during this procedure, but the 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 [suggest not disconnecting, but simply turning off utility

power thereby preserving earthing]. Allow the unit to run on battery until it turns off completely. Make

sure a 30% load is present! Plug the UPS back into the wall outlet [switch utility power back on] 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.

Background:

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 99%, 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 plus 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.

For a Matrix UPS:

It is unnecessary to subject a battery bank to an excessively long calibration. Remove battery packs

or increase the load (space heaters are good dummy loads) to obtain a reasonable time length for the

calibration (under an hour if possible).

At the start of a calibration, the Matrix microprocessor saves the Estimated Run Time displayed.

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APC SU1400XLT User Manual Page 52

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