Manually Resetting an APC Smart-UPS Battery Constant After New Battery Replacement

Posted on March 27, 2011 1:03 PM

I came across a Smart UPS 1500 that needed a battery replacement recently.  After the replacement battery was installed, I ran a self-test like I normally do to clear alarms on the unit.  I noticed that the self-test reported that the battery had a runtime remaining of 0 minutes and a 20% capacity.   I decided to let the battery charge up to 100% and then try a runtime calibration.

Later that evening, the UPS was reporting that the battery had 100% capacity and a runtime of 3 minutes with a very minimal load.  I ran the runtime calibration and the runtime dropped immediately to 0 minutes with a 20% charge.  I thought that the battery might be faulty at this point. 

The customer happened to have another battery there to try.  We put the battery in and testing showed the same exact symptoms.  Therefore the problem must be with the UPS and not the batteries.

APC’s forum quotes “The battery constants give the battery status via their life expectancy. If the battery ages and is ‘exhausted’, the constant is overwritten. The management software calculates the runtime of the UPS with these constants.  If the battery is now replaced, a self test must be done with the new batteries. Through it, the red battery replace indicator goes out and the battery constants should be reset to the standard settings. This does not occur in some cases. Therefore, the constants must be reset manually in order to correct this situation.”

Through research, I came across this article which describes how to reset the battery constant manually.  The only problem is that this has to be done by physically connecting the serial cable to the UPS, so I was not able to try this out yet.  Since each UPS has different constant variables, you will have to call APC support and ask them what to set it to.

Here are the steps listed using Hyperterminal from the hyperlink above:

In order to successfully reset the battery constant, all accompanying devices (SmartSlot Accessories such as Interface Expander, Web/SNMP Management Card) must be removed from the SmartSlot or from the Com port of the UPS.

  1. Please shut off all connected load, switch off the UPS, pull the power plug of the UPS.
  2. Switch off the UPS once again till you hear a click.
  3. Remove all accompanying devices.
  4. Turn on the UPS again and connect a computer with Windows 95/98/ME, Windows NT 4.0 or Win 2000, which runs on Hyperterminal using one of the cables mentioned under the requirements.
  5. Close Powerchute plus-Server. With Windows NT/2000, the UPS service must be stopped. If you are using PowerChute Business Edition, stop the Agent *V service.
  6. Perform a Battery Constants check.
  7. Start a Hyperterminal session with the UPS.  Note: Ensure that there are no accessories plugged into the UPS. (Web Management cards, IO Relay cards etc)
  8. Start Hyperterminal by going to Start, Programs, Accessories, Communications, Hyperterminal.
  9. You will be requested to enter a name and a symbol. Enter a favourite name and click on OK. When a message that a modem must be installed appears, you can ignore this message.
  10. Select the serial port to which black serial cable is connected to.  The correct settings for the COM-connection are 2400 Baud, 8 data bits, 1 Stop bit, no parity, protocol Xon/Xoff. In this window, click on Advanced and make sure that the option FIFO activated is unchecked. Click twice on OK.
  11. Check if there is a connection (Type Shift + Y, should return **SM** ). Do not enter any other characters via Hyperterminal other than that described in these instructions because this can cause irreparable damage to the UPS
  12. Type **1**, wait 2-3 secs and type **1** again (Should return **Prog**)
  13. Enter a **0** and the UPS reports the present value of the battery constant.  If this value does not correspond to the default value that was given to you by RM Support or APC , it must be changed.
  14. If this value is not correct, press **+** or **-** until the correct value is returned.
  15. Press **R** to close the session. (Should return **Bye**)
  16. Enter **<Shift> Y**, the UPS reports again with **SM**.
  17. Enter **0** once again and check if the UPS reports back the standard setting that has been set.
  18. Close Hyperterminal, start the UPS again and check the UPS runtime in the management software.

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Comment by Rasto

May 19, 2011 3:59 AM

I had similar issue with battery constant out of whack on APC Smart-UPS SC420
battery constant was 44 and with 32.5% load reported 600sec left with 50%load => 180sec which set LB flag
I've found out, that changing value to higher number increased number of seconds, so after some tests it is set on 50 and reports almost real values about seconds left on battery.
50 with 32.5%load now 1140sec and with 50%load 540sec

Comment by Marvin Miller

September 27, 2011 6:16 PM

There's a much easier way to do this - do a search for apcfix.exe
It's a program that interfaces with the UPS and will reset the battery constant on a variety of APC UPS models.

No Hyperterminal or 'steps' required Smile

Comment by Scott

November 8, 2011 7:09 AM

^ Correct - In power chute personal edition, i just clicked the "battery" under the Run Self-Test page. There's a battery that says "APC Recommends that....please click the battery icon when you replace your battery." I replaced batteries and the runtime was 2 minutes @ 1/2 load - when I clicked the icon, the runtime immediately reverted to 21 minutes. I assume this was sort of a rough calibration reset.

Comment by UPS

December 6, 2012 4:13 PM

Thanks for this, I've only just got myself my first UPS and to be honest thought replacing the battery would be a simple plug and play operation. Standard procedure though, it's never that easy..

Comment by UPS batteries

March 19, 2013 12:58 AM

Works as a great replacement battery for my old APC UPS. So far no problems and the UPS has stopped beeping about the old dead battery. Much cheaper than other replacement options and works perfectly.

Comment by Yasir

August 4, 2013 5:04 PM

i have APC SUA1000I and attach two batteries par battery 90Amps but battery is not of APC company and i have calibrate the ups but its not working the battery gives 25mints backup hardly and the software in my pc show me 380mints or more battery backup time but its not give the maximun time its give 25 to 30mints backup hardly. please give the solution for this problem

Comment by Phil

September 29, 2013 1:06 PM

If needed, you can adjust the external battery count easily with a basic terminal emulator. (Such as HyperTerm or PuTTY in windoze) This will increase runtime by multiples of the original. (so if runtime is 20 min, setting external battery count to 1 will make it 40, 2 will be 60, etc.)

Here's how:
1. Hook up a computer to the UPS via a APC "smart" serial cable. If you don't have a serial port on your computer, you can use a USB to serial converter. You must use an APC cable, as the UPS uses a non-standard pinout.
2. Start up a terminal emulator such as HyperTerm or PuTTY (with serial support).
Port settings are: 2400 baud, 8 data bits, 1 stop bit, no parity, flow control is Xon/Xoff. When using HyperTerm, make sure FIFO buffer is NOT set.
3. When connected, you will NOT be greeted by any prompt! Typing in Shift + Y should show the letters SM in the terminal window, this will confirm your connection.
4. Press > to see the current battery pack count. If no battery packs were installed, it should say 0.
Pressing + will add one pack to the count, - will subtract the count by one. If you have multiple packs, press + several times to add them all. When finished, press > again to check the count.
5. When finished, you can simply close the window (or end the connection in HyperTerm).


Comment by FBMBoomer

May 3, 2015 4:33 PM

I found a way to make my APC 1300 run again after an F04 error. I disconnected the UPS. I took it to my work bench and removed the batteries. After five minutes, I replaced them and then plugged in the UPS and checked the LCD for proper operation. Good so far. Next I brought it to my computer desk and hooked up the power again. I did not hook up the USB connector. Everything ran well. I then uninstalled the power chute software to make sure it would not remember the F04 error. I then reinstalled the latest power chute software and plugged in the USB cable. It all worked just fine. So, I do not know what caused that F04 error, but it now works. Probably some digital glitch.

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