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Use Hyperterminal to Reset APC UPS Battery Constant

Change the APC UPS battery constant to restore functionality.

This page describes how to reset the battery constant parameter in the American Power Conversion Smart-UPS 700, model no. SU700NET, which will stop the blinking of the battery level LED bank. This is because the UPS thinks the battery's capacity is much less than what it really is. Note: this fix may apply to other APC Smart UPS models but this has not been tried.

Symptoms are that the UPS with new battery shows it with a full charge but it returns that it has a few minutes or less of run time and it is not overloaded. Also, the LED bank on the right (battery level) might be blinking like it has less than 2 minutes run time but the entire bank (five LED's) are lit showing full charge.

Follow these steps carefully:

  1. Disable Powerchute or any other UPS software that might be communicating with the UPS. No programs can be using the COM port that the SU700NET is using. Also, the black cable that came with the SU700NET must be used to connect to it.
  2. Open Hyper-terminal, enter "APC UPS" for the session name.
  3. Select the COM port that the UPS is on.
  4. Set the port parameters to 2400 baud, 8 data bits, no parity, 1 stop bit, Xon/Xoff.
  5. The SU700NET UPS should be connected to Hyperterminal now. If not, other problems exist.
  6. Make sure the CAPS LOCK is on.
  7. Enter Y and the UPS should return SM.
  8. Enter 1 and if the UPS does not return PROG then wait a few seconds and enter 1 again, PROG should now be on screen.
  9. Enter 0 (zero) and the UPS should return the battery constant. This should be 96 for a brand new SU700-NET battery.
  10. To change the battery constant parameter, press + until 96 is found.
  11. If a APC UPS other than the SU700NET is being used then the new battery constant likely will be different.

This procedure should be done everytime the battery in the SU-700NET is replaced.

Hyperterminal No Longer Supplied with Windows

Because Hyperterminal is no longer supplied with Windows, it maybe necessary to install Windows XP Professional on an old computer with a COM port such as an old notebook PC/laptop PC.

Alternatively, try PuTTY.

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