How to Recalibrate an APC UPS

If you are finding the run time on a APC UPS is not the best as it could be or you have installed new battery’s it time to do a Recalibration.
 
It’s quite an easy thing to do and it should not cause disruption to your powered equipment.
 
First of all you need the correct Serial Cable to connect to the UPS. They are usually black serial RS-232 cables with the Part Number 940-0024C. If you don’t have one of these cables you can easily make these cables if you are electronically minded. There are pin outs available on the internet.
 
Connect the UPS via serial cable to a machine that has a terminal client installed. This can be HyperTerminal or TeraTerm. In this case im using TeraTerm. Open the software, A new connection window will appear and select “Serial” and choose which port you want to use. Click “OK’
 
Now we need to change the Baud rate from the default 9600 to 2400. To do this go into “Setup” select “Serial Port” and change the “Baud Rate”, Click “OK” and you should be ready.
 
To make the UPS talk in “Smart Mode” and before anything will work enter a capital Y. The UPS should return SM.
 
If you want to check the Power Load enter in capital P and it will show the load in % of the UPS VA rating.
To check Battery Levels enter in lower case f (see screenshot – in this case 32.5% load and 48% battery charge)
 
 
The Battery’s need to be changed to 100% before the test will start.
 
To start the test enter a capital D
 
The UPS will then run on battery till around 25% battery remaining. This can take time depending on which battery’s you have installed and load. The beeping will drive you mad.  It will then switch back on mains power. You should load the UPS around 30 to 40% load. If you wish to cancel the calibration you can hit D again anytime and it will revert back to mains power.
 
I would recommend doing this Calibration every 6 – 12 months. Don’t do it any sooner than this as deep cycling the battery’s does reduce the life of them. A load of less that 40% does not put as much stress on the battery’s. You can sometimes hear the gases escaping the battery’s when in a discharge cycle.