HCJes

I have alwayed asked a Nortel Ceritified Vendor to do this.

slagburn

What he said... however you might want to look for a vendor that does battery and power as they will have the tools to accuratly test the batteries. I know out here that our 'Nortel Certified' vendor won't touch batteries or power, I have to sub that part out to a battery / power company.

Since your're dealing with a DC system there should be a meter somewhere near the rectifiers that will tell you how much total load is on the plant, you can add up the total for all of your UEMs but that might not take into consideration other things like power inverters that might be on the DC system with the PBX. When looking at the amp meter it helps to take an average over a period of time as the load will vary throughout the day depending on your enviroment. (Number of single line users, power inverters etc...)

Once you know the average load on the plant then you have to know the amphour rating of your battery system this information combined with the power conversion factor for the batteries (varies by type and manufacturer) will give you a very rough (there are a few other factors)paper estimate of how much time you can expect from your power system. This paper estimate does not take in to consideration the condition of your batteries which is why you want a vendor who understands batteries and how to properly test them doing this type of work for you.

slagburn

To actually answer your question look on page 90 of NTP 553-3021-120