It is simply not true that one cannot test the battery in a DC power plant. In actual fact, it is a lot easier and safer to do this than test a UPS battery. My company is doing this for clients on a daily basis. Telecommunications companies have been doing it for almost a hundred years. The procedures are simple and are historically well defined. In many methods the battery does not even have to be taken off-line. Both IEEE 450 – Recommended Practice for Maintenance, Testing and Replacement of Vented Lead acid Batteries for Stationary Applications, and IEEE 1188 – Recommended Practice for Maintenance, Testing and Replacement of Valve-Regulated Lead-Acid (VRLA) Batteries for Stationary Applications, address the subject in depth.

Years of operational records has proved that a properly designed battery backed DC power system is much more reliable than a UPS. Why do you think the telecommunications companies have always used this architecture? It is no accident that they have the most reliable systems and networks. The battery plant (batteries seem to get the blame for all system outages) in a DC system are usually designed for a minimum of four hours reserve and often features redundant battery strings and real time monitoring. A sudden battery failure should never happen. I suspect in the Internap case that either poor system design, lack of an adequate maintenance plan, poor maintenance or inadequate battery status trending data, or a combination of all of the above, caused the “battery failure.”

Any battery system owner that truly cares about their battery reliability should have a proper battery maintenance and test program in place. All too often money is not a hurdle when it comes to the maintenance of other equipment in a data center or other critical location but when it comes to the humble battery this often ignored.

A good reference document, which addresses all aspects of maintenance in simple terms, is IEEE 1491 – Guide for Selection and Use of Battery Monitoring Equipment in Stationary Applications.

True health in a battery plant is much more than just battery maintenance. You have to know that your AC feed will handle the surge presented when all of the rectifiers restart simultaneously, and you absolutely need 20% of capacity (or one additional rectifier) in the plant beyond the load in order to have enough power to recharge the batteries after an extended AC failure.