The
Benefits of Monitoring Batteries
Batteries are the most likely cause of a UPS
failure. Batteries are the most likely cause of a generator start failure. We
have been involved in automated battery monitoring since the early 1990s. It has
been well proven that batteries that are not maintained with a thorough PM and
replacement program will fail and will cause a loss of power to the critical
load equipment. Annual, semi-annual or quarterly checks are good but that is not
frequent enough to be certain the batteries will be good until the next visit.
Batteries, particularly the sealed type which are the predominant battery today,
most often fail in a 3 to 5 week period from good to failed status. Thus,
inspections or testing need to be performed at least at monthly intervals if not more
frequent. The only method of doing this is to automate the process. Benefits of
automation are 1) the system does not forget to do the test, 2) the testing is
done the same way at the same test points every time and 3) the system even monitors
between specific testing.
Upon realization that automation is the best
way to go, the question is how to test. There are two accepted methods. The
older way is load testing wherein a significant load is placed on the battery
and the voltage drop is compared to known good values. If the battery holds
voltage up it is good at that time. For voltage monitoring systems a load is
required, either put on by the test equipment or by actual outages. If the test
equipment introduces the load, the test itself ages the battery and that is not
the best thing to do. If actual site load is used, the testing may not be done
often as there may not be frequent enough and long enough outages to get
meaningful data. Thus the monitoring system may be present but incapable of
running as needed. If scheduled test outages are used, we are back to degrading
the battery which is not good.
The second method is battery impedance. In this
system an AC signal at high frequency is passed through the batteries during the
test and the battery impedance is measured. This test does not degrade the
batteries and can be done at any time. Battery impedance is a documented
predictor of battery health and is the best early warning characteristic
available to measure. The automated battery impedance test technology was
invented by BTECH and is patented by BTECH. We have utilized BTECH equipment for
years at critical sites and it has prevented many a failure.
Deciding whether or not to invest in the BTECH
system is a decision to be based upon economics. The cost of the system needs to
be compared to the cost of downtime. When downtime prevention warrants a UPS it
probably also warrants automated battery monitoring.
A word of caution to those who believe the
built-in battery monitoring in a UPS means their batteries are already
monitored. UPS based built-in monitors are looking at overall DC voltage. The
UPS cannot determine individual battery health as a bad battery is masked by the
overall system. It is just not possible. If the overall battery plant is
drastically failing a UPS based system may find out but it is already too late
to solve without an expensive total battery changeout. Monitoring individual
batteries as the BTECH does allows you to correct the bad battery before it
causes the whole battery plant to fail.
Below are samples of battery analysis via the
BTECH system. A history of every battery in a plant will be recorded and
analyzed automatically through the automated system software.
