How to Measure Battery Backup Operations
With a simple voltage connection to the battery pack, many
aspects of the operation of a UPS system may be determined. For
example, we recently tested the battery system of a mini UPS user
our MeasuringPad instrument.
The 12V battery of the unit under test (UUT) is connected to
the MeasuringPad using the MP30V (30 Volt) Pod. The instrument is
configured without any monitoring limits and is set to simply
record a value one a second.
With the UUT power off, a quick look at the MeasuringPad meter
panel yields a voltage reading of a little over 7 volts. Knowing
that the pack is NiCad (cell voltage of 1.2V) we can infer that
there are 6 cells in the pack.
Monitoring is started and the UUT is switched on. The terminal
voltage immediately jumping up to around 8 volts so the battery
charger operation is verified.
The cell voltage eventually climbs to just under 10 volts. This
is about the full charge point for this type of cell. As charging
continues, the cell voltage then will start to decline a little,
indicating the onset of overcharging. The charging circuit has
detected this, terminates the charge cycle, and the cell voltage
drops back to around 8.5 volts. Based on our testing, we were able
to determine that the charge time was about 1 hour and 45 minutes
and the charge termination circuit works.
The run time on battery is measured in a similar manner. The
line cord is disconnected causing the battery inverter to operate.
This causes a sudden drop in the terminal voltage as power is
being drawn from the battery. As the battery discharges, the
voltage will approach a nominal value where it will remain for
most of the discharge. As the point of exhaustion is approached,
the voltage will begin to drop off rapidly from this value. A
properly designed power supply will protect itself from over
current by sensing this point and shutting itself down. When this
occurs, the sudden removal of the load from the battery will cause
the terminal voltage to jump up. The battery runtime can be
determined from the time difference between the sudden drop and
the jump up. The threshold of the shut down point can be
determined from the minimum voltage observed. In this case, the
run time was about 40-45 minutes, the shutdown circuit worked and
its voltage trip point was about 5.3 volts.
Using the Dranetz-BMI MeasuringPad we were able to determine:
- When the battery kicked in and the duration of the time that
it provided power.
- If it protected itself when load shut off suddenly.
- If and when it reached full capacity by recharging and how
long that took.
And finally......
- If and when it stopped recharging when it was appropriate to
do so to protect itself and the load.
If you have any questions about these test procedures, you can
contact our tech support at 800-372-6832 x 335 (Ed Russo) or x 321
(Frank Kinder, Hardware Engineer for DBMI) who supplied us with
this case study.
RPM Trade-In Program is Back (But Not For Long)!
Back by popular demand, we are happy to offer the RPM Trade-In
Program once again. Some of you may own a RPM instrument that is
either inoperable, gathering dust and/or you just don't want to go
through the hassle of trying to get it fixed and being charged
outrageous costs to just look at your RPM instrument. Don't worry,
we feel your pain and want to turn something that is worthless
into a new, fully functional Dranetz-BMI comparable or upgraded
power quality instrument. You can trade in your useless RPM unit
and receive $500, $750 or $1,000 dollars credit towards one of the
Dranetz-BMI units. A lot of people have already taken advantage of
this offer so don't miss out on "cleaning out your work area" and
getting your hands on a brand new Dranetz-BMI unit. Remember,
this offer expires August 31, 2008 so you must act now!
For more details on this great deal, please
Dranetz-BMI Sightings.....
Trade Shows
Dranetz-BMI continues to hit the road bringing its products and
vast knowledge in power quality and energy management across the
country. Coming up in the next few months are:
NECA being held in Chicago, IL 10/5-10/7
AFCOM Fall being held in Orlando, FL 10/5-10/8
AEROTEST America 2008 being held in Ft. Worth, TX 11/17-11/20
Also, we've signed up two shows for 2009, NETA in San Antonio
and NFMT in Baltimore. If you are in the vicinity of any of these
locations and want to learn more and see more of our complete line
of power quality and energy management instruments up close you
should make a point to visit us at these events. For our complete
list of trade shows, please
Seminars
The final touches of our Fall Seminar schedule is still in
process, but we are glad to announce our 3 West Coast seminars
that are quickly coming up. We will be co-partnering our "Power
Monitoring as a Cost Savings Tool" seminar with Toshiba
Uninterruptible Power Systems and their seminar on UPS systems at
Phoenix, AZ (10/15) and Greenwood Village, CO (10/16) and we will
be doing a solo seminar, "How Power Quality and Reliability Impact
your Business" in Spokane, WA on September 25th. There will be 4
hours of jam packed information in whichever seminar you attend so
you don't want to miss them. To register for this seminar,
