Securitron PSM_Series - Manual (Page 2)

PN# 500-16200
Page 2 Rev. D, 08/11
3.2 BATTERY TEST
The only way to reliably test a battery pack is to disconnect it from its trickle charge circuit,
apply a load to it and measure the performance of the battery pack. A perfect test would
duplicate the actual load and conduct the test for the amount of time that the pack could be
expected to operate the load. Such a complete test would not only verify that the battery pack
was prepared to operate the load for some time, but would verify the full rated capacity of the
pack.
In a working installation, such a test is obviously impossible. It would not only take too long but
would risk leaving the batteries in a discharged state at the moment that a real power failure
occurs. It is important therefore to understand what Securitron's PSM battery test signifies. The
battery pack is automatically disconnected and a heavy test load of two Amps is applied. The
test duration is three minutes every eight hours and during this time, the battery voltage is
monitored. If it does not fall below 11.5V (for a 12 volt pack) or 23V (for a 24 volt pack), the
test is considered passed and no alarm signal is sent. Such a test indicates that the batteries
are properly connected and charging and that they have no major defect such as an internal
shorted or open cell. The end user is assured that in an actual power failure the batteries will
operate the working load for some time, but it is possible that they may not deliver their full
rated capacity. Battery performance varies with temperature and degrades over time.
Batteries must be replaced every five years minimum. It is vital that the presence of the
Power Supply Monitor not lead to a false sense that as long as the Monitor does not
signal an alarm, the batteries are in perfect condition.
Another concern in automatic battery testing is that during the test, the batteries are
disconnected from the trickle charge voltage source. It is possible that an actual power failure
could occur during the test and, if so, the test must be immediately terminated so that the
batteries can return to their primary function of backing up the working load. In Securitron's
model PSM, this is automatically accomplished by detecting an actual DC output power failure
and terminating any concurrent battery test as well as preventing any test from beginning
during the period of power failure.
Battery test reporting is as follows. A yellow LED on the enclosure cover illuminates during the
test duration (three minutes every eight hours). If the test fails, it terminates at the failure
point and a red "loading failed" LED comes on. The Sonalert sounds a continuous tone and the
"trouble" relay contacts switch. Note that this automatic test will not be conducted if the PSM is
in alarm from another condition such as voltage out of range. To reset the unit, the reset toggle
on the enclosure cover should be momentarily depressed. Be sure to replace the battery
pack upon any battery test failure.
It is possible to trigger a battery test manually at any time the PSM is in normal condtion.
Simply press the momentary "load test" toggle on the enclosure cover.
4. "ON BATTERY" REPORTING AND SYSTEM DISCONNECT
The PSM also reports any power failure when the batteries have switched in and are operating
the load. A yellow "on battery" LED will illuminate showing that the batteries are active and the
"on battery" SPDT remote contacts will switch. The Sonalert will not sound from this effect as
this is not a test failure condition, but after 30 seconds, a low DC failure will also be detected so
the Sonalert will begin to pulse and the "trouble" contacts will switch. Note that the term "power
failure" does not only refer to a line voltage failure. The power supply could have an internal
failure which has either terminated or lowered its DC output. Any of these conditions will lead to
the batteries taking over the load and the PSM will report that fact regardless of the cause.
Once the batteries have been switched in, they will only be able to operate the load for a defined
period of time depending on their capacity and on the current being drawn by the load. The
PSM's signal that the batteries have been switched in, can therefore be considered a type of
advance warning. If DC power is not restored, the installation will go down. The end user
should have an idea of how much reaction time he has by knowing the installation load current
and the battery pack size.
Under battery operation, the load will receive nearly the correct voltage until the batteries are
close to the end of their capacity. At that point, battery voltage will begin to fall off rapidly. The
PSM will detect the point at which battery voltage has dropped to 88% nominal (10.5V or 21V)