GasSens
Gas Detection System
Sec
tion 4 - Optional Equipment
O & M Manual
A14-RK, 8/06
4
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2
Electrical connection is made between the battery back-up unit and the power supply module. The
circuit board mounted on the battery contains a 2 position plug-in terminal block marked plus and minus.
The plus terminal is connected to terminal B+ of the power supply and the minus terminal is connected to
B- of the power supply.
Operation
When power is applied to the power supply module, a relay on the battery back-up circuit board
energizes and places the battery back-up into operation. There are no user adjustments in the battery
back-up unit. If the battery is not fully charged, the power supply will begin supplying charge current to the
battery, and will float charge the battery as long as the power supply is on.
Should the power supply loose its input power, the battery back-up will immediately supply power to
receiver modules to maintain detection system operation without interruption. The back-up period will vary
depending on whether the detector is single channel or two channel, on whether displays are in normal or
high intensity mode, and on how many relays are configured for fail-safe operation. The minimum period
expected for a single channel system is 12 hours and for a two channel system is 6 hours. Normally, the
back-up period is twice as long as the minimums.
The circuit board attached to the battery serves two functions. First, it regulates the charging current
to the battery to a maximum of 0.75 amps. This prevents possible damage to the battery due to an
excessively high charge current. Second, it isolates the battery from the detection system when the
battery voltage falls below 10 volts. This is done through a relay, and protects the battery against damage
caused by very deep discharge.
The isolation relay that protects against deep discharge will also protect the battery against an
external short circuit of the wires connected to the battery. If a short occurs, the relay will immediately
open, protecting the battery and limiting the current that the battery will deliver.
Removal from Service
The relay that isolates the battery when the 10 volt level is reached is energized as soon as power is
applied to the power supply module. Once energized, the coil current is supplied from the battery if
needed. If the gas detection system supported by the battery back-up is started up for testing and then
shut down, the battery back-up relay should be de-energized manually. Otherwise, the relay coil will
continue to draw power from the battery until the 10 volt level is reached. While this will not cause
damage, it means that the battery will be discharged when the detection system is started up again.
To de-energize the relay, slide the control circuit board off the battery terminals briefly and then slide it
back on. As soon as the battery connection is broken, the relay coil will drop out, and will not energize
until power is applied to the power supply module in the system. This procedure is recommended any
time the detection system is to be shut down for more that a few days.
