PREMIER POWER PACK INSTRUCTION MANUAL
GLT.MAN-138
PAGE 3
Issue: 1.13 27/7/2012 N.R.P.J.
CHANGES TO EN54-4 (THE FIRE ALARM EQUIPMENT POWER
SUPPLY STANDARD)
In 2006 the Fire alarm Power Supply Equipment standard changed, adding the requirement that a PSU should
monitor the internal resistance of its batteries, and give a warning when it is above a certain level.
The reason for this is that when a battery’s internal resistance increases, it will reach a point where the battery
will no longer be able to supply the rated output voltage of the PSU under full load conditions. So under a mains
fail condition, the Power supply, running on batteries only, could not supply it`s rated load.
For Example, if a 5 Amp power supply has batteries with 2 ohms internal resistance, when running on batteries,
and supplying full load, there would be a 10V (V=IxR = 5 x 2 = 10 Volts) drop across the battery, meaning that the
output voltage would be outside the working range of the power supply.
The Premier Power Pack range of power supplies will give a Battery Hi Internal resistance fault when the internal
resistance for that power supply’s rating is close to the level that would cause the working voltage to be out of
range.
NOTE: Batteries reporting a high internal resistance WILL NOT BE CURED BY CHARGING ALONE. Either replace the
batteries, or discharge & charge 3 or 4 times (Note that this will take several days, and is not guaranteed to cure
the problem)
