Maintenance Manual

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©2021 Broadcast Electronics
We suggest using sealed batteries for small systems, 20 to 40 A/hour rated. Higher capacities, like 40
± 100 A/hour and more, may be achieved at low cost from car-type batteries: in this case always
install the batteries in a well vented place, because acid gas produced during battery charging may
damage the electronic equipment.
GTX and RTX battery inputs may be wired together to the same battery array, provided they both are
internally set to 27.6V, as regular. In this case the power supplies appear to be in parallel (with some
redundancy) and they both charge the battery array at a higher rate.
Plumb batteries are usually made up to 12 V nominal voltage, so two batteries are required in series.
Wire them with proper section wire: 1 sq. mm is usually enough to connect them to the transmitter
and/or the receiver; bigger sections may be used in case of long wiring.
Install batteries capable of sustaining the system for the maximum foreseen period of mains failure.
Avoid to completely discharging the batteries or permanent damage may occur to them. Even if the
battery manager disconnects the battery when the voltage is lower than 22V, a small test current,
nearly 10-15mA is sunk by the circuitry in absence of mains power. This current is capable to deeply
discharge the battery array in case of prolonged mains absence. Always remove the battery array if
the system is off-line
1. Battery Life
We recommend following the literature from you battery manufacturer for correct installation and
maintenance of the battery system. In absence of that literature, some common practices:
- Use batteries whose capacity is at least 2.5 - 10 times higher than the maximum expected power
absorption, on prolonged mains loss.
- Never permit batteries to undergo below minimum safe voltage, on prolonged discharges.
Following these guidelines, battery life expectation may range from 2 to 5 years, depending on duty
factor and temperature (low temperature decreases the capability but increases the life).
2. Back-up and recharge time
An estimate of the backup time, i.e. the capability of the batteries to power up the equipment in case
of mains failure, may be done by considering that:
- The manufacturers usually specify the nominal capability of a battery, discharged in a period of 10
or 20 hour.
- For discharge faster than 10 hour, the capability will be reduced. For slower discharges, it may be
increased. Typical values are 70 % for discharge in 2 hours and 110 %, for discharges in 50 hours.
- The capability will diminish with time and usage: typical derating may be 10 -30 % / year.
- Taking in count all previously said, with a real capability which is derived from the nominal one
with the suggested corrections, the backup time is given by the capacity in A/hour divided the
absorption of the equipment which makes up the load, in A.
- The supplied recharge current delivered by the equipment is nearly 0.5-1.0 A by the GTX and 1.5-
2.0A by the RTX18, when the batteries are almost discharged.
- While the charge voltage is roughly constant, the charge current is not. The charge time may be
rather long, even some day, especially in case of deep discharge and heavy load on the equipment
As a reference we give the following table with estimated maximum backup times for some
combinations of equipment and batteries, which are valid only for new, fully charged batteries. The
current absorption for GTX transmitter is typical for SHF version @ 5W output power or a 900MHz
version @ 10W.
Higher output power will increase this absorption up to 20-30%, while lowering the output power
will reduce the current absorption to roughly the same 20-30%.