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6 Battery operation and power saving mode
PLICSMOBILE T81/B81/S81 • External GSM/GPRS/UMTS radio unit
55234-EN-170206
Note:
Make sure that the two cores of the connection cable are energized
when the solar module is already connected and not covered. Avoid
a short circuit during mounting and connection. Also pay attention to
this when shortening the cable, if that should be necessary.
6.4 Battery sizing
When selecting an external battery/accumulator, the following points
must be observed:
Power consumption in power saving mode:
If you use a battery or accumulator that cannot be automatically
recharged cyclically, the power saving mode should be activated.
With an operating voltage of e.g. 12 V, a standby power consumption
of 0.4 mW must be taken into account. With an assumed lifetime of
e.g. one year, the requirement is approximately 3.5 Wh, which cor-
responds to a battery capacity of 0.29 Ah at 12 V. The standby power
consumption at specific operating voltages is stated in the "
Technical
data
".
Power requirement for a complete measurement cycle incl.
measured value transmission:
A measurement cycle lasts approximately 60 to 120 seconds (de-
pendent on sensor type and network quality) and includes automatic
switching on of the sensor (HART multidrop mode with 4 mA),
recording of the measured value, measured value transmission and
a return to the power saving mode. During this time, approximately
15 mWh of energy is required. For example, with one measurement
per day, this adds up to approx. 7.3 Wh per year, which corresponds
to a battery capacity of approx. 0.6 Ah at 12 V.
Examples for battery capacity depending on the number of
transmission cycles
Number of mes-
sages/day
Annual consumption PLICSMOBILE
Standby energy
demand
Energy demand
for message
transmission
Required battery
capacitance with
12 V
1
3.5 Wh
7.3 Wh
0.6 Ah
2
3.5 Wh
14.6 Wh
1.5 Ah
4
3.5 Wh
29.2
2.7 Ah
8
3.5 Wh
58.4 Wh
5.1 Ah
24
3.5 Wh
175.2 Wh
14.9 Ah
Note:
Due to the nature of the system, each battery and accumulator has a
self-discharge which can vary considerably dependent on the type.
This is very important for the calculation of the required capacitance.
In the listed examples, this self-discharge is not taken into accunt. The
available capacitance depends also considerably from the tempera-
ture. The specifications refer to a temperature of 20 °C (68 °F).
