User's Manual

Radio/Serial Telemetry Module User Manual
Page 12 © March 2000
2.2.3 Solar Supply
The power supply also includes a 12 V solar regulator for connecting 12V solar panels of up to
30W, and solar batteries of up to 100AHr. The unit may not be powered from a solar panel without
a battery. An 18W solar panel is sufficient for most solar applications. The size of the solar battery
required depends on the I/O used. Batteries are sized for a number of sunless days with 50%
battery capacity remaining as follows:
No. of sunless days = Battery capacity (AHr) x 0.5
Module load (A) x 1.2 x 24
The Module load depends on the I/O connected and can be calculated as follows:
Module Load(A) = 0.07 + (0.01 x No. of DI’s) + (0.025 x No. of DO’s)
+ (2 x Analogue loop load).
The analogue loop load is the total signal current for the AI’s and AO’s which are powered from the
internal 24V supply. Externally powered loops are not included in this.
The solar panel is connected to the "SOL" (positive) and "GND" (negative) terminals and the battery
connected to the "BAT+" (positive) and "GND" (negative) terminals. Solar panels must be installed
and connected as per the panel manufacturer's instructions. The positive lead of the battery should
be protected by a 2A fuse installed as near as possible to the battery terminal.
Where a solar panel larger than 30W is required, an external solar regulator should be
used.
2.2.4 Multiple Modules
Where more than one module is installed at the one location, a shared power supply and battery
may be used, provided the total load does not exceed the power supply.