For sites with snow in the winter months, the increased angle helps to shed snow. A solar panel covered in snow produces
little or no power.
5.5.3 Recommended Solar Configurations
These solar panel and battery combinations assume direct sunlight for at least two to three hours a day. Solar insolation
maps provide approximate sun energy for various locations. The depth of battery discharge is assumed to be 50 percent.
Table 8: Solar panel and battery combinations for a DXM system
Solar Panel
Output (W)
Battery Capacity (Ahr)
Days of
Autonomy
DXM Current
(mA)
DXM Model
5
10
10
25
DXM-Sx models with an ISM radio and I/O base board
20
14
10
30
DXM-Bx models with an ISM radio and no cellular modem
20
20
10
35
DXM-Bx models with an ISM radio and cellular modem
Battery capacity (amp hour) is a standard amp rating taken for 20 hours. Battery capacity should be monitored for reliable
system power and may need to be increased for cold weather locations.
5.5.4 Monitoring Solar Operation
The DXM solar controller provides Modbus registers that allow the user to monitor the state of the solar panel input voltage,
the battery voltage, the charging current, and the temperature in °C. The DXM100 can be configured to monitor the health of
the charging system as well as send an alert message when the battery is too low.
The charts show a typical charging cycle, with each vertical grid representing about eight hours. The chart shows three days
of charging.
Figure 4. Solar Panel Voltage (mV) -- Cloudy First Day
Figure 5. Battery Voltage (mV) - Cloudy First Day
Sure Cross
®
DXM100-Sx Wireless Modbus Slave
34
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