percent of its capacity will have approximately 500 charge/discharge cycles. Discharging 100 percent leaves the battery with
only 200 charge/discharge cycles.
Use this information as a guide to the approximate state of charge and in determining when to apply conservation measures.
Batteries degrade over time based on discharge/charge cycles and environmental conditions. Always monitor the battery
system to obtain the best performance of the solar powered system.
Solar Panel
Banner solar panels come in two common sizes for the DXM: 5 Watt and 20 Watt. Both panels are designed to work with the
DXM but provide different charging characteristics. Use the 5 watt panel for light duty operation and use the 20 watt panel
when you require greater charging capabilities.
Solar Panel
Voltage
Current
Typical DXM Configurations
5 Watt
17 V
0.29 A
DXM Controller configured as a slave, ISM radio, I/O base board
20 Watt
21 V
1 A
DXM Controller with ISM radio and Cellular modem
Photovoltaic panels are very sensitive to shading. Unlike solar thermal panels, PV solar panels cannot tolerate shading from
a branch of a leafless tree or small amounts of snow in the corners of the panel. Because all cells are connected in a series
string, the weakest cell will bring down the other cells' power level.
Good quality solar panels will not degrade much from year to year, typically less than 1 percent .
To capture the maximum amount of solar radiation throughout the year, mount a fixed solar panel to optimize the sun's
energy. For the northern hemisphere, face the panel true south. For the southern hemisphere, face the panel true north. If
you are using a compass to orientate the panels, compensate for the difference between true north and magnetic north.
Magnetic declination varies across the globe.
A solar panel's average tilt from horizontal is at an angle equal to the latitude of the site location. For optimum performance,
adjust the tilt by plus 15 degrees in the winter or minus 15 degrees in the summer. For a fixed panel with a consistent power
requirement throughout the year, adjust the tilt angle to optimize for the winter months: latitude plus 15 degrees. Although in
the summer months the angle may not be the most efficient, there are more hours of solar energy available.
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.
9.5.3 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 34: 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.
9.5.4 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 DXM 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.
Sure Cross
®
DXM100-Bx and DXM1000-Bx Wireless Controllers
www.bannerengineering.com - Tel: + 1 888 373 6767
87