Banner DXM150-S Series Instruction Manual Download

Page: 13 / 43

Battery capacity is a function of the ambient temperature and the rate

of discharge. Depending upon the specific battery, a battery operating

at –30 °C can have as much as 40 percent less capacity than a battery

operating at 20 °C. Choose enough battery capacity based on your

geographical location.
A larger capacity battery typically lasts longer for a given solar

application because lead-acid batteries do not like deep cycling

(discharging a large percentage of its capacity). Depending upon the

battery, a battery discharging only 30 percent of its capacity before

recharging will have approximately 1100 charge/discharge cycles. The

same battery discharging 50 percent of its capacity will have

approximately 500 charge/discharge cycles. Discharging 100 percent

leaves the battery with only 200 charge/discharge cycles.
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.

Use this as a guide to the approximate state of
charge and in determining when to apply
conservation measures.

Average Voltage Readings Relative to Battery

Change

State of Charge (%)

Open Circuit Voltage

100

13.0 or higher

12.6

12.1

11.66

11.4 or less

Solar Panel

Banner solar panels come in two common sizes for the DXM Modbus Slave: 5 Watt and 20 Watt. Both panels are designed

to work with the DXM Modbus Slave 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 slave controller, 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 .
Solar Panel Mounting
To capture the maximum amount of solar radiation throughout the year, mount a fixed solar panel to optimize the sun's

energy throughout the year. 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.

4.3.3 Recommended Solar Configurations

These solar panel and battery combinations assume direct sunlight for 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.

Solar panel and battery combinations for a

DXM Modbus Slave

system

Solar Panel

Battery Capacity1

Days of Autonomy

DXM mA

DXM Controller