Solar
panels are economical and powerful tools for recharging
batteries at the gage house and remote monitoring. You can
keep the batteries powering your datalogger and remote
telemetry units permanently charged with a properly sized
solar panel. Use of a proper charging system is important
to ensure long, reusable service from the battery. We
don't recommend using car batteries for remote monitoring
- they don't recover well from being fully discharged.
Rule of Thumb for sizing Solar Panels: figure out the
average current draw of the remote device that you need to
power in Milliamps (MA). We're assuming a 12 VDC system.
Pick a solar panel with a current rating of at least 10
times this number. Example: your remote Solar Panels
device draws 6 MA average. Pick a solar panel of at least
60MA output current, or to calculate power (watts) would
be 60MA x 12 VDC = 720 MW which is 7.2 watts so a 10 watt
panel will work great for this system.
Rule of Thumb for Batteries: you will want your device
to run for 3-5 days without any sun, depending on your
weather conditions. (Actually the solar panel will charge
a little bit every day, even under sunless conditions.)
Example: if your device draws 100MA, figure .1A x 24
hr/day x 5 days = 12 AH (Ampere-Hours). You can only use
about 1/2 of the rated battery output so pick a battery
rated at at least 24 AH.
Small gel-cell batteries are in the 5-26 AH range,
while marine batteries range from 60 AH to 105 AH. You can
connect batteries in parallel (+ to + and - to -) to
double or triple the available output.
We offer two types of solar panels: framed glass and
flat urethane coated. Framed glass panels put out more
amps per square inch. Our glass panels come mounted on an
aluminum panel with a clamp for a 2" pipe, which holds the
panel at approximately 45 degrees to the sun for ideal
charging. Our flat urethane coated panels are rugged and
they are framed in urethane plastic, with no mounting
hardware. They are ideal for gluing to the top of an
enclosure where they are not visible.
Note: For most gaging stations with telemetry, modem or
other communications systems a 20 watt panel will meet
power requirements. However, if the station is a shady
site in a valley where it might only receive 2 to 3 hours
a day of available sun a 50 watt panel would be
recommended. See the Technical Data Section for more
sizing information.
Also recommended for a solar charging system is a
charge controller (regulator). These controllers consist
of blocking and zener diode protection to keep the battery
from discharging back through the panel during periods of
no sunlight and over-charging protection to the battery:
902-025
2 amp charge controller - for use w/ 10 watt panel
1 lb.
902-026
4 amp charge controller - for use w/ 20 watt and 50 watt
panels 1.7 lbs.
