Operator`s manual

SECTION 14. INSTALLATION AND MAINTENANCE
14-4
TABLE 14.3-2. 21XL Battery and AC
Transformer Specifications
Lead Acid Battery
Battery Type Gates #810-0011X
Float Life @ 25
o
C 8 years minimum
Capacity 2.5 amp-hour
Shelf Life, full charge Check twice yearly
Charge Time (AC Source) 40 hr full charge,
20 hr 95% charge
AC Transformer
Input: 120V AC, 60 Hz
Isolated Output: 20V DC @ 350 mA
max.
There are inherent hazards associated with the
use of sealed lead acid batteries. Under normal
operation, lead acid batteries generate a small
amount of hydrogen gas. This gaseous by-
product is generally insignificant because the
hydrogen dissipates naturally before build-up to
an explosive level (4%) occurs. However, if the
batteries are shorted or overcharging takes
place, hydrogen gas may be generated at a rate
sufficient to create a hazard. Campbell
Scientific makes the following
recommendations:
1. A 21X equipped with standard lead acid
batteries should NEVER be used in
applications requiring INTRINSICALLY
SAFE equipment.
2. A lead acid battery should not be housed in
a gas-tight enclosure.
14.4 SOLAR PANELS
Auxiliary photovoltaic power sources, such as
Solarex Models MSX5, MSX10, and MSX18
Solar Panels may be used to maintain charge
on lead acid batteries.
TABLE 14.4-1. MSX5 and MSX10 Solar Panel
Specifications
MSX5 MSX10 MSX18
Typical Peak Power 4.2 8.9 18.6
(Watts)
Current @ Peak .27 .59 1.06
(Amps)
Amp Hrs/week 6.4 14.4 26.4
NOTE: Specifications assume 1 kW/m
2
illumination at a panel cell temperature of
25
o
C. Individual panel performance may
vary as much as 10%.
When selecting a solar panel, a rule-of-thumb is
that on a stormy overcast day the panel should
provide enough charge to meet the system
current drain (assume 10% of average annual
global radiation, kW/m
2
). Specific site
information, if available, could strongly influence
the solar panel selection. For example, local
effects such as mountain shadows, fog from
valley inversion, snow, ice, leaves, birds, etc.
shading the panel should be considered.
Guidelines are available from the Solarex
Corporation for solar panel selection called
"DESIGN AIDS FOR SMALL PV POWER
SYSTEMS". It provides a method for
calculating solar panel size based on general
site location and system power requirements. If
you need help in determining your system
power requirements contact Campbell
Scientific's Marketing Department.
14.5 DIRECT BATTERY CONNECTION
TO THE 21X
Any 10 to 13V DC supply may be connected to
the 12V and ground terminals on the 21X. Be
careful not to short the leads together when
connecting them to the datalogger.
A blocking diode prevents the external battery
from charging the internal alkaline batteries.
14.6 VEHICLE POWER SUPPLY
CONNECTIONS
When a vehicle's starting motor is engaged, the
supply voltage drops considerably below the
nominal 12 volts. If the 21X is connected
directly to the vehicle's power supply, the 21X's
batteries are also pulled down causing an E08
error each time the vehicle is started. Avoid this
problem by placing a diode (1N4001) and a 3
ohm, 5 watt resistor in series with the positive
lead going to the +12V terminal (Figure 14.6-1).
The diode allows the vehicle to power the 21X
without the datalogger attempting to charge the
vehicle. The ground lead should be 16 AWG or
larger to reduce the potential for ground
reference errors in the measurements.