Campbell Scientific CR23X Micrologger - Manual (Page 231)

SECTION 14. INSTALLATION AND MAINTENANCE
14-5
acid battery specifications are given in Table
14.3-3.
The leads from the charging source connect to
a wiring terminal plug on the side of the base.
Polarity of the leads to the connector does not
matter. A transzorb provides transient
protection to the charging circuit. A sustained
input voltage in excess of 40V will cause the
transzorb to limit voltage.
The red light (LED) on the base is on during
charging with 17 to 24 VDC or 18 V RMS AC.
The switch turns power to the CR23X on or off.
Battery charging still occurs when the switch is
off.
Should the lead acid batteries require
replacement, consult Figure 14.3-2 for wiring.
BLACK
RED
WHITE
6V 7AH
LEAD ACID
BATTERY
6V 7AH
LEAD ACID
BATTERY
LEAD ACID BATTERY REPLACEMENT
- -
+ +
FIGURE 14.3-2. Lead Acid Battery Wiring
Monitor the power supply using datalogger
Instruction 10. Users are strongly advised to
incorporate this instruction into their data
acquisition programs to keep track of the state
of the power supply. If the system voltage level
consistently decreases through time, some
element(s) of the charging system has failed.
Instruction 10 measures the voltage internal to
the CR23X, not the voltage of the lead acid
battery. The measured voltage will normally be
about 0.3 V less than the voltage at the internal
or external 12 V input. This voltage drop is on
account of a Schottkey diode. External power
sources must be disconnected from the CR23X
to measure the actual lead acid battery voltage.
TABLE 14.3-3. CR23X Rechargeable Battery
and AC Transformer Specifications
Lead Acid Battery
Battery Type
Yuasa NP7-6
Float Life @ 25 o C 3 years minimum
Capacity 7.0 amp-hour
Shelf Life, full charge 6 months
Charge Time (AC Source) 40 hr full charge,
20 hr 95% charge
Operating temperature -15°C to 50°C
charge
-20°C to 60°C
discharge
AC Transformer
Input: 120 VAC, 60 Hz
Isolated Output: 18 VAC 1.11 Amp
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 CR23X 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.
14.3.3 LOW PROFILE CR23X
The low profile CR23X option is not supplied
with a battery base. See Section 14.5 and 14.6
for external power connection considerations.
14.4 SOLAR PANELS
Auxiliary photovoltaic power sources may be
used to maintain charge on lead acid batteries.
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