Campbell Scientific CR5000 Measurement and Control Module - Manual (Page 27)

Section 1. Installation and Maintenance
1-3
BLACK
RED
WHITE
6V 7AH
LEAD ACID
BATTERY
6V 7AH
LEAD ACID
BATTERY
LEAD ACID BATTERY REPLACEMENT
- -
+ +
FIGURE 1.3-1. Lead Acid Battery Wiring
Monitor the power supply using datalogger Instruction “ Battery” . Incorporate
this instruction into 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. Battery measures the
voltage at the CR5000 electronics, 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 CR5000 to
measure the actual lead acid battery voltage.
TABLE 1.3-1. CR5000 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 -40°C to 60°C
AC Transformer
Input: 120 VAC, 60 Hz
Isolated Output: 18 VAC 1.2 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 recommends:
1. A CR5000 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.