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Installation and Adjustment
The CP Controller is usually
installed in the container or the shed housing the battery bank.
Under these conditions a NEMA 3-R enclosure is usually adequate
for protection from the elements. Temperature compensated battery
charging is strongly recommended and is the only type of PV charge
control provided by ETA. Although the CP Controller may be mounted
in any position (Mercury relays are not used) it should normally
be mounted upright to maintain the drip-proof features of the NEMA
3R enclosure.
Normally the battery cable is
connected first to the Controller. Adequate cable size and short
lengths are imperative for good system efficiency. The output Circuit
Breaker (normally provided on larger systems) should be left open
at this time. Next the Ground Bed (+) and Cathode (-) cables are
connected. Again, it usually pays to oversize the cables. A rough
Rule-of-Thumb is that remote power costs about $10 per installed
Watt; therefore copper costs can be increased until they are equal
to the cost of the power lost (I*I*R losses). As a result, wire
sizing is usually several times larger than that required by ampacity
ratings alone. ETA may be contacted for details. The PV input wiring
should be of the size recommended by the designer. The PV cables
or wires may be attached to the individual regulator(s) or main
terminal block as indicated by the CP Junction Box Wiring and Layout
Diagram.
This is a Positive Ground
system which differs from many other electronic designs. PV module
frames and supporting rack(s) should be grounded with at least AWG
#6 cable(s) and a good ground rod(s). Grounding the PV wires or
the battery with a separate ground is not recommended, (the
battery positive is grounded through the Ground Bed). This approach
minimizes the chance of lightning damage while providing a path
for static bleed-off. The positive ground approach eliminates electronics
in the ground path, giving more accurate meter readings and less
chance of failure due to lightning. The negative output voltage
is regulated by the electronics through several stages of lightning
protection circuitry.
Once connected as per the diagram,
the meter (see below) should be set to read Vin, the battery voltage.
This should be in the nominal operating range of (12.5+, 25+, 50+
vdc) for proper operation. If the battery is below this level, the
Low Voltage Disconnect (if utilized) may prevent operation until
the battery is more fully recharged. The control should not be operated
without a battery connected! Next the meter should be set to Vout
to monitor the actual output voltage. The anticipated output voltage
may now be set by turning the "Vo" multi-turn pot adjustment
screw with a miniature screwdriver or adjustment tool. The Vo pot
is located in the lower left corner of the CP control board. Turning
the pot CW increases the output voltage and turning CCW decreases
the voltage. Set the voltage somewhat below the anticipated value
since the initial load will normally be higher, until the the ground
bed and cathode have fully polarized. Now set the meter to the "Io"
position and reconnect the output circuit breaker. You should be
able to read the output current assuming that the Io pot is turned
CW sufficiently. If the current is above that desired, turn the
Io pot CCW. If the current is set too low, the output voltage will
drop to the point where only the set current is provided to the
load. At this time a maximum current can be set then a maximum voltage
can be set with the load turned off. This determines the maximum
power that can be delivered to the load and hence the amount of
average input power required for a given site. Good designs usually
include a significant safety factor to allow increased output in
the future, when protective coatings or ground bed resistance deteriorate
in the future. For longer 9-volt battery life, turn the meter switch
off when done.
After the first few days of operation
the load will stabilize and you may wish to do a final adjustment.
The CP controller requires no further adjustment or maintenance.
"Golf Cart" type batteries are recommended since they
are usually the most cost effective. Distilled water should be added
every six months. The meter readings, time of day, recent weather
conditions, and date should be recorded at each visitation to track
long term trends.
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