Morningstar PS-15 Manual

Installation
ProStar Operator’s Manual
23
22
3.0
STEP 1: Check Controller Limitations
Verify that the highest temperature compensated solar
array open-circuit voltage (Voc), and load current do
not exceed the ratings of the ProStar version being
installed.
Multiple controllers can be installed in parallel on the
same battery bank to achieve greater total charging
current. In this type of system, each ProStar must have
its own solar array. The load terminals of multiple
controllers can only be wired together if the total load
draw does not exceed the nameplate current of the
LOWEST rated controller.
STEP 2: Battery Voltage Sense Wires
Due to connection and cable resistance, voltage drops
are unavoidable in power cables that carry current,
including the ProStar battery cables. If Battery Sense
wires are not used, the controller must use the voltage
reading at the battery power terminals for regulation.
This voltage will be higher than the actual battery bank
voltage while charging the battery.
Battery voltage Sense connection enables the ProStar
to measure the battery terminal voltage precisely
with small gauge wires that carry very little current,
and thus have no voltage drop. The sense wires,
when connected directly to the battery, will improve
battery charging accuracy. Battery voltage sense wires
are recommended if the controller is more than five
meters from the battery.
Generally accepted wiring practice is to limit voltage
drops between the charger and the battery to 2%.
Even properly sized wiring with 2% drop can result in a
0.29 Volt drop for 14.4V charging. voltage drops will
cause some undercharging of the battery. The con-
troller will begin Absorption or limit equalization at a
lower battery voltage because the controller measures
a higher voltage at the controller’s terminals than is
the actual battery voltage. For example, if the control-
ler is programmed to start Absorption at 14.4V,when
the controller “sees” 14.4V at its battery terminals, the
true battery voltage would only be 14.1V, if there is a
0.3V drop between the controller and battery.
Note that the battery sense wires will not power the
controller, and the sense wires will not compensate
for losses in the power wires between the controller
and the battery. The battery sense wires are used to
improve the accuracy of the battery charging.
The two sense wires, can range in size from 1.0 to 0.25
mm
2
(16 to 24 AWG), and should be cut to length as
required to connect the battery to the voltage sense
terminals. A 2-position terminal (see figure 3.3) is
used for the battery sense connection. A twisted pair
cable is recommended but not required. Use UL rated
300 Volt conductors. The voltage sense wires may be
pulled through conduit with the power conductors.
Observing correct polarity, connect both battery
voltage sense wires to the ProStar at the 2-posi-
tion Battery Sense terminal, and to battery (+) and
(-) terminals. No damage will occur if the polarity is
reversed, but the controller cannot read a reversed
sense voltage.