Installation
ProStar Operator’s Manual
31
30
3.0
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
controller 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 controller 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-position
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.
Tighten the connector screws to 5 in-lb (0.56 Nm) of
torque.
The maximum length allowed for each battery voltage
sense wire is 98 ft (30m).
Connecting the voltage sense wires to the RTS
terminal will cause an alarm.
NOTE:
If the battery input voltage is greater
than 5 Volts different than the Battery Sense,
due to voltage drops or faulty connections, the Battery
Sense input will not be recognized by the ProStar.
A battery voltage sense connection is not required to
operate the ProStar controller, but it is recommended
for best performance.
