If the PV array’s output increases above the 40-amp level due to reflection or “edge of
cloud effect,” the C40 will continue to operate until the heatsink reaches a safe operating
temperature. This will take several minutes to occur depending upon the ambient
temperature involved. When the heatsink reaches the maximum safe temperature, the C40
will reduce the current, cooling the transistors and the heatsink. This will occur only if the
current flow exceeds the 40-amp level and the C40 is located in a very hot environment.
If the current from the PV array reaches 63 amps, the C40 will turn off to self protect. This
should never occur in a properly designed system. Ten minutes after shutting off to self
protect, the C40 will automatically restart.
The C40 charge controller rapidly cycles the current source on-and-off to control the
charging current and voltage of the battery. This occurs in both the charge control mode
and the diversion control mode. The amount of time the current source is connected to the
battery is varied to control the average current flow. This is often referred to as “pulse width
modulation” (PWM) and allows the current to be tapered, rather than coarsely turning the
current off and on as with relay type PV array charge controllers.
Each night the PV array is automatically disconnected from the battery to prevent reverse
leakage of power. This eliminates the need for a blocking diode between the battery and
the PV array. If thin-film or amorphous solar modules are being used, diodes may still be
required to prevent damage from partial shading conditions. Check the documentation
provided with the PV modules.
The C40 can operate as a 40-amp diversion control to manage battery charging from
alternative-energy sources such as wind or hydro-electric generators. Systems utilizing
solar arrays do not have a requirement for diversion loads since a solar module can be
open-circuited without damage. However, even with a solar based system it is desirable to
use excess power to operate DC loads. When used in this way, the C40 controls a
Automatic PV Array Night Disconnect
Diversion Control Mode
Operating Modes
The C40 controller can operate as either a photovoltaic charge controller, a diversion
controller, or a DC load controller. The C40 cannot operate as both a charge controller and
a DC load controller at the same time. If both are required in a system, two C40’s must be
installed. Use one C40 for each mode desired.
with three-stage regulation and automatic or manual
battery equalization cycle. When this mode is selected, the status LED will indicate either
blinking green or solid green. It will alternate red/green when in equalization mode.
for PV, hydro-electric, wind generator, or mixed source systems
with three-stage regulation and automatic or manual battery equalization cycle. When this
mode is selected the status LED will indicate either blinking green or solid green.
turns off the DC loads when battery voltage is low. When this
mode is selected, the status LED will typically indicate blinking red or solid red.
The C40 can regulate up to 40-amps of continuous photovoltaic (PV) array current at 12, 24
or 48-volt DC for charging batteries. This rating includes the NEC required deratings - it is
directly comparable to other controllers rated at 60 amps. When used in this mode, ensure
that the operating mode jumper is on the Charge Control pins. To enable the Photovoltaic
Charge Control Mode, see the section of this booklet.
Photovoltaic Charge Control Mode
Diversion Control Mode
DC Load Control Mode
Photovoltaic Charge Control Mode
User Configuration Options
4
Copyright Trace Engineering Co. Inc. Tel (360) 435-8826 Part Number 2680 Rev. C
5916 195 Street, NE Fax (360) 435-2229 November 4, 1998
Arlington, WA 98223 USA www.traceengineering.com Page
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