Morningstar SunSaver Duo SSD-25RM User manual

SUNSAVER DUOTM
Installation and Operation Manual
….
Dual Battery Charging Solar Controller
for RVs, Caravans, and Boats
….
Ratings
……………………………….…………
Nominal Voltage 12 Volts
Rated Solar Current 25 Amps
www.morningstarcorp.com

2
SUNSAVER DUO DIMENSIONS

3
Contents
1.0 Important Safety Information ................................................................................. 4
2.0 General Information ................................................................................................ 5
2.1 Overview.............................................................................................................. 5
2.2 Morningstar Accessories...................................................................................... 7
3.0 Installation ............................................................................................................... 8
3.1 General Installation Notes.................................................................................... 8
3.2 Adjusting DIP Switches........................................................................................ 9
3.3 Mounting ............................................................................................................ 11
3.4 Wiring................................................................................................................. 12
4.0 Operation ............................................................................................................... 19
4.1 LED Indications.................................................................................................. 19
4.2 Charging Information ......................................................................................... 20
4.3 Protections......................................................................................................... 21
4.4 Inspection and Maintenance .............................................................................. 22
5.0 Troubleshooting .................................................................................................... 23
5.1 Error Indications................................................................................................. 23
5.2 General Problems .............................................................................................. 23
6.0 Limited Warranty................................................................................................... 25
7.0 Technical Specifications ...................................................................................... 26

4
1.0 Important Safety Information
SAVE THESE INSTRUCTIONS:
This manual contains important safety, installation and operating instructions for the
SunSaver Duo solar controller.
The following symbols are used throughout this manual to indicate potentially
dangerous conditions or important safety instructions.
WARNING: Indicates a potentially dangerous condition. Use extreme caution when
performing this task.
CAUTION: Indicates a critical procedure for safe and proper operation of the
controller.
NOTE: Indicates a procedure or function that is important for the safe and proper
operation of the controller.
General Safety Information
Read all of the instructions and cautions in the manual before starting the
installation.
There are no user serviceable parts inside the SunSaver Duo. Do not disassemble
or attempt to repair the controller.
Disconnect all sources of power to the controller before installing or adjusting the
SunSaver Duo. Ensure that both batteries and the solar power have been
disconnected before opening the access cover.
There are no fuses or disconnects in the SunSaver Duo. Power must be removed
externally.
Do not allow water to enter the controller.
Confirm that the power wires are tightened to avoid excessive heating from a loose
connection.

5
2.0 General Information
2.1 Overview
Thank you for selecting the SunSaver Duo solar charge controller. The SunSaver Duo
is an advanced PWM dual-battery charge controller for RV’s, caravans, boats, and other
installations that require simultaneous battery charging of two separate (isolated)
batteries. The controller features a solar input connection and two battery connections.
The SunSaver Duo will charge one battery or two batteries simultaneously using an
advanced multi-stage charging algorithm.
A Status LED indicates charging progress and controller operating state. Battery
charging and operating parameters are adjusted using five (5) Settings DIP Switches.
The SunSaver Duo also features self-diagnostics and electronic error protection.
Corrosion resistant power terminals and an epoxy-encapsulated circuit board provide
maximum environmental protection. The SunSaver Duo also provides connections for a
Remote Temperature Sensor (RTS) and Remote Meter (RM-1).

6
The major features of the SunSaver Duo are shown in figure 1 below. An explanation of
each feature is provided.
Remote Temperature Sensor (RTS)
Terminals Settings
DIP Switches
RemoteMeter
Connection
(RJ-11)
Local Temperature
Sensor Status LED
Indicator
Battery #1
Power Terminals
Battery #2
Power Terminals
Solar Input
Power Terminals
Figure 1. SunSaver Duo features
Remote Temperature Sensor (RTS) Terminals
A connection point for a Morningstar RTS (optional) to remotely monitor battery
temperature.
Local Temperature Sensor
Measures ambient temperature. Battery regulation is adjusted accordingly.
Status LED Indicator
Provides system status and error indication.
Settings DIP Switches
Adjustment switches that define the operating parameters of the SunSaver Duo.
Battery #1 Power Terminals
Power connections for battery #1.
Solar Input Power Terminals
Power connections for solar module(s).
Battery #2 Power Terminals
Power wire connections for battery #2.
Remote Meter Connection (RJ-11)
A communication port for the Morningstar Remote Meter.

7
2.2 Morningstar Accessories
Remote Temperature Sensor (Model: RTS)
The RTS measures battery temperature for accurate temperature compensation.
Use when the ambient battery temperature differs from the ambient controller
temperature by +/- 5 degrees C or more. An RTS can be attached to the
SunSaver Duo at any time. The SunSaver Duo will automatically use the RTS for
battery temperature compensation when installed. The standard cable length is
25 ft (7.6 m), and this can easily be extended to 100 ft (30 m) or longer.
Installation instructions are provided with the RTS.
Remote Meter (Model: RM-1)
The digital Remote Meter displays system operating information, error
indications, and self-diagnostic read-out. Information is displayed on a backlit 4-
digit custom LCD display. The large numerical display and icons are easy to read
and large buttons make navigating the meter menus easy. Additionally, a status
LED and three (3) battery SOC LEDs provide a quick reference to system
operation.
The meter can be mounted in a wall or on the surface of a wall in a frame. The
RM-1 is supplied with 32.8 ft (10.0 m) of cable, a mounting frame, and mounting
screws. The RM-1 connects to the MeterBus port on the SunSaver Duo.
PC MeterBus Adapter (Model: MSC)
The MSC converts the MeterBus RJ-11 electrical interface to a standard RS-232
interface which allows communication between the SunSaver Duo and a PC. The
MSC is required for programming custom charging setpoints and for logging
data. Visit Morningstar’s website for more information.

8
3.0 Installation
3.1 General Installation Notes
Read through the entire installation section before beginning installation.
Be very careful when working with batteries. Wear eye protection. Have fresh
water available to wash and clean any contact with battery acid.
Use insulated tools and avoid placing metal objects near the batteries.
Explosive battery gasses may be present during charging. Be certain there is
sufficient ventilation to release the gasses.
Do not install in locations where water can enter the controller.
Loose power connections and/or corroded wires can melt wire insulation, burn
surrounding materials, or even cause fire. Ensure tight connections and use
cable clamps to secure cables in mobile applications.
Only charge lead-acid batteries.
Each of the two SunSaver Duo Battery connections may be wired to one battery
or a bank of batteries. The following instructions refer to a singular battery, but it
shall be implied that each battery connection can be made to either one battery
or a group of batteries wired in parallel to form a 12 volt battery bank.

9
3.2 Adjusting DIP Switches
Battery #1 Type
Battery #2 Type
Battery Charging Priority
Custom Setpoints
Regulation Type
ON
OFF
Figure 2. Setting DIP switch definitions
DIP Switches 1 & 2 –Battery Type Select
The SunSaver Duo charges both sealed and flooded lead-acid batteries per the
charging specifications in table 1 below. Sealed batteries are typically
maintenance-free batteries that do not require water. Flooded batteries have
removable caps that allow the addition of water when needed. DIP switches 1 &
2 select the battery type for Battery #1 and Battery #2 respectively. Choose the
correct battery type for each battery.
DIP Switch OFF: Sealed battery type (factory pre-set)
DIP Switch ON: Flooded battery type
Setpoint
Battery Type
Sealed
Flooded
Absorption Voltage
14.1 V
14.4 V
Float Voltage
13.7 V
13.7 V
Boost Voltage
X
14.8 V
Boost Time
X
2 hrs
Boost Interval
X
28 days
Table 1. Standard battery charging programs
DIP Switch 3 –Battery Charging Priority
Select the percentage of available charge current to each battery.

10
The 90% / 10% priority setting allows Battery #1 to receive 90% of available
charging current, while Battery #2 receives 10% of charging current. This setting
is ideal for RV and boat systems where a “house” bank requires most of the
available charge current and a separate engine starter battery requires only a
“trickle charge” to remain topped-off. When Battery #1 reaches full charge, more
charge current will be diverted to Battery #2 as needed.
The 50% / 50% priority setting splits available charge current equally between
two battery banks. This priority setting is ideal for systems with two equal-sized
battery banks that require simultaneous charging. If one battery bank reaches full
charge before the other, more charge current will be diverted to the lower state-
of-charge battery.
DIP Switch 3 OFF: 90% / 10% Priority (factory pre-set)
DIP Switch 3 ON: 50% / 50% Priority
DIP Switch 4 –Custom Setpoints
If the standard battery type settings are not suitable, custom charging setpoints
can be programmed using a PC and a Morningstar Serial to Meterbus adapter
(not included). See Morningstar’s website for more information.
DIP Switch 4 OFF: Factory settings (factory pre-set)
DIP Switch 4 ON: Custom programmed settings
DIP Switch 5 –Regulation Type
The SunSaver Duo is a PWM charge controller. Some systems with sensitive
equipment may experience noise interference from PWM charging. Refer to the
FAQ in section 4.0 Troubleshooting for tips on how to reduce or eliminate PWM
noise.
If the noise cannot be satisfactorily reduced, place DIP switch 5 in the ON
position. While less efficient, Slow Switching regulation will significantly reduce or
eliminate PWM noise.
DIP Switch 5 OFF: PWM Regulation (factory pre-set)
DIP Switch 5 ON: Slow Switching Regulation

11
3.3 Mounting
NOTE: When mounting the SunSaver Duo, ensure free air flow through the controller
heat sink fins. There should be at least 3 inches (75 mm) clearance above and below
the controller to allow for cooling. If mounted in an enclosure, ventilation is highly
recommended.
WARNING: Never install the SunSaver Duo in a sealed enclosure with vented
(flooded) batteries! Do not install in a confined area where battery gasses can
accumulate. Risk of explosion!
1. Locate the SunSaver Duo on a vertical surface protected from direct sun, high
temperatures, and water.
2. Place the SunSaver Duo in the location where it will be mounted. Verify that
there is sufficient room to run wires and that there is ample room above and
below the controller for air flow.
HEATSINK
FINS
WARM AIR
COOL AIR
At least
3" (75 mm)
At least
3" (75 mm)
MOUNTING
HOLES
Figure 3. Mounting and cooling
3. Use a pencil or pen to mark the four (4) mounting hole locations on the mounting
surface.
4. Remove the controller and drill 3/32” (2.5 mm) holes in the marked locations.
5. Place the controller on the surface and align the mounting holes with the drilled
holes in step 4. Secure the controller in place using the mounting screws
(included).

12
3.4 Wiring
Three system wiring examples are provided for RV’s and caravans, boats, and non-
mobile installations. Reference the appropriate wiring diagram for your installation.
CAUTION: Protect system wiring from sharp edges and foot traffic. Use grommets and
wire loom where necessary.
NOTE: Power connection order is not critical. A connection order has been provided
for each installation type for instructional purposes only.
NOTE: Wiring charts on the back page of this manual provide minimum
recommended wire size.
NOTE: The SunSaver Duo can charge just 1 battery connected to either the Battery
#1 or Battery #2 connections. If Battery #1 or Battery #2 is missing, the remaining
battery will be charged with 100% of available power regardless of the charging
priority setting.
RV / CARAVAN INSTALLATION
+-
+-
Vehicle Chassis
Common Ground
Battery
#1
Battery
#2
+
-
=
30A Fuse30A Fuse
Figure 4. Typical RV / Caravan wiring diagram
NOTE: To ensure good vehicle chassis ground connections:
- remove all paint, grease, debris at grounding point.
- use sandpaper/emory cloth to expose chassis bare metal.
- use ring terminal and star- or lock-washer to secure cable.
- dielectric grease can be used to minimize corrosion.

13
NOTE: A wire jumper is installed across the Remote Temperature Sensor (RTS)
terminals at the factory. The jumper can prevent false RTS detection due to
condensation on the SunSaver Duo. Do not remove this jumper unless an
optional RTS is to be installed.
Before proceeding, mount the solar module(s) per the manufacturer’s instructions. If
adding batteries that are not factory installed, they should be safely secured in their
desired location. The SunSaver Duo should be mounted per the instructions in section
2.3 Mounting.
Step 1: Ground SunSaver Duo
Ground a negative terminal of the SunSaver Duo to the vehicle chassis. The
SunSaver Duo has a common negative; it does not matter which negative
terminal is grounded. Use wire with black insulation, appropriately sized for the
system charging current (see back page).
Step 2: Battery #1 (“house” battery bank)
Connect Battery #1 to the SunSaver Duo as shown in figure 4. In RV
installations, Battery #1 should be the “house” or cabin battery.
If the cabin battery was factory installed, battery negative should already be
grounded to the vehicle chassis. Use a short piece of black wire to ground the
cabin battery if necessary. Use red wire for battery positive. Use wire
appropriately sized for the system charging current (see back page).
An in-line fuse holder should be wired in the positive line no further 12” ( 305 mm
) from the battery post. Do not insert a fuse in the fuse holder at this time.
Step 3: Battery #2 (engine battery)
Connect Battery #2 to the SunSaver Duo as shown in figure 4. The engine
battery should already be grounded to the vehicle chassis. Use red wire for
battery positive. Use wire appropriately sized for the system charging current
(see back page).
An in-line fuse holder should be wired in the positive line no further 12” ( 305 mm
) from the battery post. Do not insert a fuse in the fuse holder at this time.
Step 4: Solar
Ground the solar module(s) to the vehicle chassis with black wire. Multiple 12V
nominal solar modules may be wired together in parallel and grounded with one
wire. Use red wire for the solar positive connection to the SunSaver Duo. Use
wire appropriately sized for the system charging current (see back page).
Confirm that the solar modules are wired for 12V nominal output before
connecting them to the SunSaver Duo. In full sun, the output voltage of the solar
modules should be 18 –25 Volts before connection to the SunSaver Duo.

14
Upon connection of the Solar positive wire, the SunSaver Duo should begin the
start-up sequence, flashing the Status LED 3 times.
Step 5: Remote Temperature Sensor (optional)
An optional Remote Temperature Sensor (purchased separately) measures the
temperature directly at the battery for more accurate battery charging. Remove
the wire jumper from the RTS terminals before installing the sensor. The RTS
includes full installation instructions.
Step 6: Insert Fuses
Insert a 30 A dc-rated fuse into the fuse holder in each of the battery positive
wires. If the solar module(s) is in full sun, charging should begin.

15
BOAT INSTALLATION
WARNING: Only ground the DC system to battery negative (one-point ground). Never
ground the DC system to the boat bonding system or to any metallic part, fixture, or
component on the boat.
NOTE: An existing common ground wire may connect the negative battery terminals
of two or more on-board batteries. This cable will not interfere with the SunSaver Duo
operation.
NOTE: A wire jumper is installed across the Remote Temperature Sensor (RTS)
terminals at the factory. The jumper can prevent false RTS detection due to
condensation on the SunSaver Duo. Do not remove this jumper unless an
optional RTS is to be installed.
+
-
+-+-
Battery
#2
Battery
#1
Common
Ground Wire
30A
Fuse
30A
Fuse
Solar PV
Array
Engine Starter Battery
“House” Bank
Figure 5. Typical boat wiring diagram
Before proceeding :
Install the solar module(s) per the manufacturer’s instructions.
Batteries should be installed per the U.S Coast Guard regulations for
pleasureboats. The batteries must be secured to prevent movement and the
battery terminals covered to prevent arcing. A battery box to contain any
spilled battery acid is strongly recommended.
The SunSaver Duo should be mounted per the instructions in section 2.3
Mounting.

16
Step 1: Battery # 1 (“house” battery bank)
Wire the negative terminal of the “house” battery to the negative Battery 1
terminal on the SunSaver Duo with black wire as shown in figure 5. Wire the
“house” battery positive power cable as shown in figure 5. Wire a DC-rated in-line
fuse holder in the cable. The length of cable between the Battery (+) post and in-
line fuse holder should be no longer than 12” ( 305 mm ). Use wire with red
insulation, appropriately sized for the system charging current (see back page).
Do not insert a fuse in the fuse holder at this time.
Step 2: Battery # 2 (“engine” battery)
Wire the negative terminal of the engine battery to the negative Battery 2 terminal
on the SunSaver Duo with black wire as shown in figure 5. Wire the engine
battery positive power cable as shown in figure 5. Wire a DC-rated in-line fuse
holder in the cable. The length of cable between the Battery (+) post and in-line
fuse holder should be no longer than 12” ( 305 mm ). Use wire with red
insulation, appropriately sized for the system charging current. Do not insert a
fuse in the fuse holder at this time.
Step 3: Solar
Connect the solar module(s) output to the Solar input connection of the
SunSaver Duo. Multiple 12V nominal modules may be wired together in parallel
and wired to the SunSaver Duo with one pair of wires. Use red wire for solar
positive and black wire for solar negative.
Confirm that the modules are wired for 12V nominal output before connecting
them to the SunSaver Duo. Double-check polarity before connection. In full sun,
the output voltage of the solar modules should be 18 –25 Volts before
connection to the SunSaver Duo.
Upon connection of the Solar positive wire, the SunSaver Duo should begin the
start-up sequence, flashing the Status LED 3 times.
Step 4: Remote Temperature Sensor (optional)
An optional Remote Temperature Sensor (purchased separately) measures the
temperature directly at the battery for more accurate battery charging. Remove
the wire jumper from the RTS terminals before installing the sensor. The RTS
includes full installation instructions.
Step 5: Insert Fuses
Insert a 30 A dc-rated fuse into the fuse holder in each of the battery positive
wires. If the solar module(s) is in full sun, charging should begin.

17
NON-MOBILE / PERMANENT DWELLING INSTALLATION
+
-
+-+-
Battery
#2
Battery
#1
30A Fuse 30A Fuse
Solar PV
Array
Earth
Ground
Earth
Ground
Earth
Ground
Figure 6. Terrestrial wiring diagram
NOTE: Earth grounding is recommended but not required. Grounding helps protect
against lightning by providing a direct path to earth. In areas prone to frequent
lightning strikes, external lightning arrestors and/or other means of protection may be
needed.
NOTE: If a Remote temperature Sensor (RTS) is not used, inserting a jumper across
the RTS terminals can prevent false RTS detection due to condensation on the
SunSaver Duo. Secure a short piece of wire across the RTS terminals.
Step 1: Battery #1
Connect Battery #1 to the SunSaver Duo as shown in figure 6. If charging priority
is set to the default 90% / 10% setting, battery 1 will receive 90% priority. Use red
wire for battery positive and black for battery negative. An in-line fuse holder
should be wired in the positive line no further 12” ( 305 mm ) from the battery
post. Earth ground the battery negative post if desired using a short piece of
black wire appropriately sized for the system charging current (see back page).
Do not insert a fuse in the fuse holder at this time.
Step 3: Battery #2
Connect Battery #2 to the SunSaver Duo as shown in figure 6. Use red wire for
battery positive and black for battery negative. An in-line fuse holder should be
wired in the positive line no further 12” ( 305 mm ) from the battery post. Earth
ground the battery negative post if desired using a short piece of black wire
appropriately sized for the system charging current (see back page). Do not
insert a fuse in the fuse holder at this time.

18
Step 4: Solar
Connect the solar module(s) output to the Solar input connection of the
SunSaver Duo. Multiple 12V nominal modules may be wired together in parallel
and wired to the SunSaver Duo with one pair of wires. Use appropriately sized
red wire for solar positive and black wire for solar negative.
Confirm that the modules are wired for 12V nominal output before connecting
them to the SunSaver Duo. Double-check polarity before connection. In full sun,
the output voltage of the solar modules should be 18 –25 Volts before
connection to the SunSaver Duo.
Upon connection of the Solar positive wire, the SunSaver Duo should begin the
start-up sequence, flashing the Status LED 3 times.
Earth ground solar negative if desired using a short piece of black wire
appropriately sized for the system charging current (see back page). Do not
insert a fuse in the fuse holder at this time.
Step 5: Remote Temperature Sensor (optional)
An optional Remote Temperature Sensor (purchased separately) measures the
temperature directly at the battery for more accurate battery charging. Remove
the wire jumper from the RTS terminals before installing the sensor. The RTS
includes full installation instructions.
Step 6: Insert Fuses
Insert a 30 A dc-rated fuse into the fuse holder in each of the battery positive
wires. If the solar module(s) is in full sun, charging should begin.

19
4.0 Operation
4.1 LED Indications
The Status LED indicates system operational state and any existing error conditions.
Table 1 below defines the Status LED indications.
Status LED
Operating State
Off :
5 second heartbeat¹
Night
Green :
on solid ( 5 second heartbeat² )
Bulk Charging
Green :
Flashing ³
Absorption, Float, or Equalize
Red :
flashing
Error
Red :
on solid ( 5 second heartbeat² )
Critical Error
Table 1. Status LED definitions
¹heartbeat indication flickers the Status LED on briefly every 5 seconds
² heartbeat indication flickers the Status LED off briefly every 5 seconds
³ Battery 1 and Battery 2 must both be in regulation
Red (flashing) Errors
-reverse polarity battery connection.
-reverse polarity solar connection.
-solar over-current condition.
-high temperature.
-damaged or disconnected Remote Temperature Sensor.
-high voltage disconnect.
Red (on solid) Critical Errors
-damaged local temperature sensor.
-damaged heatsink temperature sensor.
For more information on errors, see Protections section 4.3

20
4.2 Charging Information
The SunSaver Duo is an advanced, fully automatic solar battery charger. No
adjustments are required except to select the battery type at installation. Each battery is
charged independently. The SunSaver Duo has a 4-stage charging algorithm as shown
in figure 7.
NIGHT NIGHT
1
BULK
CHARGE
2
ABSORPTION
3
FLOAT
TIME
VOLTAGE
4
BOOST
Figure 7. SunSaver Duo charging algorithm
1. Bulk Charge –Recharging with 100% of available solar energy.
2. Absorption –PWM constant-voltage regulation to prevent heating and
excessive battery gassing. Pulse charging to restore full battery capacity.
3. Float –After battery is fully charged, SunSaver Duo reduces to a float or “trickle
charge”.
4. Boost (Flooded battery type only –Every 28 days) –A boost charge for flooded
batteries, bringing uneven cell voltages into balance and extending battery life.
Sometimes called an equalization charge.
NOTE: A 15V maximum battery voltage limit prevents damage to sensitive DC loads.