MorningStar SunSaver MPPT 15 Amp 12/24 Volt MPPT Charge Controller
Manufacturer Part Number: SS-MPPT-15L
Morningstar’s SunSaver MPPT solar controller with TrakStar Technology™ (SS-MPPT-15L) is an advanced maximum power point
tracking (MPPT) battery charger for off-grid photovoltaic (PV) systems. The controller features a smart tracking
algorithm that maximizes the energy harvest from the PV and also provides load control to prevent over discharge
of the battery.
The SS-MPPT battery charging process has been
optimized for long battery life and improved system
performance. Self-diagnostics and electronic error protection
prevent damage when installation mistakes or system faults
occur. The controller also features four (4) settings switches
for adjustability, a meter port, and terminals for remote
battery temperature measurement (optional).
The SunSaver MPPT is well suited for both professional and consumer PV applications including automatic lighting control. Its charging process has been optimized for long battery life and improved system performance. This product is epoxy encapsulated for environmental protection, may be adjusted by the user via four settings switches or connection to a personal computer, and has an optional remote meter and battery temperature sensor.
Maximizes Energy Harvest
TrakStar MPPT Technology features:
- peak efficiency of over 97%
- almost no power losses
- recognition of multiple power peaks
during shading or mixed PV arrays
- excellent performance at low solar
Use of High Voltage Modules
Enables the use of high voltage and thin film modules
for off-grid battery charging.
Converts 36V or 24V PV Arrays
Provides a means to use up to a 36V PV array to charge
either a 24V or 12V battery.
Lower System Cost
Less expensive than other MPPT controllers and is
affordable in smaller PV systems up to 400Wp. Allows
system costs to be reduced by down-sizing the PV
array, using on-grid or thin film modules and
decreasing cable sizes.
Automatic Lighting Control
Up to four programmable timer sequences for
PV lighting applications.
Mechanical dimensions are less than other MPPT
controllers, making it easier to install in equipment
Efficient electronics, a conservative thermal design and
tropicalization result in high reliability and long life.
User selection via on-board switches or PC connection.
Extensive Electronic Protections
Fully protected against most system errors and faults.
Longer Battery Life
Efficient MPPT tracking and 4-stage charging increases
The status LED’s and optional meter provide extensive
controller and system data.
Records key operating parameters of the PV system
and includes 30 days of data logging.
|Peak Efficiency|| 97.5%|
|Nominal Battery Voltage|| 12 or 24 volts|
|Max. Battery Current|| 15 amps|
|Battery Voltage Range|| 7-36 volts|
|Max. PV Open Circuit Voltage|| 75 volts|
|Nominal Max. PV Input||
12 volt battery 200 Watts|
24 volt battery 400 Watts
|Output Rating|| 15 amps load control|
|Self Consumption|| 35 milliamps|
|Transient Surge Protection|| 4 x 1500 Watts|
- Operating Temperature: –40°C to +60°C
- Storage Temperature: –55°C to +100°C
- Humidity: 100% non-condensing
|Tropicalization:|| Epoxy encapsulation|
|Marine rated terminals|
- PV: Overload, Short Circuit, High Voltage
- Load: Overload, Short Circuit
- Reverse Polarity: Battery, PV and Load
- Lightning and Transient Surges
- High Temperature
- Reverse Current at Night
The SS-MPPT provides four (4) different battery types
as shown in the table below. Use Settings Switch 1 and the
Battery Select Jumper to choose the battery type.
|Battery Type|| Battery Jumper|| Switch 1|
|Gel* ||INSERTED|| ON|
|Sealed|| INSERTED|| OFF|
|AGM*|| REMOVED ||ON|
|Flooded ||REMOVED|| OFF|
*Setpoints for this battery type can be modified with custom programming.
- Battery Types: Gel, Sealed, AGM,
- 4 Stage Charging: Bulk, absorption, float,
|Coefficient:|| –5mV/°C / cell (25°C ref)|
|Range:|| –30°C to +60°C|
|Set points:|| Absorption, float, equalize|
- Dimensions: 16.9 x 6.4 x 7.3 cm / 6.6 x 2.5 x 2.9 inch
- Weight: 0.60 kg / 1.3 lbs
- Power Terminal: 16 mm2 / #6 AWG
- Enclosure: Die cast aluminum with plastic cover
- Remote Meter
- Remote Temperature Sensor
- PC MeterBus Adapter
- DIN Rail Mounting Clips
- CE Compliant
- RoHS Compliant
- Manufactured in a certified ISO 9001 facility
The SS-MPPT utilizes Morningstar’s TrakStar Maximum
Power Point Tracking technology to extract maximum power
from the solar module(s). The tracking algorithm is fully
automatic and does not require user adjustment. Trakstar
technology will track the array maximum power point voltage
(Vmp) as it varies with weather conditions, ensuring that
maximum power is harvested from the array through the
course of the day.
The features of the SunSaver MPPT are shown below. An explanation of each feature is provided.
- Status LED
An LED indicator that shows charging status and also
indicates when a solar input fault condition exists.
- Power Terminal Block
Power terminations for system Solar, Battery, and Load
- Battery Select Jumper
A removable jumper to select the battery type.
- Meter Connection
A communication port for the Morningstar Remote Meter
or Personal Computer (PC) connection. A MSC adapter is
required, available separately.
- Settings Switches
Adjustment switches that define the operating parameters
of the SunSaver MPPT.
- Remote Temperature Sensor (RTS) Terminals
Connection point for a Morningstar RTS (optional) to
remotely monitor battery temperature.*
- Local Temperature Sensor
Measures ambient temperature. Battery regulation is
adjusted based on ambient temperature unless an optional
RTS is installed.
- Battery Status LEDs
Provides approximate battery state of charge indication
and also indicates when a system or load fault condition
*The use of a Remote Temperature Sensor is
strongly recommended. Controller location, air flow, and
system power can drastically affect the local temperature
sensor reading. A RTS will provide optimal charging
In many cases, TrakStar MPPT technology will "boost" the
solar charge current. For example, a system may have 2
Amps of solar current flowing into the SS-MPPT and 5 Amps
of charge current flowing out to the battery. The SS-MPPT
does not create current! Rest assured that the power into
the SS-MPPT is the same as the power out of the SS-MPPT.
Since power is the product of voltage and current (Volts x
Amps), the following is true assuming 100% efficiency:
(1) Power Into the SS-MPPT = Power Out of the SS-MPPT
(2) Volts In x Amps In = Volts Out x Amps Out
If the solar module’s Vmp is greater than the battery
voltage, it follows that the battery current must be
proportionally greater than the solar input current so that
input and output power are balanced. The greater the
difference between the maximum power voltage and battery
voltage, the greater the current boost. Current boost can be
substantial in systems where the solar array is of a higher
nominal voltage than the battery as described in the next
High Voltage Strings and Grid-tie Modules
Another benefit of TrakStar MPPT technology is the ability
to charge 12 Volt or 24 Volt batteries with solar arrays of
higher nominal voltages. A 12V battery bank can be charged
with a 12 V, 24 V, or 36 V nominal off-grid solar array.
Certain grid-tie solar modules may also be used as long
as the solar array open circuit voltage (Voc) rating will not
exceed the SS-MPPT 75 V maximum input voltage rating at
worst-case (coldest) module temperature. The solar module
documentation should provide Voc vs. temperature data.
Higher solar input voltage results in lower solar input
current for a given input power. High voltage solar input
strings allow for smaller gauge solar wiring. This is
especially helpful for systems with long wiring runs between
the solar array and the SS-MPPT.
An Advantage Over Traditional Controllers
Traditional controllers connect the solar module directly
to the battery when recharging. This requires that the
solar module operate in a voltage range that is below the
module’s Vmp. In a 12 V system for example, the battery
voltage may range from 10 - 15 Vdc but the module’s Vmp is
typically around 17 V. The Figure below shows a typical current vs.
voltage output curve for a nominal 12V off-grid module.
The array Vmp is the voltage where the product of current
and voltage (Amps x Volts) is greatest, which falls on the
"knee" of the solar module I-V curve as shown in the figure.
Because Traditional controllers do no operate at the Vmp
of the solar array, energy is wasted that could otherwise be
used to charge the battery and power system loads. The
greater the difference between battery voltage and the Vmp
of the module, the more energy is wasted.
TrakStar MPPT technology will always operate at the
Vmp resulting in less wasted energy compared to traditional
Battery Charging Information
The SunSaver MPPT has a 4-stage battery charging
algorithm for rapid, efficient, and safe battery charging.
In this stage, the battery voltage has not yet reached
absorption voltage and 100% of available solar power is
used to recharge the battery.
When the battery has recharged to the Absorption voltage
setpoint, constant-voltage regulation is used to prevent
heating and excessive battery gassing.
After the battery is fully charged the SS-MPPT reduces
the battery voltage to a float charge which is sometimes
called a trickle charge.
Depending on battery history, the battery remains in the absorption stage for 3 or 4 hours before transitioning to the
Equalize (flooded battery type only)
If the auto-equalize feature is enabled, the SS-MPPT
will equalize a flooded battery for three (3) hours every 28
days. Equalize charging raises the battery voltage above
the standard absorption voltage so that the electrolyte
gasses. This process prevents electrolyte stratification and
equalizesthe individual cell voltages within the battery.
Load Control Information
The primary purpose of the load control function is to
disconnect system loads when the battery has discharged
to a low state of charge and reconnect system loads when
the battery is sufficiently recharged. System loads may be
lights, pumps, motors, DC appliances, and other electronic
devices. The total current draw of all loads must not exceed
the SS-MPPT 15 Amp maximum load rating.
Load Control Settings
Load control is fully automatic. Choose between two (2)
factory Low Voltage Disconnect (LVD) and Low Voltage
Reconnect (LVR) settings by adjusting switch #2. See
Section 3.2 Configuration for more information.
All LVD and LVR setpoints are current compensated.
Under load the battery voltage will sag in proportion to the
current draw of the load. A short-term large load could cause
a premature LVD without the current compensation feature.
LVD and LVR setpoints are adjusted lower per the following
|System Voltage|| Current Compensation|
|12 Volt|| -15 mV per amp of load|
|24 Volt|| -30 mV per amp of load|
As the battery discharges the Battery Status LEDs will
transition from green to yellow and then from yellow to
flashing red. The flashing red indication is a warning that a
low voltage disconnect event will occur soon. The amount of
time between a green SOC indication and load disconnect
will depend on many factors including:
- rate of discharge (amount of load draw)
- capacity of the battery
- health of the battery
- LVD setpoint
If the battery discharges to the LVD setpoint the load will
disconnect and a solid red Battery Status LED indication
will be displayed.
General Load Control Notes
- A 15 V maximum regulation voltage limit (30 V @ 24 V
nominal) exists for all battery types. This limit ensures
that the battery and load terminal voltages will never
exceed 15 V/30 V. This protects certain DC loads that
may be damaged by high input voltage.
- Do not wire multiple SunSaver MPPT load outputs
together in parallel to power DC loads with a current
draw greater than 15A. Equal current sharing cannot
be guaranteed and an over-load condition will likely
occur on one or more controllers.
- Exercise caution when connecting loads with specific
polarity to a live load circuit. A reverse polarity connection
may damage the load. Always double check load
connections before applying power.
(No LED indication) The SunSaver MPPT will limit battery
current to the 15 Amp maximum rating. An over-sized
solar array will not operate at peak power. The solar array
should be less than the SS-MPPT nominal max. input power
rating for optimal performance.
(Battery Status LEDs: R/Y-G sequencing) If the load
current exceeds the maximum load current rating, the SSMPPT
will disconnect the load. The greater the overload the
faster the load will be disconnected. A small overload could
take a few minutes to disconnect.
The SS-MPPT will attempt to reconnect the load two (2)
times. Each attempt is approximately 10 seconds apart. If
the overload remains after two (2) attempts, the load will
remain disconnected until power is removed and reapplied.
Solar Short Circuit
(Charging Status LED: OFF) Solar input power wires are
short-circuited. Charging automatically resumes when the
short is cleared.
Load Short Circuit
(Battery Status LEDs: R/Y-G sequencing) Fully protected
against load wiring short-circuits. After two (2) automatic
load reconnect attempts (10 seconds between each
attempt), the fault must be cleared by removing and
High Voltage Input
(Charging Status LED: R flashing) If the solar input open
circuit voltage (Voc) exceeds the 75 volt maximum rating the
array will remain disconnected until the Voc falls safely below
the maximum rating.
Battery Reverse Polarity
(No LED indication, not powered) Fully protected against
reverse battery connection. No damage to the controller will
result. Correct the miswire to resume normal operation.
Damaged Local Temperature Sensor
(Charging Status LED: R on solid) The local ambient
temperature sensor is short-circuited or damaged. Charging
stops to avoid over- or under-charging. This is a critical
error. Contact your authorized Morningstar dealer for
Damaged Internal Temperature Sensor
(Charging Status LED: R on solid) The internal heatsink
temperature sensor is damaged. This is a critical error.
Contact your authorized Morningstar dealer for service.
(Battery Status LED: R-Y sequencing) The heatsink
temperature has exceeded safe limits and the load is
disconnected. The load will automatically reconnect when
the heatsink cools to a safe temperature.
Remote Temperature Sensor (RTS)
(Battery Status LED: R/Y - G/Y sequencing) A bad RTS
connection or a severed RTS wire has disconnected the
temperature sensor during charging. Charging automatically
resumes when the problem is fixed. To resume operation without a RTS ,
disconnect all power to the SunSaver MPPT and then reconnect.
High Voltage Transients
Solar, battery, and load power connections are protected
against high voltage transients. In lightning prone areas,
additional external suppression is recommended.
Warranty: Five year warranty period. Contact Morningstar for complete terms.