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.

Features

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 insolation levels

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.

Smaller Size

Mechanical dimensions are less than other MPPT controllers, making it easier to install in equipment enclosures.

Highly Reliable

Efficient electronics, a conservative thermal design and tropicalization result in high reliability and long life.

Fully Adjustable

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 battery life.

More Information

The status LED’s and optional meter provide extensive controller and system data.

Data Logging

Records key operating parameters of the PV system and includes 30 days of data logging.

Specifications

Electrical

Environmental

• Operating Temperature: –40°C to +60°C
• Storage Temperature: –55°C to +100°C
• Humidity: 100% non-condensing

• Tropicalization:	Epoxy encapsulation
  	Conformal coating
  	Marine rated terminals

Electronic Protections

• 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

Battery Charging

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.

*Setpoints for this battery type can be modified with custom programming.

• Battery Types: Gel, Sealed, AGM, Flooded
• 4 Stage Charging: Bulk, absorption, float, equalize (optional)
• Temperature Compensation

  Coefficient:	–5mV/°C / cell (25°C ref)
  Range:	–30°C to +60°C
  Set points:	Absorption, float, equalize

Mechanical

• 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

Options

• Remote Meter
• Remote Temperature Sensor
• PC MeterBus Adapter
• DIN Rail Mounting Clips

Certifications

• CE Compliant
• RoHS Compliant
• Manufactured in a certified ISO 9001 facility

Detailed Description

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.

Features Diagram

The features of the SunSaver MPPT are shown below. An explanation of each feature is provided.

1. Status LED

   An LED indicator that shows charging status and also indicates when a solar input fault condition exists.

2. Power Terminal Block

   Power terminations for system Solar, Battery, and Load connections.

3. Battery Select Jumper

   A removable jumper to select the battery type.

4. Meter Connection

   A communication port for the Morningstar Remote Meter or Personal Computer (PC) connection. A MSC adapter is required, available separately.

5. Settings Switches

   Adjustment switches that define the operating parameters of the SunSaver MPPT.

6. Remote Temperature Sensor (RTS) Terminals

   Connection point for a Morningstar RTS (optional) to remotely monitor battery temperature.*

7. Local Temperature Sensor

   Measures ambient temperature. Battery regulation is adjusted based on ambient temperature unless an optional RTS is installed.

8. Battery Status LEDs

   Provides approximate battery state of charge indication and also indicates when a system or load fault condition exists.

*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 performance.

Current Boost

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 section.

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 controllers.

Battery Charging Information

The SunSaver MPPT has a 4-stage battery charging algorithm for rapid, efficient, and safe battery charging.

Bulk Charge

In this stage, the battery voltage has not yet reached absorption voltage and 100% of available solar power is used to recharge the battery.

Absorption

When the battery has recharged to the Absorption voltage setpoint, constant-voltage regulation is used to prevent heating and excessive battery gassing.

Float

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 float stage.

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.

Current Compensation

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 table.

LVD Warning

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.

Protections

Solar Overload

(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.

Load Overload

(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 reapplying power.

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 service.

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.

High Temperature

(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.