• 115V Version

  • 220V Version


The SureSine™ is a pure sine wave inverter delivering AC power in off-grid solar applications, including rural electrification, telecom, remote homes, RVs, caravans and boats. A cast, anodized aluminum enclosure with no internal cooling fan needed ensures long-term reliability in the harshest conditions. The SureSine’s combination of performance, features and competitive price provides the best small inverter value on the market. It is highly reliable, having no internal cooling fan or other moving parts prone to failure.

Key features and benefits

  • Improved Load Operation
    • Pure Sine Wave – provides quality AC equivalent to grid power.
    Toroidal transformer design generates good wave form throughout the range of input voltages. 600W peak/surge power.
    • Outstanding Surge Capability – handles a 200% surge during
    load start-up, to a maximum of 600W.
  • More Power Available
    • High Efficiency – a high peak efficiency will reduce heating and
    make more solar energy available for powering loads.
    • Low Self-Consumption – The SureSine consumes only 450mA of
    current during operation with a full sine-wave present at the AC
    output. During periods where no load is detected, solar energy
    is not wasted because the SureSine automatically powers down
    to standby mode, reducing self-consumption to one-tenth of
    operating consumption.
  • Extremely High Reliability
    • Extensive Electronic Protections – the SureSine has
    extensive electronic protections that will automatically protect
    against faults and user mistakes such as short circuit, overload,
    high temperature and low voltage disconnect. Recovery from
    most faults is automatic.
    • No Internal Cooling Fan – a key design objective since fans often
    fail in harsh environments and are noisy, consume power and
    blow dirt into the electronics.
    • Tropicalization – the SureSine uses epoxy encapsulation,
    conformal coating, stainless steel hardware, and an anodized
    aluminum enclosure to protect against harsh tropical and marine
  • Other Features
    • More Information – the two LEDs provide important information
    to the user about system status and any fault conditions. An
    optional digital meter may be connected to the SureSine to
    display additional system information.
    • Remote On/Off – improves safety by making it easy to install
    the SureSine in an inaccessible location or enclosure. Reduces
    system cost by avoiding the need to add an AC safety disconnect
    to the system.
    • Adjustability & Communications – four DIP switches provide
    easy adjustability of several system parameters. Additional
    adjustability is possible using Morningstar’s USB MeterBus
    Adapter (UMC-1) to connect to a PC. Free 3rd-party MODBUS
    software is available for custom programming. IP-based
    communication, including SNMP, is enabled through
    Morningstar’s Ethernet MeterBus Converter (EMC-1).
A. Premium high-frequency CoilCraft surface mount inductors

They’re worth it, because they provide the faster power “tracking” that lets us engineer this much power and control into a compact design.

B. High-frequency design

Combined with premium, “over-spec’d” components, this greatly improves control response which guards against system transients, regulation overshoot and overcurrent/overload conditions

C. Built-in 4500W Transient Voltage Surge Suppression for lightning protection

Nature do your worst–this controller can take it

D. Large diameter, high torque, corrosion resistant terminals

If you’ve ever trashed a lesser terminal during an installation, you’ll appreciate some “overkill” here

E. DirectFET™ MOSFET power devices

Allows the surface-mounting of critical components underneath the main board next to the heat sink, which reduces heat travel distance and keeps the controller even cooler

F. Highly-conductive aluminum heatsink extrusion

As opposed to cast aluminum, which is less effective in passive cooling applications

G. Communications/data port with serial/meter auto detect

“Talks solar” with standard industry language, for system monitoring and cloud connectivity-speaks Modbus, and SNMP (with the EMC-1)

H. Lithium foldback circuit

Lithium batteries are expensive and vulnerable to cold temperatures. When it gets close to freezing, the controller backs-off charging to avoid damaging batteries

I. High-speed ARM processor

All-digital calibration for high accuracy, using the same efficient technology found in advanced mobile device

J. TrakStar™ Technology

Morningstar’s hallmark MPPT technology precisely seeks and locks onto the true maximum power point quickly and accurately, to ensure the highest output possible from a solar array

K. Large format, high-resolution backlit LCD

When you’ve been in the field installing, you appreciated being able to read a crisp, high contrast display on site

L. 5 year warranty

Up to 2 1/2 times longer than some competitors in this class

M. Self-diagnostics

ProStar is smart enough to monitor and analyze system performance, and alert you when you need to know

N. High temperature architecture

Heat is the enemy of all electronics. That’s why Prostar’s critical components are rated to withstand temperatures right up to the boiling point of water (100°C)

O. Lexan polycarbonate UL listed case

Protects the precision electronics inside with an impact strength 30 times greater than the acrylic thermoplastics commonly found on lesser controllers

P. Cooling Fan

Just kidding. We’ve never needed them

Specifications and Certifications

Model SI-300-115V-UL (60 Hz) SI-300-220V (50 Hz)
Continuous Power Rating 300 Watts @ 25C 300 Watts @ 25C
Pek Power Rating (15 min.) 600 Watts @ 25C 600 Watts @ 25C
DC Input Voltage 10.0V - 15.5V 10.0V - 15.5V
Waveform Pure sine wave Pure sine wave
AC Output Votage (RMS) 220V or 115V +/– 10% 220V or 115V +/– 10%
AC Output Frequency 50 or 60 Hz +/– 0.1% 50 or 60 Hz +/– 0.1%
Nominal Battery Voltage 12V 12V
Peak efficiency 92% 92%
Total Harmonic Distortion (THD) <4% <4%
Self Consumption (Inverter ON - no load) 450mA 450mA
Self Consumption (Inverter OFF) 25mA 25mA
Self Consumption (Standby) 55mA 55mA
Operating Temperature Range -40 C to +45C -40 C to +45C
Warranty 5 Years 5 Years
CE and RoHS compliant Yes Yes
ETL Listed [UL-458] Yes
FCC Class B Part 15 Compliant Yes Yes
Manufactured in a Certified ISO 9001 Facility Yes Yes


ProStar MPPT Controller - 4 minute video

This short video highlights the high quality of the ProStar MPPT solar charge controller, and its ability to regulate charging of lead acid, lithium, or nickel cadmium batteries in off-grid solar applications. The video also addresses lighting control, self-diagnostics, data logging, MODBUS communications, array oversizing, and low noise design.

Morningstar Charging Experts featuring ProStar MPPT

This 5 minute video highlights the ProStar MPPT solar charge controller’s circuit board that differentiates it from other brands. In addition to the capacitors, inductors, processors, surge protectors, and other over-spec’d internal components, the quality of the controller’s heat sink and outer casing is also addressed. The video concludes with mention of features and capabilities related to communications, datalogging, lithium battery charging, and high quality and reliability.  

New ProStar MPPT Solar Charge Controller

Recorded Webinar

This 30 minute recorded webinar gives a more in depth overview of how the ProStar MPPT solar charge controller fits into the existing Morningstar portfolio. The recording also includes answers to questions about operating temperatures, the display meter interface, and protections, faults and alerts.


  • EIA-485/RS-232 Communications Adapter [RSC-1]

    converts RS-232 to EIA-485 so up to 128 MS products can communicate on the same bus

  • Ethernet MeterBus Converter

    enables IP-based networking and internet connectivity for select Morningstar products

  • PC MeterBus Adapter

    converts a controller's RJ-11 meter port to a RS-232 serial connector for connection to a PC

  • Relay Driver

    programs conditional generator start/stop, high/low voltage alarms, load control and more

  • Remote Meter

    provides voltage, current and temperature readings up to 10 meters away from system

  • MeterHub

    enables up to 15 Morningstar products on a single MeterBus network

  • USB MeterBus Adapter

    converts RJ-11 interface to USB 2.0 interface to allow MS product to communicate with a PC


It’s a recommended best practice to install your product’s latest firmware to ensure access to all up-to-date features, accessory compatibilities, and code modifications. Watch this 5 minute video for instructions on how to download and update ProStar MPPT firmware.

After watching the video, click here to download the firmware.

System Diagrams

    Off-Grid Diagram with DC Load

The schematic diagram above, illustrates how the ProStar MPPT regulates power to batteries and a direct current (DC) load in an off-grid system.

  1. Sunlight contacts the solar modules, which convert solar into DC electrical power that it delivers to a charge controller.
  2. The charge controller regulates the amperage and voltage that is delivered to the loads and any excess power is delivered to the battery system so the batteries maintain their state of charge without getting overcharged.
  3. During the evening when there is no sunlight, battery power is used to run the load.



    Off-Grid Diagram with AC Load

The schematic diagram above, illustrates how the ProStar MPPT regulates power to batteries and an alternating current (AC) load in an off-grid system.  This diagram is very similar to the DC load diagram above it except an inverter has been added.

  1. Sunlight contacts the solar modules, which convert solar into DC electrical power that it delivers to a charge controller.
  2. The charge controller regulates the amperage and voltage that is delivered to the battery system so the batteries maintain their state of charge without getting overcharged.
  3. Batteries deliver power to the inverter which converts DC to AC power that it delivers to the load.  Notice that  the inverter is connected to the battery, not the controller’s load terminals, like we did in the DC load example.  That’s because the inverter can have a high energy surge upon start up, and this high current surge might be higher than the rated capacity of the charge controller, whereas the batteries will be able to meet the high energy surge requirement.