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Morningstar SK-12 > SunKeeper 12 Amp 12 Volt PWM Charge Controller

Morningstar SunKeeper 12 Amp 12 Volt PWM Charge Controller - SK-12

Our Price: $99.00
Warranty: 5 Years


Description Datasheet

MorningStar SunKeeper 12 Amp 12 Volt PWM Charge Controller

Manufacturer Part Number: SK-12

Morningstar’s SunKeeper (SK-12) solar controller provides a low cost regulated output directly from the solar module to maximize battery life in small solar power applications. The SunKeeper is epoxy encapsulated and rated for outdoor use. By mounting directly to the module junction box and wiring through the junction box knockout, the connection is weather-proof. This eliminates the need for an additional housing for the controller.

The SunKeeper is available in a 6 amp or 12 amp version (both at 12 volts DC). To withstand the high temperatures at the solar module, the controller has been designed using extremely efficient power electronics and is rated to 70°C. The SunKeeper is also certified for use in Class 1, Division 2 hazardous locations, making it an ideal controller for solar powered oil/gas applications.

SunKeeper System

A typical SunKeeper System.


High Reliability

Rated to 70°C to operate in high temperatures at the solar module. More reliable than controllers mounted inside the junction box. Uses very low on-resistance power MOSFET’s. No need to re-rate.

Outdoor Rated

ETL approved for outdoor use without an additional enclosure. Rugged IP65, UV resistant case. Epoxy encapsulated printed circuit board and watertight connection to the module junction box.

Extensive Electronic Protections

Fully protected against reverse polarity, short circuit, overcurrent, lightning and transient surges, high temperature and reverse current at night.



SunKeeper SK-6 SK-12
Rated Solar Input: 6 amps12 amps
Nominal System Voltage 12 Volts
Min. Battery Voltage 0 Volts
Max. Solar Voltage 30 Volts
Self-Consumption Charging: 7 mA
Night: 2 mA
Voltage Accuracy +/- 150 mV
Battery Charging
Regulation Voltage 14.1 Volts (at 25°C)
Float Voltage 13.7 Volts (at 25°C)
Type of Charging Series PWM
3 stage: bulk, PWM and float
Temperature Compensation (3 choices) Reading temp at controller: –30 mV / °C
Attaching remote temp sensor: –30 mV / °C
Disable temp comp: Defaults to 25°C

Electronic Protections

  • Reverse Polarity
  • Short Circuit
  • Overcurrent
  • Lightning and Transient Surges
  • High Temperature
  • Reverse Current at Night


  • Operating Temperatures: – 40°C to +70°C
  • Humidity: 100%
  • Tropicalization: Encapsulated in epoxy

    UV resistant plastic enclosure

    Conduit connection with rubber gasket seal


  • Dimensions: 99 x 51 x 13 mm

    (3.9 x 2.0 x 0.5 inches)
  • Weight: 0.11 kg / 0.25 lbs
  • Enclosure: IP65
  • Fitting to Module J-box: PG 13.5, M20, 1/2 inch conduit
  • Wire Size: 2.0 mm2 (#14 AWG)
  • Wire Terminations: #8 fork connectors

Bi-color LED

Green Blink 3 Times Successful installation
Green On Solar charging battery
Green Blink Fast In regulation
Green Blink Slow Normal nighttime operation
Red On Controller damaged
Red Blink System problem
LED Off No power


  • Remote Temperature Sensor (RTS)


  • CE Compliant
  • Hazardous Locations: Class 1, Division 2, Groups A-D,

    UL 1604

    CSA 22.2 No. 213-M1987
  • Complies with U.S. National Electric Code
  • Manufactured in a Certified ISO 9001 Facility

Detailed Description

Longer Battery Life

Series PWM with 3 stage charging: bulk, PWM regulation and float. Includes temperature compensation at the controller or alternatively at the battery when using optional remote temperature sensor. Able to charge a zero voltage battery.

The SunKeeper battery charging algorithm is optimized for sealed lead-acid batteries. There are four main stages to the charging algorithm:

  • Night – There is no solar power available, the solar module is disconnected from the battery to prevent nighttime reverse current leakage.
  • Bulk Charge – Solar power is available, the battery is recharging and has not yet reached full state-of-charge.
  • Regulation – The battery has charged to the Regulation setpoint, the SunKeeper is limiting solar charging current to prevent battery overcharge while bringing the battery to full state-of–charge.
  • Float – The battery has reached full state-ofcharge and the SunKeeper has reduced battery voltage to the lower Float setpoint.


  • Temperature Compensation - Lead-acid battery chemistry changes with temperature. The SunKeeper adjusts the Regulation and Float voltage setpoints as temperature changes so that the battery is correctly charged. The user may choose to add an RTS (purchased separately), or use the internal temperature sensor. Temperature compensation can also be disabled.
  • Maximum Charge Voltage – The SunKeeper limits the charge voltage to 15V, regardless of ambient temperature, so that voltage-sensitive DC loads are not damaged.
  • Night Disconnect – The SunKeeper periodically checks for nighttime condition. When night is detected, the SunKeeper disconnects the solar module to prevent reverse current leakage. An external blocking diode is not required.

Rated for Hazardous Locations

Specifically designed for solar power systems in the oil/gas industry. Approved for use in Class 1, Division 2, Groups A,B,C,D.

More Information

Bi-color LED is easy to read from the ground when the solar module is pole-mounted. Indicates solar charging, regulation, normal nighttime operation and any controller or system faults.

Easy to Install

Fits standard half inch conduit knockout (PG 13.5, M20) in module junction box. Quickly fastens with included locknut. Wires have fork connectors for easy connection to solar module terminals.


The SunKeeper is fully protected against system faults listed below. Recovery is automatic except where noted below. Refer to section 3.0 for fault LED indications.

  • Reverse Polarity Solar (LED OFF) – no charging, disconnects solar module until wired with correct polarity.
  • Reverse Polarity Battery (red blinking LED) – no charging, displays fault until battery wired with correct polarity.
  • Short Circuit Solar (LED OFF) – stops charging until short clears or will enter Night stage (LED OFF) if fault persists.
  • Charging Over-current (red blinking LED) – charging current has exceeded SunKeeper current rating; fully automatic recovery; retry every 10 seconds.
  • High Temperature Condition (red blinking LED) – ambient temperature is too high; charging automatically resumes when SunKeeper has cooled to a safe temperature.
  • Temperature Sensor Failure (red blinking LED) – detects a failure in the SunKeeper’s internal temperature sensor or a disconnect of the Remote Temperature Sensor (if used). Fault persists until the problem is corrected.


  • System Wiring: Use copper wire only. Power conductors should be joined or spliced using insulated butt splice solderless crimp connectors or by brazing, welding, or soldering wire ends. If soldered, the spliced joint should be mechanically and electrically secure before soldering. All splices and joints should be covered with insulation equivalent to that of the conductors.
  • System Fusing: The battery positive lead should be fused no further than 12 inches (305 mm) from the battery.
    SK-6 8A fuse
    SK-12 16A fuse
  • Temperature Compensation Select: The SunKeeper has three temperature compensation options. The blue Temperature Compensation Loop can be configured for the following temperature compensation options:
    • Loop not cut: Internal temperature sensor used for temperature compensation (factory default).
    • Loop cut, left open: No temperature compensation. Insulate/cap loose ends.
    • Loop cut, connected to RTS: Remote Temperature Sensor (RTS) used for temperature compensation.
  • Plastic mounting feet are included with the SunKeeper to allow for surface mounting.

Warranty: Five year warranty period. Contact Morningstar for complete terms.

Average Customer Review: Average Customer Review: 4 of 5 4 of 5 Total Reviews: 1 Write a review.

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  2 of 2 people found the following review helpful
4 of 5 Moderate price, poor temp compens, no MPP tracking September 6, 2011
Reviewer: Engineering Guy from Fort Collins, CO United States  
The SK-12 can work reasonably well, designed for easy weather-proof installation with a j-box on a solar panel. Device includes compensation for battery temperature, and pulse width modulation charging. Unfortunately for the battery temperature compensation, which is important, the temperature at each panel (typical installation) is likely substantially different from the battery. A simple remote sensor for battery temperature is the obvious low-cost way to correct. For this design, that device should be included, instead it's a separate option. Temperature compensation is badly skewed without it, so at the base price, charging performance suffers.

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