MorningStar SunSaver 20 Amp 24 Volt PWM Charge Controller

Options: LVD Override Protection
Manufacturer Part Number: SL-20L-24V

Morningstar’s advanced SunLight (SL-20L-24V) solar charge controller combines the SunSaver design with a microcontroller for automatic lighting control functions.

This technology provides:

• Proven Reliability
• Precise Lighting Control
• PWM Battery Charging

The MorningStar SunLight controllers combine the features of the SunSaver controllers (including LVD) with an adjustable automatic lighting control circuit. This allows you to connect a DC light and have it come on at dusk for a set period of time or dusk-to-dawn. It's 10 position rotary switch lets you choose exactly how your DC light will operate.

Features

Three Versions Available:

• 12 Volt: 10 and 20 amp ratings
• 24 Volt: 10 amp rating

General

• Microcontroller digital accuracy
• Fully automatic operation
• Ten field adjustable lighting control options
• Special on/off/on functions
• Manual test capability
• LVD override protection
• Detects day and night using the PV array
• Suitable for all 12/24 Vdc lamps
• Sealed/Flooded battery select
• Temperature compensation
• Parallel with a SunSaver for 40 amps solar
• Includes SunSaver battery charging circuit

Operation

• Rotary digital switch to select among 10 lighting options (see back)
• Test button flashes red LED to confirm correct rotary switch selection
• Test button turns lights on for 5 minutes (in LVD limited to 3 times)
• LVD overrides lighting timer
• Sunrise overrides lighting timer
• Timer accuracy is within 2 seconds

Specifications

LED Indicators

Green: The green LED indicator will light whenever sunlight is available for battery charging. The green LED will turn off at night. Because the SunLight uses a PWM constant voltage charging process, there is usually some amount of energy going into the battery at all times. Although the charging current falls to very low levels when the battery reaches full charge, the green LED will continue to stay ON all day. This is to indicate that the controller is working and that energy is available from the PV array for charging.

Red: The red LED is an indicator for 3 different functions:

• Automatic low voltage load disconnect (LVD) If the battery charge state falls below the LVD setpoint, the light will be disconnected and the red LED will light. This indicates the controller has disconnected the load to protect the battery from further discharge and possible damage. The red LED will turn off when the battery recovers to about 50% of its rated capacity and the load is automatically reconnected.
• Initial controller start-up When the SunLight is properly connected to the battery, the red LED will flash 3 times.
• Confirm lighting control selection When the TEST button is pressed, the red LED will confirm the lighting control option selected by the rotary switch

Lighting Control

To select a lighting option, turn the rotary digital switch to the desired position. An arrow in the rotary switch will point to the selected position. This is a digital switch, so it will click into each of the ten positions:

Mechanical

• Wire size: #10 AWG (5.2 mm2)
• Anodized aluminum case
• Marine rated terminals
• Epoxy encapsulated
• Weight: 9 oz (0.26 kg)

Detailed Description

Protections

• Polarity Protection

  The SunLight is generally protected from reversed connections, but the system operator and other equipment will be at risk when polarities (+ and –) are reversed. Carefully check before making each connection to be certain the polarity is correct.

• Brownout Protection

  If battery voltage sags below 8 volts for any reason (such as pressing TEST in LVD with a weak battery), the microcontroller may reset. This is to prevent a low voltage condition from causing the microcontroller to lock-up at an unattended site. Note that a brownout reset will begin a new start-up sequence for measuring night length.

Functions

• 100% Solid State

  All power switching is done with FETs. No mechanical relays are used in the controller.

• Battery Charge Regulation

  SunLight uses an advanced series PWM charge control for constant voltage battery charging. A true 0 to 100% PWM duty cycle is very fast and stable for positive charge control under all system conditions.

• Day-Night Transition

  The SunLight uses the solar array to detect day and night. The transition to night requires a solar insolation level less than 2 percent. The transition back to day requires a high solar array open-circuit voltage. Both state changes require 10 minutes of continuous transition values before making the change. These constraints avoid false transitions due to lightning or dark storm clouds.

• Measure Night Length

  The LIGHTING CONTROL options that turn the lights on again before sunrise require that the SunLight measure the length of the night. Therefore, the controller cannot turn the lights on before sunrise the first night after installation (or after reconnecting the battery). If the solar array is disconnected during service, the controller will then measure a faulty night length. Either reset the controller by reconnecting the battery, or this short “night” will be automatically corrected by the controller after 4 days of service.

• Temperature Compensation

  A sensor next to the green LED measures ambient temperature conditions. The SunLight corrects the constant voltage setpoint –27 (or –54) mV per °C with a 25°C reference. This correction matches the battery charging to the changing electrochemical properties of the battery, and works best if the battery and controller are in a similar thermal environment.

• Sealed / Flooded Select

  Flooded batteries require more vigorous charging to avoid stratification, and sealed batteries require precise control to avoid outgassing. The SunLight constant voltage setpoints are 14.4 volts for flooded batteries, and 14.1 volts for 12 volt sealed batteries.

• LED Indicators


• Low Voltage Disconnect (LVD)

  If the battery falls below 11.7 (or 23.4) volts, the load is disconnected from the battery to protect against harmful deep discharges. A one minute delay prevents load disconnects from transients. The load is automatically reconnected when the battery voltage recovers to 12.8 (or 25.6) volts.

• Battery Disconnect

  If the battery is disconnected during the daytime, the PV array will continue to provide power to the controller. The SunLight will immediately go into PWM and provide power at a constant voltage to the load. This will continue as long as sufficient power is available from the PV array.

• Parallel Controllers

  Morningstar controllers work very well in parallel configurations. No blocking diodes are required. The only constraint is that each controller must have an independent and separate PV subarray and load. Make sure that each controller’s rating for PV and load current is not exceeded.

• Auxiliary Generators

  Engine generators and other sources of power may be connected directly to the battery for charging. It is not necessary to disconnect the SunLight from the battery. However, do not use the SunLight to regulate these other generators.

• Reverse Current

  The SunLight prevents the battery from discharging through the PV array at night. There is no need to install a blocking diode for this purpose.

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