SRNE ML Series MPPT Solar Charge Controller User Manual

1. Product Introduction

1.1 Product Overview

The SRNE ML Series MPPT Solar Charge Controller is designed to efficiently manage power from solar panels to charge batteries in off-grid photovoltaic systems. It continuously monitors the solar panel's generating power and tracks the maximum power point (MPPT) to optimize charging. The controller features an LCD screen for displaying operating status, parameters, and logs, allowing users to monitor and modify settings. It supports standard Modbus communication protocol for remote monitoring and includes comprehensive electronic fault self-detection and protection functions to prevent damage from installation errors or system failures.

1.2 Product Features

• Advanced MPPT Technology: Utilizes dual-peak or multi-peak tracking for accurate maximum power point tracking, even with shadowed panels.
• High Efficiency: Built-in MPPT algorithm significantly improves energy utilization efficiency by 15% to 20% compared to conventional PWM methods, with an optimum MPPT tracking efficiency of up to 99.9%.
• Digital Power Supply: Advanced digital power supply technologies ensure circuit energy conversion efficiency up to 98%.
• Battery Compatibility: Supports various battery types including gel, sealed, open, and lithium batteries.
• Limited Current Charging: Automatically lowers charging power and current to the rated level when solar panel power exceeds a certain threshold.
• Load Support: Supports instantaneous large current startup of capacitive loads.
• Automatic Battery Voltage Recognition: Automatically detects and adapts to battery voltage.
• Fault Indication: LED fault indicators and an LCD screen display abnormality information for quick system fault identification.
• Data Storage: Historical data storage function available for up to a year.
• Communication: Equipped with LCD screen for data monitoring and parameter modification. Supports standard Modbus protocol for communication.
• Protection Mechanisms: Built-in over-temperature protection, temperature compensation for extended battery life, and TVS lighting protection.

1.3 Exterior and Interfaces

The controller features several key interfaces and indicators:

• Charging Indicator (①): Indicates the controller's current charging mode.
• Battery Indicator (②): Indicates the battery's current state.
• Load Indicator (③): Indicates the load's On/Off state.
• Abnormality Indicator (④): Indicates system malfunctions.
• LCD Screen (⑤): Displays operating data and parameters.
• Operating Keys (⑥): For navigation and setting parameters.
• Installation Hole (⑦): For mounting the controller.
• Solar Panel + Interface (⑧) & Solar Panel - Interface (⑨): Connections for the photovoltaic array.
• Battery + Interface (⑩) & Battery - Interface (⑪): Connections for the battery.
• Load + Interface (⑫) & Load - Interface (⑬): Connections for the DC load.
• External Temperature Sampling Interface (⑭): For connecting an external temperature sensor.
• RS232/RS485 Communication Interface (⑮): For communication with external devices or monitoring software.

1.4 Introduction to Maximum Power Point Tracking Technology (MPPT)

MPPT is an advanced charging technology that optimizes power output from solar panels. Solar arrays have a maximum energy output point (MPPT) on their power curves. Unlike conventional controllers, an MPPT controller continuously tracks this point by adjusting the solar panel's input voltage and current in real time, ensuring maximum power delivery to the battery. For example, in a 12V system, if the solar panel's peak voltage is 17V and the battery is 12V, a conventional controller would limit the panel voltage to 12V, losing potential power. An MPPT controller, however, adjusts to deliver the maximum possible power.

1.5 Charging Stages Introduction

The charging process involves several stages to ensure optimal battery health and performance. MPPT is used during the fast charging stage, alongside boost charging, floating charging, and equalizing charging.

• Fast Charging: The controller performs MPPT charging with maximum solar power until the battery reaches the set equalizing/boost voltage. Constant voltage charging then begins.
• Sustaining Charging: Once the battery reaches the sustaining voltage, the controller switches to constant voltage charging. MPPT is not performed, and the charging current gradually decreases. This stage includes equalizing charging (activated every 30 days) and boost charging (default 2 hours, adjustable).
• Floating Charging: After sustaining charging, the controller lowers the battery voltage by diminishing the charging current, maintaining the battery at a full state. Loads can access most solar power during this stage. If loads consume more power than the solar panel provides, the controller will exit floating charging and re-enter fast charging.

2. Safety Instructions

Please read this manual carefully before operating the controller and complete safety operation training. Failure to follow these instructions may result in injury or damage.

• This controller deals with voltages that exceed human safety limits.
• Do not attempt to disassemble or repair the controller, as it contains no user-serviceable internal components.
• Install the controller indoors, away from direct sunlight, high temperatures, and water intrusion. Ensure good ventilation, as the radiator can reach high temperatures during operation.
• It is recommended to install a fuse or breaker outside the controller.
• Before installation and wiring, disconnect the photovoltaic array and the fuse or breaker near the battery terminals.
• After installation, verify all connections are solid and reliable to prevent loose connections and heat accumulation.

⚠ Warning: Indicates dangerous operations requiring proper preparation.

⚡ Note: Indicates operations that may cause damage.

💡 Tips: Provides advice or instructions for the operator.

3. Product Installation

3.1 Installation Precautions

• Battery Handling: Be very careful when installing batteries. For open lead-acid batteries, wear goggles. Flush with water immediately if battery acid contacts skin.
• Prevent Short Circuits: Do not place metal objects near the battery.
• Ventilation: Ensure the ambient environment is well ventilated, as acid gas may be generated during battery charging. Keep the battery away from fire sparks.
• Outdoor Installation: If installing outdoors, protect the battery from direct sunlight and rainwater.
• Connections: Loose or corroded wires can cause excessive heat. Ensure all connections are tightened securely. Fix wires properly with ties to prevent swaying.
• High Voltage Warning: The output terminal's voltage may exceed human safety limits. Use insulation tools and keep hands dry if operation is needed.
• Battery Configuration: The controller can connect to a single battery or a pack. Follow battery manufacturer's safety advice.
• Wiring Density: Select connection wires with a current density not larger than 4A/mm².
• Grounding: Connect the controller's earth terminal to the ground.

⚠ Warning: Risk of explosion! Never install the controller and an open battery in the same enclosed space, or where battery gas may accumulate.

⚠ Warning: Danger of high voltage! Photovoltaic arrays can produce very high open-circuit voltage. Open the breaker or fuse before wiring, and be very careful during the wiring process.

⚡ Note: Ensure sufficient airflow around the controller's radiator. Leave at least 150 mm of space above and below the controller for natural convection. If installed in an enclosed box, ensure reliable heat dissipation.

3.2 Wiring Specifications

Wiring and installation must comply with national and local electrical specifications. Select battery and load wiring according to rated currents. Refer to the table below for wiring specifications:

3.3 Installation and Wiring

Follow these steps for installation and wiring:

1. Choose Installation Site: Select a location indoors, away from direct sunlight, high temperatures, and water. Ensure good ventilation.
2. Mark Mounting Points: Place the installation guide plate, mark the 4 mounting points, and drill holes.
3. Fix Controller: Align the controller's fixing holes with the drilled holes and mount the controller.
4. Wire Connections: Remove the two screws on the controller.

⚠ Warning: Risk of electric shock! Install fuses or breakers on the photovoltaic array, load, and battery sides. Ensure fuses/breakers are open before wiring.

⚠ Warning: Danger of high voltage! Photovoltaic arrays can produce very high open-circuit voltage. Open the breaker or fuse before wiring, and be very careful during the wiring process.

⚠ Warning: Risk of explosion! Short-circuiting battery terminals can cause fire or explosion. Exercise extreme caution.

Wiring Order:

1. Connect the battery first.
2. Connect the load.
3. Connect the solar panel.

Power On:

1. After connecting all power wires, check for correct wiring and polarity.
2. Close the fuse or breaker of the battery. Observe if LED indicators light up and the LCD screen displays information. If not, recheck connections.
3. If the battery functions normally, connect the solar panel. If sunlight is sufficient, the charging indicator will light up or flash, and charging will begin.
4. Finally, close the fuse or breaker of the load. Manually test the load's on/off function.

⚠ Warning: Disconnecting the battery during normal charging can negatively affect DC loads and potentially damage them.

⚠ Warning: If battery poles are reversely connected within 10 minutes after charging stops, internal components may be damaged.

⚡ Note:

• Install the battery's fuse or breaker as close to the battery as possible (recommended distance not more than 150mm).
• If no remote temperature sensor is connected, the battery temperature defaults to 25 °C.
• If an inverter is used, connect it directly to the battery, not to the controller's load terminals.

4. Product Operation and Display

4.1 LED Indicators

The controller has several LED indicators to show its status:

• PV Array Indicator: Indicates the controller's current charging mode.
• BAT Indicator: Indicates the battery's current state.
• LOAD Indicator: Indicates the load's On/Off and state.
• ERROR Indicator: Indicates whether the controller is functioning normally.

4.2 Key Operations

The controller features four keys for navigation and settings:

• Up (▲): Page up; increase parameter value in setting.
• Down (▼): Page down; decrease parameter value in setting.
• Return (↶): Return to previous menu (exit without saving).
• Set (↵): Enter into sub-menu/save; turn on/off loads (in manual mode).

4.3 LCD Startup and Main Interface

Upon startup, the four indicators will flash successively, followed by a self-inspection. The LCD screen will then display the battery's voltage level, which is either a fixed voltage selected by the user or an automatically recognized voltage.

The main interface displays key system information, including:

• Main monitoring page
• Component voltage
• Charging current
• Abnormality code
• Battery voltage
• Load mode
• Load current
• Device temperature
• Discharging capacity
• Charging capacity

4.4 Load Mode Setting Interface

The controller offers 5 load operating modes:

1. Sole Light Control (0): Load switches on when no sunlight is present (PV voltage below light control on voltage) and off when sunlight emerges (PV voltage above light control off voltage), after a time delay.
2. Light Control + Time Control (1-14): Similar to sole light control, but the load switches off after working for a preset period of time (1 to 14 hours).
3. Manual Mode (15): User can manually switch the load on or off using the keys, regardless of day or night. Useful for debugging and specific loads.
4. Debugging Mode (16): Used for system debugging. Load is shut off with light signals, and switched on without light signals.
5. Normal On Mode (17): Load remains continuously on, suitable for loads requiring 24-hour power supply.

To adjust load mode: Press and hold the Set key to enter, use Up/Down keys to select mode, then press and hold Set to save and exit. Tap Return to exit without saving.

Manual Load On/Off: In Manual Mode (15), tap the Set key on any main interface to switch the load on/off.

4.5 System Parameter Settings

To enter the parameter setting interface, press and hold the Set key from any interface other than load modes. Use Up/Down keys to adjust values and Set key to save. Tap Return to exit without saving.

⚡ Note: After changing system voltage, the power supply must be switched off and then on again for the new setting to take effect.

The controller allows customization of parameters. Parameter settings must be done under professional guidance to avoid system malfunction. Refer to the table below for parameter setting cross-reference:

5. Product Protection Functions and System Maintenance

5.1 Protection Functions

• Waterproof: IP32 rated.
• Input Power Limiting Protection: Limits solar panel power to the rated power to prevent damage from excessive currents.
• Battery Reverse Connection Protection: Prevents damage to the controller if the battery is reversely connected.
• Photovoltaic Input Side Too High Voltage Protection: Automatically cuts off PV input if voltage is too high.
• Photovoltaic Input Side Short-Circuit Protection: Halts charging if PV input is short-circuited and resumes when cleared.
• Photovoltaic Input Reverse-Connection Protection: Prevents breakdown if PV array is reversely connected.
• Load Overpower Protection: Enters delay protection if load power exceeds rated value.
• Load Short-Circuit Protection: Quickly implements protection and attempts to switch on the load again after a delay (up to 5 times/day).
• Reverse Charging Protection at Night: Prevents battery discharge through the solar panel.
• TVS Lighting Protection: Provides protection against lightning surges.
• Over-Temperature Protection: Decreases charging power or halts charging if controller temperature exceeds set value.

5.2 System Maintenance

To maintain optimal performance, check the following items twice a year:

• Ensure airflow around the controller is not blocked; clear dirt or debris from the radiator.
• Check for damaged wire insulation (due to sunlight, friction, rodents, etc.). Repair or replace as necessary.
• Verify indicators function correctly. Address any faults or displayed errors.
• Check all wiring terminals for corrosion, insulation damage, overheat, or discoloration. Tighten terminal screws firmly.
• Clean any dirt, nesting insects, or corrosion.
• If the lightning arrester has lost efficacy, replace it promptly.

⚠ Warning: Risk of electric shock! Always cut off all power supplies before performing checks or operations.

5.3 Abnormality Display and Warnings

The controller displays abnormality codes on the LCD screen to help identify issues:

6. Product Specification Parameters

6.1 Electric Parameters

6.2 Battery Type Default Parameters (Monitor Software Settings)

When selecting 'User' as the battery type, parameters are self-customized. Default system voltage parameters align with sealed lead-acid batteries. When modifying charging and discharging parameters, adhere to the following rules:

• Over-voltage cut-off voltage > Charging limit voltage ≥ Equalizing voltage ≥ Boost voltage ≥ Floating charging voltage > Boost return voltage.
• Over-voltage cut-off voltage > Over-voltage cut-off return voltage.
• Low-voltage cut-off return voltage > Low-voltage cut-off voltage ≥ Discharging limit voltage.
• Under-voltage warning return voltage > Under-voltage warning voltage ≥ Discharging limit voltage.
• Boost return voltage > Low-voltage cut-off return voltage.

6.3 Conversion Efficiency Curve

The conversion efficiency of the SRNE ML Series MPPT Solar Charge Controller is high, especially for 12V and 24V systems. The curves illustrate how efficiency varies with output power and different maximum power point voltages (Vmp).

MPPT 12V Conversion Efficiency (12V Battery)

The efficiency for a 12V battery system generally stays above 90%, reaching up to 95% or more, across various output power levels and Vmp values (20Vmp, 40Vmp, 60Vmp, 75Vmp).

MPPT 24V Conversion Efficiency (24V Battery)

For a 24V battery system, the conversion efficiency consistently remains above 90%, often exceeding 96%, for different output power levels and Vmp values (40Vmp, 50Vmp, 60Vmp, 75Vmp).

6.4 Product Dimensions

The physical dimensions of the controllers vary by model:

ML2420:

• Product dimensions: 210*151*59.5mm
• Hole positions: 154*131mm
• Hole diameter: Φ3mm
• Applicable wire: max. 8 AWG

ML2430/ML2440:

• Product dimensions: 238*173*72.5mm
• Hole positions: 180*147mm
• Hole diameter: Φ3mm
• Applicable wire: max. 8 AWG

7. User Tips

• Performance in Cloudy Weather: Users have noted that the SRNE controller performs exceptionally well in cloudy conditions, generating significantly more power compared to some other trackers. This makes it a strong choice for environments with variable sunlight.
• Energy Absorption: The device is effective at maximizing energy absorption from solar panels, contributing to efficient system operation.
• Interface and Build Quality: The controller features a convenient interface and a high-quality plastic casing, indicating good usability and durability.
• Monitoring Watts: While some models (e.g., Z-) may only display Amps and Volts, and not Watts directly, Watts can be easily calculated by multiplying Amps and Volts.

8. Frequently Asked Questions (FAQ)

Q: What does error code E3 represent?

A: Error code E3 indicates an "Under-voltage warning." The controller will show a battery level indication, and the ERROR indicator will be steady on.