Mastervolt MLI Ultra Lithium-Ion Batteries

Mastervolt MLI Ultra batteries deliver high-performance lithium power for demanding marine, mobile, off-grid and industrial installations.

Premium Lithium Iron Phosphate cells are combined with Mastervolt’s proprietary Battery Management System in a robust housing designed to withstand high charge and discharge currents, moisture, mechanical shock and vibration.

Integrated battery monitoring provides accurate information including voltage, current, consumed capacity and state of charge. MasterBus, CZone and NMEA 2000 communication allows the battery to exchange operating information with compatible charging, monitoring and power-management equipment.

A self-learning balancing algorithm predicts the behaviour of each individual cell and balances the cells proactively. This improves charging efficiency, reduces unnecessary cell stress and helps maximise battery service life.

MLI Ultra batteries provide up to 70% savings in space and weight compared with traditional batteries, support rapid charging and deliver approximately 3,500 cycles at 80% depth of discharge under Mastervolt’s specified test conditions.

The MLI Ultra 1250 models feature an integrated battery safety switch and thermal heating pad. The larger MLI Ultra 3000 and 6000 models require an external safety relay as a mandatory part of the installation.

Product details are based on Mastervolt’s current official MLI Ultra range, including the MLI Ultra 1250, MLI Ultra 12/3000, MLI Ultra 12/6000 and MLI Ultra 24/6000.

Key Features

• Heavy-duty LiFePO4 battery technology
• Integrated Mastervolt Battery Management System
• Self-learning cell-balancing algorithm
• Approximately 3,500 cycles at 80% depth of discharge
• Fast charging within approximately 60 minutes
• Up to 70% savings in space and weight
• Integrated battery monitoring
• MasterBus communication
• CZone and NMEA 2000 compatibility
• High charge and discharge capability
• Overvoltage, undervoltage and overtemperature protection
• M8 battery terminals
• IP65-rated electronics compartment
• Upright or long-side installation
• Series and parallel connection options
• Designed and tested for demanding marine and mobile environments

Typical Applications

• Marine service battery banks
• Sailing yachts and motorboats
• Commercial marine installations
• Motorhomes and campervans
• Emergency and specialist vehicles
• High-power inverter systems
• Off-grid energy systems
• Industrial power storage
• Hybrid power systems
• Rapid-charging applications

Available Models

Dimensions include terminals and grip handles and are stated as length × width × height.

Electrical Performance

Communication and Monitoring

Every current MLI Ultra model supports:

• MasterBus
• CZone
• NMEA 2000
• Integrated voltage monitoring
• Integrated current monitoring
• State-of-charge information
• Battery condition and protection data

Communication with compatible Mastervolt equipment enables coordinated charging and system monitoring.

MLI Ultra 1250 Features

The 12/1250 and 24/1250 include several features specific to the compact range:

• Integrated battery safety switch
• Integrated thermal heating pad
• Low-temperature charging control
• Automatic configuration with supported Mastervolt chargers
• Fully waterproof housing
• Drop-in format for Group 31 and Group 49 battery spaces
• Series connection up to 48V

The heating system uses power from the connected charger to warm the battery cells when charging in freezing conditions.

MLI Ultra 3000 and 6000 Safety Relay Requirement

Mastervolt specifies an external safety relay as a mandatory component for the larger MLI Ultra models.

The MLI Ultra 1250 models already contain an integrated safety switch.

The appropriate fuse, cabling, isolation and communication accessories must be selected separately according to the system design.

Connection Options

*System design, protection, communication and installation must comply with the current Mastervolt manual. High-voltage installations require additional safety measures.

Certifications and Compliance

Depending on the selected model, the MLI Ultra range carries or complies with:

• UN 38.3
• CE
• E-Mark
• FCC
• RVIA
• UL1642 for battery cells
• RINA type approval on the MLI Ultra 24/6000

Certification requirements should be confirmed against the selected model and installation.

Important Installation Information

MLI Ultra batteries are advanced system batteries and should not be treated as simple drop-in replacements without reviewing the complete electrical installation.

Installation must account for:

• Compatible lithium charging equipment
• Correct MasterBus, CZone or NMEA 2000 communication
• Required external safety relay
• Appropriate Class-T or manufacturer-approved fuse protection
• Correctly sized battery cables
• Suitable battery isolation
• Alternator charge control
• Correct system configuration and commissioning

Professional installation is strongly recommended.

Delivery Information

Delivery or Collection

A €75 pallet delivery surcharge applies when shipment is required. Available for delivery within Ireland only. Collection may also be selected where available.

Lithium batteries are subject to specific transport requirements and delivery arrangements may vary by location.