Victron Cyrix-Li-Intelligent Charge Relay 12/24V-120A

Victron Cyrix-Li-Intelligent Charge Relay 12/24V-120AVictron Cyrix Li Charge 12 24V 120A: Intelligent Charge Relay for LiFePO4 Battery Systems Precision Charge Control for Lithium Battery Protection The Victron Cyrix Li Charge 12 24V 120A is a specialised intelligent charge relay designed to integrate seamlessly with Victron VE. Bus BMS and LiFePO4 lithium batteries. It acts as a critical secondary protection layer, automatically connecting and disconnecting charging sources to prevent cell overvoltage

Victron Cyrix-Li-Charge 12/24V-120A: Intelligent Charge Relay for LiFePO4 Battery Systems

Precision Charge Control for Lithium Battery Protection

The Victron Cyrix-Li-Charge 12/24V-120A is a specialised intelligent charge relay designed to integrate seamlessly with Victron VE.Bus BMS and LiFePO4 lithium batteries. It acts as a critical secondary protection layer, automatically connecting and disconnecting charging sources to prevent cell overvoltage and over temperature conditions. Unlike generic relays, the Cyrix-Li-Charge responds instantly to BMS signals, ensuring your expensive lithium battery bank remains within safe operating limits at all times.

Engineered for 12V and 24V DC systems, this relay handles continuous currents up to 120A, making it suitable for high-power chargers and alternators. Its intelligent logic monitors both the BMS control input and battery voltage, providing automated reconnection only when conditions are safe. This reduces the risk of battery damage from faulty chargers or unexpected voltage spikes, a common issue in mobile and off-grid installations.

How the Cyrix-Li-Charge Protects Your Investment

In a Victron lithium system, the VE.Bus BMS serves as the primary safeguard. However, not all chargers can be directly controlled by the BMS. The Cyrix-Li-Charge bridges this gap by acting as a controllable switch. When the BMS detects an imminent cell overvoltage or high temperature (above 50°C), it sends a signal to the Cyrix, which disengages immediately—cutting off the charging source within milliseconds. This rapid response prevents thermal runaway and extends battery lifespan.

After disconnection, the relay intelligently manages reconnection. It waits for the BMS signal to return high and verifies that the charger output is above 13.7V (12V system) or 27.4V (24V system). A 3-second delay ensures stability before re-engaging. If repeated faults occur, the delay extends to 10 minutes, preventing rapid cycling that could stress system components. Additionally, if battery voltage drops below 13.5V (27V for 24V) for an hour, the relay disengages to avoid unnecessary drain.

Key Features at a Glance

• Instant BMS-driven disconnection for overvoltage and over temperature protection
• 120A continuous rating at 12V/24V, with 40A breaking capacity at 48V
• Automatic reconnection logic with progressive delays to prevent cycling
• Low power consumption (<4mA when open) ideal for energy-conscious systems
• Compact, robust design (46x46x80mm, 0.11kg) with IP54 protection
• Built-in transient voltage suppression to protect against inductive spikes
• Clear status LED for quick operational diagnostics

Seamless Integration with Victron Energy Systems

The Cyrix-Li-Charge is purpose-built for Victron's ecosystem, connecting directly to the VE.Bus BMS control output. It requires a minimum of 2V on its battery terminal to operate, ensuring it remains open if accidentally disconnected from the battery—a safety feature that prevents uncontrolled charging. The relay's 3/8"-16 (Approx. M10) stud terminals accommodate heavy-duty lugs up to 4/0 AWG (approx. 95mm²), ensuring secure, low-resistance connections for high-current applications.

For installers, the integrated mounting tabs and pre-drilled holes simplify fixed installations in battery compartments, engine bays, or electrical cabinets. The IP54 rating provides protection against dust and water splashes, making it reliable in marine, RV, and off-grid environments where conditions can be harsh.

Applications: Where Precision Charging Matters

This relay is essential for any Victron lithium setup where charging sources cannot be directly managed by the BMS. Typical use cases include:

• Marine and RV electrical systems with high-output alternators or shore power chargers
• Off-grid solar installations using MPPT controllers that lack BMS communication
• Backup power systems where generator or grid chargers need automated disconnect
• Industrial battery banks requiring fail-safe charge termination

By isolating the charger during fault conditions, the Cyrix-Li-Charge prevents overcharging that could lead to cell degradation or safety hazards. It also eliminates the need for manual intervention, allowing unattended systems to operate safely.

Why Choose the Cyrix-Li-Charge Over Generic Relays?

Standard automotive relays lack the intelligence to interpret BMS signals or monitor voltage thresholds. They simply switch on or off, offering no protection against overvoltage or temperature extremes. The Cyrix-Li-Charge, in contrast, actively communicates with the BMS and applies conditional logic to ensure charging only occurs when safe. This reduces the risk of battery failure, which can be costly and dangerous in lithium systems.

Additionally, the built-in transient voltage suppressor protects against voltage spikes that occur when the relay disconnects under load—a common cause of contact welding in inferior relays. This extends the relay's operational life and maintains system integrity.

Installation and Compatibility Notes

The Cyrix-Li-Charge is designed for use with Victron LiFePO4 batteries and the VE.Bus BMS. It is not a standalone battery protect device; for load disconnection, consider the Victron BatteryProtect. Always ensure proper fusing and cable sizing according to system current. The relay's control input engages when high (approx. battery voltage) and disengages when free-floating or pulled low, making it compatible with standard BMS outputs.

For systems requiring combined charging and load control, the Cyrix-Li-ct (battery combiner) or Cyrix-Li-load (load disconnect) variants may be more appropriate. Contact our team for assistance with system design if you're unsure which model suits your application.

Secure Your Lithium Battery System Today

Protect your investment with the Victron Cyrix-Li-Charge 12/24V-120A. Whether you're upgrading an existing installation or building a new off-grid power system, this intelligent relay provides the precision control needed for safe, reliable lithium charging. Order now to ensure your battery bank operates within safe limits, every cycle.