Victron Cyrix-Li-Charge 24/48V-120A: Intelligent Charge Relay for LiFePO4 Battery Systems

Precision Charge Control for Lithium Battery Protection

The Victron Cyrix-Li-Charge 24/48V-120A is a specialised intelligent charge relay designed to integrate seamlessly with Victron VE.Bus BMS and LiFePO4 battery systems. It acts as a critical second line of defence, automatically connecting and disconnecting chargers to prevent cell overvoltage and over temperature conditions. This ensures your lithium battery bank operates within safe parameters, extending service life and maintaining system reliability.

Unlike generic relays, the Cyrix-Li-Charge responds directly to BMS signals, providing a coordinated protection strategy that reduces the risk of battery damage. Its low current consumption (under 4 mA when open) makes it suitable for energy-conscious installations, while the IP54 rating offers protection against dust and water spray, ideal for demanding mobile and off-grid environments.

How the Cyrix-Li-Charge Enhances System Safety

In a Victron LiFePO4 system, the VE.Bus BMS monitors individual cells. When it detects an imminent overvoltage or high temperature, it signals the Cyrix-Li-Charge to disconnect the charger immediately. This rapid response prevents stress on the cells, which can degrade capacity and lead to premature failure. The relay reconnects the charger after a 3-second delay once conditions normalise, with an adaptive re-engagement logic that extends the delay to 10 minutes after two rapid cycles, avoiding unnecessary switching.

Additionally, the relay disengages after 1 hour if battery voltage remains below 13.5 V (27 V or 54 V for 24/48 V systems), preventing unintended discharge. This intelligent behaviour distinguishes it from simple voltage-sensitive relays, offering tailored protection for lithium chemistry.

Key Features

• BMS-controlled charge disconnect for LiFePO4 batteries
• 120 A continuous rating at 12/24 V; 40 A breaking capacity at 48 V
• Low power draw: less than 4 mA when open
• IP54 protection against dust and water ingress
• Compact design: 46 x 46 x 80 mm for easy integration
• Clear on-device wiring diagram and status LED
• Built-in transient voltage suppression for safe disconnection

Reliable Integration with Victron Energy Ecosystem

The Cyrix-Li-Charge is engineered for straightforward installation within Victron systems. Its control input connects directly to the VE.Bus BMS charge disconnect terminal, ensuring plug-and-play compatibility. The heavy-duty M8 stud terminals (approx. 5/16"-18) accommodate secure cable connections, while the integrated mounting tabs allow firm attachment to flat surfaces. A multi-colour status LED provides immediate visual feedback on relay state, simplifying diagnostics.

For installers and system integrators, this relay eliminates the need for complex external logic, reducing wiring complexity and potential points of failure. It is particularly valuable in applications where chargers cannot be directly controlled by the BMS, such as alternators or non-Victron chargers.

Applications for Mobile and Off-Grid Power

This charge relay is suited to a range of scenarios where lithium battery protection is paramount:

• Marine electrical systems with LiFePO4 house banks
• RV and caravan solar setups using Victron components
• Off-grid cabins and remote power systems
• Commercial vehicle auxiliary power
• Industrial backup systems requiring precise charge control

By ensuring chargers only operate when safe, the Cyrix-Li-Charge helps maintain battery health in environments where temperature extremes and variable charging sources are common.

Protect Your Lithium Investment

Incorporate the Victron Cyrix-Li-Charge 24/48V-120A into your energy system to safeguard your LiFePO4 batteries against overcharge events. Its intelligent, BMS-driven operation provides peace of mind, whether you're at sea, on the road, or managing a remote installation. Add this essential protection to your setup today.