Victron Cyrix-Li Battery Combiner and Disconnect Guide

Key Takeaways

• Select the correct Cyrix-Li variant to isolate DC loads, control charge sources, or combine battery systems.
• Connect the control terminal directly to the VE.Bus BMS output to ensure automatic protection without manual intervention.
• Respect continuous current limits of 120A or 230A at 12V/24V and observe reduced breaking capacity on 48V DC circuits.
• Monitor LED flash patterns on 230A models to distinguish between normal standby operation and critical overvoltage or temperature alarms.

How do Cyrix-Li switches protect lithium battery banks and combine charging circuits?

Victron Cyrix-Li switches are microprocessor-controlled solid relays designed for LiFePO4 energy storage systems. They interface directly with a VE.Bus BMS to automatically disconnect loads during low-voltage events, isolate chargers during overvoltage or temperature extremes, and combine starter and lithium banks with minimal standby power consumption.

Cyrix-Li Functional Variants and Circuit Roles

Lithium iron phosphate cells require independent control over charge and discharge paths. Victron provides three purpose-built Cyrix configurations:

• Cyrix-Li-load: Intercepts DC distribution circuits supplying inverter loads or DC appliances. The switch disengages immediately when the BMS control input goes free floating or low due to low cell voltage to isolate the bank. To prevent oscillatory cycling, if the contact attempts to re-engage 3 times under recurring load drops, it locks out until battery voltage exceeds 13V (26V for 24V banks, 52V for 48V banks) for at least 30 seconds.
• Cyrix-Li-Charge: Controls battery chargers, solar charge controllers, or alternator feeds to isolate charging circuits. It closes after a 3 seconds delay once the BMS Charge Disconnect signal goes high, provided it detects at least 13.0V (26.0V on 24V, 52.0V on 48V) on the charger terminal and 2V or more on the battery terminal. While engaged, it disengages once every 1 hour to test whether the charge source remains active.
• Cyrix-Li-ct: Combines a lead-acid starter battery and a LiFePO4 auxiliary battery. It closes when one terminal senses 13.4V (or 26.8V) or higher, and disengages when battery voltage drops below 13.2V (or 26.4V) or when the BMS signals high cell voltage. It features an emergency start assist feature where a short negative pulse holds the relay closed for 30 seconds.

Hardware Specifications and Breaking Capacities

Cyrix-Li combiners are engineered for heavy-duty DC environments across two primary current ratings:

Control Wiring and System Integration Procedure

Integrating a Cyrix-Li device into your DC power system involves four key wiring steps:

1. Mount the Contactor: Install the IP54 enclosure on a flat vertical surface near your battery bank or Lynx Distributor DC busbar.
2. Connect Power Cables: Terminate high-current conductors to the threaded copper studs using appropriately sized cable lugs and torque specifications.
3. Wire Ground Reference: Connect the thin negative wire to the system common negative busbar to energize the internal logic circuit.
4. Connect BMS Signal: Wire the control input terminal directly to the corresponding VE.Bus BMS Load Disconnect or Charge Disconnect output.

For comprehensive battery telemetry, monitor total current flowing through your combiner using a battery monitor or integrate the system with a Victron MultiPlus-II inverter-charger.

Optical LED Status Diagnostics on 230A Chassis

The 230A models include an optical status LED indicating operational state and fault conditions:

• Continuous LED On: Relay contacts are fully closed and carrying current.
• 10-Second Flash: Relay is open in normal standby mode.
• 2-Second Flash: Relay is verifying voltage stability prior to closing.
• 2-Second Blink: Relay is opening due to voltage drop or BMS signal loss.
• 0.25-Second Rapid Blink: System alarm triggered by over temperature, voltage exceeding 16V, both batteries falling below 10V, or a single battery below 2V.

Safety and Overcurrent Protection Guidelines

Always fit appropriately rated fuses on positive conductors entering the Cyrix terminals to safeguard against short circuits. Never bridge the control input terminal to bypass BMS safety protection during cell imbalance conditions.

When to Seek Professional Support

If your Cyrix-Li switch exhibits continuous rapid alarm blinking, fails to engage after battery voltage recovery, or produces abnormal contact resistance under load, consult an authorized Victron Energy technician to test internal coil resistance and BMS communication signaling.\n