Victron Cyrix-Li-Charge 120A Battery Combiner

The Victron Cyrix-Li-Charge 120A is a microprocessor-controlled, VE.Bus BMS-managed battery combiner designed to automatically connect and disconnect an alternator, charger, or other charging source to a Victron LiFePO₄ battery bank — acting as a second line of protection against cell overvoltage and overtemperature in lithium battery systems. Available in two voltage versions — 12/24V (CYR010120430) and 24/48V (CYR020120430) — both rated at 120A continuous, it provides automatic charge switching without any voltage drop, making it a direct replacement for diode isolators in lithium battery installations.

The Cyrix-Li-Charge works in combination with the VE.Bus BMS or SmallBMS. The Charge Disconnect output of the BMS — which is normally high and goes free floating in the event of cell overvoltage or overtemperature — is connected to the control input of the Cyrix-Li-Charge. When the BMS output is high (normal operation) and the charger output voltage is at or above the connect threshold (13.0V for 12V systems, 26.0V for 24V systems, 52.0V for 48V systems), the Cyrix-Li-Charge connects the charger to the battery after a 3-second delay. When the BMS Charge Disconnect output goes free floating — signalling a cell overvoltage or overtemperature fault — the Cyrix-Li-Charge disconnects the charger immediately, protecting the lithium battery bank.

The Cyrix-Li-Charge addresses the need to control chargers and charging sources that cannot be directly switched off by the VE.Bus BMS Charge Disconnect output — such as high-current alternators, standalone battery chargers, and DC-DC converters that require a relay to break the charging circuit rather than a signal wire to disable them. A built-in transient voltage suppressor limits voltage spikes that may occur when the Cyrix-Li-Charge suddenly disconnects a charging source, protecting both the Cyrix and connected equipment from transient damage.

Both the 12/24V and 24/48V versions are identical in physical size, current rating, and functionality — the difference is the voltage range of operation, with the 24/48V version supporting 24V and 48V lithium battery systems. Both variants are rated IP54 for dust and water splash resistance, making them suitable for marine, RV, and off-grid installations.

Features

VE.Bus BMS Controlled — Automatic Charge Protection

Controlled directly by the Charge Disconnect output of the VE.Bus BMS or SmallBMS — connecting the charger when the BMS output is high (normal operation) and disconnecting it immediately when the BMS output goes free floating due to cell overvoltage or overtemperature, providing automatic second-line-of-defence protection for the lithium battery bank.

Switches Chargers and Charging Sources Not Directly Controllable by BMS

Designed for high-current alternators, standalone battery chargers, and DC-DC converters that cannot be disabled directly by the BMS signal wire — providing a relay-based charge interruption solution that the BMS can control regardless of the charging source type or brand.

Voltage-Sensing Connection Logic — No Unnecessary Switching

The Cyrix-Li-Charge only connects the charger when it senses that the charger output voltage is at or above the connect threshold (13.0V / 26.0V / 52.0V) — preventing connection of a dead or off charger and avoiding unnecessary relay cycling. Connection occurs with a 3-second delay; disconnection on BMS fault is immediate.

Automatic Reconnection After Cell Overvoltage Reset

In the event of a cell overvoltage alarm, the BMS disconnects charging. Once the overvoltage condition resets after charging has stopped, the Cyrix-Li-Charge automatically reconnects the charger after a 3-second delay — restoring charging without manual intervention once the fault is cleared.

Hourly Reconnect Check

When the Cyrix-Li-Charge is engaged, it disconnects briefly every hour to verify that the charger is still active. If the charger output immediately returns to the connect threshold voltage, the Cyrix reconnects with a 3-second delay — preventing silent charger failures from going undetected over long charge periods.

Built-In Transient Voltage Suppressor

A built-in transient voltage suppressor limits the voltage spike that occurs when the Cyrix-Li-Charge suddenly disconnects an active charging source — protecting both the combiner and connected equipment from transient damage during emergency disconnection events.

Available in 12/24V and 24/48V Versions

Available in a 12/24V auto-ranging version (CYR010120430) for 12V and 24V lithium battery systems, and a 24/48V version (CYR020120430) for 24V and 48V systems — both rated at 120A continuous and identical in physical dimensions and IP rating.

IP54 Weatherproof Rating

Rated IP54 for protection against dust ingress and water splashing from any direction, making the Cyrix-Li-Charge suitable for installation in marine, RV, and off-grid electrical compartments where moisture exposure is a risk.

Specifications

Datasheets and Manuals

Datasheet