The Victron Cyrix-Li-ct is a microprocessor-controlled battery combiner built for lithium-ion battery systems running at 12V or 24V. It takes the place of a conventional VSR in setups where a Li-ion battery works alongside a starter or auxiliary lead-acid battery. Rather than switching on voltage alone, it is controlled directly by the battery management system, so it only connects the batteries when the BMS allows it.

Why not a standard VSR

A voltage-sensitive relay connects batteries purely on measured voltage. That works fine for lead-acid, but a lithium battery can sit at a high voltage while still being unsafe to charge further. The Cyrix-Li-ct instead reads the BMS charge-disconnect or load-disconnect signal directly. When the BMS calls for charging to stop, the unit opens immediately and isolates the Li-ion bank from the alternator or charger, whatever the voltage happens to read.

Key features

• Continuous current rating, 120A
• System voltage, 12V or 24V, one unit covers both
• Control input, BMS charge-disconnect or load-disconnect signal, not voltage detection
• Weight, 0.12 kg
• Logic, microprocessor-controlled response to BMS commands
• Compatibility, works with Victron BMS units and compatible third-party BMS outputs

Applications

Common uses include marine installations combining a Li-ion house bank with a lead-acid starter battery, motorhomes and campervans with a lithium leisure battery charged from the vehicle alternator, and commercial vehicles or off-grid systems needing controlled split-charging between Li-ion and lead-acid banks.

Installation notes

A compatible BMS charge-disconnect or load-disconnect output is required; the Cyrix-Li-ct will not work as a standalone voltage-sensing relay. Cabling must be rated for the full 120A continuous load, with appropriate fusing on both battery connections. Installation should be carried out by someone familiar with lithium battery systems.

What's in the box

• 1 x Cyrix-Li-ct 12/24V-120A battery combiner unit