The Victron Cyrix-Li-ct is a microprocessor-controlled battery combiner built for 12V and 24V lithium-ion battery systems. It replaces a standard voltage-sensitive relay in dual-battery setups where a lithium service bank sits alongside a lead-acid or AGM starter battery, letting the two share charge without exposing either to damage.

Key features

• Continuous current, rated at 230A.
• System voltage, works on 12V and 24V installations.
• BMS control input, charge/discharge control terminals accept a signal from a compatible Li-ion BMS.
• Weight, 0.3 kg.
• Starter protection, stops the lithium bank from drawing down the starter battery.

How it works

A conventional VSR connects batteries once it sees a threshold voltage, with no regard for battery condition. The Cyrix-Li-ct instead takes its cue from the BMS. When the BMS output signals a fault, such as over-voltage or over-temperature, the combiner opens and isolates the lithium bank from the rest of the circuit. The ct designation refers to these charge/discharge control terminals: they let the unit act on battery state rather than voltage alone, which matters with lithium chemistries that hold a flat voltage curve right up to the point of trouble.

Because it covers both 12V and 24V, one unit serves either voltage, useful for installers who would otherwise stock two separate combiners.

Applications

Fits marine vessels running a lithium service bank next to a lead-acid or AGM starter battery, and campervans, motorhomes or HGVs pairing lithium leisure batteries with a vehicle starter battery. Also suited to off-grid vehicles where an alternator charges a Li-ion bank.

Installation notes

Fit this by a qualified electrician or marine/vehicle electrical engineer. The Cyrix-Li-ct needs to be wired to the charge/discharge control output of a compatible Li-ion BMS for its protection function to work; without that signal, the isolation feature will not operate. Cable and fusing on both battery connections should be rated for the 230A continuous load, and marine installs should follow the wiring standard for the vessel class.

What's in the box

• 1 x Victron Cyrix-Li-ct 12/24V-230A battery combiner