The Victron Cyrix-ct is a microprocessor-controlled battery combiner for 12V and 24V dual-battery systems. It joins two battery banks in parallel while charging voltage is present, then separates them once charging stops, protecting a starter battery from being drained by a leisure or service bank. This retail kit (CYR010120110R) is rated at 120A continuous current.

Key features of the Cyrix-ct battery combiner

• Microprocessor-controlled relay connects batteries when charge voltage is detected and disconnects them when it drops
• Automatic voltage detection works across both 12V and 24V systems without manual setup
• 120A continuous current rating
• Ignition input terminal (the "ct" designation) lets the combiner join batteries whenever the engine is running, regardless of alternator output
• Solid-state relay with no moving parts
• No voltage drop across the combiner when closed, so both batteries receive full charge voltage

How it works

The unit monitors voltage across the two battery banks. When the alternator or charger raises voltage above the combine threshold, the internal relay closes and both banks charge together. When voltage drops below the disconnect threshold, the relay opens and the banks separate again. Built-in time delays stop the relay switching on and off during brief voltage fluctuations.

Applications

The Cyrix-ct suits motorhomes and campervans with a starter and leisure battery, marine vessels needing isolation between an engine start battery and a domestic bank, commercial vehicles running auxiliary equipment such as refrigeration or tail lifts, and off-grid vehicle builds. It is an alternative to diode-based isolators in installations where their voltage drop is a problem.

What's in the box

• Victron Cyrix-ct 12/24V 120A battery combiner unit
• Mounting hardware and installation accessories (retail kit)

Installation notes

Fit this with correct cable sizing and fusing at each battery terminal given the 120A rating. The ignition input wire needs a switched live that is only active with the engine running. Mount the unit somewhere dry and ventilated, away from fuel lines and heat sources. Weight is 0.9 kg.