Victron Cyrix-ct 12/24V 120A Intelligent Battery Combiner

The Victron Cyrix-ct is a microprocessor-controlled battery combiner designed for 12V and 24V systems carrying up to 120A continuous current. It automatically connects batteries in parallel when one battery is being charged, then disconnects them when charging stops, protecting the starter or primary battery from being drained by auxiliary loads. It is suited to marine, vehicle and off-grid installations where two battery banks need to be managed without manual switching.

Key Features

• Microprocessor-controlled logic connects and disconnects battery banks automatically based on voltage thresholds, with no manual intervention required.
• Rated for 120A continuous current on 12V or 24V DC systems, making it suitable for high-demand auxiliary loads.
• Connects batteries in parallel when the system voltage rises to a charge level, and disconnects when voltage drops back to a resting level, preventing cross-discharge.
• Compact and lightweight at 0.12 kg, allowing installation in tight spaces such as engine bays, caravans and boat bilge areas.
• Compatible with standard lead-acid, AGM and gel battery chemistries commonly used in dual-battery systems.
• Solid-state design with no moving parts, reducing the risk of mechanical failure in vibration-prone environments.
• SKU: CYR010120011 | GTIN: 8719076022138

Product Overview

The Cyrix-ct operates by monitoring the voltage of both battery banks. When the voltage on either bank rises above the connect threshold (indicating a charge source is active), the unit closes its internal relay to join the banks in parallel. Both batteries then charge simultaneously from the available source, whether that is an alternator, shore power charger or solar charge controller. When the charge source is removed and voltage falls back below the disconnect threshold, the relay opens and the banks are isolated again.

This behaviour protects the starter battery in vehicle and marine applications. If the auxiliary bank is heavily discharged, it cannot pull down the starter battery because the combiner only connects the banks during active charging. The voltage thresholds are pre-set by Victron and are appropriate for standard lead-acid chemistry. The "ct" designation indicates this unit is intended for use with conventional alternators and battery chargers, as opposed to the Cyrix-Li variants designed for lithium battery systems.

The unit requires a connection to an ignition or charge-detect signal in some installation configurations, allowing it to respond correctly when an alternator is the charge source. Wiring is straightforward, with clearly labelled terminals for both battery banks and the control input.

Specifications

• SKU: CYR010120011
• System voltage: 12V or 24V DC
• Continuous current rating: 120A
• Weight: 0.12 kg
• GTIN: 8719076022138
• Compatible battery chemistries: Lead-acid, AGM, Gel

Applications

• Dual-battery systems in motorhomes and campervans, keeping the starter battery isolated from leisure loads.
• Marine installations where a dedicated engine-start battery must be protected from auxiliary drain.
• Agricultural and commercial vehicles with high auxiliary electrical loads running from a secondary battery bank.
• Off-grid cabins or small solar installations using two battery banks that need automatic parallel charging.
• 4x4 and overland vehicles with auxiliary battery setups for winches, lighting or refrigeration.

What Is Included

• 1 x Victron Cyrix-ct 12/24V 120A intelligent battery combiner

Installation Notes

Installation should be carried out by a qualified auto-electrician or marine electrician familiar with dual-battery wiring. Ensure the cable sizing to and from the unit is rated for at least 120A and that appropriate fusing is fitted on both battery connections as close to each battery terminal as practical. The Cyrix-ct is designed for lead-acid, AGM and gel battery systems only. Do not use this unit with lithium (LiFePO4) battery banks without first confirming compatibility, as lithium systems have different voltage profiles that may require a Cyrix-Li variant instead.