The Victron Cyrix-ct is a microprocessor-controlled battery combiner for 12V and 24V systems, rated at 120A continuous current. It joins battery banks in parallel while a charge source is active and separates them once charging stops, so the starter or primary battery is not drained by auxiliary loads.

Key features

• System voltage, 12V or 24V DC
• Continuous current rating, 120A
• Weight, 0.12 kg
• Battery chemistries, lead-acid, AGM, gel
• Solid-state design, no moving parts
• SKU, CYR010120011, GTIN 8719076022138

How it works

The unit watches the voltage on both battery banks. When voltage on either bank rises to the connect threshold, an alternator, shore charger or solar controller is assumed to be active and the internal relay closes, putting both banks in parallel so they charge together. When the source is removed and voltage drops back to the disconnect threshold, the relay opens and the banks separate again. This stops a discharged auxiliary bank from pulling down a starter battery. The thresholds are pre-set by Victron for standard lead-acid chemistry. The ct designation marks this as the version for conventional alternators and chargers, distinct from the Cyrix-Li range built for lithium systems. Some installations need a connection to an ignition or charge-detect signal so the unit responds correctly to an alternator.

Applications

Used in motorhomes and campervans to keep a starter battery isolated from leisure circuit loads, in marine dual-battery setups protecting the engine-start battery, and in agricultural, commercial and 4x4 vehicles running auxiliary loads such as winches, lighting or refrigeration from a second bank. It also suits off-grid cabins and small solar setups with two banks needing automatic parallel charging.

Installation notes

Fitting should be done by a qualified auto-electrician or marine electrician. Cable sizing to and from the unit needs to handle at least 120A, with fuses fitted close to each battery terminal. This combiner is built for lead-acid, AGM and gel batteries; check compatibility before using it with a lithium (LiFePO4) bank, as a Cyrix-Li variant may be needed instead.

What's in the box

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