Battery Combiners

Intelligent Battery Combiners for Dual and Multi-Battery Systems

A battery combiner lets one charge source, usually an alternator, charge two or more battery banks automatically. It also stops house loads from draining the starter battery. This range covers voltage sensitive relays (VSRs), automatic charge relays (ACRs) and solid-state battery diodes for 12V, 24V and 48V systems in caravans, 4WDs, boats, trucks and commercial vehicles.

Victron Cyrix-ct Intelligent Battery Combiners

The Victron Cyrix-ct monitors system voltage. It connects the starter and house batteries when a charge source is detected and separates them again when voltage drops, so the starter battery stays reserved for cranking. Cyrix-ct models suit 12V and 24V systems. They are available in 120A and 230A versions, and the 120A model also comes as a convenient kit. Because they combine through a relay rather than a diode, there is negligible voltage drop between banks.

Lithium-Ready Cyrix-Li-ct Combiners

LiFePO4 house batteries have a different voltage profile from lead-acid batteries, which can cause a standard VSR to connect and disconnect at the wrong points. The Victron Cyrix-Li-ct intelligent Li-ion battery combiner uses connect and disconnect thresholds suited to lithium chemistry. It is available in 120A and 230A ratings for 12V and 24V systems.

High-Current Combiners for 24V and 48V Systems

Larger alternators and high-capacity banks need a heavier-duty relay. The Victron Cyrix-i 400A comes in 12/24V and 24/48V versions, which makes it a strong option for 48V RV systems, commercial vehicles and large vessels. For 24V marine and truck installations, the Blue Sea 24V 500A ML Series Auto Charge Relay provides a high-current, automatic combining solution.

Victron Battery Diode Combiners

Victron battery diodes in 40A and 80A ratings split a single charge source across two batteries using solid-state components with no moving parts. Diodes do introduce a forward voltage drop, so they work best with charge sources that can compensate for it. Where you need to isolate banks rather than combine them, compare these options with the dedicated battery isolators and splitters.

Selection Tips for Matching a Combiner to Your Setup

• Current rating: Choose a continuous rating above your alternator's maximum output. Our guide on why continuous current ratings matter explains why peak figures can be misleading.
• System voltage: Cyrix-ct and Cyrix-Li-ct models suit 12V and 24V systems. Choose the Cyrix-i 24/48V model for 48V banks, or the Blue Sea ML Series ACR for 24V.
• Battery chemistry: Use a Cyrix-Li-ct where a lithium house battery is involved.
• Smart alternators: Variable-voltage alternators may not reliably trigger a VSR. Check whether a DC-DC charger is a better fit for your vehicle.
• Protection and monitoring: Fit correctly rated fuses near each battery. Consider adding battery monitors to track charge across both banks.

Choose the Victron Cyrix, Blue Sea or battery diode combiner that matches your system voltage and alternator output. Contact our team before ordering if you would like help confirming the right current rating for your caravan, 4WD, boat or truck.