The Victron Cyrix-i 24/48V-400A is a microprocessor-controlled battery combiner for 24V and 48V systems that need high-current parallel charging between two battery banks. It replaces diode-based isolators and voltage-sensing relays, avoiding the voltage drop and heat losses those methods create.

Key features

• Current rating, 400A continuous, for high-demand 24V and 48V battery systems.
• Smart control, a microprocessor monitors both battery voltages and connects the banks only when charging conditions are met, stopping unwanted discharge between them.
• Dual voltage, works on 24V or 48V nominal systems, so one part number covers both configurations.
• No voltage drop, closed-relay operation avoids the 0.6V to 0.7V loss typical of diode isolators.
• Automatic disconnect, opens below the disconnect threshold, protecting the starter or primary bank from auxiliary loads.
• Weight, 0.9 kg, suitable for confined installation spaces.
• Battery compatibility, works with AGM, gel and flooded lead-acid batteries.

How it works

The Cyrix-i watches the voltage on both banks continuously. When either rises above a preset threshold, showing a charger or alternator is active, the internal relay closes and the banks parallel up to charge together. Once voltage falls back below the disconnect point, the relay opens and the banks separate again.

At 400A it suits systems fed by large alternators or multi-stage chargers. Because there's no voltage drop across the unit, charger voltage settings don't need adjusting to compensate, so charging accuracy is maintained. It works alongside Victron chargers, inverter/chargers and BatteryProtect units, but also operates independently in third-party systems.

Applications

• Split-charge systems on commercial vehicles, coaches and HGVs with 24V electrics.
• Marine vessels with separate starter and house battery banks at 24V or 48V.
• Off-grid installations where a generator or solar charger feeds multiple banks.
• Industrial and telecoms backup power needing isolated banks with automatic parallel charging.
• 48V electric vehicle auxiliary systems.

What's in the box

• 1x Victron Cyrix-i 24/48V-400A intelligent battery combiner

Installation notes

Fit this by a qualified electrician or marine/vehicle electrical specialist experienced with high-current DC systems. At 400A, correct cable sizing, fusing and terminal torque matter. Mount in a ventilated spot away from flammable materials, and follow Victron's wiring guidelines along with local electrical regulations.