The Cyrix-Li-Charge is a microprocessor-controlled charge relay from Victron Energy, built to combine a lithium battery bank with a secondary battery or charging source across 24V and 48V systems. It suits off-grid, marine and vehicle installations where lithium and lead-acid batteries need separate management but share a common charge source.

Key features

• Current rating, 120A continuous, for 24V and 48V systems.
• Control logic, microprocessor-controlled, monitors battery voltage and connects or disconnects the charge circuit automatically.
• Battery chemistry, designed for lithium cells, preventing incorrect charge sharing that could damage them.
• Weight, 0.12 kg, easy to fit into confined spaces.
• System fit, works alongside Victron's battery management range, including BMV monitors and BMS units.

How it works

The relay watches the voltage of the starter or secondary battery. Once that voltage shows active charging, the relay closes and lets current flow into the lithium bank. When charging stops and voltage drops, it opens again, isolating the two banks so the lithium battery cannot discharge back into the starter circuit or alternator.

Rated at 24V and 48V, this unit is meant for larger off-grid and commercial vehicle systems where 12V isn't enough. At 120A it manages substantial charge currents without needing an oversized relay or extra controller, and the automatic logic cuts out manual switching in unattended setups.

This relay works with, not instead of, a dedicated lithium BMS. It does not provide cell-level protection on its own: the BMS must retain that control, with the Cyrix-Li-Charge only handling the charge-source combining task.

Applications

• Off-grid solar systems with a 24V or 48V lithium bank and a secondary lead-acid starter battery.
• Marine installations charging a lithium house bank from an alternator without a direct alternator-to-lithium connection.
• Commercial vehicles and motorhomes running split 24V or 48V battery systems.
• Hybrid battery setups requiring isolation during discharge but combination during charging.

What's in the box

• 1x Victron Cyrix-Li-Charge 24/48V 120A intelligent charge relay

Installation notes

Fit this by a qualified electrician or accredited installer familiar with lithium systems. It must be paired with a compatible lithium BMS, since it does not provide cell-level protection independently. Check polarity and use cabling rated for the full 120A load. Marine fitting should follow applicable NMEA and flag-state wiring standards, and the unit should not go into a sealed, unventilated enclosure without confirming thermal suitability.