The Cyrix-Li-charge 12/24V-120A is a microprocessor-controlled charge relay from Victron Energy that combines a lithium (LiFePO4) service battery with a lead-acid starter battery in 12V or 24V systems. It lets an alternator or charger top up both banks at once while keeping the lithium battery protected from unsafe charging conditions.

Victron split charge relay for lithium and lead-acid banks

• Continuous current, rated at 120A.
• Voltage handling, works on 12V or 24V systems without configuration.
• Connect voltage, closes at approximately 13.2V on a 12V system or 26.4V on a 24V system, once the starter battery shows charging is underway.
• BMS integration, compatible with the Victron BMS charge disconnect output, so the relay opens immediately if the BMS signals a charge disconnect.
• Weight, 0.12 kg.

How it works

Unlike a standard battery combiner, which closes whenever either battery reaches a set voltage, the Cyrix-Li-charge treats the lithium side as passive. The relay only closes when starter battery voltage rises, showing that charging is actually taking place. This stops the lithium bank feeding back into the starter battery when the engine is off. When a Victron lithium battery's BMS sends a charge disconnect signal, perhaps because the battery is full or a cell imbalance has been detected, the relay opens straight away and isolates the lithium bank from the charging source.

Applications

Fits motorhomes and campervans running a lithium leisure battery alongside a vehicle starter battery, narrowboats and canal boats with a lithium service bank next to a lead-acid engine start battery, and marine or off-grid vehicle builds where alternator charging feeds a lithium system. It suits any dual-battery installation where a Victron lithium BMS needs to interrupt the charge circuit.

What's in the box

• 1x Victron Cyrix-Li-charge 12/24V-120A intelligent charge relay