The Cyrix-Li-load is a microprocessor-controlled load relay from Victron Energy that protects lithium batteries from over-discharge. It disconnects non-essential loads once the battery reaches a critically low state, and is rated for 12V and 24V systems at 120A continuous. Installers working on marine, vehicle and off-grid projects use it where lithium battery protection matters.

Key features of this battery isolator switch

• Current rating, 120A continuous on 12V and 24V DC systems
• Microprocessor control, monitors battery voltage and disconnects loads automatically below a safe threshold
• Lithium-specific logic, responds to the steeper voltage curves of LiFePO4 and similar cells
• Automatic reconnection, loads restore once voltage recovers, no manual reset needed
• Weight, 0.12 kg, suitable for confined installation spaces
• BMS integration, accepts a remote on/off signal from a Victron battery management system

How it works

The relay monitors terminal voltage and opens when the battery approaches full discharge. Because lithium cells have a flat discharge curve until near the end of capacity, the microprocessor logic allows accurate disconnection without shedding loads prematurely during normal use.

It sits between the lithium battery and non-essential loads such as lighting circuits or auxiliary consumers, while essential loads are usually wired separately. Paired with a Victron BMS, the BMS can force the relay open independently of the voltage threshold during a fault or cell imbalance event.

Applications

• Lithium battery load protection on marine and narrowboat electrical systems
• Auxiliary load disconnection in campervans, motorhomes and off-road vehicles with lithium house batteries
• Off-grid cabin and caravan systems needing over-discharge protection for LiFePO4 banks
• Secondary load management in 12V or 24V commercial vehicle fit-outs
• Automated load shedding when integrated with a Victron BMS

Installation notes

Fit this by a qualified electrician familiar with lithium systems. Wire it in series with the load circuit being protected, not in the main battery positive feed, and fuse the circuit correctly for the cable rating. This unit is not for lead-acid systems, where a standard Cyrix combiner should be used instead.

What's in the box

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