The Victron Cyrix-ct 12/24V-120A battery coupler (MPN CYR010120011R) is a high performance microprocessor controlled relay that automatically connects batteries in parallel when one of them has reached a predetermined voltage level (indicating that the battery is being charged) and disconnects the batteries when the voltage drops below the float voltage level (indicating that one or both batteries are being discharged). Cyrix battery couplers are ideal for replacing isolating diodes. Their main feature is that there is virtually no voltage loss, so there is no need to increase the output voltage of the alternators or battery chargers.

Important product features of the Cyrix-ct 12/24V-120A

• Continuous current: 120A
• max. peak current (5 seconds): 180A
• Operating voltage range: 12V / 24V (auto detection)
• Manufacturer's MPN: CYR010120011R

Intelligent battery monitoring to prevent unwanted switching

Some battery couplers (also called voltage-controlled relays or split-charge relays) disconnect a battery when a short but high-amperage load occurs. Sometimes a battery coupler will not couple a large but discharged battery bank because the DC voltage immediately drops below the disconnect threshold after the batteries are connected.

The Cyrix-ct 12/24 software performs more functions than simply connecting and disconnecting based on the battery voltage and with a set time delay. The Cyrix-ct 12/24 observes the general trend (voltage increases or decreases) and only reverses a previous action if a trend has reversed during a certain period of time. The time delay depends on the extent to which the voltage deviates from the trend.

(For battery couplers with multiple connection/disconnection profiles, please refer to the Cyrix-i 400).

Long bolts so that more than one power cable can be connected
Cyrix 12/24-120: 13 mm (M6) Cyrix 12/24-230: 16 mm (M8)

LED status indicator

LED status indicator (Cyrix 12/24 230 only)
LED on: coupled LED lights up for 10 s: decoupled
LED lights up for 2 s: being connected LED flashes every 2 s: being disconnected
LED flashes every 0.25 s: alarm (overheating; voltage > 16 V; both batteries < 10 V; one battery < 2 V) (multiply by a factor of 2 for 24 V)

Cyrix battery couplers are ideal for replacing isolating diodes. Their main feature is that there is virtually no voltage loss, so that the output voltage of the alternators or battery chargers does not need to be increased.

The starter battery takes priority

In a typical set-up, the alternator is connected directly to the starter battery. The auxiliary battery and possibly also a bow thruster and other batteries are each connected to the starter battery via Cyrix battery couplers. When a Cyrix detects that the starter battery has reached the connection voltage, it closes to allow parallel charging of the other batteries.

Voltage detection in both directions and power supply from both batteries

The Cyrix measures the voltage of both connected batteries. It therefore also switches on if, for example, the additional battery is being charged by a battery charger.

The Cyrix-ct 12/24 has a dual power supply. It therefore also closes if the voltage on one of the batteries is too low to operate the Cyrix.
To prevent unintentional operation during installation or if one of the batteries has been disconnected, the Cyrix-ct 12/24 will not close if the voltage at one of the two battery connections is below 2 V (12 V battery) or 4 V (24 V battery).

Parallel connection for emergencies (Start Assist)

The Cyrix can also be switched on via a push button (Cyrix remains in operation for 30 seconds) or via a switch to connect the batteries in parallel by hand.
This is particularly useful in an emergency if the starter battery is discharged or damaged.

Scope of delivery:
1x Victron CYR010120011R Cyrix-ct 12/24V-120A battery coupler
1x instruction manual