The Cyrix Battery Combiner is a microprocessor controlled heavy duty relay that automatically connects batteries in parallel when one of them has reached a pre-set voltage (indicating that the battery is being charged), and disconnects when the voltage decreases below float level (indicating that one or more batteries are being discharged). Cyrix Battery Combiners are an excellent replacement for diode isolators. The main feature is that there is virtually no voltage loss so that the output voltage of alternators or battery chargers does not need to be increased.

The LiFePO4 battery: preventing cell under voltage, overvoltage and over temperature
The first line of protection is cell balancing. All Victron LiFePO4 batteries have integrated cell balancing.
The second line of protection consists of:
- shut down of the load in case of imminent cell under voltage, and
- shut down or reduction of the charging current in case of imminent cell over voltage, high temperature (>50°C) or low temperature (<0°C).
The VE.Bus BMS is the core of the second protection line.
However, not all loads or chargers can be controlled directly by the VE.Bus BMS.
In order to shut down such loads or chargers several VE.Bus BMS controllable Cyrix switches are available.

Cyrix-Li-ct
The functionality of the Cyrix-Li-ct is analogous to the Cyrix-ct.

The Cyrix-Li-ct will parallel connect a lead acid starter battery and a LiFePO4 battery:
- if the charge disconnect output of the VE.Bus BMS is high, and
- if it senses 13,4 V (resp. 26,8 V) or more on one of its power terminals.

The Cyrix will disengage immediately:
- when its control output becomes free floating, signalling cell over voltage or cell over temperature, and/or
- when battery voltage drops below 13,2 V.
Start assist function: a short positive pulse will close the relay during 30 seconds (see figure on page 2).

A built-in transient voltage suppressor will limit the voltage spike that may occur when the Cyrix suddenly disengages due to cell overvoltage or over temperature.