stocksy avatar image
stocksy asked

Cyrix li CT issues

Hi all,

I have just got the above battery combiner and found that the stated voltages in the documentation to be inaccurate.

It states that the unit will combine the batteries if the voltage is 13.7v or more on either terminal. I've done serveral tests with the use of 3 multimeters and the BMV 712 battery monitor installed and the unit is engaging when the batteries are at just 13.3 V.

Also, something I didn't think about, but the 13.2 V disconnection, in my opinion, is too low. My lithiums sit at around 13.2 V and once connected both they and the starter battery stays that way unless I place a heavy load on it dropping the lithiums and said starter battery down below 13 V. I would have thought that having the disconnection set at 13.4 V would make more sense and give a disconnection once any charging source has been removed.

I'll live with the issues, but does spoil what could be a brilliant device as I feel all my other Victron products are (MultiPlus, Venus GX, Isolator Transformer, BMV 712, Battery Protects...)

If I'm missing something here then please let me know as I hope I'm wrong and can get this functioning as originally intended.



Cyrix Battery Combiner
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1 Answer
Justin Cook avatar image
Justin Cook answered ·

@stocksy, the trigger voltage of the Cyrix-Li-CT is 13.4v (which, if you're seeing it engage at 13.3v, is within design parameters); the original printed user manual included with the devices incorrectly listed the trigger voltage of the Li-CT as 13.7v, but this has been updated in the online manual. See here:

This is applicable to both the 120A and 240A models.

13.7v remains the trigger voltage for the Cyrix Li-Charge.

In regard to disconnecting, since a typical starter battery is fully charged at 12.8v resting, we find that in practice, as soon as any minimal load is applied to the LFP house bank, any surface charge on the starter battery that leaves it above 12.8 is fairly immediately consumed and the Cyrix disconnects the banks, so in reality you're not actually discharging the start battery at all, you're just burning off the surface charge - which doesn't have any current behind it anyway, it's not useful.

For those who still dislike the Cyrix leaving the banks connected until a load is applied, I've found that a simple momentary-off switch wired inline to pin 86 works wonders, as a momentary ground interrupt will manually disconnect the relay. I know it's kind of a hassle, but the reality is that it's unnecessary to do it at all, so a specific instruction for it is not something I'd fault Victron for failing to provide.

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