question

marcj avatar image

Victron Cyrix CT 120A cable and fuse

Hi,

I find it a bit difficult to understand which cable thickness and fuse I would need to use for the Cyrix CT 120A.

For the main connections (30/ 87) I plan to use a 25mm² wire and 120A fuse as is described in the product's datasheet. The cable length would be about 6M.

What I don't understand is which thickness and fuse to use for the start assist (85) and connection to the battery (86). The datasheet says the fuse can be 0,1A, which would indicate a rather thin wire can be used. But I don't understand how that's possible: my starter engine would draw a lot more than such a small fuse and wire could handle.

Second question: do I really need to connect the negative of my "appliance battery" to the negative of the "start battery"? Can't I just ground them both?

Kind regards,

Marc



Cyrix Battery Combiner
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The large charging current is going from the alternator/starter battery through the cyrix 30/87 to the 2nd battery.

86 is only needed to power the electronics inside the cyrix.

You can also connect both batteries to the chassis.

Depending on the cable length and the current the alternator can deliver, 25mm² can be to small.

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marcj avatar image
marcj answered ·

Danke Schön :). That answered all my questions and one I didn't knew I had.

Marc

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