Victron cyrix relais or other solution.(charging starter battery)

DIY
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1

Hi,

I have the following setup in a Ford Transit Camper.

3 victron solar inverters.(3different size solar panels on the roof) connected to 3 x 200ah lithium victron batteries. A cerbo unit with victron shunt to measure the power drawn and 2000W victron 220V inverter. I use buck boost(victron) of 50A to charge the batteries whilst I am driving. I have a Victron display to check everything and connected some level meters to have a nice overview of everything.

The camper is sometimes stored for a longer time and I want to use the excess of solar power to trickle charge my starter battery.

The problem is the following. Of all victron devices, I have no extra output to charge the starter battery. I would like to use the Victron Cyrix relay, but from what I read in the specs this is only designed for charging in the other direction. (alternator/starterbattery → lithium battery) In my case i goes the different direction. (solarpanels/lithiumbattery→starterbattery)

When the lithium pack is charged it stays around 13V(a acid battery will drop to 12.6V) so i think the Cyrix relay will not switch off and will unnessarely discharge my lithium pack.

Does anyone have some experience with this? Or has a different idea how to overcome this problem? My inverters have no extra charge output.

Many thanks,

Floris

2

The Victron Cyrix relais is bi-directional. That mean you can load in both directions. I had such a relais (the 120A version) for years in my old T4 van and this worked absolutly fine.

In your case I see the problem, that the relais would also connect the starter battery/generator to your lithium batteries in parallel to the DC-DC charger. This might cause problems.

3

Yes, you are right. I found and ordered this unit. I think it will do the trick

Standby Charger Pro votronic