Installation with a CYRIX 120 in boat with bat1=87=startbattery and bat2=30=domestic consumer, and a IP22 charger.
Start battery goes flat , the CYRIX does not open , only charging the consumer battery.
Bat1(87) has gone down to 11.4 V (replace) and bat2(30) charging and standby 12.7 V. Thats the voltage on the CYRIX bolts too.
If I remove the 86 minus connection spade and put it back, I hear the click indicating open, and can measure charger voltage on boths batteries.
My conclusion indicates a defect in CYRIX, and solution is replace of the CYRIX (and Bat1)
But can it be anything else ?
12.7V is not enough for the Cyrix to close, you need at least 13.0V.
I guess connecting the minus triggers the internal relay regardless of voltage, then it stays connected for up to three minutes since the voltage is under 12.8V.
Sorry, the problem is not at standby without the charger (IP22).
It is with the charger running 14.4 V and more than 13.8V on bat 2 and less than 12.0 V on bat1 for long time. Disconnect/connect the 86 minus then change the status
,
Do both batteries use a common negative?
Hi Chrigu
Thank you for response and sorry for delayed answer.
Yes both batteries use same (common negative) just as the Cyrix diagram shows. I have disconnected (not used) the 85 startassist, but no other differece (but other devices connected, mainswitches, motor operation panel aso).
I have been back to the boat and gone thru step-by-step waiting 5 muinutes when apropiate. Measure voltage on batteries and Cyrix conections. With and without IP22 on.
Geb´nerally IP22 voltage is 14,72 and motor battery as low as 11.92, except when 86 bat- sensor is disconnected-reconnected , then the voltage on startbattery (and 87 + bat) raise to above 14V and stay so (measured far more than 5 min ).
I dont know how long this has been the status, because normally the motorgenarator keeps the start battery alive, and normally the voltage is only observed at concumer battery. I observed this behavior after resently installing a PICO simarine battery monitor
I will buy a new Cyrix 
j
according to 4) in answer from Justin in https://communityarchive.victronenergy.com/questions/15779/cyrix-ct-120-draining-both-batteries.html the disconnect negative seems to be close to normal ( A momentary disconnect of the ground will open the CT, at which point it will remain open until charging voltage is again sensed at either of the batteries. )
The relay opening once the negative is removed is indeed normal, it needs the negative to energize the coil. The Cyrix activating on charging voltage is also normal.
But yours is activating when the negative is reconnected, which may or may not be normal. But for sure what is not normal is that yours does not activate upon charge voltage.
Thank you for comments and clarifying.
I am convinced that the solution is to follow the first conclusion - replace cyrix and start-battery and keep wiring unchanged.
