Hi, I have some strange behaviour of my system onboard the boat. I have starter and service battery connected via cyrix ct where first starter battery is battery 1 and service battery is battery 2 on cyrix. Solar panel is connected via pwm duo lcd 1220 and used to charge first service battery and then starter battery (80/20 ratio). I noticed that when engine is running that alternator is charging starter battery but not service battery. Both batteries are fully charged. Meanwhile, on pwm I noticed that battery 1 as service battery is never getting those 80% but battery 2 is getting that voltage from controller. Any explanation to sort this out? Thanks.
As far as I remember, the Cyrix CT relais is only working with voltages. So you can’t really decide on SoC levels when one battery shall be charged or not.
The limits are given in the datasheet. So once the starter battery ist charged to a voltage above the activation voltage level, the service battery will be connected to be charged as well.
Once the voltage drops again, the service battery is disconnected again.
The same is valid vor the service battery that is charged via solar. Once the service battery is “full” (decided only on a voltage level) then the starter battery is connected…
So it might be the case, that the relais is connecting the starter battery too early and not getting fully loaded. This is depending on the battery.
Which battery typed to you have for the starter and the service battery?
Service battery is victron agm 110Ah while starting battery is regular flooded 70Ah
Ok, i guess, the AGM battery has a higher absorption voltage then the starter battery. You can check the datasheet.
But anyway, the cyrix relais will connect both batteries depending on voltage, but will have no effect on the settings you set.
So which settings do you have e.g. for the AGM Battery?
And what max. voltage does the generator deliver?
And finally a general question, - did you connect the Relais as designed? Means Battery 1 should be the starter battery acc. to this shematics:
But question is what voltage is required that cyrix will connect both batteries to charge when it needs to first fully charge starter battery and then service battery?
I have connected starter battery to 87 and service battery to 30.
Alternator is delivering up to 14.3-14.4V
Then you did it not as recommended. Then the proirity of the Relais is not given as designed.
Here is the datasheet: Datasheet Cyrix CT
This are the values out of the datasheet:
So if connected as shown in the diagramm above (this is out of the datasheet), the starter battery will get charged from the generator, as soon as the voltage rises above the limits (in the corresponding time), the service battery will be connected. The both get charged. So finally, if the runtime of the generator is long enough, both batteries will be charged to the max voltage that the generator is delivering.
I know that this workes fine, I had this setup in my previous Camper van. So please connect the relais as recommended and the report us if it works or not. 
How you mean it is not as recommended? Can you explain?
The recommended connection acc. to the Victron design is to have a priority on the starter battery. The assumption is, that you always want to be able to still start the vehicle or boat motor. That’s why the relais would disconnect the starter battery from the service battery when the voltages get too low. Then you can discharge the service battery as deep as you “want”, but the starter battery is kind of “protected” from getting discharged too much.
Note: I just edited my last post.
But I have connected correctly, starter battery as first priority and then service
Oh yes sorry, my fault. I read it wrong… Your connection is right, then the system “should” work as defined.
Can you see that the relais is connecting, when the generator is running for some time?
But keep in mind, the relais might already be closed when the starter battery is charged from the solar system.
Or did you connect a manual switch to the relais? Maybe this switch is somehow causing problems and the relais is connected all the time?
If starter battery is charged, why the relay isn’t charging service battery?
Manual switch is not connected
Can you measure the voltage of the starter battery when the generator is running?
Maybe the voltage is still too low to connected the service battery?
Take the table and check in which voltage range the starter battery is, and if the relais will close the contact to the service battery within the defined time.
If this is not working, the relais might be defective…
Voltage when engine is running is around 14.2-14.3V on starter battery
I suspect relay as well
Well, then the relais should close the contact within a few seconds.
What did you measure at the relais between contact30 and GND? Is this the voltage of the service battery or what is there? Do you have a fuse installed like shown in the schematics?
Is the fuse ok?
It is voltage from the service battery, can’t measure alternator voltage there.
Fuse is okay
Ok… and the negative from the starter battery is also connected (terminal 86) and not broken somehow?
What you could also check is (if the gnd connection is fine) to manually trigger the relais by just connecting the terminal 85 on Vbat. If you can’t heat the relais clicking, then it is defective.
85 and 86 I didn’t connect at all, if I have urgency I will just connect them when needed
All gnd from batteries are connected together
Another thing, if relay is just bridging 87 and 30 it means both batteries are charging in parallel what will tell us that we are charging two different types of batteries and it should not be
Oh, there is the problem. You have to connect the GND. This is needed for the electronics inside this relais. It is kind of a smart relais. Without this it can’t measure the voltage at all. It does not know which levels the voltages are. So you have to connect the 86 to GND.
GND of both batteries are connected together, - this is correct.
Your are right, if the relais contact is closed, then both batteries are just connected together in parallel. And yes, the relais does not know anything about the battery types and it can’t controll anything about that. This is something you have to know and design in your system.
That’s why I previously asked what types of batteries you use.
While the AGM is able to be charged to a slightly higher voltage, it is also fine with 14,4V from the generator. And the Solar system must also be set up in a way, where it can’t overcharge one of the batteries. So the type of battery with the lowest absorbtion voltage gives the max charge voltage for the whole system.
In your case you should ensure the battery is not charged over 14,4V in case the relais is closed and both batteries are connnected.