How do I get the Cerbo GX to feed Smart Shunt data to Skylla-i charger, supply amps and batt temp inputs to the charger’s algorithm.
Setup:
() Skylla-i charger’s output goes to a 24VDC buss.
() The Skylla-i charges one of two 24VDC battery banks that are connected to the buss.
() Both banks are monitored by SmartShunts, including battery temp.
() Skylla-i and both SmartShunts connected to Cerbo GX.
The retailer that sold me the system said that the Cerbo GX would pass the SmartShunt data to the Skylla-i. Both power readings and battery temp.
I’ve spent weeks installing and learning how this system works.
How do I test to see if the Cerbo is indeed passing this data along, or not?
Conceptually, is there a setting? Can’t find it. And can’t figure how the Cerbo would figure out the relationship on its own.
I have many situations in which the Skylla reports to the Cerbo that it is putting out more amps than the Shunt is reporting. For example Skylla says 10 amps, and the Shunt says 3 amps.
I assume this is because the Skylla is reporting what it is generating. Whereas the Shunt is reporting the net, that is combining charge amps and load amps. So, in example above a load of 7 amps is why Shunt says 3 when Skylla says 10. Correct?
I want Skylla to be driving it’s charging state algorithm using the Shunt’s amp reading, because otherwise the batteries might be given more charge than they should. Is this correct?
I certainly want the Skylla to be using the Shunt’s temp reading. Otherwise, I’ll have to install more temp sensors plus a switch so that when you put a bank on the buss you also connect it temp sense to the Skylla. Correct?
I’m in the weeds. Need help!!!
You are correct, the Skylla reports its output, some of that goes to loads so the battery current on the SmartShunt is lower.
The usual mechanism of sharing battery voltage, temperature and current from a SmartShunt to the Cerbo GX and to other connected devices is DVCC. The Skylla chargers are not fully integrated into DVCC control so you will need to check this all works. See the DVCC Section in the Cerbo manual. You can only nominate one of your SmartShunts as the master controller, the other one will be monitored but data from it will not be shared. I am assuming you have lead acid. Enable DVCC, set SVS, STS and SCS to on (share voltage sense, share temperature sense, share current sense) and where requested, choose the sensor to use for that data.
If as your write up suggests, you are swapping banks then the whole issue of DVCC becomes a mess because you would need to swap the sensors each time you switch banks. The easiest may well be to just leave the Skylla in control and accept it is not perfect, or configure your system to a single bank.
https://www.victronenergy.com/media/pg/Cerbo_GX/en/dvcc—distributed-voltage-and-current-control.html
Imho cerbo only supports one shunt
Thank you!
I will give it a try. Good to learn how it works.
Skylla docs say must use temp compensation if either (a) batt temp > 30C and the boat will be in the tropics where both the air and water temp will exceed this; and (b) charge current exceeds 15A per 100Ah batt capacity, and we are charging at 90+A with a 420Ah capacity.
Is there any documentation on the expected effect on charging when temp compensation is working?
In “stand alone”, the Skylla seems to Float until it hits a time limit and then moves to Storage.
Skylla DS 3 is on, and the documentation says Float time = 20 * (Bulk Time); min 4 hours; max 8 hours.
With the Skylla “virtually” connected to the proper Smart Shunt, will SCS cause the Skylla to move from Float (27.6V) to Storage (26.4V) sooner because (in the example) it’s now sensing the 3A instead of 10A? Or will the algorithm remain as documented by DS3?
See attached Cerbo screenshots.
There are three shunts. In the DVCC screens, Cerbo is using the “product name” instead of the “custom name” for the Shunts. Therefore I’m at a loss as to how to select the right shunt. In the device list it uses the “custom name”.
If the absorption can be terminated by battery tail current then it will go to float earlier. With temperature compensation, at temperatures above 20 or 25degC the absorption and float voltages will be reduced.
In terms of setting the master battery monitor I have not done it myself with identical devices available. The only work around I can think of is temporarily disconnect the 2 devices leaving your chosen one.
OK. Is there a way to read what the Cerbo is “publishing” as the STS/SVS/SCV values? This would be useful for debugging. With that I could probably also figure out the “order” that it has the devices, and chose them based on their position in the list. OMG that’s disgusting. But not as disgusting as popping the cables in/out of the Cerbo, which is not exactly convenient to get to. If I enable Signal-K for example, would these values appear in the data that Signal-K makes available? Is there a mechanism for submitting bug reports to Victron? Seems like not using the “custom name” is surely a bug.
I do not know, I will raise this with the expert users. I suggest you make a new post titled selecting one SmartShunt on Cerbo as battery monitor.
Link to the new post:
Hi @GAjet,
Thanks for the report, I have escalated it to the Venus OS team to look into how this can be better handled. Hopefully a quick fix.