question

I'm not using the charge current assistant, but I am using DVCC with my MultiPlus-II (2x120), a SmartSolar, and a pair of "dumb" LiFePO4 batteries to implement what I like to call storage mode, setting the DVCC current to 0 if I've clicked the "Storage Mode On" button and the SOC is above 60%. When the DVCC is set to 0 both the SmartSolar and Multi remain in Bulk mode (the Multi does *not* go into Passthru) with a 0A output. I actually consider then better (for my case) than going into full passthru, as the Multi and/or SmartSolar will output power on the DC side to match whatever draws there are on the DC system.

Not directly related, but may be useful info for you: I also have a 60A DC-DC charger (my setup in in an RV) that is enabled (using the Cerbo Relay) via NodeRed when the Multi is not charging, the tow vehicle is hooked up and running (determined via SmartShunt seeing the voltage of the tow vehicle's battery is above 13v), the trailer battery bank SOC is below 90%, or if there's high AC draw (the trailer air conditioner is running). When NodeRed enables the DCDC charger is sets the DVCC current to my battery bank max charge current - 60A. The charge from the DCDC shows up as a negative current on "DC System" in Venus. Unfortunately, even though the battery shows a positive (charging) current on the Cerbo, DVCC doesn't take that DC charging current into account when controlling the Multi and SmartSolar.

I've done quite a bit of work with this so I'm happy to share any information and NodeRed flows if you'd like.

Well...
I can absolutely control charge current using the assistant, which sets CC based on an analogue input. To keep this GX based, I am/was using the relays to set a charge rate in 4 steps, 0 and 3 levels above that. Solid but clunky.

Folk with that know more than I do, about Victron nuance, have said that ESS can do this without the relay/analogue hack/fix and provided that the result is the same, or at least broadly similar, it would be a cleaner solution.

I am not 100% convinced yet... Basically the first paragraph of the ESS manual states that off grid installations should not use ESS and as it is potentially varying voltage, and frequency, to do what it dose, I can see why that would be a thing.

I also have to contend with...

My CCGX cant do much other than stock firmware, so no Node Red.
My Cerbo GX is still a GX, despite enhancements, and will only play as it should when it is the controller/interface for, a single 'system'.

I want/need a single local dashboard that displays both Victron systems as a single cogent system for my home and neither GX can do that natively. In fact looking at documentation/questions/comments I think installing Node Red dashboard nodes on a GX is likely to be hard and difficult to support.

The ESS setpoints for the charge current control may well make sense. I can use Modbus to allow the flows on the Cerbo, 24V system, to access data, and control points, made available on the 48 by the CCGX.~
This should allow me to build up a 'system' that is essentially autonomous and, aware/in control of, the 24 and 48, hosted on the 24's Cerbo.

However this 'system' will still have to communicate with another external node red instance to show its status and accept high level commands telling it what its current goals are... Like ESS basically, but with two separate, yet interconnected, systems with a common UI.

I expect it sounds worse than it is... Assuming adequate control of the Multi's, the logic is fairly simple with just a few modes of operation, as a system making, sense.

I am more than happy to share flows, but you need to be aware that I am not an expert, yet, and everything I am doing/proposing is either skirting supported or simply isn't supported.
That said it isn't a hack either... I will only be setting parameters, not messing with sub-systems or hardware so although I could, and probably will, make a mistake, logically, hardware damage shouldn't occur. feeding one inverter with another isn't supported, so far as I know, anyway so in that respect, and with a healthy dose of caution, I guess I don't have much to loose.

I will play with ESS tomorrow but from Sun, I am away working and will not be back in the saddle until Fri next week at the earliest.

I don't think I can, or want to, mess with DVCC on the 48 as the BYD BMS is using that to manage the battery. Anyway if I need to limit charge from AC I can easily use the AC limit, although I cant see a need to do that right now. AC limit, yes obviously to manage the generator load but the charging can just do its thing. On the 24, I need to manage charge current without impacting the AC limit so I can effectively choose where any available charge current ends up. Loads will always take priority but assuming I have the input available, AC or DC, it will charge the 24 first, because that is a load on the 48, unless I restrict that behaviour.

To force the 24 to discharge, I just need to shut down or limit the 48, or the 24's AC input.
I will of course need a loop that lifts the limit if the house load go's up, maintaining headroom in terms of output capability.

DVCC current control is working just fine on the 48.
When set to 0 the battery go's idle but the unit is not going into Passthru, like it dose when the Charge Current assistant is controlling things and has disable charger at 0 current checked.

I tried running both, thinking that DVCC would override the assistant setpoint, in the hope that I could use the assistant to disable charging all together whilst still using the DVCC setpoint when charging was enabled but it seemed unstable/unresponsive so I took the assistant out again.

I have read through the documentation for ESS again and I am concerned that adding LOM protection will cause problems with the generator whilst removing it an enabling ESS, even with export disabled could potentially back-feed the 48 and as I do not know what that may do I decided not to go there without further advice.