question

If you enabled DVCC you could set the system charge limit, and it can be changed via node red.

If I set DVCC current, then this influences not only the Multiplus charging current, but also the MPPT current (which I don't want)

If I set to inverter only, then the Multiplus doesn't do passthu.

How can the charging current of the Multiplus only be set without setting the MPPT current as well ?

There is another method, all be it a bit clunky....

From an answer I gave about additional IO options.... HERE

"I am mentioning Analogue output modules because that allows you to spoof a tank/temp/voltage which offers control of stuff not directly available as a writable parameter, modifying export control for example or limiting charge current without having to mess with a configured DVCC setup.

BTW. Charge current can also be limited with an assistant, it can be linked to an analogue Input and driven with your IO module of choice.

If you need Analogue and don't like the price, get a cheap digital output board and go old-school.

R-2R Ladder DAC Digital to Analog Converter (microcontrollerslab.com)

An 8 bit R-2R ladder with a simple totem-pole BJT driver, or an OpAnp, hanging of the end of it will give you 256 discrete signal levels on a low impedance output, no smoothing of or high frequency PWM noise to worry about. 12 Bits, a common IO relay board width gets you 4096 levels or a more sensible range and some unused digital outputs."

I was using this method, just using 2 relays and a couple of resistors, Off / Low / Hi, before I realized I could utilize DVCC to do the job directly on my second system which was not already using DVCC.

As far as I am aware the assistant setup is modifying the physical MP setpoint, as if you were setting it using VEConfigure, so it should be override any ESS/DVCC control but I strongly recommend checking that, because I haven't, and I don't know what priority the three, potentially competing setpoints are applied in.

You might also want to consider what it is you are actually wanting to achieve overall and how you go about it, Consider...

For whatever reason a combination of ESS and DVCC is not ticking all your system performance characteristics. In my case I had to use DVCC because it is required by my BYD battery setup and ESS just isn't, well wasn't at least, well suited to doing what I wanted in an off grid situation.

I chose to set up the systems in an overall 'safe' configuration to make sure that the setpoints I was going to mess with externally couldn't do any harm. Then I used NodeRed to 'manage' what me basic safe system was doing at any given point in time and in a range if deferent circumstances, specific to my requirements.

I now have a generator feeding MP 5000/48 feeding an MP 5000/24 feeding my property. The 48 pack also has a solar charger. The 24 pack provides DC supply to critical loads, coms, home automation and and emergency/backup lighting.

In my case I get great redundancy and flexibility at the cost of complexity. ESS out of the box simply cant do the job I need and there is no reason to assume any manufacturer is going to anticipate someone wanting to do what I have.

But because Victron have integrated NodeRed and provided access to setpoints over Modbus I have a way to implement this stuff without messing with too much hardware.

It is a little frustrating to find that seemingly obvious setpoints can be manipulated directly but you have to keep in mind that complex systems like these are essentially a box of hard/soft modules that all have to play nice, as a system. The more the designers expose to external manipulation, to facilitate customization, the harder it becomes to produce a robust, off the shelf, design that will protect itself despite us!

I think in some cases there is an argument for ditching the ESS module entirely, as opposed to trying to bend it into shape, and then implementing whatever energy / system / property / equipment management system you require based around a Victron system in its default safe configuration.

There is absolutely no reason why a basic setup, safe when left in any condition, cant be fully automated controlling SOC charge/discharge limits, grid import and export in a G100 scenario, AC or DC solar, load management and just about anything else you want to dream up.

I look at Node Red as a pseudo operator, I am not relying on it, or more importantly the code I put into it, to manage my battery's at a charging algorithm level, I let the inverters do that.

All NodeRed is doing is orchestrating the various operating modes/parameters of my interconnected equipment to achieve an overall goal for the system as a whole, in various circumstances.

Those circumstances include manual operation, in part or in full, which I use after discovering a niche case I haven't considered previously, to understand what will work in that case and carry me through until I have time to add strategic code to deal with it.

Case in point...

I just added a storage heater, its cleaver but not nearly clever enough to do what I need. I have worked out how the get it to be a little dumber without bypassing its internal control and safety systems so it will charge if I turn that circuit on and switch between a daytime time/temp schedule and a night setback. In setback only, with auto boost it just try's to keep room setpoint, even if that takes more energy that it has stored.

What I need is all that basic functionality linked yo my systems SOC and the weather/solar forecast... If I add contactors that override it units fan and boost element circuits I can effectively choose when to let it discharge its thermal store and weather that discharge includes any additional boost output.

These extra controls will then be handled by NodeRed flows ensuring I capture as much execs solar as is possible and then make best use of that heat once I have it.

I expect a few iterations of a control strategy will be required along with some data capture and analysis so manual mode/s will be in there from the outset.

Sorry that was a bit long but I wanted my comments on the how too, to reflect my take on the why too.