Input Current Limit based on SOC or voltage without ESS

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aihngeltech asked May 15, '24

Input Current Limit based on SOC or voltage without ESS

Good Day,

I would like to limit my input current based on SOC but don't see a way to do it with anything besides ESS.

Application: My batteries are higher than I need them to be (charging from solar) and instead of kicking back and forth with AC IN IGNORE I'd like to just limit my AC draw from the grid. This would allow my MPPT to keep sucking power from the sun but apply it to my loads instead (safely).

Things to note:

I'm doing this in an RV (ESS is not an option)

Multiplus 3000/120

SmartSolar 100/50

Cerbo

SmartShunt

MultiPlus Quattro Inverter Charger cerbo gx ESS MPPT SmartSolar feed-in limit

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Modifications Space

Node Red Space

Answer 1 · 2024-05-15T20:11:35Z

Alistair Warburton answered · May 15 at 08:11 PM

Two options... (That I know of)

1. AC current limit, min is 4A I think, as in you can set it lower, but it will not actually function below 4A, ish. you can control it using Node red on the Cerbo or any external controller capable of talking Modbus TCP. One other wrinkle... If you are using power assist be careful with the initial boos setting as it is a multiple of the AC limit so could be unpredictable if you don't detect the generator/shore power and adjust accordingly.

2. Charge current can be dynamically limited using the DVCC functionality, again managed by Node Red... Provided you are not already using that as a bridge to an external, integrated, BMS.

It may be possible override a BMS sending a higher limit than you actually want, you would have to look at the docs/detail. Personally I have a BYD battery, on my 48, that uses DVCC to manage the charge current, from the inverter and solar, so I don't mess with it at all on that system.

My 24 on the other hand... DVCC charge limit, driven only by Node Red, controls how much energy, and more importantly when, I allow the charger to run. Obviously the AC has to be on, in my case from the 48 but it works great... When the generator is running, feeding the 48 and thus the 24 I set the current to get both batteries up to my cutoff at about the same time. I almost never charge the 24 from the 48 on battery. when I want to use energy from the 24 all I have to to is set the 48 to Charge or put the 24 in Invert as opposed to Both. (The latter being my choice as I think Charge still provides pass through of the AC, although I am not entirely sure now I think about it.)

Give me a shout if you want details... Happy to provide them but probably not relevant for the most part.

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Alistair Warburton commented · May 16 at 06:06 AM

I just realized that both Charge Current and Import/Export can be adjusted/modified from an assistant based, on an analogue input value if the above isn't going to work for you.

See comments on IO in:-

https://community.victronenergy.com/questions/150596/node-red-multiplus-ii-primary-relay.html

BTW. I checked and setting an AC input limit below 4A is possible, but the lowest import I see on a Multiplus is circa 4.6A Cant speak for a Multiplus II, Quatro or anything else for that matter.

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Answer 2 · 2024-05-16T06:42:41Z

nickdb answered · May 16 at 06:42 AM

Easiest way is to use nodered. You can construct a simple matrix of "IF SOC >, < or = X then current limit = Y"

This is also easy to change on the fly, whereas assistants are rigid and require reprogramming of the inverter.

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