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erichabg asked

MP - Which assistant should I use?

I have a CerboGX, a Multiplus 24/3000 (old one, no II), a 24V/280Ah battery and some MPPTs (in total 2kWp Solar). Which Assistent should I use for the following use case?
I want to use solar energy first, then energy from the battery (if SOC > 30%), and last from the grid. Normally the battery should not be charged from the grid (AC input) but this should be possible by hand in exceptional cases.
If the power demand exceeds a certain level (i.e. 1800W), then Power assist should be switched on.

Up to now I have controlled this via a raspberry pi with my own software, but I think this should also be possible via CerboGX and the matching Assistant and may be a nodered flow?
Regards
Erich

Assistants
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JohnC answered ·

Hi @erichabg

This is fairly simple using the Generator Start And Stop Assistant. But instead of using an output relay you switch ACIN (via General Flag). This is usually called Ignore AC, which would be your standard state when solar is sufficient, then 'not ignored' when SOC <30% or Load >1800W. To switch it off you also need to set the other end limits and perhaps times for these functions.

First up I'd invoke DVCC in the GX so that all your kit sees the same data. Then set the Multi's charge settings 0.1V lower than the mppt's. That will ensure the mppt always has priority charging batts.

The Grid always takes priority over the inverter serving loads, but you can set whatever AC input and charge limits you want in the Multi.

To add in a manual override to the IgnoreAC switch, you could hardwire an external switch to a Multi Aux port, even input from a Cerbo relay. Your imagination rules there..

Multiple Assistants usually results from setting up something like this, but they have to be in a logical order. Have fun..

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erichabg answered ·

Thank you for your answer!

You wrote "To add in a manual override to the IgnoreAC switch, you could hardwire an external switch to a Multi Aux port, even input from a Cerbo relay. Your imagination rules there.. ".
I was not able to use this. I have tried to use "programmable relay" in additon to the generator start/stop assistant. I have set the programmable relay to use also the General flag. But there is no reaction IgnoreAC doesn't change when I set/unset the AUX1 (or T-Sense) of the MP. (But depending of the order of the assistants the generator start/stop assisant stops working.)

The second problem is that I don't want the battery to be charged from the mains under normal circumstances. If the battery drops below a certain SOC (mostly at night), the MP should go into the "Passthrough" state, but the battery should not be charged again until the MPPTs supply power (or I manually activate charging,).

I am now at a bit of a loss.

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JohnC avatar image JohnC ♦ commented ·

@erichabg

Great to see you having a good go at this. Sure it can be tricky to get working the way you want, but you're on the right track.

The Programmable Relay(s) is the right one to use for that override thing, but you might just have got the on/off 'polarity' wrong. As you've found, the order is all-important, and you'll likely find you need multiple instances of PR at times. Always remember that if something is turned 'on' then it won't turn off or return to default unless you tell it to. Getting your head around how multiple Assistants work together is the key, so don't give up yet.

Having the charger switch off under passthru is a little trickier. I haven't tried this myself (and it might seem stupid), but there's also a Charge Current Control Asst. It needs input from a hard port (0-5V, but should 'pull-up' with an on/off signal), So try driving say K1 and hardwiring a signal pair across. Sounds stupid, but I can't think of anything else as easy..

Hard to help you with your logic path without seeing the hard data. Post it if you get desperate, and I'll try to help. But I'd rather see you master this yourself.

And oh, not sure what signal ports you have on your particular Multi, hope you don't run out.. :)


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