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assyntdavid avatar image
assyntdavid asked

Can I trigger a relay based on scheduled charging times?

I am running a Victron ESS system (Multiplus 2 with CERBO GX, Pylontech batteries and SolarEdge inverter). I have a local situation which could be solved/improved if it were possible to program one of the Multiplus relays to operate according to whether the system is within or outside a set scheduled charging period. That output would then be used to operate a high current relay to switch part of the load. Does anyone know if something like this is possible? I can't see a way of doing it but it feels like it should be possible.

Many Thanks

ESS
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assyntdavid answered ·

Having abandoned this 'problem' in February as it looked challenging to solve, I revisited it again yesterday only to realise there is an easy and pretty straightforward zero cost solution. So I am answering my own question here in the hope it may help someone else.

The issue: The house runs on batteries during the day and the batteries are charged at night on cheaper electricity. The Multiplus is in the plant room next to the lounge. It is noisy and a nuisance when holding out the mains daytime so the system is isolated fom the mains (noticably quieter) during the day and reconnected at night. This is done manually and prone to forgetfulness, I wanted to automate it. I also thought a costly external relay would be needed.

The solution:

Yesterday it occured to me that I might be able to use the internal relay in the multiplus on ACin, and that the mains is really just a generator for which there are many control options.

On the Cerbo GX go to:

Menu->Device List->Settings->Generator start/stop->Settings->Conditions->Periodic run

There I set the 'Run interval' to 1 days, and the 'Start time' and 'Run duration' to match the scheduled charging period.

I ran a simple two core wire from Relay 1 on the Cerbo GX (NO & COM) to Aux 2 input under the Multiplus.

I used VEconfigure to set up 3 assistants; 'general flag user' to switch off/ignore ACin, 'programmable relay' to set the flag to 1 and 'programmable relay (1)' to set the flag to 0. The summary looks like this.

screenshot-2023-12-02-150824.pngAnd of course the mains (generator) can be easily manually controlled via the VRM dashboard. I think this may have been what @JohnC had in mind but I didn't get it then.

David


screenshot-2023-12-02-150824.png (33.1 KiB)
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JohnC avatar image JohnC ♦ commented ·

Good work @assyntdavid

Not exactly what I suggested, but close. I proposed switching ACOut2 because you asked how to switch certain loads. Those loads would of course be wired to ACOut2. But I suppose I did mention the ACIn briefly.

But if what you've devised works for you, then great.

The beauty is it's free.. :)


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JohnC avatar image
JohnC answered ·

Hi @assyntdavid

Take a look at the Generator start functionality in the GX. This has 'quiet times' settings which might be able to be worked into your logic chain.. https://www.victronenergy.com/upload/documents/Cerbo_GX/CCGX__Venus_GX__Cerbo_GX__Cerbo-S_GX_Manual-en.pdf

Section 16.

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assyntdavid avatar image
assyntdavid answered ·

Thanks @JohnC

That does seem to be an option. I can't find any tech info for the recommended Relay 1, eg current rating, etc - it would be a shame to accidently overload it. The usually good Victron documentation does not seem to include this. Have you seen anything.

It seems that linking the relay directly to the scheduled charging times isn't an available option. That would certainly be better as the whole system would then automatically respond to any change of charging schedule when cheaper electricity is available. I am desperately trying NOT to set up a house ESS system not no-one else can understand or work.

Better still would be for the noise level of the House Multi 2 when under load to be significantly lower! I had assumed that 'pass through' was just that, a simple pass through. My house Multi 2 is much noisier than my off-grid hut Multi. The House Multi is in a central 'plant room' and my fear is that the Multi will simply keep the whole house awake if I use the likes of an EV charging station (7kW) at night. I dread to think what the system would sound like if anyone actually pushed it to the 100A AC current input limit! I am toying with the notion of using a relay to switch the EV circuit from the Multi ACout to run direct from the mains feed at night.

Regards,

David

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JohnC avatar image JohnC ♦ commented ·
@assyntdavid

I can't help much with the relay capacities. I tend to look at the signal relays as being very limited in V and A levels, and at best maybe capable of working an SSR. If you're specific about borderline worries, someone should be able to help with further advice.

There's one big relay in the Multi though, ACOut2. Can be driven with Assistants, the issue there is that they don't know the time of day. But a signal pair across from the GX could fix that. Just thinking aloud here, and where you head is ultimately up to your inventiveness.

There's been some discussion on MPII noise in threads here, with various outcomes. Even firmware updates, so don't give up on that yet. Try the Search option.

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assyntdavid answered ·

Thanks John, I think you have summed it up nicely. In my off grid hut set up I wanted to power a 400W heater based on battery SOC. Numerous ways of doing this but the installer pointed me firmly to use of AC2 and Gen start stop Assistant - works a treat. Documentation suggests that Cerbo GX Relay 1 slightly more robust than Relay 2, but the lack of data suggests they are signal relays. As you say I could link to the Aux inputs and use AC2 out which is currently not used.

I'm thinking that I just go ahead with the EV charging station and hold these options as a backup if the noise level proves to be an issue that demands attention.

Re noise levels, the house Multi is the 10kW model, the hut is 5kW. House multi is significantly noisier under comparable operating conditions - strange. In the evenings with circa 400W load the mains hum can be intolerable. I have noticed the hum worsens with increasing mains voltage, which is always high around here and typically rises to 250V or higher on an evening. (So much for the nominal 230V!) I have taken to disconnecting the Multi every day so it runs soley in inverter mode, that gets rid of the mains hum so noise becomes tolerable (and also reduces power self consumption). Down side is a have to remember to reconnect the mains at bedtime to let the batteries recharge overnight.

I am very pleased overall with Victron kit, it's versatility is staggering. My off grid set up has reached or exceeded all expectations. Improve the noise situation and I'd be just as happy with the house ESS set up.

All the best to you. Thanks for bothering to respond. Much appreciated.

David

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JohnC avatar image JohnC ♦ commented ·
@assyntdavid

You can also programme in that mains disconnection with Assistants if you want, no memory needed. :)

Good luck with it all..


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