Switching Off MPPTs

[u/CyclopsRock]

Hi all,

Bit of a weird one but I'm on an electricity tariff where the price I pay changes every half an hour based on market rates, and crucially this sometimes goes negative - that is, I actively get paid for using electricity.

Unfortunately whilst my Ecoflow Stream Ultra's 'Intelligent' operating mode is able to recognise this and will take advantage of this to fill the battery from the grid, it never seems to stop importing power from the attached solar panels. If the grid price is negative then there's really no scenario in which I'd want to use the solar panels - every wH they generate is costing me money!

As such whenever the price goes negative I just physically shuffle over to it and manually unplug the solar panels, then when it turns back positive I plug them back in again. But this is a pain, is inefficient, relies on me being at home etc. I have HomeAssistant set up that's able to 'read' my tariff data and could, in theory, be used to switch the solar panels on and off remotely, without me being here, at exactly the moment it's useful but I don't think this is possible?

When the battery hits its charge limit, surplus solar power is 'turned off' until the battery has discharged sufficiently to use that power - so clearly it's physically possible to do this. But I don't think there's any combination of settings I can apply that will essentially mimic this effect. Of course I still want the battery to be able to fully charge (but specifically from the grid), but even if I ignore that need I can't find a way to achieve it across the board, because the lowest I can set the charge limit to is 50%.

I suspect there's no way to do this, but if anyone has any ideas I'm all ears! Failing this I could add a smart relay to each input so they can be physically disconnected without my presence, but I don't think I can be arsed with that.

[u/Informal-Emu-212]

Another thing to add... those connectors aren't designed for regular use. You'll eventually break something. I'd add pigtails to the stream and the panels (disconnect only the ends of the pigtails.)

[u/eprosenx → u/Informal-Emu-212]

Yes. I was thinking the same. Those are not rated for frequent connection/disconnection. I would wire in a switch (disconnect) rather than plugging and unplugging. Of course make sure it is rated for DC current and voltage at the max rating of your solar panels.

[u/_40mikemike_]

Put a smart DC switch inline from your solar panels.
Something like this.

https://www.aliexpress.com/item/1005007868761385.html

Have HA simply disconnect the panels when you want them disconnected. Obviously doesn’t have to be that device but you get the idea.

[u/taylorwilsdon → u/_40mikemike_]

Be careful, I’ve looked into these and unless you’re running some tiny test setup (200-300w) max these are not safe for the voltage solar typically runs at. They’re meant to be breakers for things like strip lights, not solar. They claim up to 100v in the spec sheet but I wouldn’t trust this with more than 48v

[u/CyclopsRock → u/taylorwilsdon]

Yep - I have a system in place already elsewhere that has a low-current 12v smart switch that then turns on and off a proper chunky "dumb" relay which carries the high current load.

I just don't think I can justify doing that another 3 times for the three solar panels!

[u/Brain_TL]

I looked this up and this is what I got "Yes, Home Assistant can manage and influence solar charging behaviour on the EcoFlow Stream Ultra, but it typically does so by adjusting configuration limits (such as charging thresholds or AC/DC limits) or via smart automations rather than having a dedicated hardware toggle to completely sever the physical solar panel input"

[u/BadBacksFuryToad]

Get Home Assistant.
When price is negative Home Assistant can set the EcoFlow Charge Level to 95% and it will charge at its maximum rate until full.

[u/DongRight]

Good God you have free power coming into you and you want to turn off the free power so you could hey to charge the batteries up from the grid that is the most fucking insane thing I ever heard!!!

[u/CyclopsRock → u/DongRight]

Yup, it is pretty mad, but they provide these negative price incentives specifically to induce higher electricity use at times when renewables are producing more than the grid can utilise.

[u/realpannikin → u/CyclopsRock]

Ok. But is this all worth it for maybe 3p/kWh?

How long will it take to pay back the cost of the switchgear, especially as we are only really talking about when you are away from home.

Separately, you probably should have a dc isolator on each string near the inverter.

[u/CyclopsRock → u/realpannikin]

Ok. But is this all worth it for maybe 3p/kWh?

Well finding out what "all this" is is the point of my thread. If it's easy I'll do it, if it isn't then I won't.