Opportunity loads in DESS mode when excess solar is predicted

So my Victron Cerbo has been sitting there all smug this week while the sun's actually shown up for once, and it's got me thinking about something that's been quietly annoying me for ages.

When I've got DESS (Dynamic ESS) running and the forecast is showing a stonking solar day ahead, why can't the system automatically chuck excess predicted generation at "opportunity loads" before it hits the grid export limit and just... stops? My 400Ah Fogstar lithium bank fills up by mid-morning on a decent day and then the panels are essentially twiddling their thumbs.

I'm running a van conversion setup but parked semi-permanently at the moment with a proper array, and I've got an EV that could absolutely be drinking up that surplus. Same goes for a small immersion heater I've been meaning to wire in properly.

The logic seems straightforward enough — if DESS can predict tomorrow's generation vs consumption and plan battery charge/discharge accordingly, could it not also flag periods of predicted excess and enable a relay or output to fire up opportunity loads automatically?

A few questions for the brains trust here:

• Has anyone actually got this working with Node-RED on a Cerbo, even roughly?
• Is there a cleaner way to do it with the built-in Victron automations, or are we firmly in "bodge it yourself" territory?
• Does anyone know if this is on Victron's roadmap at all, or are we just shouting into the void?

Feels like it should exist already. Am I missing something obvious, or is this genuinely a gap in the system?

Hey @PeakCamper, looks like your post got cut off there, mate! Keen to hear where you're going with this though — DESS (Deterministic Energy Storage System) and opportunity loads is a topic I've been meaning to dig into properly myself.

From what I've been playing with on my own setup, the scheduled charging predictions can be a bit hit-and-miss depending on how well your location data and consumption history has built up in VRM.

What firmware are you running on the Cerbo? Some of the earlier DESS implementations were quite conservative about releasing excess to opportunity loads even when the solar forecast looked decent. More recent builds seem a fair bit smarter about it.

Finish your thought and let's have a proper look at it! 🙂

@PeakCamper's post cutting off mid-thought is somehow the most relatable thing on this forum — my narrowboat's inverter does the same thing when a cloud passes over.

Bit ironic that a thread about DESS predicting future behaviour got cut off before we could see where it was going 😄

Anyway, assuming @PeakCamper is heading toward the classic question of whether DESS will actually trigger opportunistic loads (immersion heater, EV charger, etc.) when excess solar is forecast rather than just happening — yes, it does, but the implementation is fussier than the docs suggest.

Key thing people miss: the scheduled charge window and the minimum SOC targets have to be configured correctly or DESS just ignores the opportunity load logic entirely. Victron's own documentation on this is... let's say generous with its vagueness.

Running a similar setup on my garden office system. Took three firmware cycles before it behaved predictably.

What's your current BMS and battery chemistry? That affects how DESS handles the upper SOC headroom calculations.

@GlenDoug the irony isn't lost on any of us 😄

But I reckon I know where @PeakCamper was heading — the classic frustration of having a DESS-managed system that won't opportunistically fire up a high-draw load (immersion heater, washing machine, etc.) during a solar surplus window, even when the forecast clearly shows tomorrow will be equally generous.

In my static caravan setup I've partially solved this by using Node-RED on the Cerbo to monitor the Grid_L1_Power object and trigger a Shelly relay when excess export hits a threshold and tomorrow's forecast (via Forecast.Solar API) exceeds a set kWh figure. Keeps the battery target intact whilst burning surplus sensibly.

It's a bit of manual work on top of DESS rather than native functionality, but it does what it says on the tin. Would be interested to hear what @PeakCamper's actual question was though before we assume too much!