Dynamic ESS not charging batteries to cover forecasted consumption

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john-rig asked 2 days ago

Dynamic ESS not charging batteries to cover forecasted consumption

I have a very simple Dynamic ESS setup. No feed-in, Octopus Go price tariff - 5 hours overnight cheap rate. So in essence Dynamic ESS has just got to keep the batteries adequately charged to cover the next days predicted consumption and forecasted solar.

But I have found over the past couple of weeks that frequently the forecasted battery SOC will be down to minimum and from time to time even predict grid consumption during the day when there was overnight opportunity to charge the batteries. Here's the graph right now showing tomorrow's forecast. Batteries being charged, but no where close to available capacity, and during the day consumption from grid. And the predicted SOC is down to minimum by end of the day, so not permitting any headroom should the forecast be out.

I have an MPII 3000 and Pylontech bank (4 x US3000, 1 x US5000). Am I missing something in the config (there aren't many variables in my setup!), or is this a feature of the algorithm?

dynamic ess

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Answer 1 · 2024-07-15T13:26:17Z

john-rig answered · yesterday

As a follow-up to my previous post, here's the forecast for today. No overnight charging at low rate, then peak rate electricity usage in the evening. And even a short period of charging the battery during peak cost. I am trying very hard to see the logic - financial or otherwise - in this algorithm. Far from saving money, DESS seems to be doing the opposite. Target SOC seems to be way too low, and there seems to be no provision for uncertainty or probability of the forecasts.

Can anyone from Victron perhaps comment on why the forecasting is so far out from what would seem to be sensible?

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Answer 2 · 2024-07-16T09:40:47Z

Dirk-Jan Faber (Victron Energy) answered · 13 hours ago

The algorithm was expecting the solar energy to be enough for the night, but it turned out it wasn't. Since Dynamic ESS is need-based it simply leads to not charging ‘for no reason’ during the low price energy hours.

If you compare your first image to the actual one, you see that the solar yield was a lot less than anticipated.

In hindsight the system should have charged during the cheap hours. But hindsight logic is always easy and you can't change te past.

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