Moment to charge battery is not most cost effective in Dynamic ESS

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devilmastah asked Jun 7, '24

Moment to charge battery is not most cost effective in Dynamic ESS

Hi there,

i am quite new to the whole dynamic ESS and victron in general. So i might be overlooking something.
I have my small installation with 4.8 kwh of battery running for about one month now, it works quite well and does cover my evening and night use more or less perfectly, i will add more storage to it once budget allows.

The question i have comes down to this, i am having a dynamic energy tarif with Tibber in the Netherlands. Meaning i get basicly the same amount for every kWh i deliver back as i would pay for buying a kWh. But i notice that every day where there is sun the battery starts to charge ASAP. For example today it started charging at 7 in the morning while sending back to the grid is almost 10 cents more lucrative then at 13:00. I am wondering if there is a way to get it to charge later on the day instead of first thing in the morning, i know this would be a risk as the solar prediction might be off and there might be clouds later in the day. But from what i see it is a risk worth taking.

I was thinking that it might be possible to trick the system by modifying the pricing rules for buying and selling, but that would mean that the statistics would be off.

Here is a screenshot of what i am referring to:

dynamic ess scheduled charge

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dutchsolarfreak commented · Jun 10 at 10:48 AM

I am not an expert but lets try to help you.

Looks a bit funny but to be able to give you some advice we need to know your DESS settings. Could you please post your VRM DESS setting?

It looks you configured green mode right? Did you try the trade mode?

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Answer 1 · 2024-06-10T07:55:59Z

pim57 answered · Jun 10 at 07:55 AM

I use the gbb optimizer, which works much better than the Victron Dynamic ESS.

Gbb will not charge the battery while prices are high, but will wait till the afternoon. Just what you want.

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Answer 2 · 2024-06-10T11:53:11Z

Arie Kraan answered · Jun 10 at 11:53 AM

I am curious as in my install it works well. At higher prices it deliveres back and lateron it charges the battery. So first the orange color and lateron the green and even purple one. It could be that you put in the wrong numbers in the prices (like swapping delivery back and charging)

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Answer 3 · 2024-06-12T15:35:16Z

devilmastah answered · Jun 12 at 03:35 PM

@Pim57, i will have a look at that, but am otherwise quite happy with what this provides, i am also looking in building my own application with some machine learning, but that will be a whole project to come.

@DutchSolarFreak, yes it is on green mode, i have not tried trade mode yet as my main goal was self suffiency and backup power for some small scale server stuff. The green mode does exactly what i want / expect from it, except for the charging first thing in the morning where it would be better to feed back to the grid money wise. Will post a screenshot of the settings down here.

@Arie Kraan see settings as well if you like.

Other notes:
- the solar forcast is bang on most of the days, (sunny day ~ 22kwh at the moment, so a lot more then goes into the battery, so my main goal on such a day would be to just put it back into the grid as cost effective as possible of course).
- like in the first screenshot sometimes the system decides to later sell some energy as well, it does that where i would expect it (when price is high, and there is more energy in the battery then needed to cover the night), so at least that seems right :)

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