Unexplainable Grid to Consumption at night - not comnsumed from Battery

Q&A and troubleshooting DESS
, ,
1

Hi!

I have observed this strange behavior that my Victron Multi Plus 5000 setup was during the night all of a sudden consuming Power from the grid twice.

Here the screenshot from VRM:

image
image2216×1010 111 KB

where you can see that between 1 and 2 am there was about 0.32kWh of consumption that is not really explainable - no real peaks or anything.

I also looked at home assistant graphs and found this between 0:00 and 3:00:

image
image4588×1828 431 KB

where you can see that there are to windows of consumption from the grid:
01:04 - 01:22
and
01:37 to 02:01

You also see that while there was this spike the load of the battery was reduced from -11.5A to -2.4A.

Any ideas why this could have happened?
How can I avoid something like this in the future?

Thanks

Has something like this been seen before?

2

From the screenshots i presume you run DESS? Looks like DESS calculated it needed to use the grid to get to the desired SOC. Why that was the desired SOC? Depends on your prices and settings in DESS.

3

Yes - I have enabled DESS but as I am at this moment self efficient this should not happen - and the buy price was definitely not the cheapest (2-3am was slightly cheaper - not to mention around noon)

image
image1504×2000 158 KB

Also what is suspicious to me is the fact that it was twic for 20 minutes - if it had been for 15 minutes or 1 hour I could probably under stand it!

As for Soc: it was at that time between 74 and 78%.

image
image1668×844 81.1 KB

So I wonder why DESS would come up with the idea of not charging the battery (but just taking less from the battery for those intervals.

Are there any logs on the GX device that could help understand this? If so which ones?

4

Dess does not know that and apparently calculated differently.

DESS adjusts to get back on track for the running hour, this takes however long it takes, not 15 or 60 minutes.

So probably target SOC was 78%

I’ve observed this behaviour frequently, hopefully it will get better with time. For the moment it’s annoying but not a dealbreaker for me.

5

Well - I am still getting my feet wet with DESS but I find this behaviour annoing (and an unnecessary waste of money).

It actually happened this morning again - at the highest local price to buy from the grid!

image
image2250×2168 336 KB

With the battery at 61-62% (as per VRM for that time)

The effective Power cost (including Gird and taxes): 0.10Eu.

Which is minimal but it would sum up in the long run!

Right now I start to think how to do DESS without using DESS as an alternative.

Some hints on which logs on my GX/VenusOS device would explain the behaviour of DESS would also be appreciated!

6

I agree, but i fail to find a better system that works out of the box.

Seeing you use home assistant maybe this thread can be of help. That way you can log what the DESS strategy is in home assistant.

7

Thanks for that link!

I already got an MQTT server in my setup (for other sensors) and adding an additional one is not supported - only possibility would be replicating from the Venus MQTT server…

8

MQTT Servers can be bridged.

I have done this with mosquitto on my Homeassistant server.