question

philia avatar image
philia asked

more consumption when PV working

Good evening! Somebody has an explication why in my system when solar panel are working the consumption is also growing ? it seems a non sense because there is nothing switching on. This is a simple solar system in a sail boat at the moment located in Italy with 2 sun power panels 110w and 2 mppt 75/15 (no cc load connected) , cerbo gx , smart shunt and phoenix 12/1200 (disconnected).

I explain better: as you can see during night and still early in the morning the diagram shows low consumptions then when at 9 with sun solar panel start to produce the consumption is growing; then in the afternoon after sun set again consumption goes lower. This is a normal trend not due to occasional consumption (like a bilge pump starting...). The 12v system is always on just to give energy to a router, a web cam, and of course to the victron systems; so normally the basic consumption is more or less 13w (or 1,2 Ah) and there is no reason why grew up during the day (9 am-16 pm just at the same time PV is working). Thank you for an explication.

Schermata 2023-01-14 alle 20.53.45.png

BMV Battery Monitor
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

7 Answers
klim8skeptic avatar image
klim8skeptic answered ·

Do you have "Has DC system" enabled?

Via remote console, settings > system setup > has dc system.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

JohnC avatar image
JohnC answered ·

Hi @philia

My first suspicion is that the shunt is wired incorrectly. Perhaps even the wrong way round and needs a Zero Current Calibration too.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

philia avatar image
philia answered ·

Good morning! yes DC system enabled.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

philia avatar image
philia answered ·

@JhonC good morning! I think the shunt ic correctly wired but I check; about zero calibration I did not it. I check how to do . Thank you!

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

pwfarnell avatar image
pwfarnell answered ·

If your shunt is on the battery then there is no direct measure of the DC power, the reported value is a calculation, it calculates the power being produced, the power flowing into or out of the batteries and subtracts these to give the balance which it calls the DC power. If there are small errors between the solar panel power and the smartshunt power then those errors end up being reported as DC power. The same is true for any cable losses. My boat behaves exactly the same. The DC power is only an estimated value.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

philia avatar image
philia answered ·

@pwfarnell Hi Thank you! just now looking to "zero currente calibration" I have read an information of another member and then I understood the error in my system is that the negative coming from MPPT is connect directly to the negative of the battery not to the "load pole" of the shunt; so when PV produce energy the shunt reads it as a "consumption" just at the same time; I will move this negative pole to the correct position of the shunt. Thank you all for the help! really a fantastic community! ;)

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Michelle Konzack avatar image
Michelle Konzack answered ·

This looks like a DC load is running and if the Solarpanels start charging, the Voltage increase hence the Power also

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.