Electrical puzzle

[pessimist]

We're not at the boat at the moment so the main electrical supply is switched off. The batteries are being maintained by solar. The graph below shows the current over the last 24hrs. The step just after midnight suggests a drop of about 0.2amp. Not something to worry about (I don't think) but I am curious. The same thing happens between midnight and 0200 every night. The only devices attached to the batteries are a BM1 and BM2 battery monitor, an Epever solar controller and the RPI running the monitoring software. I assume it must be some kind of parasitic load but what?

 

[sarabande]

Could it possibly be a failed diode in the array ? That might explain the apparent discharge, and then the fairly high demand as the sun comes back on to the panels. ?

Is the RPi running any other system (alarm/monitoring/comms, etc ) ?

 

[lustyd]

The RPi runs Linux presumably, so may well be running maintenance routines or attempting updates on a schedule. This will use more power than sitting doing nothing.

 

[KompetentKrew]

cron jobs on the Pi - check root's crontab (crontab -l) and also there might be a directory of cron scripts in /etc.

 

[GHA]

What other data do you have? Voltage might be interesting. Initially thought you were running openplotter/signalk which would allow plotting lots of things going on under to hood on the Pi to see if that's the culprit. Don't know anything about skippersmate though sorry.
Can you get into the Pi over the web to run some commands?
Might be interesting to turn off the solar completely overnight & have another look next time you're down at the boat. Sometimes it's quicker just to randomly search. ?

Edit - thinking a bit more about this, it seems unlikely to be the Pi, a change of 0.2A is a lot.
I run a PiZero2W 24/7, recently it was getting grumpy & load average was up which turned out to be influxdb keeping maybe a years worth of data clean, set it to just save a week cheered it up, but even working flat out there wasn't too much more current getting used. Power in these graphs is for a PiZero, ESP32, a few usb/serial devices & memory stick.

Spikes are mainly a hifi amp plugged onto of the pi playing music streamed from the web by the Pi.

 

[pessimist]

Could it possibly be a failed diode in the array ? That might explain the apparent discharge, and then the fairly high demand as the sun comes back on to the panels. ?

Is the RPi running any other system (alarm/monitoring/comms, etc ) ?

Don't think it could be a failed diode, I believe the controller 'disconnects' tne panels when there is no sunlight.
When we are not at the boat the RPi is currentl being used only for battery monitoring - I'm trying to see what I get get away with running over the winter months.

 

[pessimist]

The RPi runs Linux presumably, so may well be running maintenance routines or attempting updates on a schedule. This will use more power than sitting doing nothing.

No maintenance routines or updates.

 

[pessimist]

cron jobs on the Pi - check root's crontab (crontab -l) and also there might be a directory of cron scripts in /etc.

Sorry, no cron jobs other than a database back up every hour. The blip only occurs once a night.

 

[pessimist]

What other data do you have? Voltage might be interesting. Initially thought you were running openplotter/signalk which would allow plotting lots of things going on under to hood on the Pi to see if that's the culprit. Don't know anything about skippersmate though sorry.
Can you get into the Pi over the web to run some commands?
Might be interesting to turn off the solar completely overnight & have another look next time you're down at the boat. Sometimes it's quicker just to randomly search. ?

Edit - thinking a bit more about this, it seems unlikely to be the Pi, a change of 0.2A is a lot.
I run a PiZero2W 24/7, recently it was getting grumpy & load average was up which turned out to be influxdb keeping maybe a years worth of data clean, set it to just save a week cheered it up, but even working flat out there wasn't too much more current getting used. Power in these graphs is for a PiZero, ESP32, a few usb/serial devices & memory stick.

Spikes are mainly a hifi amp plugged onto of the pi playing music streamed from the web by the Pi.

Don't worry about the skippersmate bit - it's just providing the VPN to allow access to the boat. I'm not running Openplotter but am running SignalK and Grafana.
I have full ssh and root access to the Pi so can run anything you like, but I'm out of ideas
I do have a graph of the volts as well, I can post it if you like but there is no corresponding blip. If you are familiar with Grafana you can view the live graphs here.

 

[pessimist]

Thanks to everyone for the replies so far. Sadly none seem to fit the bill. My brain hurts.

 

[lustyd]

If it’s that regular it’s something scheduled. It can’t be solar or the time would change.

 

[Bran]

The 0.2 step is in a positive direction so there is a small decrease in the current drawn, not an increase so it is not parasitic.
Is there any external lighting that comes on and has the right wavelength to give a little solar energy ?
As mentioned before, try switching the solar off for one or two evenings and see if the blip disappears.

 

[pessimist]

If it’s that regular it’s something scheduled. It can’t be solar or the time would change.

Agree, but the time does change. Anytime between 1200 and 0200.

 

[pessimist]

The 0.2 step is in a positive direction so there is a small decrease in the current drawn, not an increase so it is not parasitic.
Is there any external lighting that comes on and has the right wavelength to give a little solar energy ?
As mentioned before, try switching the solar off for one or two evenings and see if the blip disappears.

No external lighting. Tricky to switch off the solar as we're not on board and when we are there are other loads which I think will disguise the blip. Where is the head scratching emoji?

 

[Draystone]

Possibly a (falling) temperature related error in the measuring system.

 

[pessimist]

Possibly a (falling) temperature related error in the measuring system.

That's an interesting thought. I'll see about recording temperature. Seems a bit of an abrupt change though.

 

[GHA]

I have full ssh and root access to the Pi so can run anything you like, but I'm out of ideas
I do have a graph of the volts as well, I can post it if you like but there is no corresponding blip. If you are familiar with Grafana you can view the live graphs here.

signalk has quite a good Raspberry Pi monitoring app,
GitHub - nmostovoy/signalk-raspberry-pi-monitoring: Signal K Node Server Plugin for Raspberry PI monitoring (based on signalk-raspberry-pi-temperature),
which should flag up anything odd going on there.

Though seems unlikely to reduce power by 0.2a instantly.

 

[bedouin]

Could it be some form of state change in the Solar controller? Maybe disconnecting itself entirely after not providing power for a certain amount of time? Maybe triggered by the voltage of the batteries that will fall slightly over night. The small drop early in the morning could be it being connected again

 

[pessimist]

Could it be some form of state change in the Solar controller? Maybe disconnecting itself entirely after not providing power for a certain amount of time? Maybe triggered by the voltage of the batteries that will fall slightly over night. The small drop early in the morning could be it being connected again

That's an interesting idea and sounds plausible. I don't have enough knowledge of the internals of solar controllers to make a judgement but maybe someone more knowledgeable than me will be along................

Edit - just checked the tech. spec. for the controller and self discharge is quoted at 15mA so I don't think that's the cause.

 

[sarabande]

Is there anything connected to the Load terminals of the controller ? Bedouin might have something there; a load that switches itself off/on when a minimum V is reached.

On Victron kit you can adjust the parameters for Load disconnect.