State of Charge

[wineteam]

Boondocking last week and used the Victron Connect app to watch my electrical usage and gauge the condition of my Expion lithium batteries. We have five 90W solar panels and were in partial shade. We drop the temp on the thermostat at night so the furnace only ran sparingly. Third night the temps dropped low and the furnace ran the batteries down to 10.47V at which point nothing worked. The Victron app showed 90%+ SOC when we went to sleep and I didn't focus on the voltage. First time I had run into this.

My question is there a way to program the Victron Connect app to more accurately represent how much potential power we have? The app will show how many days/hours of power are left but obviously if the furnace kicks in the draw goes up significantly and drains the batteries quickly. (Side note I will be installing a Camco catalytic propane heater for the future so we won't need the furnace)

Screenshot of the next day with 10.96V but showing 98% SOC and 10 days of power available. I would think at 11V I would only have 20% SOC if that. Understand it is based upon the watts being drawn but at the low voltage there would be some variable in the algorithm that would lower the SOC value.

Thanks for any ideas.

[OutdoorIdaho]

I am curious about your settings. How do they compare to these recommendations from AM Solar?

https://amsolar.com/rv-solar/support

[Silvr_Bullet]

Originally Posted by wineteam

Boondocking last week and used the Victron Connect app to watch my electrical usage and gauge the condition of my Expion lithium batteries. We have five 90W solar panels and were in partial shade. We drop the temp on the thermostat at night so the furnace only ran sparingly. Third night the temps dropped low and the furnace ran the batteries down to 10.47V at which point nothing worked. The Victron app showed 90%+ SOC when we went to sleep and I didn't focus on the voltage. First time I had run into this.



My question is there a way to program the Victron Connect app to more accurately represent how much potential power we have? The app will show how many days/hours of power are left but obviously if the furnace kicks in the draw goes up significantly and drains the batteries quickly. (Side note I will be installing a Camco catalytic propane heater for the future so we won't need the furnace)



Screenshot of the next day with 10.96V but showing 98% SOC and 10 days of power available. I would think at 11V I would only have 20% SOC if that. Understand it is based upon the watts being drawn but at the low voltage there would be some variable in the algorithm that would lower the SOC value.



Thanks for any ideas.

When you are seeing ‘x’ # of days left, that’s at your current draw of the battery.

[field & stream]

This is a puzzle. Would be helpful to know how many Amp hours your batteries have and how many Amps your furnace draws when running.

I don’t think the app can “more accurately” forecast days remaining because the future rate of usage is too variable. The screenshot makes no sense. I suggest you fully recharge the batteries, resynch the Victron, and try this again.

[62olander]

[QUOTE=field & stream;2594863]This is a puzzle. Would be helpful to know how many Amp hours your batteries have and how many Amps your furnace draws when running.

The readings on the App are dependent on how you set up the monitor connections on your battery bank. Also need to get the settings correct, especially the total Amp hours of the batteries in your system. It took me a little while to get this correct on my smart shunt installation.

[Silvr_Bullet]

The stater battery is reading .02v, maybe that’s not even enough to power the shunt for an accurate readout.

[ITSNO60]

Originally Posted by Silvr_Bullet

The stater battery is reading .02v, maybe that’s not even enough to power the shunt for an accurate readout.

Or the starter battery is not connected, when not connected the Smart shunt shows a very small voltage like .01-.02V

[ITSNO60]

Originally Posted by Silvr_Bullet

When you are seeing ‘x’ # of days left, that’s at your current draw of the battery.

I believe this is it, the "X" days left is not a meaningful estimate when the load varies more than a few watts. To get a meaningful estimate the OP would need to calculate it based on the known consumption of what he is running and the approximate time each load will be running, no way the SS can know that info and I don't believe the SS actually uses voltage in any of it's calculations.
The "X" days remaining is also figuring in the input at that particular time, which in the case of the solar will disappear from the equation during the night.
Pretty sure the OP understands all this and just wants a way for the SS to use the voltage to adjust it's estimate, not sure if any of them can do that.

[field & stream]

Originally Posted by ITSNO60

Or the starter battery is not connected, when not connected the Smart shunt shows a very small voltage like .01-.02V

Yes, mine is not connected and the Victron display shows .03v constantly.

[ITSNO60]

Originally Posted by wineteam

Understand it is based upon the watts being drawn but at the low voltage there would be some variable in the algorithm that would lower the SOC value.

Thanks for any ideas.

In my experience with mine there is no such algorithm, I believe the voltage reading is totally unrelated to the "time left" or the "SOC" calculation which is simply a mathematical calculation using watts in and watts out. If you apply a heavier load does the "days left" drop to almost nothing? What happens to the SOC? Or is there no load that the batteries will even support at this point? The 98% SOC is a bit confusing, are you positive all the negatives pass thru the shunt?

[ITSNO60]

We need Bob to explain the 98% SOC

[wineteam]

So total amp hours is 240 (2 x 120).

Yes, no way the app can predict future load and I have seen the Time Remaining drop down to a few hours available.

I will resynchronize the system tomorrow. The trailer is stored in my driveway and in full sunlight with very little load. I will also double check the AM Solar Victron settings OutdoorIdaho provided in his link against the settings in the app.

I appreciate the input! More to learn.

[field & stream]

Originally Posted by wineteam

So total amp hours is 240 (2 x 120).

Yes, no way the app can predict future load and I have seen the Time Remaining drop down to a few hours available.

I will resynchronize the system tomorrow. The trailer is stored in my driveway and in full sunlight with very little load. I will also double check the AM Solar Victron settings OutdoorIdaho provided in his link against the settings in the app.

I appreciate the input! More to learn.

This is helpful info, thanks. So, assuming the Victron was correct that you were at 90% SOC, then you had about 200Ah of stored power at bedtime. To run the batteries down to the shutoff point in about 8 hours the heater would have to draw 25 Amps while running and have run constantly all night. Neither of these are remotely possible — so something else is wrong.

(I don’t know enough to say this is what happened in your case, but I had a similar experience with my Battle Born battery and the internal battery management system had failed. Battle Born was great about it and promptly replaced the battery for free.)

I suggest you plug into shore power to get to full charge, then synch the Victron, then run a test. Make note of how much power the heater consumes while running.

[ITSNO60]

Just a thought, do you have "Battery Starts Synchronized" turned on in the settings menu? You should only have that turned on if you remove the batteries or disconnect them and charge then re-install them. With battery starts synchronized turned on the SOC will go to 100% each time the battery is re-connected regardless of it's real SOC. If you drained the batteries so low that everything quit working the SS could have lost power for a moment then upon re-power and set to "battery starts synchronized ON" it would have gone to 100%.