Maximizing solar for AC loads without grid feedback

[bb12489]

I've done a lot of research over the past few days after realizing that my setup is probably not configured correctly to fully utilize our solar capability while being plugged into shore power on our bus. A brief overview of our system is below. Basically we want to be able to have the solar support our daily loads and charge our batteries. Then use the battery, and grid as fall backs when the solar can't keep up with higher AC loads. Right now our loads are always supported by the grid, and our charge controllers are sitting there doing nothing. The only way I've found around this is to toggle the inverter to "Inverter Only" while the sun is shinning, then back to "On" when the sun goes down.

I've read that ESS is what I'm looking for, but Victron states not to use this in a mobile application due to the fear of feeding power back into the grid, even though there is an option to not feed in to grid (does it actually not feed back power?). The other method I've seen involved setting up a virtual switch to ignore ac input under certain conditions (battery voltage and power draw). I messed around with setting some voltages for absorption/float higher on the charge controllers than on the inverter, but I think I'm missing some info here. I still can't get the solar to pick up the loads during the day. I also tried the new setting for solar priority, but that's not really doing what I want either.

I would appreciate any help on this, and I'm happy to share screenshots of my settings from ve.configure, and Venus OS if that helps.

1. Quattro 24/5000 Inverter
2. 3x 24v EG4 LiFePower4 batteries
3. 2x 150/60 Solar Charge Controllers
4. Victron Smart Shunt 500
5. Lynx Power in
6. Lynx Distributor
7. 8x 360w LG NeON panels
8. Rpi4 with latest Venus OS

 

[timselectric]

Paging @sunshine_eggo
he is the victron guru.
He will have the answers.

 

[sunshine_eggo]

You absolutely, positively don't want ESS.

Do you actually have everything connected to the RPi?
shunt?
both MPPT?
inverter?
batteries?

The solar priority is only for battery charging. AC will still pass through to loads. Best to disable it.

Since you don't actually have a Cerbo, virtual switch is probably your best bet, but it can be a little tricky to setup. It can't be time-based. It simply need to be voltage based.

When VS ON = use AC input.

Deselect "invert virtual switch usage" and select "ignore AC input...":


VS on (use AC input) if voltage < 24V for 30 seconds or more (or any of the alarm conditions):


VS off (ignore AC input) once bulk charging (according to inverter absorption voltage setting) has been finished for 15 minutes, i.e., after 15 minutes of absorption:


Note that you have to set the "when no VS on condition for" -1 minutes - it defaults to 0, which basically will immediately turn VS back off.

You can add other criteria if you want.

If you want to base it on SoC as well, there's an assistant that can do it based on SoC, voltage, and a few other critieria.

 

[bb12489]

You absolutely, positively don't want ESS.

Do you actually have everything connected to the RPi?
shunt?
both MPPT?
inverter?
batteries?

The solar priority is only for battery charging. AC will still pass through to loads. Best to disable it.

Since you don't actually have a Cerbo, virtual switch is probably your best bet, but it can be a little tricky to setup. It can't be time-based. It simply need to be voltage based.

When VS ON = use AC input.

Deselect "invert virtual switch usage" and select "ignore AC input...":
View attachment 194409

VS on (use AC input) if voltage < 24V for 30 seconds or more (or any of the alarm conditions):
View attachment 194412

VS off (ignore AC input) once bulk charging (according to inverter absorption voltage setting) has been finished for 15 minutes, i.e., after 15 minutes of absorption:
View attachment 194414

Note that you have to set the "when no VS on condition for" -1 minutes - it defaults to 0, which basically will immediately turn VS back off.

You can add other criteria if you want.

If you want to base it on SoC as well, there's an assistant that can do it based on SoC, voltage, and a few other critieria.

Yes, I forgot to mention that everything is connected to the Pi over ve direct, and the mk3 adapter for the inverter. I had suspicions that solar priority was not going to be much help here. Why does Victron have this and market it towards boats and RV's then? I'll try these settings out for virtual switch and see how it works for me.

Being the Victron guru here, could you possibly take a look at my current settings for charging? I looked through the EG4 manual for the correct float and absorption values, but wanted to make sure I have this tuned properly.

 

[bb12489]

Ahh I see this virtual switch config will generate a grid lost alarm. I guess if that's the biggest annoyance; I can live with that!

 

[sunshine_eggo]

Yes, I forgot to mention that everything is connected to the Pi over ve direct, and the mk3 adapter for the inverter. I had suspicions that solar priority was not going to be much help here.

That feature was very recently added... like in FW 506 just a short while ago. It was added because people asked for it.

Why does Victron have this and market it towards boats and RV's then?

Imagine a time where you want to draw from the grid because power is very cheap, but you still don't want to charge the battery unnecessarily if you have PV or wind power available.

I'll try these settings out for virtual switch and see how it works for me.

It may take some tweaking, and you may find yourself charging from grid when you'd rather be charging from solar. You may find the solar priority coupled with the ignore AC input VS may be advantageous to you.

Being the Victron guru here, could you possibly take a look at my current settings for charging? I looked through the EG4 manual for the correct float and absorption values, but wanted to make sure I have this tuned properly.

You're set for 3.55V/cell absorption, 1 hr and 3.375V/cell float. That's fine. If you're not in a hurry to charge, I'd pull that back to 3.45V/cell or 27.6V and 2 hr absorption. That's a little less stressful to the batteries (topped off at lower voltage and lower current over a longer period of time), and it might give them more time at elevated voltage to ensure balancing occurs.

Ahh I see this virtual switch config will generate a grid lost alarm. I guess if that's the biggest annoyance; I can live with that!

You can turn that off in the GX:

Menu -> Settings -> System Setup -> Monitoring for Grid Failure = Disabled

 

[bb12489]

That feature was very recently added... like in FW 506 just a short while ago. It was added because people asked for it.



Imagine a time where you want to draw from the grid because power is very cheap, but you still don't want to charge the battery unnecessarily if you have PV or wind power available.



It may take some tweaking, and you may find yourself charging from grid when you'd rather be charging from solar. You may find the solar priority coupled with the ignore AC input VS may be advantageous to you.



You're set for 3.55V/cell absorption, 1 hr and 3.375V/cell float. That's fine. If you're not in a hurry to charge, I'd pull that back to 3.45V/cell or 27.6V and 2 hr absorption. That's a little less stressful to the batteries (topped off at lower voltage and lower current over a longer period of time), and it might give them more time at elevated voltage to ensure balancing occurs.



You can turn that off in the GX:

Menu -> Settings -> System Setup -> Monitoring for Grid Failure = Disabled

Thanks for the assistance. If I wanted to make sure the battery doesn't deplete past a certain percentage, rather than rely on voltage, how would I do that? Or is it best to just use voltage?

 

[sunshine_eggo]

Thanks for the assistance. If I wanted to make sure the battery doesn't deplete past a certain percentage, rather than rely on voltage, how would I do that? Or is it best to just use voltage?

That requires the use of two assistants.

Ignore AC input using the Generator Assistant [Victron Energy]

www.victronenergy.com

You do NOT need the PV inverter support referenced.



Those are example start/stop criteria. You can play around with the assistant on your own and figure out what works best for you...

The BIG downside is that any changes you make to the assistant will cause the inverters to reboot with a brief power outage.

Example SOC based:





You will also need to enable the Inverter's Battery Monitor on the general tab and GX setup to enable DVCC with SVS and SCS enabled. Smartshunt as the battery monitor.