Autonomous SOC control Solar Assistant

[Skypower]

The end game is as little system interaction as possible. And I’m getting close. The goal is to use the grid as little as possible and only during off peak rates as needed to supplement solar if insufficient because of weather or high demand. Also maintain optimal state of charge for emergency use with frequent excursions into the balance voltage at least several times a week. In the past when I first started out I’d simply intervene and trip a charge manually to USB or set the back to grid voltage to do it. But both of those would not stop until full state of charge and not disengage grid to let the solar handle the brunt of the work. For about a year I’ve been using the built in timer and current, varying those two values for just the right amount, but that is always a guess plus insight Willy weather UV predictions. Soooo…
Now I’m trying the “Maintain battery state of charge” feature in Solar Assistant. It’s been very successful so far but it’s early and it could be dumb luck so I’ll let it run for a while before perhaps some more tweaks on times, SOC points and charge current. Summer off peak rates are midnight to noon so I think I got that covered. The idea is if the state of charge is sufficient it’ll fly right over the trigger SOC and depend on solar. If it insufficient, it’ll run into the trigger SOC continue to charge till it reaches the release to SBU program. Should the actual SOC contact trigger SOC lower than average it simply charges longer but the net result is about the same when the panels start producing. Here’s a couple of screenshots that show it tripping on grid at 2AM and back to SBU at 4.55AM. Also my setting in SA.

 

[wattmatters]

I do my load source control using Home Assistant automations.

I was looking again at this feature but I don't think it will work for me because:
- our time of use tariff periods vary depending on day of week
- the options provided are to switch between SUB and SBU, when I want USB as the first choice.

Solar Assistant have been promising more functionality on this for a while, so I'll wait to see what they offer. In the meantime I'll keep running with my own automation. I have been contemplating how I might tweak them after adding a bit more storage capacity last week.

 

[Skypower]

I do my load source control using Home Assistant automations.

I was looking again at this feature but I don't think it will work for me because:
- our time of use tariff periods vary depending on day of week
- the options provided are to switch between SUB and SBU, when I want USB as the first choice.

Solar Assistant have been promising more functionality on this for a while, so I'll wait to see what they offer. In the meantime I'll keep running with my own automation. I have been contemplating how I might tweak them after adding a bit more storage capacity last week.

Use what you got, what you know and what you got dialed in. That’s always a win.

 

[Skypower]

Latest tweak;

 

[Skypower]

It’s working great so far. The small peaks are grid assist. Deep valleys are caused by hvac need and reduced in the last few days. Next to no unnecessary grid usage since implemented.

 

[wattmatters]

Nice that it's getting the outcome you want.

I made a tweak to my system today for when the supplemental grid charging starts and stops.

I've applied a kind of golf handicap approach - made the trigger to turn on less sensitive than the trigger to turn it off.



Can see how this morning it was flipping between adding supplemental grid charging and then turning it off again.

That's because my wife put the heater on in the office this morning . It was duty cycling the power on and off and the breaks between duty cycles was just long enough for my system to kick on supplemental charging but then the heater would come back on and now I was drawing from the grid when I don't want that. The battery will eventually stop drawing from the grid but it's not instant, there is some delay in response (to avoid the false trigger / passing cloud scenario).

The trigger I use is based on an exponentially weighted moving average of our grid power flow (it needs a minimum level of grid export power to be sustained) - however it was still a little too quick to switch on.

So I change the trigger to use a longer time constant for turning on supplemental charging and also for when to increase the max grid charge current setting.

But I left the same level of sensitivity for ramping down the max charge current setting or switching off the supplemental charging.

It's all because we are heading into our first Winter with this system and today was the first time my wife needed to use the office heater. So it's a new energy demand pattern I haven't needed to account for until now. Indeed we've needed to put the ducted AC heating on for the last couple of nights - as it's getting a bit chilly. Set point of 18°C (~64°F).

 

[wattmatters]

I also think it could hang onto to using the battery for a little longer in the morning before flipping over to passing through grid power. So I also increased the time constant I use for that trigger.

Since I recently added some extra battery capacity it means there is no need to switch to over to grid power quite as quickly.

 

[Skypower]

“ I love it when a plan comes together” George Peppard “ A Team”

 

[Skypower]

My biggest problem is keeping my hands off it. So far I’ve resisted the temptation to tweak it. Good decision.

 

[Skypower]

I didn’t even realize it, but it decided that it didn’t need grid support for a few days. I ran the clothes dryer amongst other things and that’ll probably cause a pull on some grid tomorrow morning.

 

[Skypower]

Yup, it did ?

 

[DIYPV]

I didn’t even realize it, but it decided that it didn’t need grid support for a few days. I ran the clothes dryer amongst other things and that’ll probably cause a pull on some grid tomorrow morning.

What inverters are you using?
I’ve experienced the same on my EG4 6000EX.

 

[Skypower]

MPP LV 6548 twins. The “it” that I was referring to is the Solar Assistant’s “Maintain battery state of charge” program that’s running and overseeing the inverters now. So far so good. “It” has been without intervention (tweaking) by me for several weeks now. I don’t have room for more solar so I use to set the timer to go to grid during off peak in high demand or bad weather and guess my needs. This seems to do a better job.

 

[wattmatters]

Only change I made in last few days was increasing the max charge current setting which made sense since I had added more battery. Means they can charge up a little more quickly than before.

 

[Skypower]

Well, it fouled up this morning. I went to open the icon for SA I put on my phone’s home screen and it opened with you need to login. I did no problem but when SA’s Home Screen opened I could tell it hadn’t gone to grid like it should’ve(cloudy the day before). While I was looking at it, it must have reset because it just went to grid like it was supposed to, just two hours late. Now if SA hadn’t done what it was supposed to, the inverter would have taken it back to grid at 49 volts and all the way to full charge, but not necessarily at off peak. Not the end of the world. Some kind of glitch, just hope it doesn’t happen too frequently. I’ll do a reset on SA and close some open windows on my phone maybe if got overwhelmed by a window request errrr somethin?

 

[Skypower]

Well, it’s been working flawlessly since the glitch, but now I made a change in the system that changed the equilibrium a bit. I added another battery. So I got to play with timing in “Maintain Battery State Of Charge” in SA and grid current to find the sweet spot again. Gives me somethin to do like I don’t.

 

[Jazzmonger]

I use two set points

This keeps my soc above 60% at all times during the evening (in case of a power outage) and grabs PV to charge on the last cycle in the AM as the sun comes up.

 

[Skypower]

Mine is set so it has to do it in the morning IF it runs into the red peak. (Cheapest utility rates) And so it doesn’t see sun and drop off the charge because if it sees any PV it stays connected to grid drops off to a flat line and waits for the sun to do the rest which kinds screws with the plan and may or may not bring it to a full SOC. Latest tweak;

 

[jlemke]

My off grid cabin is up and running for about 3 weeks now. I have a Growatt 24v 3000, 2x 24v EG4 Lifepo4 batteries, 1320watts on the roof, all tied together with my Solar assistant. The only thing for back up would be a generator if need be. We have about a constant 25w load with the wifi router, modem, inverter standby, and other parasitic loads. I am not fully understanding the settings talked about above to maintain charge. For instance today was very sunny. Topped off batteries to 100% around noon. Since then the batteries are at about 95% and not pulling any power from the PV. Any thought on how I should be setting the parameters? Thanks

 

[Skypower]

The main theme of this thread is how to augment grid charging when solar is insufficient to support the system on its own as well as institute “time of use” charge( use the grid only when the electricity is cheaper).

It sounds like you have plenty of PV area. It also sounds like it charges to bulk/absorb and after a bit it releases which is probably just what it’s intended to do. Rinse and repeat next day. The main thing with any system is if the absorb + tail current time gives sufficient time to balance the cells. I’m not familiar with your particular inverter but I’m positive someone on the forum is. I’d search the forum for answers or open a thread with your question in the header/ title.