question

Hi @iot

I thought that was how it should work, ie if there is infact adequate solar no grid power is used, but in theory you shouldnt really end up in that scenario if there is adequate solar as you'd never hit that lower SoC limit anyway.

ie if you have adequate solar the SoC wont be dropping if it's not dropping then you are in the first scenario you noted.

If it does happen to drop to the limit the grid will kick in to keep battery at that limit. If there's adequate solar or if grid draws too much the SoC would go just above the SoC and back to scenario one.

ie Say SoC minimum set to 40%. If you're below 40% then system needs to use all power to charge battery to 40% as that's the minimum you've defined.

However if your system always had grid connection then grid will only kick in if SoC drops below 40% (inadequate solar to cover loads so the SoC has dropped to below 40). If solar becomes "adequate" then you'll only use grid for 1% to get you above 40%

So you're only in the scenario of using grid to get back to 40% if

1. you had inadequate solar and grid goes down (SoC dropped to cover load).

Or

2 you had inadequate solar and SoC dropped to 40% then you get adequate solar in which case grid is only used to charge 1%.

I do see what you're saying though, would be nice if there was a setting to say "dont charge from grid if I've got barely any loads/loads of solar even if below min SoC as solar will cover it soon" but then there's not really a concrete way of defining adequate solar in that situation ie below min SoC. As sun could drop and then you're below your min SoC if grid goes down.

Thanks a lot @matt1309

Yes i get what you are saying.

The SOC can drop below set value (say 40% in the example you used) when grid goes out during night time. So the grid is not restored back say until the next day by noon but around noon you have solar production of say 7200w and the inverter is in "inverter" mode using about 500w to power loads connected to AC out and therefore 6700w is going into the battery to charge it and now the battery is about 35% SOC.

Now it is noon and the grid is restored back and you still have over 6000w of solar, this is what I was referring to as "adequate" solar. What happens is that the inverter now pulls 500w from Grid to support AC loads and allow battery to be charge using solar (when you set limit AC charge to 0w in ESS on the GX).

My assumption was that even though the grid was restored and there was still "adequate" solar, the grid should not be used to power AC loads, the solar can handle both AC loads and charging of battery if it followed the priority stated earlier:

i. Power Loads connected to AC out then

ii. Charge batteries then

iii. Export excess to grid if so configured

But it seems not to be the case. Once you are below set SOC and there is grid, it powers AC loads with grid and charges battery back to SOC using both solar and grid (if so configured).

No worries @iot

I was under the impression that the grid would not just cover AC Loads when below min SoC but also charge the battery to get to min SoC of 40% as quickly as possible? Or have you disabled that somehow?

I suppose what you're after isn't really a minimum SoC as you're happy to go below if there's a decent amount of solar. I guess the difficulty is defining "decent"

I guess the logic of Victron is if 40% is minimum then all power sources should be used to get to that minimum if available. Otherwise it's not really a minimum.

More obvious if you've got loads of solar like you mention but say solar is only 600w. That's adequate enough to cover the 500w load but only 100w into battery is never going to get you back to that minimum SoC if you have a somewhat large battery.

Possible Solution:

Saying that if you do really want the configuration you describe you can probably get it using node red easily enough.

Get Node red to automatically lower the min SoC from 40 to a lower number temporarily if there is "adequate" solar and then you can define what you're happy to call adequate solar in Node red yourself.

(maybe something like if solar is 3 x the AC loads and it's middle of the day ie suns going to be up for a while. You could get infinitely more complicated with the criteria but that's a basic example to get start with i suppose)

Could even change the below example so that it varied if SoC was super low. ie allowed grid charging at really low SoC but medium low SoC and good solar it wouldn't

ie basic example of Pseudo code for node red:

if (SoC < 40%) and (Solar > 3 x AC loads) {

then Lower the min SoC to less than current SoC

}else {

Set min SoC 40%

}

That above example will prevent Grid covering loads below SoC of 40 if you've got 3 times as much solar as loads (that's what I've defined in the example as "adequate" solar). Of course you can get super complex with the if criteria but hopefully the basic logic makes sense if you did want to implement something like that.

What is your grid "set-point" configured at?

There is a short period(deliberately programmed) after your minimum SOC% is reached when the battery charging is prioritised over AC loads, this is to prevent the battery continuously going in and out of ESS#1 (low limit SOC). So, there is a few % of SOC recovery before the ESS goes back into normal operation ie trying to achieve your grid set-point. Is this what you are referring to?

hi @gazza

how does the grid set point impact all these? i have mine set to 20W