AIOs with Configurable Input Priority - Do They Power the Load and Charge the Batteries at the Same Time?

[forbin]

The subject pretty much says it all. Many all-in-ones can be configured to use PV first, then battery, then utility (generator), or some other sequence. The question is, if the inverter is sending power directly from the panels to the load, does the charger still send any unused power to the batteries, or do they just sit there not getting charged at all?

 

[Mattb4]

There are different models out there that do it differently. Many of them can not charge from AC while powering with inverter and must be in AC bypass mode to do so. They also can not choose to supply loads from solar ahead of the battery since the SCC outputs to the battery and inverter common DC bus. Common bus means the SCC outputs amperage based on the load of the battery being charged and its charging program, plus supplying the load of the inverter, eventually the battery gets charged and the SCC decreases output. At this point the battery is now discharging to supply the inverter.

I have heard that some inverters will use AC to create DC for supplying the common DC bus. Doing this would mean that AC could be used while not in bypass mode for DC load supply. Not the greatest thing since you are using AC to create DC to create AC.

 

[forbin]

There are different models out there that do it differently. Many of them can not charge from AC while powering with inverter and must be in AC bypass mode to do so. They also can not choose to supply loads from solar ahead of the battery since the SCC outputs to the battery and inverter common DC bus. Common bus means the SCC outputs amperage based on the load of the battery being charged and its charging program, plus supplying the load of the inverter, eventually the battery gets charged and the SCC decreases output. At this point the battery is now discharging to supply the inverter.

I have heard that some inverters will use AC to create DC for supplying the common DC bus. Doing this would mean that AC could be used while not in bypass mode for DC load supply. Not the greatest thing since you are using AC to create DC to create AC.

Thank you. Since that's the case, I'm not sure how the configurable input priority feature is all that helpful. I guess the point is to allow the load to be run directly from the panels so you don't wear the batteries. But if the batteries need to be charged, and the only way to charge them is to use them to power the load, that seems self-defeating.

 

[x98myers7]

the idea is that the PV input is enough to power the loads and charge the batteries simultaneously.

 

[Mattb4]

Sorry but your reply is confusing. The batteries are charged either by solar or by mains AC when operating the inverter in Bypass mode. That is the preference you can select as well as battery charging current for either. Also you can select to charge solar only, utility only or both.

The batteries being hooked to the SCC and the inverter is a limitation in the sense that the SCC job is to charge the battery.

 

[forbin]

the idea is that the PV input is enough to power the loads and charge the batteries simultaneously.

Exactly. If I have 7000W coming from my array, but I'm only using 4000W in my house, I want the house to be powered directly from the array (not the batteries) and I want that excess 3000W to charge the batteries if they need it.

 

[x98myers7]

Exactly. If I have 7000W coming from my array, but I'm only using 4000W in my house, I want the house to be powered directly from the array (not the batteries) and I want that excess 3000W to charge the batteries if they need it.

right. so, you probably want a "Solar first" setting. for Growatt's it's setting #1= SOL.

 

[Mattb4]

Exactly. If I have 7000W coming from my array, but I'm only using 4000W in my house, I want the house to be powered directly from the array (not the batteries) and I want that excess 3000W to charge the batteries if they need it.

You can not select which loads to feed (a discharged battery is just another load) and unless you have a way to isolate a charged battery it is going to want to feed the loads in tandem with the SCC. It all works out great as long as the battery needs charging. But there is no direction you can make as to only charge the battery when the solar supply is more than needed for AC loads. That requires a battery level charge control.

 

[Mattb4]

This is my megarevo hybrid at the moment.
Ran load of the house from the batteries.
When solar started producing, it first took over the load of the house, when it had surplus started charging the batteries. once batteries are full or at the max of their charging amps it will start feeding back into the grid
View attachment 110754
View attachment 110755
and just when I was taking the screenshots, the batteries reached their max charging current and now doing 3 things:
feeding load, charging batteries at max charge rate & feed back into the grid
View attachment 110756

Being grid tied allows AC load sharing. Off grid it is a different matter.

 

[forbin]

right. so, you probably want a "Solar first" setting. for Growatt's it's setting #1= SOL.

Understood, but I'm confused because I read somewhere that the setting does not work as one might expect. Regardless of the source, the destination is either the load or the batteries, not both at the same time. Maybe I misread that.

 

[x98myers7]

Understood, but I'm confused because I read somewhere that the setting does not work as one might expect. Regardless of the source, the destination is either the load or the batteries, not both at the same time. Maybe I misread that.

must be. I'm literally watching my Growatt aio charge my batteries at 1200w + power my 350w loads. PV input is 1550w.

 

[Mattb4]

Understood, but I'm confused because I read somewhere that the setting does not work as one might expect. Regardless of the source, the destination is either the load or the batteries, not both at the same time. Maybe I misread that.

It is always both at the same time. They are hooked to a common DC bus. Just like if you have many cells of a battery hooked together you charge them all as one. And a load draws from all of them at the same time.

 

[forbin]

It is always both at the same time. They are hooked to a common DC bus. Just like if you have many cells of a battery hooked together you charge them all as one. And a load draws from all of them at the same time.

Perfect, I think that answers the question. Now I think I will have to go back and see where I got the impression that it was either/or.

 

[forbin]

And a load draws from all of them at the same time.

Wait, I thought the whole idea was to enable battery-less operation when needed. One of the inverter vendors told me that they can power the load (meaning the house) directly without drawing from any attached batteries.

 

[meetyg]

I'm not totally convinced that @Mattb4 is correct...
Look at this setting:


LBU mode sounds like it will be able to power loads AND charge the battery, as long as the battery is above the threshold.
Or is my interpretation wrong?

 

[Mattb4]

Wait, I thought the whole idea was to enable battery-less operation when needed. One of the inverter vendors told me that they can power the load (meaning the house) directly without drawing from any attached batteries.

Some claim to do that. It would only be possible if it has a way to disconnect the batteries. Common DC bus. If something is hooked to it it shares the voltage.

 

[Mattb4]

I'm not totally convinced that @Mattb4 is correct...
Look at this setting:
View attachment 110761

LBU mode sounds like it will be able to power loads AND charge the battery, as long as the battery is above the threshold.

That device must communicate with the battery to isolate it. Probably uses the batteries BMS to accomplish the task.

 

[TomC4306]

must be. I'm literally watching my Growatt aio charge my batteries at 1200w + power my 350w loads. PV input is 1550w.

Mpp Solar works the same.
2400 watts from the panels, 800 watts load, 1600 watts charging.
Solar/battery/utility output mode, solar first charging priority.

 

[Mattb4]

I hope I am not simplifying it too much when I state that the battery is just another load when not fully charged. It is a bit more complicated than that since a battery voltage and amperage draw (internal resistance) changes as it is charged and discharged. Understanding batteries is fundamental to understanding how a charge controller must function.

If you parallel two batteries of different voltage the higher voltage battery will charge the lower voltage battery and be discharged doing so.

 

[Samsonite801]

Wait, I thought the whole idea was to enable battery-less operation when needed. One of the inverter vendors told me that they can power the load (meaning the house) directly without drawing from any attached batteries.

I know a bunch of the all-in-ones can support batteryless operation (while only in single and not stacked topology), I would only operate like that in a bind, perhaps in a mobile or emergency situation. Even if I didn't want batteries, I would at least install some small ones, and it can greatly add to the surge capacity for starting motors (even though it wouldn't have much KWh capacity behind it), it would help settle out the peaks and dips, which seems to me it would help things last longer, and not put your AC output circuits at the same risk for surges or brownout type behavior which could be harder on appliances.

Ian at watts247 had a nice demo of this on an LVX6048 batteryless video on You Tube I liked, he showed batteryless, and then with some small batteries, and it handled surges better for starting motor loads. Batteries help the inverter input to handle inrush load better as it provides a good buffer in between, like a shock absorber in the circuit...

That's just my rough opinion on running batteryless.