How to fix Voltronic inverters self powering from the grid.

[Aridom82]

I have 3 Voltronic Max Axpert 8kw. In SBU mode, they will get the power they need to function (40w each, 120w in total), from solar when is available, but when the night comes they power themselves from the grid, even if the battery is full. It bothers me using 1-1,5kwh from the grid every night so i found a solution.

The solution is to set them up in USB mode, utility first, and put a contactor in the AC in that is controlled by a device that reads the battery voltage and switches it on when the battery is low, and switches it off when the battery has charged enough. I tried to use the dry contact on the inverter itself but is not fast enough so i have made an Arduino module with a voltage divider to read the battery voltage and a relay module to control the contactor.

So normally the contactor in the AC in is off so the inverters get all their power from solar or the battery. And when the battery reaches the low voltage switch we want, the arduino switches the contactor on and the inverters start using the grid until solar energy charges the battery over the reconnect voltage we want.

I know that people use solar assistant with home assistant to control devices based on battery voltage but is gonna be a while until i figure them out, for now the arduino module is working fine and i have eliminated completely all grid power use.

 

[timselectric]

When I was setup this way, I used the dry contacts.
What do you mean by "wasn't fast enough" ?

 

[Aridom82]

When I was setup this way, I used the dry contacts.
What do you mean by "wasn't fast enough" ?

In the usb mode, once the battery is low and you have to switch to grid using the dry contact, the ac in has to be reconnected fast or the inverter shuts off because after battery there is nothing else. My inverters are setup in three phase mode and it takes around 7-8 seconds for the inverters to read the ac three phases coming in and synchronize with them before they can pass to grid ac. Otherwise you could have a 400v difference in the lines at the moment of the switch.

So when the battery low voltage is reached and the dry contact is turned on, they shut off before the grid three phases are recognized and synchronized with. It seems that there is no logic programmed into the voltronic that prevents them from shutting off during this process after the battery low voltage threshold is hit.

 

[timselectric]

In the usb mode, once the battery is low and you have to switch to grid using the dry contact, the ac in has to be reconnected fast or the inverter shuts off because after battery there is nothing else. My inverters are setup in three phase mode and it takes around 7-8 seconds for the inverters to read the ac three phases coming in and synchronize with them before they can pass to grid ac. Otherwise you could have a 400v difference in the lines at the moment of the switch.

So when the battery low voltage is reached and the dry contact is turned on, they shut off before the grid three phases are recognized and synchronized with. It seems that there is no logic programmed into the voltronic that prevents them from shutting off during this process after the battery low voltage threshold is hit.

I see. That makes sense.
I think that the difference is that I was using SUB mode. Which isn't available for all versions.
So, I never lost power. The dry contacts would turn on the input power. And the transition was seamless.
Without SUB mode, it's probably not doable.
Now, my only grid connection is through a Chargeverter. (Also controlled by the dry contacts)

 

[wattmatters]

I think it's a handy thing to be able programmatically or remotely be able to switch the AC input on/off. I don't have that capability, just manually.