Good day all. Is this possible? From what i see, (and read) it should be.

(My system is currently on the Sunsynk 5kw inverter, but I want to de-load it and share smaller loads with the Axpert King (Voltronic) inverter witch is currently just around. I'm assuming that the loads, will manage their own requests via the Inverters and the Sunsynk, will manage charging the batteries. (The BMS should be able to manage the power it needs regardless of the different sources as they will be in the common busbar)

On a high lever, 2 different inverters, connected to the same battery bank, is like a car battery supplying different loads, no? (Some 5 amps others 15 amps etc, but all 12v. (Or 220/230V in the case of a house) 

• On same Phase, Same Ground and Neutral IN
• NOT parallel
• No Solar
• Only one inverter does the BMS comms.
• 2 Separate loads (on separate neutrals, 1 per inverter)

13 hours ago, BigotedUncle said:

I want to de-load it and share smaller loads with the Axpert King (Voltronic) inverter

[ Edit: Sigh. I had misread the diagram. ]

NO! You can't parallel the output of two AC devices unless they are carefully synchronised and matched in voltage. Paralleling two 12 V batteries is different; DC has no phase considerations. AC most certainly does. When Axperts parallel with each other, they have to have near-identical firmware, identical specifications, paralleling boards with appropriate cabling, and suitable settings.

You can split the loads (not parallel the outputs); that's OK, but then you might still overload one inverter when the other has capacity.

Having one inverter communicating with the BMS is more or less OK, but you lose some of the benefit of that communication. For example, if one cell becomes too high in voltage, the BMS can tell the Sunsynk to charge less or not at all, but the King will continue to charge the battery. The battery's BMS will have no choice other than to disconnect from both inverters, with unknown consequences.

13 hours ago, BigotedUncle said:

I'm assuming that the loads, will manage their own requests...

No. Loads are dumb, they don't request via any communications protocol or the like. If the loads are split, then each load will get its power from the inverter it's connected to; that's the extent of the "request" a load can make.

13 hours ago, BigotedUncle said:

The BMS should be able to manage the power it needs regardless of the different sources as they will be in the common busbar

In you proposed configuration, the BMS has no way of telling the King to charge more or less, impose a voltage or current limit, etc. The Sunsync should do as it is asked, but the King will more or less "go rogue" with only simple voltage and current limits.

Edited December 4, 20232 yr by Coulomb

"You can split the loads (not parallel the outputs); that's OK, but then you might still overload one inverter when the other has capacity" 

That's the idea, NOT to parellel, but have 2 separate loads, keep in mind Load 1 and load 2 are on separate Neutrals. Would synching still be an issue?. Currently I have both load 1 and 2 on the 5kw sunsynk it is "overloaded" while the old king is sitting in a box, in the storeroom. Still functional.

@BigotedUncle

I think the best method it to just use your Axpert as a micro inverter, and connect it to the SS Aux port, and define it as a GEN (i.e. input port). Just note that this port has a limit (2 -3 kW at best). The Axpert should have it's own PV, and pref it's own battery as well, but using a single battery source may also work (if anybody has tried this before, please chip in). The battery stats may just be way off.

1 hour ago, BigotedUncle said:

That's the idea, NOT to parellel, but have 2 separate loads, keep in mind Load 1 and load 2 are on separate Neutrals. Would synching still be an issue?. Currently I have both load 1 and 2 on the 5kw sunsynk it is "overloaded" while the old king is sitting in a box, in the storeroom. Still functional.

That should work - but just remember the max load of the battery. Max continuous discharge is only 5.4kW - it can only keep one inverter running at full load anyway.

I also have no idea what the Sunsynk will do when the BMS is reporting substantially different charge/discharge to what it is measuring.  You may need to disconnect both BMS cables to keep the inverters happy.

1 hour ago, BigotedUncle said:

That's the idea, NOT to parallel, but have 2 separate loads, keep in mind Load 1 and load 2 are on separate Neutrals.

My apologies, I misread your diagram. That's fine, no need to synchronise.

1 hour ago, JustinSchoeman said:

That should work - but just remember the max load of the battery. Max continuous discharge is only 5.4kW - it can only keep one inverter running at full load anyway.

I also have no idea what the Sunsynk will do when the BMS is reporting substantially different charge/discharge to what it is measuring.  You may need to disconnect both BMS cables to keep the inverters happy.

From what I know, and see, the Sunsynk 100% relies on the battery BMS (Meaning it ignores ALL settings on Inverter) If it was conscious, it would wonder why the battery is so insatiable...🤣

1 hour ago, JustinSchoeman said:

That should work - but just remember the max load of the battery. Max continuous discharge is only 5.4kW - it can only keep one inverter running at full load anyway.

I also have no idea what the Sunsynk will do when the BMS is reporting substantially different charge/discharge to what it is measuring.  You may need to disconnect both BMS cables to keep the inverters happy.

"Max continuous discharge is only 5.4kW"

Interesting. Why do you say 5.4kW? I thought it would be 3 x all the below.

Meaning:

• Nominal Power 3 x 1.08kW = 2.16kW*
• Max Power 3 x 2.4kW = 7.2kW*
• Peak Power 3 x 2.64kW = 7.92kW *

*The info above and the image below is from the manual that came with the battery.

7 hours ago, Coulomb said:

[ Edit: Sigh. I had misread the diagram. ]

NO! You can't parallel the output of two AC devices unless they are carefully synchronised and matched in voltage. Paralleling two 12 V batteries is different; DC has no phase considerations. AC most certainly does. When Axperts parallel with each other, they have to have near-identical firmware, identical specifications, paralleling boards with appropriate cabling, and suitable settings.

You can split the loads (not parallel the outputs); that's OK, but then you might still overload one inverter when the other has capacity.

Having one inverter communicating with the BMS is more or less OK, but you lose some of the benefit of that communication. For example, if one cell becomes too high in voltage, the BMS can tell the Sunsynk to charge less or not at all, but the King will continue to charge the battery. The battery's BMS will have no choice other than to disconnect from both inverters, with unknown consequences.

No. Loads are dumb, they don't request via any communications protocol or the like. If the loads are split, then each load will get its power from the inverter it's connected to; that's the extent of the "request" a load can make.

In you proposed configuration, the BMS has no way of telling the King to charge more or less, impose a voltage or current limit, etc. The Sunsync should do as it is asked, but the King will more or less "go rogue" with only simple voltage and current limits.

*Edit: Sigh. I had misread the diagram.*

It's not you, it's the diagram 🤣

13 minutes ago, BigotedUncle said:

Interesting. Why do you say 5.4kW? I thought it would be 3 x all the below.

Sorry - missed the 'recommended':

"Recommended Max. Continuous Discharge Current: 37.5A"

I see absolute max continuous is indeed ~2.5kW.

So you have 7.5kW available - but you also need to remember that the inverters have no way to communicate among themselves, so you should set one up for 5kW max discharge, and the other for 2.5kW, or you may get BMS trips which take down everything.

6 minutes ago, JustinSchoeman said:

Sorry - missed the 'recommended':

"Recommended Max. Continuous Discharge Current: 37.5A"

I see absolute max continuous is indeed ~2.5kW.

So you have 7.5kW available - but you also need to remember that the inverters have no way to communicate among themselves, so you should set one up for 5kW max discharge, and the other for 2.5kW, or you may get BMS trips which take down everything.

Yes, but fortunately the BMS/batteries were never in danger as they have+-7Kw output. The 5kW Sunsynk Inverter is being "Maxed" out by both Load 1 and Load 2 (not healthy).

On top of that, I desperately needed to add 500W to the existing backup, but that would exceed the Sunsynk inverters threshold 5.5kW in Lab/ideal conditions. So splitting 5.5kW into 3kw on Sunsynk and 2.5Kw on King, will still be below 7kW.) Heck, if it works, I'll add a 4th Battery (On bus bars or 2 x 25mm2) 

Excuse my crude diagrams... 🙈

3 hours ago, Sidewinder said:

@BigotedUncle

I think the best method it to just use your Axpert as a micro inverter, and connect it to the SS Aux port, and define it as a GEN (i.e. input port). Just note that this port has a limit (2 -3 kW at best). The Axpert should have it's own PV, and pref it's own battery as well, but using a single battery source may also work (if anybody has tried this before, please chip in). The battery stats may just be way off.

The OP indicated that neither inverters have PV connected. 

Good suggestion but this seems like getting complicated. 

I would rather put the Axpert loads on non essential so that it does not go into overload and limit the loads when no grid power.