Daisey Chain Inverters

[SYC]

Quick one guyz,

AV input from Mains to AC input of Axpert inverter, AC output of Axpert to Infini Solar AC input and AC output to Load (in my head should be possible)

Pros, Cons or am I nuts?

[Ironman]

You are nuts...

Why?

You would be overly complicating the system.

pros: could be more resilient to loadshedding, clouds, etc

cons: cost, and you would be doubling your failure exposure in the longer run. Any unit fails, your load dies. 

[Gerrie]

7 hours ago, sulyc said:

in my head should be possible

It sounds possible if the Axpert feed the Infini as a UPS, but I would think you might have a worsened efficiency by adding the Infini. 

I feed a small UPS for a PC, from my Axpert and it seems to work ok.

[Jaco De Jongh]

7 hours ago, sulyc said:

(in my head should be possible)

A short story. A client had a 2730AH 12 Volt Victron Phoenix Setup for the last 8 years. The Lead Acids are on its last legs, so we replaced the complete setup with a 48Volt Victron and Pylontechs. He did not want to switch the old system off in the hope that he can run the last life out of the batteries, so he asked if he can connect the output of the old system to the input of the new, and when the pylons reach 60% SOC the new inverter must draw current from the old system. 

I doubted that it will work, but still told him that we should at least try it to know for sure. The new inveter sees the 230 volt coming from the old inverter and connects to it for 2 seconds, then disconnect. It tries it 2 or 3 times only. After that is still sees it but dont connect to it anymore? I never went into dept of why, all that i can tell you is with victron inverters this cant be done. 

I would also like to know why you would attempt this. 

EDIT: Currently the client still uses the old system to feed his workshop and the new system to feed the house. 

 

EDIT2: Now I remember your situation, you want to use the Axpert to stabilize your low grid voltage issue?

 

[SYC]

20 minutes ago, Jaco de Jongh said:

I would also like to know why you would attempt this.

Too get longer up time on Infini Coz it feeds the houses (average load 1100w only max 3000w when inverter aircon is switched on)

Axpert only runs pools pump during the 6 or 8 hours (max load 900w)

 

21 minutes ago, Jaco de Jongh said:

Now I remember your situation, you want to use the Axpert to stabilize your low grid voltage issue?

My thinking it would help but of late I must says it's been way more stable

[SYC]

1 hour ago, Ironman said:

cons: cost, and you would be doubling your failure exposure in the longer run. Any unit fails, your load dies.

I have everything already.

Maybe I could connect it with in such a way that when there is load shedding only I would manually switch so that I have longer uptime in the house only needed at night

[Charl_CCU]

I'm sure someone will know for sure but here is my speculation so long - anyone please correct me if anything is incorrect:
 

I don't know much about the specifics of either brands or your setup. I'm going to make the assumption that your Axpert inverter is connected directly to your Eskom AC with all of your loads connected to AC-out and then a similar setup of your InfiniSolar inverter connected to your Axpert inverter: i.e no external power meters. Your Axpert inverter will measure how much AC is coming in from the grid and from that, adjust its production and battery charging. It's a constant game of catch-up where it's reacting to what's already happened: it's not precise. The reason some grid-tie inverters still trip the Eskom meter even when grid feed-in is set to 0 is because a small amount gets fed back into the grid in the time it takes to react to a big load being switched off.

Now when there is another inverter added on the end, you can imagine what would happen then. Both inverters are going to try produce just enough that nothing is being imported. Best case: the first inverter only charges its batteries and never outputs anything unless inverter 2's batteries are empty. Worst/likely case: inverter 2 disconnects itself because of something on the long list of grid-safety standards it has to adhere to where it feels the grid isn't being stable.

I don't know if this is possible with your setup but a similar setup would be possible with a Victron inverter running as the "master" where it will connect to and communicate with the "slave" inverter to run in AC coupled mode. It will instruct the slave inverter how much power it should be outputting. I don't know if these are Victron-specific terms/features but I'm sure @plonkster will know about that.

Again, I don't know if this a popular feature but when running in off-grid or (I'm not 100% certain about this one) UPS mode, the Victron inverter is able to create its own micro-grid which it will vary the frequency of by a fraction of a Hz to signal to other inverters (in on-grid mode) that they should increase or decrease their production. I'm sure that this approach would be quite inefficient if you are importing most of your power.

[___]

8 hours ago, Charl_CCU said:

I don't know if this is possible with your setup but a similar setup would be possible with a Victron inverter running as the "master" where it will connect to and communicate with the "slave" inverter to run in AC coupled mode. It will instruct the slave inverter how much power it should be outputting. I don't know if these are Victron-specific terms/features but I'm sure @plonkster will know about that.

You can put two identical Victron inverters in parallel. The master makes the decisions, the slave simply does the same thing (so it literally just duplicates the exact PWM switching patterns etc etc, which means you have to make sure your cabling is impedance matched otherwise all sorts of weird things happen).

You can also tie another grid-tied inverter to a Victron inverter.

But the original post here talking about putting an infini downstream from an Axpert, and that I don't think will work. The truth is that most grid-interactive inverters demand a much higher quality AC input than the one they themselves produce, and this is by necessity: The grid codes require that you disconnect if things aren't quite stable (because it might be an indication that there has been an islanding event) AND... generating a grid-like hard voltage from a battery is practically impossible, any fluctuation in the DC voltage always has an effect on the AC voltage and no matter how fast the inverter's regulation loop acts, it always plays catch-up. Also, even if you put the best inverter in the world on an oscilloscope, you never get a sine wave quite as clean as a good grid connection. There's always a bit of THD. Ask any large-scale sound guy... they prefer a good clean AC from a large Diesel generator

 

[Charl_CCU]

2 hours ago, plonkster said:

But the original post here talking about putting an infini downstream from an Axpert,

Ah yea, I was assuming @sulyc was referring to inverter 2 being the only load connected to inverter 1. Is this not the  case?

[Youda]

Long-story short, daisy chaining the Invertes is a stupid and dangerous idea.

• Especially when these inverters are Hybrids (like InfiniSolar is).
• Especially when 2nd Inverter is more powerfull than the 1st one.

Why:

• There are no real gains from this setup.
• Once the Infini will go into bypass because of low-battery, then all the loads will be immediatelly connected to the Axpert. That will cause Axpert's overload and shutdown.
• Whenever a huge load is powered off then there is an energy spike created. Normally, that spike goes to the grid. But now the spike will be sent into the Axpert's output. Depending on the size of the spike the Axpert will either throw an error, or it's IGBTs will be fried.

You CAN daisychain two offgrid inverters, like two Axperts. This type of inverters does not interact with Grid, so all the potential powerspikes are being sent to the batteries. But there's still little to no benefit of doing this.

 

The correct method of combining more inverters into a single system is:

• AC coupling for OnGrid inverters like SMA or Fronius.
• Parallel setup for OffGrid inverters like Axpert.
• Parallel setup for Hybrid inverters like InfiniSolar or Victron Multiplus.

[SYC]

46 minutes ago, Charl_CCU said:

inverter 2 being the only load connected to inverter 1. Is this not the  case?

Not exactly.

Inverter 1 runs only pool pump +- 900w for 6 to 8 hours during daylight/sunlight hours that is it no more

Inverter 2 runs all house essentials all day from solar and from 1:30am on pylon batteries till sunrise

I can swap it need be but Infini has been working flawlessly with loads even during load shedding 

I must say I'm extremely impressed as to how efficient it has being

Both Inverters thus far have impressed me being a newbie and actively using them for 10 months now

[SYC]

5 minutes ago, Youda said:

Once the Infini will go into bypass because of low-battery, then all the loads will be immediatelly connected to the Axpert.

Wont the Axpert run out of battery first?

[SYC]

The main reason is that:

1. Longer up time if need be

2.I have everything

3.One system has Pylon and the other Gel which doesn't get used

[Youda]

Trust me: sooner or later the Axpert will blow up in this daisy-chained setup.

If you like to play with expensive toys, you should connect the Infini to the AC first and then feed the Axpert via Infini. It's still a nonsense, but less dangerous.

[___]

21 hours ago, Youda said:

Trust me: sooner or later the Axpert will blow up in this daisy-chained setup.

You wil have a better chance the other way round. Put the Infini upstream of the Axpert. You may have to set the Axpert into appliance mode (right? I don't work with these things) to make it accept the slightly less-than-perfect sine wave from the Infini.

The Axpert can't take any energy flowing backwards into it. At best it will overvolt the high voltage bus. At worst it will blow something up.

Even when you tie a Fronius to a supported hybrid inverter, you have to set the country code of the Fronius to MG50 (microgrid 50Hz). Without this it will also reject the quality of the AC and disconnect frequently.

[SYC]

On 2019/10/21 at 10:31 AM, plonkster said:

You can also tie another grid-tied inverter to a Victron inverter

I now have a victron system running ess see signature want to add infini 4000w with 3000w pv as grid tied

Question

Is it possible?

DC or AC coupled ?

Thank you in advance

 

[___]

17 minutes ago, Quat Allah As Shams said:

Is it possible?

The Infini doesn't reduce power when you frequency shift, so you cannot tie it to the output of the Multi. You can put it on the input side, but all excess will go into the grid since it has no sunspec support and the Victron system cannot limit it. The Victron system also can't see what power is made by the Infini, but it will note that power is flowing backwards through the grid meter (assuming you have one installed) and attempt to import that power. This in turn will cause the consumption figures on the GX to be wrong (cause there is a power source that is unaccounted for). To get that to work properly you'll have to install an additional power meter (Carlo Gavazzi) to measure the power made by the infini.

So yeah... but are you really sure you want to? I'd sell the infini. In the load-shedding environment you should not have trouble

 

[SYC]

On 2020/03/31 at 7:06 PM, plonkster said:

In the load-shedding environment you should not have trouble

Will have to wait until lock down is over to finalize.

On 2020/03/31 at 7:06 PM, plonkster said:

To get that to work properly you'll have to install an additional power meter (Carlo Gavazzi) to measure the power made by the infini

Just a thought if I do get another energy meter, how/where would I connect it? (btn the infini and multi? , would i use the same rs485 to usb cable?)

and run a pi with ICC connected to both Pylontech and infini would it make a difference? (so that the infini could see SOC)

(Pi connects to pylontech on console port and venus on CAN port) I have tested it, it works simultaneously 

Its just that I can be productive during lock down and get this done

Lastly on a Multiplus II output2 what's the max load that it can take? (Coz i connected non-essentials and over 4000w goes into overload)

 

[___]

12 hours ago, Quat Allah As Shams said:

if I do get another energy meter, how/where would I connect it?

You connect it between the Infini and the grid, so that tie energy meter measures what the Infini is making. Just to be clear, I envision running the Infini without batteries, in other words, use it as a makeshift PV-inverter. The energy meter is then plugged into the Venus-GX and configured to take the role of PV-inverter. Then the Venus-GX can account for the energy made by the infini (but still cannot limit it).

12 hours ago, Quat Allah As Shams said:

ICC

A bit confused here. Why run ICC in a Victron setup?

12 hours ago, Quat Allah As Shams said:

Lastly on a Multiplus II output2 what's the max load that it can take? (Coz i connected non-essentials and over 4000w goes into overload)

Mmmh that makes no sense. AC-out-2 is only engaged when the grid is connected, and anything the inverter cannot supply simply comes from the grid. There'd be no reason for the inverter overload itself, since the grid is there to help. In fact the grid is doing the work... the Multi is helping. There is nothing to cause the Multi to be overloaded... the grid is strong enough.

The maximum combined load on the two AC outputs is limited to the rating of the transfer switch. So if for example you have a 32A transfer switch (quite common), then you'd be limited to just over 7kW.

[SYC]

7 hours ago, plonkster said:

You connect it between the Infini and the grid

Already have one there,where would the other one go?

7 hours ago, plonkster said:

use it as a makeshift PV-inverter

100% correct

7 hours ago, plonkster said:

A bit confused here. Why run ICC in a Victron setup?

Will it not help in controlling the infini ?

Maybe @Youda can advise on this part ?

Thank you for all the help to one and all much appreciated as always