I would appreciate any help on this:

I have two Kodak OG-Plus 5.48, and two Hubble AM2 batteries connected in parallel. My domestic load is less than 5kw, so only one inverter is needed for the load. I am about to attempt to switch the inverters on in parallel mode, but I would much rather leave the load on one inverter only, and use the other inverter simply to deal with half of the PV input, and to have both inverters charging the Hubble batteries. Is it possible to do this, i.e. use a common battery bank but not in parallel operation?

What you have just described is called DC coupling a system. There is absolutely no reason that this will not work out for you. The only thing is that if inverter comms was possible & I know that Hubble uses the Riot link only 1 inverter can take control of that & the other will be in Voltage mode. For that matter if you laugh off the Inverter to battery comms, both can reliably run on Voltage settings without any Issues. 

One inverter is just being used as a DC source to charge & the other inverter is used to supply the load. To me it's a waste of an inverter but if you want to oversize based on a Solar Array MPPT restriction then knock yourself out, more especially if you don't want to complicate life with parallel operations. 

 

Thank you, Steve.

In explanation, I'm off grid, no utility power, and I bought the second inverter when the first when in for repair... the "qualified installer" popped the MPPT due to too many amps from the newly-configured PV array. So now that I have it, I may as well use it to split the PV array and charge the batteries, and act as a back-up unit. I don't need it for load.

I read the Kodak manual, which contains lots of pidgin English, and it implies that commissioning parallel operations requires utility power - I'm not sure why, but not an option. So I'm looking for the least risky way out, and I can't afford any more blown equipment.

The Kodak has no inverter-battery comms with Hubble, so I rely on voltages, but the Hubble BMS seems very good, and it restricts charging amps all by itself as it fills up.

Thank you for the input, it's much appreciated.

Commissioning in the manual states that because the machines will share current from the grid input. But in your case there is no grid, you can parallel without any issues of having no grid the HS or master will still be a master & the SL will still be a slave & their AC output will be sychronised. 

Your original plan to DC couple is also a good plan as you don't need extra load capabilities. But of paralleled the inverters will share the load equally. So 1kW will split 500W each which I think is much more of a better plan but it's really your choice. 

Thanks, Steve. 

That makes perfect sense, and you've put my mind at ease about parallel operations.

So assuming I opt for a parallel setup, I have one more concern, which I'm hoping you might be able to help with:

On very cloudy days, I run a generator if the batteries need topping up.

In the past, this was connected to the "Utility input" on the single inverter.

So, under the new arrangement, should I connect the generator to one, or both, of the inverters? And will it present a synchronisation problem if I start it up? Or would it be better to shut down the second inverter and revert to single mode, before starting the generator?

I really appreciate your help with all these questions. I've done my best to research these points using the manuals provided, but as someone said elsewhere on this forum, the documentation available is notable for its paucity, and I'm by no means an expert on things electrical.

Glad that you have understood the operation of parallel ops.

You ask a great question: This is not a Deye or Sunsynk with a special Gene Input port. Think of the Gene power as Grid power. The inverter has no clue to distinguish between the 2. Some ppl that have Grid power available place a Changeover between the Gene and Grid that is on the Inverter AC Input side. 

The AC input is in parallel as well so i would wire the Generator output into a Dual Pole AC Breaker and then wire the output of equal wire lengths into each inverter. Do the same with the Individual output of each inverter to your loads. Into Single individual breakers for isolation purposes and then into a main dual pole breaker. Again pay attention to make the AC Cable lengths the same. It will avoid faults with Current sharing. The battery connections are exactly the same. Into a Busbar and make sure equal lengths from each battery to the busbar and into each inverter. 

If done in this way you will have your 2 options available at any time even if an inverter needs to be removed for repairs etc. All that will be required is to reprogram menu option 28 (not sure) to get back to single (SIG) inverter operations or to dual parallel (PAL) modes. 

I can't remember if the manual states this but the option 28 is only changeable if the inverter is in standby mode. If the inverter on/off switch is on you will see the menu option but it will not be manipulated. It must be OFF, use a generator or PV to keep the inverter on. If left on battery power ONLY, the inverter will switch off and this is frustrating. 

There is a long list of commission instructions. The crux of the matter is to make sure the both inverters AC output are synchronized before you actually switch on both AC output Breakers. If they are not synchronized you will burn and blow stuff up.

The outputs are synchronized when the DB9 cables and Current sharing cables are connected into each inverter and one says HS and the other SL without any faults. Then turn one breaker on at a time without any load. Then once they are synchronized the main dual pole breaker with your load. 

If you dont pay attention to this synchronization the internal capacitors can be damaged.

 

Edited January 5, 20242 yr by Steve87

52 minutes ago, Steve87 said:

I can't remember if the manual states this but the option 28 is only changeable if the inverter is in standby mode. If the inverter on/off switch is on you will see the menu option but it will not be manipulated.

Sorry to butt in here @Steve87just to confirm your above statement, ensure all breakers in Line wires of load side are open and each Neutral wires of each unit are connected together Turn on each unit and set “PAL” in LCD setting program 28 of each unit. And then shut down all units It is necessary to turn off switch( standby) when setting LCD program. Otherwise, the setting can not be programmed. Then turn on each unit.

Edited January 5, 20242 yr by TaliaB

Hi @TaliaBit's a mouth full to describe but my main point is that the mode operation settings for parallel only work with the inverters in standby. In other words with the inverter on/ off switch in the Off position. Meaning powered by a source of power to turn the main LCD on but the inverters AC output is off (disabled by the Switch in the Off position). 

If the switch is ON you see the settings but you won't be able to change them. 

Again very hard to describe in words but the output Lives must not touch until these settings are confirmed on each inverter. The big mistake comes in when any inverter switch is turned on & the Inverter is not setup for Parallel ops then you end up with 2 unsynchronized outputs making contact. 

I don't like to break Neutrals ever & a busbar is a better option. A dual Pole AC breaker also serves the purpose but is not my best preferred option. 

@Steve87, @TaliaB, thank you both for your invaluable input.

Please may I ask one more question:

When I go through the steps above: connect load "neutrals" , leave load "lives" open, configure both inverters to parallel, switch off, and switch everything on again:

If I then switch on the live breaker for only one inverter, instead of both, will that inverter still deliver power to the load? 

In other words, the two inverters are connected in parallel, and synchronised, but only one is providing power to the load. 

It seems to me that this might reduce the risk of "burning and blowing stuff up" (as per Steve), especially as I don't need the second inverter for load. I know I should ideally be using both, but I'm not an electrician, and I'm seriously worried about burning and blowing stuff up.

If I can get it all working like that, then I'll call in a qualified person, and get him/her to check everything I've done and hopefully issue a CoC. And at the same time, activate the load for the second inverter under his/her supervision.

Thank you again for all your help.

10 hours ago, JohnDM said:

@Steve87, @TaliaB, thank you both for your invaluable input.

Please may I ask one more question:

When I go through the steps above: connect load "neutrals" , leave load "lives" open, configure both inverters to parallel, switch off, and switch everything on again:

If I then switch on the live breaker for only one inverter, instead of both, will that inverter still deliver power to the load? 

In other words, the two inverters are connected in parallel, and synchronised, but only one is providing power to the load. 

It seems to me that this might reduce the risk of "burning and blowing stuff up" (as per Steve), especially as I don't need the second inverter for load. I know I should ideally be using both, but I'm not an electrician, and I'm seriously worried about burning and blowing stuff up.

If I can get it all working like that, then I'll call in a qualified person, and get him/her to check everything I've done and hopefully issue a CoC. And at the same time, activate the load for the second inverter under his/her supervision.

Thank you again for all your help.

I decided to ask Bard this question, and here is the reply. I'd be keen to know if it's correct:

 

Yes, if you have two Kodak King inverters properly connected in parallel with their neutral outputs linked, closing the live breaker for the load on only one of the inverters will provide usable power to the load. Here's a breakdown of how it works:

Parallel Configuration:

• In parallel mode, the inverters synchronize their output voltage and frequency, creating a unified power source.
• They share the load, effectively doubling the available power capacity.

Neutral Connection:

• Linking the neutral outputs ensures a common reference point for the AC voltage, crucial for proper operation and safety.

Load Isolation:

• While the inverters are connected in parallel, each has its own live breaker for load isolation.
• Closing only one breaker routes power from that specific inverter to the load, while the other inverter remains in standby mode.

 

This is a great summary you have listed here, however, one more point to add is that if under load you turn off one of the Inverters you will get a fault because the team of inverters will detect that one machine is delivering amps while the other is not & you will get a current sharing fault. 

So you need to choose, do you want parallel ops: if that's the case PAL setup as well as both breakers on. 

If not then do not tie the Lives together, they must never meet otherwise you planning for a problem. I agree you can use 2 single pole breakers & you can mechanically lock one out to protect the other inverter. 

But the danger always exists if they not synchronized. 

4 hours ago, Steve87 said:

This is a great summary you have listed here, however, one more point to add is that if under load you turn off one of the Inverters you will get a fault because the team of inverters will detect that one machine is delivering amps while the other is not & you will get a current sharing fault. 

I see that @Steve87 recommended that you put individual AC breakers on the outputs of each inverter.  Perhaps he meant isolating the inverter output with one of these breakers rather than turning off the inverter?  Switching an inverter off (using the push button switch) does not cause any faults.  It reduces that maximum load that can be supplied, and saves about 60W in power.
 

Thanks @Calvin.

I want both inverters running, ideally in parallel mode, because they each have to manage part of the PV array and charge the batteries.

My biggest fear is "burning and blowing stuff up".

I've installed individual neutral and live breakers, so that I can leave the "neutrals" connected but only one "live". I'm going to do the synchronisation this morning, and I'll report back here on it it goes.

I don't know if running the inverters in parallel has any effect on the inverters' management of the battery charging process. I'm going parallel in case it does. There's little to no documentation on this. The Hubble support desk says to run in parallel, but no reason is given, and @Steve87 advised that "DC coupling" independent inverters should work.

My ultimate fallback will be to reply on the Hubble BMS, which seems to be very good.

I must say, this is an excellent forum. Plenty of very useful advice. Thank you to all. I hope this thread might prove useful to others.

Good news!! everything connected, inverters in parallel mode, working fine!

Only one is providing load for now, but that, too, is working perfectly.

Thank you to  @Steve87, @TaliaB, @Calvin. Your help is hugely appreciated. Got me through a somewhat nerve-wracking patch!

 

53 minutes ago, JohnDM said:

Good news!! everything connected, inverters in parallel mode, working fine!

Only one is providing load for now, but that, too, is working perfectly.

Thank you to  @Steve87, @TaliaB, @Calvin. Your help is hugely appreciated. Got me through a somewhat nerve-wracking patch!

 

Hallo @JohnDM that is wonderful news.

If the steps in the manual are followed for the parallel commissioning then the chances of "burning and blowing stuff up" are almost zero.

3 hours ago, JohnDM said:

I've installed individual neutral and live breakers, so that I can leave the "neutrals" connected but only one "live". I'm going to do the synchronisation this morning, and I'll report back here on it it goes.

On the Axpert type inverters the Output Neutral And Earth is bonded so even if the Output Live and Neutral goes through an isolator the Neutral remains connected because the Output Neutral And Earth is bonded, so there is no need to use a separate breaker for the neutral. So far I know only an isolator or a switch dis-connector may be used to disrupt the current flow of a neutral conductor.

In the inverter installation that are installed at our residence where I am using 3 Kodak Max 7.2 kW inverters in parallel I used isolators and circuit breakers on the AC input as well as the AC output and I did not have any problems with the commissioning of the parallel setup whatsoever, I followed the steps as laid out in the Kodak Max's manual.

Update on the above, in case someone else follows this:

The system doesn't work with only one inverter providing load. It seems ok at low loads, but as soon as the load increases, it gives an E72.

 

3 hours ago, JohnDM said:

The system doesn't work with only one inverter providing load. It seems ok at low loads, but as soon as the load increases, it gives an E72.

This is exactly what @Steve87 said would happen.

Leave both breakers on, switch one inverter off using the push-button switch.  The push-button disables only the inverter output stage - the inverters will still operate in parallel for charging and setting synchronization.

Edited January 8, 20242 yr by Calvin

7 hours ago, JohnDM said:

The system doesn't work with only one inverter providing load. It seems ok at low loads, but as soon as the load increases, it gives an E72.

 

It does this because the current sharing cables picks up that the current is not equally shared. You can safely parallel with both output breakers on. 

The system above (two Kodak Kings, connected in parallel, twin AM2 batteries, no Eskom connection) has been working perfectly since January. But I'm hoping someone can help with a fresh question: If I want to use a generator to top up the batteries on a cloudy day, must the generator be connected to both inverters, or is is sufficient to connect it to just one? Thanks......

On 2024/04/08 at 8:36 PM, JohnDM said:

no Eskom connection) ... If I want to use a generator to top up the batteries on a cloudy day, must the generator be connected to both inverters, or is is sufficient to connect it to just one?

I'm pretty sure you can connect it to just one.