I have two Kodak OG-7.2 inverters (each with their own, dissimilar, pv string), in 1-ph parallel configuration with a shared Pylontech battery bank. 

The inverter with the battery link Comms cable will not operate as the slave SL (very quickly goes to fault mode), but even when started as master HS, fails to fault mode every few hours. 

What I see is that the output load is generally not balanced, with the SL supplying most of the load. 

Every now and then, the Bus voltage on the HS, after operating at the same level as the SL, suddenly climbs (up to 30% higher), and the inverter switches to Fault mode - F60 Power feedback protection

All cabling and connections have been checked, as have the settings. 

What might cause this unbalanced Output power allocation between the units, and what is the solution? 

Unfortunately, I only "monitor" with Watchpower, so not much data available. 

Any help would be appreciated

Hi @Jacko I seen a few typical faults like F72 as well as F80. Your F60 is the first I've come across. Out of interest can you confirm you have followed the typical troubleshooting guide?

The fact that each inverter cannot be master & slave points to a larger problem. Can you confirm the Firmware is the same. It's displayed as U1, U2 & U3 when scrolling through the memory. The master will have PYL & the slave will have USE for menu 5 battery settings...I can't think of what can cause this. Do you have the Current sharing cables installed? The Red & Black cable that has a phoenix connector at both sides ??

Edited April 2, 20242 yr by Steve87

11 hours ago, Steve87 said:

Hi @Jacko I seen a few typical faults like F72 as well as F80. Your F60 is the first I've come across. Out of interest can you  you have followed the typical troubleshooting guide?

The fact that each inverter cannot be master & slave points to a larger problem. Can you confirm the Firmware is the same. It's displayed as U1, U2 & U3 when scrolling through the memory. The master will have PYL & the slave will have USE for menu 5 battery settings...I can't think of what can cause this. Do you have the Current sharing cables installed? The Red 

Hi @Steve87 I have done all troubleshooting - plus more. 

Both inverters can adopt either the HS or SL status, but the fault condition occurs immediately when the status is "reversed". 

The Firmware is slightly different - Main CPU Firmware HS 69.06 and SL 69.05

Secondary CPU Firmware - both 12.21

The battery settings (05) are PYL and USE, and communication between the inverters appears to work iro battery levels, charge rate etc. 

I did not install the current sharing cable (as I erroneously believed this was associated with the DC output feature) but will put that in now, and report any change, forthwith - quite likely the cause. Thanks

Silly question, but looking at the pic in the manual, they show both Comms ports, and both current sharing ports connected (2 cables each). Is this necessary - I saw somewhere that the comms connection is "either port to either port"? 

 

Edited April 3, 20242 yr by Jacko
Additional query

This is imperative for single phase current sharing & your firmware must match 100% to parallel. Ask Segen Solar for the latest firmware & update. You cannot parallel without these 2 imperatives having been done. 

Thank you very much, I shall update the firmware. 

In the interim, I have linked both Comms sockets (2+2), and both current sharing ports (2+2) between the two inverters, and redone the parallel start-up procedure, and it appears to be working - under normal conditions (not high load, or bypass, or switching between modes) 

On 2024/04/03 at 3:11 PM, Steve87 said:

your firmware must match 100% to parallel.

I'm not convinced of this.

The problem is almost certainly the lack of current sharing cables.

On 2024/04/03 at 2:50 PM, Jacko said:

Silly question, but looking at the pic in the manual, they show both Comms ports, and both current sharing ports connected (2 cables each). Is this necessary - I saw somewhere that the comms connection is "either port to either port"?

? Follow the diagrams exactly.

I have not yet got round to doing the firmware upgrade - another thing to research first - but am monitoring the parallel inverters closely, and so far they are performing as (originally) expected. 

Hence I agree, the comms & current sharing cables were the root cause of the teething problems I experienced. 

I would imagine that firmware compatibility is dependent on the nature of the upgrade, and what aspect of the inverter is affected.

So not knowing it is probably recommended to match the firmware, but in some cases it won't affect certain functions. 

The system has been running reasonably smoothly for a while now on solar and battery.

Recently, because of random, frequent power cuts I added over/under voltage protection on the Grid input. 

With the Grid input CB off, the Grid voltage is around 237v, but with the inverters operating in Battery mode, and outputting power from pv input, as soon as I switch on the Grid input CB, the Grid (connected) voltage drops to around 200v. 

Any idea why this should be, and what I need to change? 

My understanding is that until the inverter goes into Bypass mode, supplying the demand from the Grid, the Grid Input L&N wires are isolated from the Inverter Output, so should not be affected

Edited February 13, 20251 yr by Jacko

On 2025/02/13 at 5:26 PM, Jacko said:

My understanding is that until the inverter goes into Bypass mode, supplying the demand from the Grid, the Grid Input L&N wires are isolated from the Inverter Output, so should not be affected

For the older models, yes. But the later models with SUB output source priority, if using that priority, will attempt to blend AC-in with battery and solar power, and to do that, the input has to be connected to the output. Obviously, the output voltage will then be the same as the grid voltage.

Maybe you can get your monitoring software to select SBU priority more often. But if you neeed to Utility charge the battery, the DC->AC converter has to be run in reverse, meaning that again AC-in has to be connected to AC-out. 

If you consistently have this problem, and if changing the AC input range setting doesn't help, you might have to consider a model with double conversion, such as an Axpert King or Axpert King II. Or a powerful battery charger that you can connect directly to your inverter's battery, leaving AC-in unconnected. 

On further investigation I discovered that there was another factor involved which was "skewing" the situation - my main grid incoming underground cable had a fault on the neutral (I suspect a break or poor connection).

Once I replaced the neutral the situation has normalised, and I don't experience the same extreme voltage drops.

The fault was difficult to determine and to locate