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Two EG4-6500EX in parallel - One unit complaining about low bus voltage

John Frum said:
@BenFromSignatureSolar since we are on the subject can you explain why so many user manuals for inverter's that can be run in parallel suggest/require equal path resistance for all the paralleled inverters?
I can't see any reason why they shouldn't work in parallel even if they are connected to completely separate battery banks.
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A lot of it boils down to sensitive components that can fail over time when given inconsistent current and voltage. This is mostly an issue on the DC side. If the positive and negative are the slightest bit imbalanced it could result in a short in the wrong conditions.

There's always a chance that it might work just fine. But over time issues are going to crop up.
 
I just configured the NON faulting inverter to be stand alone, fully disconnected PV input from it, and it inverted just fine, no faults, leading me to believe that you do not require PV input to all units. I have sent a video of this to Signature Solar (Along with other photos and videos that they've asked for). Hopefully will have a resolution to this at some point.
 
Switched everything around and performed the same test and the faulting inverter is still faulting. Non faulting still not faulting. Moved pv input to faulting inverter, still faulting.
 
BenFromSignatureSolar said:
A lot of it boils down to sensitive components that can fail over time when given inconsistent current and voltage. This is mostly an issue on the DC side. If the positive and negative are the slightest bit imbalanced it could result in a short in the wrong conditions.

There's always a chance that it might work just fine. But over time issues are going to crop up.
Click to expand...
I'm just not picking up what you are putting down.
Will come back to this with fresh eyes tomorrow.

What would short?
 
timthrifty said:
Switched everything around and performed the same test and the faulting inverter is still faulting. Non faulting still not faulting. Moved pv input to faulting inverter, still faulting.
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Sounds like you might just have 1 good unit and 1 faulty unit?
 
This morning I went out and did a pre-video test of the faulting. I wanted to send a new video of the fault occurring to Signature Solar.

Inverter 1 was fully indepedent from inverter two, just like yesterday, turned it on, immediate fault 52. So now that I knew the issue was still happening, I took a video of me repeating the process exactly. This time NO FAULT. You can hear my shock and confusion in the video. In my video, I started with just solar (Because this will not cause it to fault) and then scrolled through each setting, hoping that Signature Solar might see a setting that was wrong. I don't know if scrolling through the settings managed to reset something that was screwed up in there or what, but after scrolling through each setting and then hitting the inverter button, it all appeared to be working fine. No faults.

So since the previously faulty inverter was now working fine, I reconfigured it for 2P1 and the other for 2P2. Restarted them and....both are inverting. No issues. You DO NOT require PV input to each inverter in order for them to function. I took a video (Also uploaded) of this for Signature Solar to see, so that they can update their internal and public-facing docs. I was explicitly told that I must have PV input from separate sources to each inverter, but that clearly is not the case.

So whatever the issue was, it seems to have completely resolved itself somehow, magically.
 
timthrifty said:
This morning I went out and did a pre-video test of the faulting. I wanted to send a new video of the fault occurring to Signature Solar.

Inverter 1 was fully indepedent from inverter two, just like yesterday, turned it on, immediate fault 52. So now that I knew the issue was still happening, I took a video of me repeating the process exactly. This time NO FAULT. You can hear my shock and confusion in the video. In my video, I started with just solar (Because this will not cause it to fault) and then scrolled through each setting, hoping that Signature Solar might see a setting that was wrong. I don't know if scrolling through the settings managed to reset something that was screwed up in there or what, but after scrolling through each setting and then hitting the inverter button, it all appeared to be working fine. No faults.

So since the previously faulty inverter was now working fine, I reconfigured it for 2P1 and the other for 2P2. Restarted them and....both are inverting. No issues. You DO NOT require PV input to each inverter in order for them to function. I took a video (Also uploaded) of this for Signature Solar to see, so that they can update their internal and public-facing docs. I was explicitly told that I must have PV input from separate sources to each inverter, but that clearly is not the case.

So whatever the issue was, it seems to have completely resolved itself somehow, magically.
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That is great news! And agreed, when in parallel it is only necessary to have PV input on one inverter. I apologize for the conflicting information you received yesterday, that has since been addressed and we did a little training exercise yesterday afternoon to make sure all techs are on the same page on that. Thank you for sending us the videos, anytime we can get videos of systems in the field it helps us learn and grow. If you have any other trouble, don't hesitate to reach back out to us!
 
Do you have any idea what the problem was? Is it possible that simply scrolling through all of the settings somehow reset something that was stuck? It literally was not working and then was, without me changing anything, and that makes me a bit uncomfortable. In the WatchPower app, I see an "Eeprom Fault" on the device that was faulting. I wonder if the ROM is having issues / had corrupt data and that was causing the error condition?
 
timthrifty said:
Do you have any idea what the problem was? Is it possible that simply scrolling through all of the settings somehow reset something that was stuck? It literally was not working and then was, without me changing anything, and that makes me a bit uncomfortable. In the WatchPower app, I see an "Eeprom Fault" on the device that was faulting. I wonder if the ROM is having issues / had corrupt data and that was causing the error condition?
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I am due two in September. I'm sure many others of us are too. If there is a intermittent glitch, it will show up as we get more online.
 
I thought I was out of the woods, but nope. While the inverters ARE happily inverting together now, I'm getting only 130W of PV (Just enough to power the fans I'm thinking). Yesterday on the NON faulty inverter, it was charging the batteries perfectly. Now that I've moved the PV input over to the one that kept faulting, it seems to not want to charge for some reason.

@RV10flyer How do you like your -10? I'm (very slowly) building one down here as well.
 
John Frum said:
I'm just not picking up what you are putting down.
Will come back to this with fresh eyes tomorrow.

What would short?
Click to expand...
I've been looking into this all morning. I see all over the internet that it is recommended for the cable lengths to be the same. Voltage drops and DC ripple are the two things that keep popping up. I'm going to be totally honest here, I haven't seen an answer that completely makes sense to me. I plan on learning about this today.
 
timthrifty said:
I thought I was out of the woods, but nope. While the inverters ARE happily inverting together now, I'm getting only 130W of PV (Just enough to power the fans I'm thinking). Yesterday on the NON faulty inverter, it was charging the batteries perfectly. Now that I've moved the PV input over to the one that kept faulting, it seems to not want to charge for some reason.

@RV10flyer How do you like your -10? I'm (very slowly) building one down here as well.
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Can you take voltage readings coming from the inverter to the batteries and send the findings to the email that you've been sending the videos to? If you could take a reading of PV in with the voltmeter also, that will help.
 
Mine does that. They will only draw the PV they need to charge the batteries. When my batteries showed two bars the PV was really coming in both inverters and when the batteries got to 4 bars soc the PV input from the two strings fell way off, looks like just enough to trickle charge. Run the batterie down and check PV input again.
 
Right, I know how the charging cycle works - I've had solar for years before these units. The batteries are only at 65% SOC currently - They ought to be taking all of the PV they can take right now.

Edit: Realized that sounded dick-ish. Wasn't my intention - I appreciate the input.
 
BenFromSignatureSolar said:
Can you take voltage readings coming from the inverter to the batteries and send the findings to the email that you've been sending the videos to? If you could take a reading of PV in with the voltmeter also, that will help.
Click to expand...
I've sent the photos. Hopefully we can get something resolved today.
 
BenFromSignatureSolar said:
I've been looking into this all morning. I see all over the internet that it is recommended for the cable lengths to be the same. Voltage drops and DC ripple are the two things that keep popping up. I'm going to be totally honest here, I haven't seen an answer that completely makes sense to me. I plan on learning about this today.
Click to expand...
When an inverter has to push current to the load, which is how the "slave" inverters operate when paralleled with a master. The length of the wires is like a resistor in series with the output, it causes a voltage drop. If the resistor is larger, the inverter output voltage must go higher in order to push the same current as one where the wires are shorter, with less resistance. If the wires have more than a 2% voltage drop, then the inverter is being pushed to its max range and can't supply as much current as it should.

This is also true when paralleling to the grid. If one inverter has a higher voltage drop to the grid than another, it will have higher losses and provide less power at the point of interconnection.
 
ncsolarelectric said:
When an inverter has to push current to the load, which is how the "slave" inverters operate when paralleled with a master. The length of the wires is like a resistor in series with the output, it causes a voltage drop. If the resistor is larger, the inverter output voltage must go higher in order to push the same current as one where the wires are shorter, with less resistance. If the wires have more than a 2% voltage drop, then the inverter is being pushed to its max range and can't supply as much current as it should.

This is also true when paralleling to the grid. If one inverter has a higher voltage drop to the grid than another, it will have higher losses and provide less power at the point of interconnection.
Click to expand...
Thank you for this info! I knew it would be related to voltage drop but didn't know exactly how it would apply.
 
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