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Help Please - Only half my solar panels working


Gunners

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Hello All

My setup is as follows:

  • 24* 265W canadian panels, connected in 4 pairs of 6.
  • 2 * Axpert Inverters connected in parallel
  • 6 * 2.4KW Pylontech batteries

My axperts blew and were in for repairs. When they eventually returned, I noticed I was not getting the solar input I was getting before which was 4 - about 5.5KW during peak sun times. Now I am only getting 1.5 - 2.5Kw and it only seems to be driven from the master inverter. The slave inverter only shows an input of 25-30W. Pictures are attached. 

I have replaced fuses which has not made a difference. 

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Any ideas please?

Regards

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Edited by Gunners
Added Pictures.
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1 hour ago, Gunners said:

2 * Axpert Inverters connected in parallel

Out of curiosity what models do you have that can handle 6 panels in series?

Please can you confirm that the Current sharing cables and Communication cables are connected correctly. In the pictures its seems like the communication cable connected to Port 1 on the slave (Marked with a pen) is going to Port 1 on the Master (Pen marks also visible). If it is like that its must be swapped to mach the attached diagram.  

Current Sharing.JPG

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Also, please confirm that two strings of 6 panels are connected to one inverter, and the other two strings are connected to the other. You can't parallel the PV inputs of paralleled inverters; they have to have separate PV panels. That might possibly have been the cause of the blow up?

The battery however has to be the same for both master and slave. Is that the case? I see different coloured thick leads from the fuse box (a black and red pair, and a blue and red pair). [ Edit: the left one, which looked black to me, in hindsight is possibly blue in heavy shadow. So the question is: do these battery cables parallel when they get to the battery? ]

What are the PV input voltages for the master and slave?

It's not unheard of for the solar charge controller connectors to be plugged back incorrectly after a repair. However, I'd expect to see zero panel power in that case, and no solar panel icon.

Edited by Coulomb
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spacer.pngspacer.pngHello Gentleman. Thanks for all the replies.

@Jaco de Jongh

6 hours ago, Jaco de Jongh said:

Out of curiosity what models do you have that can handle 6 panels in series?

Please can you confirm that the Current sharing cables and Communication cables are connected correctly. In the pictures its seems like the communication cable connected to Port 1 on the slave (Marked with a pen) is going to Port 1 on the Master (Pen marks also visible). If it is like that its must be swapped to mach the attached diagram.  

Model number is: SOL-I-AX-5M. Regarding the way the panels are connected, this is what the installer told me when the system was originally installed. I do not know this as fact. Is there a way I can confirm and will that involve climbing a roof and checking how it is all connected?

I have checked the communication cables and I can confirm they are connected correctly.

@Coulomb

4 hours ago, Coulomb said:

Also, please confirm that two strings of 6 panels are connected to one inverter, and the other two strings are connected to the other. You can't parallel the PV inputs of paralleled inverters; they have to have separate PV panels. That might possibly have been the cause of the blow up?

The battery however has to be the same for both master and slave. Is that the case? I see different coloured thick leads from the fuse box (a black and red pair, and a blue and red pair). [ Edit: the left one, which looked black to me, in hindsight is possibly blue in heavy shadow. So the question is: do these battery cables parallel when they get to the battery? ]

What are the PV input voltages for the master and slave?

My knowledge is limited regarding how things are/should be connected. Is there a way you can advise me to check? I can confirm cables are definitely only blue and red. I have attached more pictures. Please see if that sheds more light. 

@Dex_

Is that calculation based on my axpert settings? I have limited knowledge, so please let me know if I should change something.

Thanks for the responses everyone. Appreciated so far!

 

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Edited by Gunners
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what time was that PV voltage photo taken? at 60V thats like 2 panels strings imo but it can't be given your number of panels

so your panels open circuit voltage is 37.7V, so 4 in series would be 150V, which imo is too high ( i beleive that units operating range is 60-115v and max is 145v) - but this is a secondary problem imo to what you are seeing or could have been the root cause.

maybe the fuses have gone?

Edited by Dex_
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11 hours ago, Dex_ said:

6 * ~35 = 210V@ ~ 20 A? = 4200W

this seems over on every angle, unless i am confused?

We were presuming 2P at that point; 265 W panels would be well under 10 A each.

It's easier to work this way: each inverter has presumably 12 panels, 12 x 265 W = 3180 W each inverter. Well under the 4000 W recommended.

But from the 88 V PV figure, it seems that each inverter has 2S6P panels, and it's a 145 V MPPT (I assumed 450 V). Presumably, sets of three strings are paralleled on the roof, so that only 4 pairs of PV cables enter the DC fusebox.

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9 hours ago, Gunners said:

Model number is: SOL-I-AX-5M.

Ah. So that's a 145 V model. So you must have 6 pairs of panels (2S6P) on each inverter.

Quote

Is there a way I can confirm and will that involve climbing a roof and checking how it is all connected?

You have already confirmed that the panels are 2S (hence the 88 V and 60 V PV voltages). That seems to indicate that 3 strings of panels are combined (paralleled) on the roof, based on your four pairs of PV cables. That means there should be PV fuses on the roof, so some of these may have blown.

Really, the best way to check your PV wiring is to do a short circuit current test on each string. But I think that's difficult for you do do safely.

What I would suggest now is to swap the PV connections to master and slave. Do this at night; swap the thin yellow and blue for the thin red and black wires that connect to the PV input. Then if the slave is doing all the PV work and the master only 15 W, then you know it's a PV issue. If the master continues to do all the work, then it's an inverter issue. Make sure that you maintain the correct polarity (red is almost certainly positive, and I expect yellow to be positive, but check at the inverter input to make sure that's the convention). If one of the cables won't reach, then tape up the one that won't and only connect the other one. We can probably learn what we need from one connection.

BTW, the PV current will be over 36 A at nominal power. So the wires from the DC fuse box to the inverter inputs should be at least 5 mm² (10 AWG). The copper part should be at least 2.6 mm diameter. Do the wires look like they are at least that size? They look a little think in the photo, but it's hard to say from a photo.

[Re battery cabling]

Quote

Is there a way you can advise me to check? I can confirm cables are definitely only blue and red. I have attached more pictures. Please see if that sheds more light. 

Not really. We need to see what's inside the box where the red and blue wires head off to the battery. It looks like the battery and that box are high up, near the ceiling, Can you open that white box and show us a photo of what's inside?

Finally, the photo of the master with 60 V and 44 W... are they when it happened to be nearly dark or very cloudy? 60 V seems low, when it's not producing much power. I do see ~60 V on my 2S system, but only in very poor light conditions, and I usually get some 25% of nominal power (in your case, some 800 W) unless it's a really thick cloud, so it's noticeably dark outside.

Edit: some more thoughts. At a time when you don't have a lot of load, try switching off the master (with the rocker switch under the inverter). The slave should turn into a master, and may suddenly start using PV power. That would be an easier way of checking the slave's panels, though I suspect it won't start using PV power.

The other thought is to check that the two inverters read close to the same battery voltage. Set them both to read battery voltage, and check that they read close to the same voltage, perhaps turning on a load like a kettle to see how they both measure the battery voltage. If the slave thinks the battery voltage is higher than it really is, it could explain why it won't charge the battery.

Finally, all your photos show the inverter in bypass mode. In that mode, you are not using PV power to support your loads. Is this intentional (i.e. you just want to be ready for load shedding), or would you prefer to be in battery mode where the PV powers the loads? Do you know if you used to be in battery mode most of the time before the repairs? Edit 2: After I wrote that, I realise that the problem is likely that the battery SOC is too low for battery mode, because of the severe lack of PV power to charge the battery. ]

Edited by Coulomb
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6 hours ago, Coulomb said:

We were presuming 2P at that point; 265 W panels would be well under 10 A each.

It's easier to work this way: each inverter has presumably 12 panels, 12 x 265 W = 3180 W each inverter. Well under the 4000 W recommended.

But from the 88 V PV figure, it seems that each inverter has 2S6P panels, and it's a 145 V MPPT (I assumed 450 V). Presumably, sets of three strings are paralleled on the roof, so that only 4 pairs of PV cables enter the DC fusebox.

yeah sorry i was working on my panels on the fly, which are a bit huge 😛 395W

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Thanks for the info and advice Coulomb!

The voltage settings I included yesterday were taken when it was almost dark. I have included new pics taken today around 10:30am. Master was around 88v and slave around 103v. 

I tried the rocker switch you mentioned, and as you stated, the slave became the master, but solar PV did not increase, remained at 29w. The master stopped feeding power to the home (after switching the rocker switch) but showed that it was still charging the batteries.

I have also noticed that when in solar mode, the slave does not indicate that solar is charging the batteries, only the master and error code 04 appears on both inverters. When utility charges the battery, both inverters show batteries are charging and 04 code disappears.

8 hours ago, Coulomb said:

What I would suggest now is to swap the PV connections to master and slave. Do this at night; swap the thin yellow and blue for the thin red and black wires that connect to the PV input. Then if the slave is doing all the PV work and the master only 15 W, then you know it's a PV issue. If the master continues to do all the work, then it's an inverter issue. Make sure that you maintain the correct polarity (red is almost certainly positive, and I expect yellow to be positive, but check at the inverter input to make sure that's the convention). If one of the cables won't reach, then tape up the one that won't and only connect the other one. We can probably learn what we need from one connection.

I will try this tonight. Do I need to power off inverters before swapping wires?

8 hours ago, Coulomb said:

Not really. We need to see what's inside the box where the red and blue wires head off to the battery. It looks like the battery and that box are high up, near the ceiling, Can you open that white box and show us a photo of what's inside?

This will be difficult since the Pylons are very close to the box. Pylons are mounted near ceiling.

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48 minutes ago, Gunners said:

The voltage settings I included yesterday were taken when it was almost dark. I have included new pics taken today around 10:30am. Master was around 88v and slave around 103v. 

Ok, so both of those sound good. The 103 is quite possibly higher because it has no load dragging it down.

Ah, of course. But the slave took over the loads, keeping them going, right?

48 minutes ago, Gunners said:

I have also noticed that when in solar mode, the slave does not indicate that solar is charging the batteries, only the master and error code 04 appears on both inverters. When utility charges the battery, both inverters show batteries are charging and 04 code disappears.

That sounds significant. The one that's usually the slave seems convinced it doesn't have to do any solar charging. You should drop setting 29 to 47 V (perhaps lower) to avoid the low battery warnings (warning or error code 04). Perhaps you should check the settings, particularly settings 02 and 11, on the slave, to see if they differ from the master. Those settings (or at least setting 02) aren't forced to be the same; you can have different settings in each paralleled inverter. I suppose that settings 01 and 16 might be different too; I don't have much experience with paralleled inverters. One of those could cause your symptoms.

48 minutes ago, Gunners said:

I will try this tonight. Do I need to power off inverters before swapping wires?

I certainly would. But then I have a contactor wired such that if my one inverter drops off, the mains supplies my loads, so it's no bother to isolate the inverters. I'd still power them off completely before making those changes, even if I had to do it by flashlight.

48 minutes ago, Gunners said:

This will be difficult since the Pylons are very close to the box. Pylons are mounted near ceiling.

Ok, let's leave the battery alone for now, but please still do report the battery voltages from both inverters. No need for photographs; you've proven to us that you can read the values properly.

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@Coulomb, thanks for all your input so far.

21 hours ago, Coulomb said:

That sounds significant. The one that's usually the slave seems convinced it doesn't have to do any solar charging. You should drop setting 29 to 47 V (perhaps lower) to avoid the low battery warnings (warning or error code 04). Perhaps you should check the settings, particularly settings 02 and 11, on the slave, to see if they differ from the master. Those settings (or at least setting 02) aren't forced to be the same; you can have different settings in each paralleled inverter. I suppose that settings 01 and 16 might be different too; I don't have much experience with paralleled inverters. One of those could cause your symptoms.

I have lowered the voltage to 47V as suggested. No warnings so far, but will continue to monitor. I have also compared the values with both inverters and they are identical.

Regarding the wire swapping ... I completed that last night and when I checked about 30 mins ago, it was exactly the same as before? I was expecting the solar PV to be swapped to the slave but that was not the case, the master is still producing all the solar PV and the slave value remains around 29w. I know I have been posting many pics, but I am including the before and after of the wire swapping to confirm I did this correctly. 

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5 hours ago, Gunners said:

to confirm I did this correctly.

That looks good. So your panels and wiring are fine; either of them can do decent power; the fact that it's not as high as before can be put down to winter.

4 hours ago, Dex_ said:

sounds like the inverters mppt then

Yes, or it still could be one of the few settings that don't get "broadcast" (for a broadcast setting, a change on one is immediately sent to all the others).

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@Dex_, @Coulomb ... thanks for the help.

On 2019/08/02 at 3:14 PM, Coulomb said:

Yes, or it still could be one of the few settings that don't get "broadcast" (for a broadcast setting, a change on one is immediately sent to all the others).

I have checked the settings for both inverters and they are identical. Are you saying the settings could be correct but the inverter is not actually using that setting? Is there a way to force it? If it is the MPPT, I assume the inverter needs to go in for repair again :(  ... took months to get it back the last time. Can you recommend where to take the unit ... I am near the Fourways area?

I also have an older Axpert which I am not using (the one with the heatsink on top, I think), not sure of the model number, will check. Could I use that inverter with the newer version inverter? If i could, I assume I would need to make sure firmware levels are the same?

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  • 1 month later...
On 2019/08/05 at 6:51 PM, Gunners said:

I also have an older Axpert which I am not using (the one with the heatsink on top, I think), not sure of the model number, will check. Could I use that inverter with the newer version inverter? If i could, I assume I would need to make sure firmware levels are the same?

You could use your old Axpert as just a Solar Charge Controller, and just leave the power (rocker) switch off. Don't wire anything to AC in or AC out. It will turn itself on at dawn and off at dusk, charging the battery in between. You can set the bulk/absorb and float settings just a little below those of the main inverter. No need to parallel, doesn't matter about firmware versions, and the parasitic power draw will be minimal. I'm actually running this setup right now. I'll actually parallel the two inverters when I get the wiring organised.

Edited by Coulomb
AC in abd out no connection.
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40 minutes ago, Coulomb said:

You could use your old Axpert as just a Solar Charge Controller, and just leave the power (rocker) switch off. Don't wire anything to AC in or AC out. It will turn itself on at dawn and off at dusk, charging the battery in between. You can set the bulk/absorb and float settings just a little below those of the main inverter. No need to parallel, doesn't matter about firmware versions, and the parasitic power draw will be minimal. I'm actually running this setup right now. I'll actually parallel the two inverters when I get the wiring organised.

Would you take the battery cables from the second Inverter through the same fuses as the main inverter

Thanks

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