Hi everyone, first of all thank for all the knowledge share on here and all those who are so willing to assist others, it is really appreciated.

I'm hoping someone can assist me with a problem i'm having around my solar setup.

I have an Axpert 3kva Plus 24v (most likely a clone) that I have been running for some time without solar. Over the weekend I installed 3 panels and was up and running for about an hour over Midday peak sun. After the hour, there was a loud bang from the inverter and orange sparks out the side where the SCC is located. The inverter / battery setup was still working but the SCC blew.

I have sent it in for repairs and they have confirmed that the FET's and some transformers on the MPPT controller blew. I'm so worried that it may happen again and am wondering if I have missed something with the calculations and specs.

The inverter is rated at max 1500w solar, MPPT voltage range is 30-115V with max input of 145V. My panels are 545w Vmpp 31.4V and VOC 37.7 with max power current of 17.37A per panel. I have 3 panels in series so this would be a total voltage of 94,2v under load and open circuit 113.1v. I was measuring VOC of 111v with a multimeter. I understand the wattage is slightly above spec (545 x 3 = 1635) but I did not think that this would be an issue given efficiency etc (but I may be wrong here).

Do you think I have over paneled by having 3 and should just use 2 or do you think there was a fault within the inverter. After paying for the repairs I would hate for it to happen again once connected. Any help / suggestions would be greatly appreciated.

So in summary:

Invert Specs - 1500w mppt, 30/115 range, max 145.

Panel Spec - 3 x 545 series panels. 31.4 Vmpp each and 37.7 VOC. 17.37 A per panel.

Thank you in advance!

 

Sorry to here about you inverter issues.

The VOC of those 545w panels seems very low. I would rather take n multimeter and measure the voltage on the panels before connecting it again.

It seems that the voltage was to high for you inverter.

I measured 111 volts before connecting, this  was just before the isolator into the inverter, so should be in range? I can post the spec sheet if it will help but definitely the figures as posted above. 
 

Do you think a slight overshoot on the wattage is a problem?
 

Thank you 

Edited August 2, 20223 yr by Andy07

Below are my inverter specs as well as the panel specs (545w model)

Thanks again

 

21 hours ago, Andy07 said:

I have 3 panels in series so this would be a total voltage of 94,2v under load and open circuit 113.1v. I was measuring VOC of 111v with a multimeter.

Everything looks to be in spec, the only thing I notice is that your voltages are quite close to the max 115VDC operating voltage of the inverter SCC. I'm not 100% sure how the inverter reacts to overvoltage there.

 

Edited August 3, 20223 yr by jumper

Thanks yeah it is quite close, I just figured with an absolute upper limit of 145 I would be ok, but like you say, not sure how it handles it. 

I have one very similar system I have been running for about 7 years now which has similar specs except the SCC is smaller and doesn't have  the operating voltage range.

This runs on 2x325W panels in parallel, yep that's 1S2P (no typo) with no problems charging 4x200Ah 12V gel batteries from PV (It's off grid, but my loads are small).

Perhaps you should try running only 2 panels in parallel and if that works then you could add the 3rd in parallel too, otherwise you might only be able to run the 2 panels in series.

Edit: P.S. my panels have a VOC of 46V and Vmp of 37V, so they are higher values than yours, but it may still work.

Edited August 3, 20223 yr by jumper

1 hour ago, Andy07 said:

I just figured with an absolute upper limit of 145 I would be ok

I also have a 5KVA with max SCC voltage of 145V which I ran on 3 panels in series for almost 3 years with a Voc of 136.6V before it eventually died one cold, frosty night, but that lasted a lot longer than yours. It also doesn't specify an operating voltage range for the SCC though, only max 145V. Just mentioning because maybe the fact that yours specifies the operating range, it may be sensitive to the max 115V.

6 hours ago, jumper said:

I also have a 5KVA with max SCC voltage of 145V which I ran on 3 panels in series for almost 3 years with a Voc of 136.6V before it eventually died one cold, frosty night, but that lasted a lot longer than yours. It also doesn't specify an operating voltage range for the SCC though, only max 145V. Just mentioning because maybe the fact that yours specifies the operating range, it may be sensitive to the max 115V.

This is quite bad. During the night one would not expect the voltage to be high. Further the 145V should be the level not to exceed and not a lower voltage. I have always been wary of getting close to the maximum provided.

Edited August 3, 20223 yr by Scorp007

15 minutes ago, Scorp007 said:

This is quite bad. During the night one would not expect the voltage to be high. Further the 145C should be the level not to exceed and not a lower voltage. I have always been wary of getting close to the maximum provided.

 

16 minutes ago, Scorp007 said:

This is quite bad. During the night one would not expect the voltage to be high. Further the 145C should be the level not to exceed and not a lower voltage. I have always been wary of getting close to the maximum provided.

Maybe I should just put 2 panels in series but I have 3 on the roof so seems a waste especially since it is all in spec but may be safer to run 2. So undecided 😅

1 hour ago, Andy07 said:

Maybe I should just put 2 panels in series but I have 3 on the roof

You'll probably be OK 95% of the time. It's when it does get cold that your Voltage may exceed the max.

3 hours ago, jumper said:

I have one very similar system I have been running for about 7 years now which has similar specs except the SCC is smaller and doesn't have  the operating voltage range.

This runs on 2x325W panels in parallel, yep that's 1S2P (no typo) with no problems charging 4x200Ah 12V gel batteries from PV (It's off grid, but my loads are small).

Perhaps you should try running only 2 panels in parallel and if that works then you could add the 3rd in parallel too, otherwise you might only be able to run the 2 panels in series.

Edit: P.S. my panels have a VOC of 46V and Vmp of 37V, so they are higher values than yours, but it may still work.

The Max PV Array open circuit voltage for the 600W SCC is 75vdc max. The mppt voltage range is 30-66v. 2 Panels in parallel will be fine. 

The technician seems to believe that the PV connections were not tightened securely, if this happens, the smallest spark burns the mosfets.
 

I’m pretty sure everything was secure though. 

4 hours ago, Scorp007 said:

This is quite bad. During the night one would not expect the voltage to be high.

Yeah, I'm aware of that now, that's why I mentioned it died on a cold night, not during PV production when one would most expect it.

4 hours ago, Scorp007 said:

Further the 145C should be the level not to exceed and not a lower voltage.

Yep, found that out too, only after it died though... school fees paid! I have rewired to 2S for my new King.

1 hour ago, Chris Louw said:

The Max PV Array open circuit voltage for the 600W SCC is 75vdc max. The mppt voltage range is 30-66v. 2 Panels in parallel will be fine.

Yeah, runs beautifully thanks, except for the standard firmware bugs of course.

I’m going to drop one panel for now and give it a go, will let you know how it turns out. Holding thumbs 

On 2022/08/02 at 10:33 PM, Andy07 said:

I have an Axpert 3kva Plus 24v (most likely a clone)

Yes, it definitely is a clone.

I believe that some genuine Axperts have similar or identical specs, so it depends on how well they copied the design. The voltages you quoted should not have blown up the Solar Charge Controller, or even caused derating of the SCC. So I'd suspect cheap components, or imperfect copying. You never know what you'll get with a clone.

You might be able to continue using the inverter by just removing the SCC ,and using an external MPPT directly to the battery.

24 minutes ago, Coulomb said:

Yes, it definitely is a clone.

I believe that some genuine Axperts have similar or identical specs, so it depends on how well they copied the design. The voltages you quoted should not have blown up the Solar Charge Controller, or even caused derating of the SCC. So I'd suspect cheap components, or imperfect copying. You never know what you'll get with a clone.

You might be able to continue using the inverter by just removing the SCC ,and using an external MPPT directly to the battery.

Thank you, I suspected the same thing. May not be the specs that are actually printed.

4 hours ago, Andy07 said:

Thank you, I suspected the same thing. May not be the specs that are actually printed.

I am using a external Epever on the very same inverter. Works well and loaded USR settings for my lithiums. It also saves quite a bit in standing power as my Axpert is left off and only switched on with LS and when I want to cycle the batteries.

Hey guys, just to give you an update, I had the inverter repaired and connected 2 of the 3 panels. All is working well as it should, only now I have a panel up on the roof doing nothing. Perhaps I should chance connecting it again or otherwise just upgrade to something bigger. Either way 2 is working for now. Thanks everyone 

On 2022/08/02 at 10:33 PM, Andy07 said:

I was measuring VOC of 111v with a multimeter.

 

16 minutes ago, Andy07 said:

Perhaps I should chance connecting it again or...

Those seem like they might be 60-cell panels, and the voltage you measured is well within specs. So allowing for another 10% with cold weather, that's still only 122 V, which should be fine. You may end up with low production with only 2 of such panels, especially in hot weather.

So I think it's worth trying 3 panels again. If that blows again, I think that's a sign that you do need something better.

Edited August 13, 20223 yr by Coulomb

19 minutes ago, Coulomb said:

So allowing for another 10% with cold weather, that's still only 122 V, which should be fine.

Hey @Coulomb, what do you think about the MPPT operating range specified as 30-115V DC as per the sticker on the side? Do you think it's ok to exceed that?

1 hour ago, Coulomb said:

 

Those seem like they might be 60-cell panels, and the voltage you measured is well within specs. So allowing for another 10% with cold weather, that's still only 122 V, which should be fine. You may end up with low production with only 2 of such panels, especially in hot weather.

So I think it's worth trying 3 panels again. If that blows again, I think that's a sign that you do need something better.

For me trying 3 again just to damage it to find out you need a bigger inverter is...... Like Chris and myself use that external MPPT for the 3rd panel. R1300 is not so much to gain 2.5kwh per day if load is connected during the day.

@jumper

I would say that is the most efficient range. No harm as long as you don't test if 145V is the maximum. I will rather give same grace for the quality of components that might be used. 125-130V I would be comfortable with.

Edited August 13, 20223 yr by Scorp007

Thanks guys, the spec sheet says they are 110 cell Mono, do you think this makes a difference? 

2 hours ago, Andy07 said:

Thanks guys, the spec sheet says they are 110 cell Mono, do you think this makes a difference? 

No need to be concerned with how many cells. At the end it is the voltage the panels generate that damages the MPPT components.

On a daily basis we deal with FETs rated at 49A being popped on PCBs that under a worse scenario only draws 13A. I would not trust equipment at the maximum rating provided in the specs. May be its just me? Rather save than repairing what could have been avoided.

Can you confirm that your panels only have 5 columns of cells instead of the normal 6?

Edited August 14, 20223 yr by Scorp007

29 minutes ago, Scorp007 said:

No need to be concerned with how many cells. At the end it is the voltage the panels generate that damages the MPPT components.

On a daily basis we deal with FETs rated at 49A being popped on PCBs that under a worse scenario only draws 13A. I would not trust equipment at the maximum rating provided in the specs. May be its just me? Rather save than repairing what could have been avoided.

Can you confirm that your panels only have 5 columns of cells instead of the normal 6?

Ok cool thank you, they do indeed have 5 columns