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Need som help from the vast knowledge in this forum (Kodak OG 5.48)


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Hi everyone. 

Need a bit of advice please on the way forward with current install with the max amount of panels I can add.
Currently the system is about a year old. Kodak OG 5.48, 8x Canadian 365w KuMax panels (8s) , 4.8kwh Shoto Lith.
Specs on Inverter: Max PV 5KW, MPPT range 120-430 VDC, max VOC 500 VDC. Not 100% confirmed but max input current on one or two sites 18A
Panels spec on 1000 W/m2: Pmax 365W, Vmp 39.8V, Imp 9.18A, Voc 47.2v, Isc 9.75A

The system is running great, powering everything on essential side, stuff left on non-essential is geyser and oven (got a gas hob). Got a plan in mind for the geyser so thats why the question regarding more panels and helps a bit with overcast.

A friend of mine who installed the same time as me and his panels are out of the same batch as mine is planning to change his 6 panels he has to 450w+ panels.
At last I can get to the question. I'm thinking of taking over his panels and maybe running a 6p2s ( 4.38Kw 18.36A, VOC 283.2v) or 7p2s (5.1Kw, 18.36A, VOC 330.4v) configuration. but with the series config I'll be pushing the input current to 18.36.

Any input will be much appreciated. roof real-estate is not a problem can accommodate parallel strings and is pointing 357 degrees (N) 


Thanks

Edited by DieITou
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Hi DielTou

These Voltronics inverters also rebranded Kodak are very robust pieces of kit. However, beware when you start to reach the edge of any sides of its envelope. Given the 18A limit & 430V PV limits, I would leave some room to play a bit. Otherwise you will damage the Solar Charge Controller & will need this unit repaired. Also pushing this amount of PV energy very close to the limit will definitely make your machine work much harder & this can cause stress to internal components. Therefore longevity can also become an issue. I would buy the said panels from your buddy but leave at least 30V-50V of thinking space on the PV side & try to keep it at a single string. 

The testing the Chinese manufacturers do is a pulse stress test. They find the absolute limits on their products & don't pay attention to constant rates of voltage during their said testing. I would take their machines close to the limits with caution as the room for margin is slim. 

87

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1 hour ago, DieITou said:

I'm thinking of taking over his panels and maybe running a 6p2s ( 4.38Kw 18.36A, VOC 283.2v) or 7p2s (5.1Kw, 18.36A, VOC 330.4v) configuration. but with the series config I'll be pushing the input current to 18.36.

 

I think you mean 2p6s and 2p7s? 

Series connections increase the voltage, parallel connections increase the current.

I would give 2p7s a try. I may be wrong but I highly doubt that an extra 0.3A is going to do anything. Besides, depending on your setup you might not even reach that amperage. What is the maximum current you get from your panels in their current configuration?

I guess if you really want to know for sure before forking out cash; rewire your panels to a 2p4s configuration and see how the inverter behaves.

Edited by tetrasection
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Posted (edited)

@tetrasectionyes sorry you are right. i swapped the 'p' and 's' around.

What I saw on nice sunny days that the panels perform way better than one would expect so that is why I'm a bit cautious. On nice sunny days  I hit 3438w and 11.7A from these 8 panels.

So either I must just get one extra panel for 9s and save up for a 5/8Kw Sunsynk

 

Edited by DieITou
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5 minutes ago, DieITou said:

@tetrasectionyes sorry you are right. i swapped the 'p' and 's' around.

What I saw on nice sunny days that the panels perform way better than one would expect so that is why I'm a bit cautious. On nice sunny days  I hit 3438w and 11.7A from these 8 panels.

So either I must just get one extra panel to doe 9s and safe up for a 5/8Kw Sunsynk

 

Those are pretty impressive numbers!

Yeah, in that case... 23.4A on an 18A inverter is really pushing it...

One possible option is to have a current limiting circuit before your inverter to keep it under 18A. You'll have to find someone else to help you with that though, since my understanding on the matter goes as far as getting confused when looking at the wikipedia entry lol

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On 2021/06/11 at 6:48 PM, tetrasection said:

23.4A on an 18A inverter is really pushing it...

Yes. Don't do it. You could end up with this (from just 20 A): https://forums.aeva.asn.au/viewtopic.php?p=80051#p80051

Have you confirmed your over-performance, e.g. with a clamp meter that you trust and know how to use properly? If it actually never exceeds 9.15 A, then you should be OK.

Edited by Coulomb
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Never checked with a clamp meter now that you mention it. Got the info from the inverter that pushes info via solpiplog(MQTT) to home assistant. The amperage that went to the batteries to charge it was high as well so I wasn't to skeptical about the values.

Going to give 6s2p a tri and see what it does as soon as the panels become available.

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