Impp - Matching cells to inputs.

Hi all,

I am currently looking at some proposed systems from an installer. Because of my roof size , my 10 panel system will probably need to be split over two aspects. I am offered a gen1 hybrid, but would prefer the Gen2 ( currently out of stock in the UK as far as I can see)

I just noticed that the panels suggested seem to be relatively low voltage/high current.
https://static.csisolar.com/wp-content/uploads/2020/06/27131650/CS-Datasheet-HiKu6All-Black_CS6R-MS_v2.0C25_EN-25-years-product-warranty.pdf

STC is vmp/imp is 30.8V/12.99A, and NMOT is vmp/imp is 28.8V/10.39A

So does that make these panels unsuitable/dangerous as the max Input current on the hybrids is 11A ?

Also I want to check, when coupled with either a gen1 or gen 2 Hybrid:

The minimum number of panels to give 120V gen1 = 4, or 150 Gen2 = 5 , and even then the voltages are marginal. Doese that mean in some cases the strings will not start up ?

Or am I over analysing the spec sheet and practically these panels fine ?

Thanks for any opinions

justpassing I'm not really qualified to answer your question authoritatively but I'd expect the installer to be taking out any risk to you regarding matching PV to your inverter. On the face of it, it looks like whichever panels you go with, you'd be better with a Gen 1 inverter to harvest from PV for longer periods. If you could increase the number of panels in each string for each orientation, it'd be a moot point. It looks to me that 120V start up compared to 150V with only five panels means you would be better off looking at the lower voltage. Unless anyone here has better-informed view ...

Those panels do seem particularly low voltage/high current for the 400 W output, and not well matched with the GE hybrid maximum current input of 11.0 Amps.

As a comparison the Trina Vertex S 425 W are STC Vmpp=41.5 V, Impp= 10.24 A, and NMOT Vmpp=39.1 V.

At 800W.m2 insolation for the NMOT values, a string of 5 panels would likely generate 5x39 = 195 V, significantly more than the G2 startup at 150 V.

https://midsummerwholesale.co.uk/pdfs/vertexs-de09r.08.pdf

Not sure anyone gets a guaranteed output figure from an installer, hence it is best to do your own research to check what is being installed is likely to perform as you expect.

There is a useful performance tool available online at:-

https://re.jrc.ec.europa.eu/pvg_tools/en/

I have an East/West split of panels across 2 inverter strings, so needed to run 2 calculations from this tool, then sum the predicted kWh outputs for each month of the year.

Thank you for the replies, Seems like I was right to be concerned., and panels aren't a good match.

The site is problematic, as I was looking at a 3.6KW system ( 10 panels) The South roof is best ( no shade) but cant fit all 10 more like 7/8. West roof is large but has some shading issues after 3pm, so want more south than west.
So the best use of sunshine would be 8+2 or 7+3. So a system that requires 5 +5 is far from ideal.

Simon_C At 800W.m2 insolation for the NMOT values, a string of 5 panels would likely generate 5x39 = 195 V, significantly more than the G2 startup at 150 V.

If I did go Trina + Gen2, would 4 panels @ 156 be perfect, or cutting it fine ?

Just to check my understanding, if the string is under 120V or G2 150V, does the whole string stay shut down until those voltages are met ? I am not clear with the dynamic nature of mtpp where you lose some efficiency and where it just doesn't work :-)

Thanks for the link also , ran that and can see moving panels west isn't disastrous, and I will lose some of the late afternoon sun in the summer which is hard to model.

justpassing its cutting it a bit fine.
Yes till Voc is met it remains asleep that string.
The other will be unaffected.
5 panels is considered the norm, unless 50v Voc then 4 seems plenty ok.

The 3.6 kW hybrid inverter is rated up to 4700 W across the 2 string inputs, so you can go for more panels than 10. In theory 11 x 425W if they were all South facing at the perfect roof slope, but they will not all be perfectly aligned with some on the West.
If the battery attached to the hybrid inverter is not already full, then the inverter is capable of receiving 4700 W from the panels whilst outputting up to 3600 W on the a/c connection at the same time as the remainder being used to charge the battery.

I would focus on the South roof and get as many as possible on that with 1 string (7 or 8 panels), as the drop off in performance from Summer to Winter (down to 25%) is not as severe as on an East or West facing roof (down to around 11-12%).

Then depending on your budget and string startup requirements, have 4 or 5 panels on the least shaded part of the West roof, wired on the second string input.

Remember the South and West facing panels will not both be generating their peak outputs at the same time of day.