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Mixing panels cos you crave an extra 35w for your electric boat

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Tara Dee

New Member
Joined
Apr 20, 2022
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Hi all,

Greetings from the UK. Not the most crucial question – am asking out of interest as much as anything.

I was going to get two of these Q-cell 375w panels and wire them in series https://midsummerwholesale.co.uk/pdfs/qcells-g10-datasheet.pdf to charge my 24v electric boat batteries via my 30a Epever Xtra MPPT.

However, the larger of the two spaces on my boat roof could accommodate this longer Q-cell 410w panel https://midsummerwholesale.co.uk/pdfs/qcells-g10-ml-datasheet.pdf

I notice that the IMP and ISC values of the 375w and 410w panels are very similar, and I have read that amps is the key parameter when wiring mismatched panels in series.

Would it be advisable/beneficial to get these slightly mismatched panels and wire in series? Would I get max power out of both? ie a theoretical 375w + 410w = 785w? Or am I best sticking to identical 375w panels for only 750w? :)
 
Tara Dee said:
Would I get max power out of both? ie a theoretical 375w + 410w = 785w?
Click to expand...
In series, add the volts and multiply by the lowest Imp.

If the Imp is as similar as you mentioned you will likely get close to 785W.

Make sure you do not exceed the SCCs max input voltage with the combined temp compensated Voc.
 
Cool! That's what I'd hoped. To do the arithmetic:

375w panel
VMP = 34.69v
IMP = 10.81a

410w panel
VMP = 38.11v
IMP = 10.76a

So, in series: (34.69v + 38.11v) x 10.76a = 783.33w

I guess all I'd ask is: is it really that simple? Or are there other considerations? To be sure, the panels are from the same Q-cell G10 range.

Obvs I'd only go for slight mismatch if there's definitely no drawbacks.
 
Thanks MisterSandals!

Just wanted to give this a nudge and check if anyone else got any thoughts as to the wisdom of this panel-mixing plan?

Before I spend my moneys this weekend..
 
Hi again, @MisterSandals or anyone else. Thanks for your help so far! Quick further question on this:

Does it matter which order I wire the panels in? I suspect not (as current is the same throughout the whole circuit, right?). But I just want to double check...

ie should series circuit be:

CC positive --> 410w panel --> 375w panel --> CC negative

OR

CC positive --> 375w panel --> 410w panel --> CC negative

375w panel
VMP = 34.69v
IMP = 10.81a
https://midsummerwholesale.co.uk/pdfs/qcells-g10-datasheet.pdf

410w panel
VMP = 38.11v
IMP = 10.76a
https://midsummerwholesale.co.uk/pdfs/qcells-g10-ml-datasheet.pdf
 
Tara Dee said:
CC positive --> 410w panel --> 375w panel --> CC negative

OR

CC positive --> 375w panel --> 410w panel --> CC negative
Click to expand...
Gosh, I never really thought about this but my guess is that it shouldn’t matter. I would be really interested to hear the results if you try it both ways (under similar conditions).
 
Nor had I until it I had to decide which way round! Hahah.

Yeah it's my hunch too, but if I end up testing both ways sure I'll let you know how it goes.

And anyone else got a technical/first hand knowledge on this please let us know!
 
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