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hookem avatar image
hookem asked

Yet another Series-Parallel setup question: 6 * 100W panels on Sprinter RV

Seeking advice on optimal setup (6 * 100W on RV roof-top, taking shade into account)
Here are the specs on the 100W panels:
Voc = 25.4V, Vmp = 20.5V
Isc = 5.23A, Imp = 4.95A

Here are the options I'm considering so far:
1) 1 MPTT 100/50 Controller: 6 panels in Parallel.
2) 1 MPTT 100/50 Controller: 3 Sets of 2 Panels in Series, with the 3 Sets connected in Parallel
3) 1 MPTT 100/50 Controller: 2 Sets of 3 Panels in Series, with the 2 Sets connected in Parallel
4) 2 MPTT 100/30 Controllers: 2 Sets of 3 Panels in Parallel, with 1 Set per controller
5) 2 MPTT 100/30 Controllers: 2 Sets of 3 Panels in Series, with 1 Set per controller
6) 3 MPTT 100/20 Controllers: 3 Sets of 2 Panels in Parallel, with 1 Set per controller
7) 3 MPTT 100/20 Controllers: 3 Sets of 2 Panels in Series, with 1 Set per controller
==> 12V System: 2* 125Ah Li <==

Thanks in advance for your feedback.

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2 Answers
dazey77 avatar image
dazey77 answered ·

thoughts

1-No (too low voltage, too thick cable)

2-Perhaps, good shading resistance, good voltage (assuming 12v battery), medium cable thickness

3-perhaps, less shading resistance than 2, smaller cables

4-No (too low voltage

5-perhaps- having redundancy is nice and you could use a 100/20 rather than the 30.

6-3 seems overkill to me and if your doing 3 mppt, why not the 75/15

7-3 seems overkill to me and if your doing 3 mppt, why not the 75/15. Prefer this series option over 6 due to higher voltage

so 2 or 5 are my favourites.

(just to clarify, where I say too low voltage, its below optimal not won't work)

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hookem avatar image hookem commented ·

Thanks for the feedback!

(*) #3 and #5 are similar (3 panels in Series per Set)
(*) #3 uses a single Controller for 2 Sets in Parallel
(*) #5 use separate Controllers per Set

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wkirby avatar image
wkirby answered ·

Only piece of information missing here is the battery Voltage.
If 24V then option 1, 4 and 6 will not work at all.
If 12V then any of the options will work.

The best option to combat shading would be number 6, but it is the most costly, perhaps even OTT.
Option 4 is only slightly cheaper.
Option 1 would be good for shading and the most cost effective. Cabling becomes more expensive.

With more that two parallel strings or modules you'll do well to fuse each string before combining them.

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hookem avatar image hookem commented ·

12V system (Edited above). Thanks!

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