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pgbsolar asked

Solar String to MPPT 100/50 wire size confirmation?

Hi All, I've just bought a Victron 100/50 MPPT and wish to confirm my wire size calculation before switching on the system.

I have 2 x 200w renogy flexible panels in a string with the following specs:

Panel Voc is 23.9v
Isc = 10.74A

Therefore,

Voltage: 47.8 [23.9x2]

Amps: 11

Distance from MPPT to Panels = 12-14m

Will my 10AWG (6mm2 - Kings cable) suffice?


FYI, I used the following formula from a previous post and came up with: 1.16mm2 (…but I must've messed something up)?

Found here: https://community.victronenergy.com/questions/18066/10050-mppt-wire-size.html

(10.75x(11*3.3)x14)/(0.05x47.8)=2,285.8368 to mm2 [1.16mm2]

Really appreciate your input, thanks Pete

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2 Answers
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kevgermany answered ·

Best to use one of the online calculators and make sure you either double the cable length, or use one that does a round trip calc. There's one in the Victron toolkit which you can download.

6mm2 cable is going to give a voltage drop of about 5%, a significant power loss. 10mm2 would be better.

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pgbsolar avatar image pgbsolar commented ·

Hey @kevgermany, thanks a lot for the reply - taking your advice, I used an online calculator at omni which resulted in:

vicomni.png

...but i'm not sure I grasp your note about doubling the wire (forgive my extreme ignorance)? Just trying to make sure I'm on the right track and that i'm not going to melt the wire? Thanks again, cheers Peter

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pgbsolar answered ·

...just as a side note (assuming the calculator is correct) - if I was to run only one panel (23.9v) - which will happen from time to time, my cable distance would have to half; as in, 6m max? Is that correct. Thanks in advance for any help

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regman54 avatar image regman54 commented ·
Don’t forget you need to size the wire for both panels being used simultaneously whether you only intend to use them together once in a while or not.
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pgbsolar avatar image pgbsolar regman54 commented ·

Indeed - thanks @regman54. I have a 12m 10AWG that I will run for both, and a 9m (10AWG) that I will cut down to 6m for when I just use the single. Thanks a lot for your input.

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Related Resources

Victron Wiring Unlimited PDF

Victron Wiring Unlimited Online

MPPT product page

VictronConnect manual

PWM or MPPT

MPPT calculator

MPPT codes

Additional resources still need to be added for this topic