jameshowison
New Member
- Joined
- Jul 30, 2021
- Messages
- 184
I have a Victron MPPT 150/35 and 11 Rich Solar "Mega 200" solar panels. https://richsolar.com/products/200-watt-24-volt-solar-panel Exactly how this came to be is a longer story 
I currently have 3 of those panels in series on the roof of the house, connected to the MPPT in the RV (ie not the roof of the RV, only works in the driveway). The panels connect to an MC4 shutoff, which then connects to a 2 conductor 10AWG wire that runs 25 feet (SJOW). The RV end of that wire connects to a Bulgin 900 series through-wall connector https://www.mouser.com/pdfDocs/900Series.pdf which is rated for 32amps. The MPPT has 10 AWG wire from it to the bus bar (very short run, like 2 feet), protected by a circuit breaker.
I would like to add more panels to the roof and I'm trying to ensure that the configuration will work. Specifically, can I do 2s5p over the 10AWG/30amp rated components from the panels to the MPPT?
The Victron MPPT calculator is useful, and here is a link to one with the Rich Solar panel details filled out (including temp coefficients) etc: https://mppt.victronenergy.com/#djE...uMDUsNS44MywyMDAsMzcuNiwtMC4yOSw0NS40LDEwLDY= Key values: lmp 5.32 and VOC: 45.4.
Bottomline is that I think I can either do 3s3p (9 panels) or 2s5p (10 panels). After the MPPT current will always be clipped to 35amps (at ~56v). I think that the 10AWG for 2 feet, with the Midnite solar breaker, is fine.
From the panels to the MPPT, though, I'm a little unsure. Series adds volts, Parallel adds amps. The MPPT calcs show me the "input volts" but not the "input amps".
So 3s3p should be ~136.2v (but when temps get low that goes up, exceeding 150v at around 16°F) with ~16amps. So 3s3p is ok until it gets really cold. I'm in Austin so it doesn't often get that cold ... but it has done (the winter storm last year got me scared) and that is when we are most likely to lose power. Also this only uses 9 panels.
2s5p should be ~90v (and even when temps are really hot sufficient voltage to start the MPPT which needs +5v over 56v, so like 62v), and ~26.6amps (5 x 5.32).
But the MPPT calculator doesn't show "input amps" at the lowest temps. When it is really cold (say -15°C/5°F) I think that could rise to ~28.6 amps (L temp coefficient of 0.05 * 25°C - (-15°C) = 0.05 * 40 = 2).
I think I need to know this to answer the basic question: can I do 2s5p over the 10AWG rated components from the panels to the MPPT? This setup would be mildly over-panelled.
Finally, do I need to derate that wire as it will be on the roof in the sun? Any guidance/calculators on that?
(I know that I have to fuse arrays above 3p)
I currently have 3 of those panels in series on the roof of the house, connected to the MPPT in the RV (ie not the roof of the RV, only works in the driveway). The panels connect to an MC4 shutoff, which then connects to a 2 conductor 10AWG wire that runs 25 feet (SJOW). The RV end of that wire connects to a Bulgin 900 series through-wall connector https://www.mouser.com/pdfDocs/900Series.pdf which is rated for 32amps. The MPPT has 10 AWG wire from it to the bus bar (very short run, like 2 feet), protected by a circuit breaker.
I would like to add more panels to the roof and I'm trying to ensure that the configuration will work. Specifically, can I do 2s5p over the 10AWG/30amp rated components from the panels to the MPPT?
The Victron MPPT calculator is useful, and here is a link to one with the Rich Solar panel details filled out (including temp coefficients) etc: https://mppt.victronenergy.com/#djE...uMDUsNS44MywyMDAsMzcuNiwtMC4yOSw0NS40LDEwLDY= Key values: lmp 5.32 and VOC: 45.4.
Bottomline is that I think I can either do 3s3p (9 panels) or 2s5p (10 panels). After the MPPT current will always be clipped to 35amps (at ~56v). I think that the 10AWG for 2 feet, with the Midnite solar breaker, is fine.
From the panels to the MPPT, though, I'm a little unsure. Series adds volts, Parallel adds amps. The MPPT calcs show me the "input volts" but not the "input amps".
So 3s3p should be ~136.2v (but when temps get low that goes up, exceeding 150v at around 16°F) with ~16amps. So 3s3p is ok until it gets really cold. I'm in Austin so it doesn't often get that cold ... but it has done (the winter storm last year got me scared) and that is when we are most likely to lose power. Also this only uses 9 panels.
2s5p should be ~90v (and even when temps are really hot sufficient voltage to start the MPPT which needs +5v over 56v, so like 62v), and ~26.6amps (5 x 5.32).
But the MPPT calculator doesn't show "input amps" at the lowest temps. When it is really cold (say -15°C/5°F) I think that could rise to ~28.6 amps (L temp coefficient of 0.05 * 25°C - (-15°C) = 0.05 * 40 = 2).
I think I need to know this to answer the basic question: can I do 2s5p over the 10AWG rated components from the panels to the MPPT? This setup would be mildly over-panelled.
Finally, do I need to derate that wire as it will be on the roof in the sun? Any guidance/calculators on that?
(I know that I have to fuse arrays above 3p)
