Need help matching used panels to Victron 100/50 SCC

[offroad]

5th wheel with 300ah 12v LiFeP04, Multiplus 3K, BMV-712, Orion 12/12-18 and I want to add some solar.
Planning on a Victron 100/50 SCC and 2-4 used panels around 800-1000w total, and concerned about getting the VOC too high but 150/70 or 85a models are nearly double the price.

Used panels Watts/VOC
250w / 37.2v and 300w / 44.6v Canadian Solar Poly
395w / 49.5v Jinko Eagle Mono

I'd like to run 2x in series but in cold temps, is the 250w (74.4v) panels my only option and then maybe I could run 2s2p?
The 300w in series would be 89.2v, is this too close to the SCC's 100v max in cold weather?
2x of the larger 395-410w panels seems easier, but I'm guessing these would have to be in parallel and is 49v high enough for good SCC performance?

On testing them should I expect to see the VOC Open Circuit or VMP Maximum Power Voltage from a multimeter?
Testing DC amps, am I looking for ISC Short Circuit or IMP Maximum Power? My meter only goes up to 10a DC.

Some defects listed: "snail trails" "internal wiring defect now repaired" "crack at the back"
What defects are ok and what should I avoid?
Some are listed as 10yr old, how old is too old?

Thanks for all advice!

 

[sunshine_eggo]

5th wheel with 300ah 12v LiFeP04, Multiplus 3K, BMV-712, Orion 12/12-18 and I want to add some solar.
Planning on a Victron 100/50 SCC and 2-4 used panels around 800-1000w total, and concerned about getting the VOC too high but 150/70 or 85a models are nearly double the price.

Used panels Watts/VOC
250w / 37.2v and 300w / 44.6v Canadian Solar Poly
395w / 49.5v Jinko Eagle Mono

I'd like to run 2x in series but in cold temps, is the 250w (74.4v) panels my only option and then maybe I could run 2s2p?
The 300w in series would be 89.2v, is this too close to the SCC's 100v max in cold weather?

2S2P, 250W would be fine. The 300W would be good down to about -5°C

2x of the larger 395-410w panels seems easier, but I'm guessing these would have to be in parallel and is 49v high enough for good SCC performance?

At 12V, more than enough. Optimal MPPT Vmp is about 1.5X system voltage. As you start increasing above that, MPPT efficiency goes down. It is often offset by improved wiring losses from higher voltage, lower current.

On testing them should I expect to see the VOC Open Circuit or VMP Maximum Power Voltage from a multimeter?

Voc

Testing DC amps, am I looking for ISC Short Circuit or IMP Maximum Power? My meter only goes up to 10a DC.

Yes.

Some defects listed: "snail trails" "internal wiring defect now repaired" "crack at the back"
What defects are ok and what should I avoid?
Some are listed as 10yr old, how old is too old?

IMHO, I would not buy panels with defects.

10 year is about 50% of design life. EXPECT them to only put out 80-90% of rated in perfect conditions.

 

[offroad]

I've got space for 4x of the 250w, or easier space for 2x of the 398w.
The 100/50 SCC shows support for up to 700w so I'd either be 300w or 100w overpaneled, is 300w too much?

 

[fratermus]

The 100/50 SCC shows support for up to 700w so I'd either be 300w or 100w overpaneled, is 300w too much?

On page 55 the manual does say "nominal panel PV power 700w" but with footnote 1A. That note says: The solar charger will limit input power if more PV power is connected. You might already know this but just in case: this clipping allows us to add panel to compensate for low- and normal- harvest, sacrificing max power under excellent conditions.

+100w would be ~14% overpaneled, which many would consider near-optimal under normal solar conditions.
+300w would be +43% overpaneled, aggressive for normal conditions but may be perfect for fair-to-middling conditions.

I don't know what the overpaneling wattage cap on the Victron line is (if any) , but there appears to be a 60A ISC limit on this model (same chart on p55). Related discussion.

 

[sunshine_eggo]

I don't know what the overpaneling wattage cap on the Victron line is (if any) , but there appears to be a 60A ISC limit on this model (same chart on p55). Related discussion.

Victron only cares that you never break Voc limit and recommends strongly that you never break Isc limit. Power doesn't matter except for output.

For the 250W panels, max array size would be 2S6P assuming panel Isc < 10A that's a 3000W array.

Matching solar modules to MPPT charge controllers - Victron Energy

Life used to be so simple; in a 12V battery system you took a ‘12V’ solar module, watched carefully that the maximum PV current would not exceed the charge controller maximum current and the system would work. Unfortunately due to the fact, that with PWM controllers the PV module is not feeding...

www.victronenergy.com

Limits to Oversizing a PV array

How to determine by how much you can oversize a PV array? This can be done with help from the spreadsheet tool. Here though is the manual explanation of how it is done.

There are two limits, when determining the maximum array size that can be connected to an MPPT:

1. The Maximum PV open circuit voltage (Voc at STC)
2. The Maximum PV short circuit current (Isc at STC)

Both values are specified in the datasheets of all our MPPT Solar Charge Controllers. Those two ratings of the PV array must not exceed these MPPT limits.

Note that these two maximum ratings must not be multiplied to determine the maximum installable peak power. Instead, each of them needs to checked by itself:

 

[Rocketman]

As a full-time RVer with the Victron mppt 100/50, I have four 200w panels hooked up in 2s2p mounted flat (although I can tilt).

You will want to be over paneled. I have only seen something close to 700w a few times (June or July between 11and1).

Usually it is much lower, today my max watts were 397w, yesterday it was 411, last week a few days about 540w.

When I tilt the panels the daily totals go up by 20-30%.

So put as much on the roof as you can (within reason).

I have 1220w on my roof, we full-time. Residential fridge, Starlink, lots of computers, as long as it is sunny- the solar keeps us charged. If bad weather - the generator needs ran anyway.

A bit ago - cloudy weather - I was getting 80 to 100wfrom the array.

Good Luck