Advice on solar panels

[Redbearded]

Hi all!  Looking on craigslist and saw some, what look to be, really nice solar panels for about $90 per. Is this a good deal? 
https://sfbay.craigslist.org/sby/for/d/used-sunpower-305w-black/6762458504.html

 

[Seminole Wind]

if i was local, i'd snatch some of those up. sunpower is a good brand, and 300+watts from that footprint is good. if you are comfortable looking them over for damage like cracked cells or something.

if you have to ship them, the cost could go up considerably and they might get damaged in shipping

 

[highdesertranger]

it's a great deal if they are in good working order. I agree if you are local I would check them out. highdesertranger

 

[John61CT]

Yes good deal, but not "fantastic".

They are 10 years old, so compare to what else may currently be available in the area, worth paying double for new if you can avoid shipping costs.

So definitely worth it **only** if you're local and especially if you are allowed to choose the ones you want, go over them with a magnifying glass.

Ideally buy more than you need and store to replace failures.

 

[jimindenver]

If local then check them out with a meter. Make sure that they produce their ratings and that you get a set that matches up.

 

[tx2sturgis]

Are you buying more than 100 of them?

From the ad:

Pricing:
1-99 panels $100 each
100 or more panels $90 each

 

[Feelit]

I paid £5,600 for my installation 2 years 9 months ago. Panels totalling 3.975 KW (Canadian Black) and a Sunny Boy Inverter with a Sunny Boy bluetooth Monitor so I would say your quote is way too high. As you're also in Cumbria you won't get as much sun as those of us further south so you'll need to factor that in to your returns as well.

 

[abnorm]

FEELIT...….The OP is looking for panels in SAN FRANCISCO USA...……..not England !

and your 4,000 watts of solar must be on a really big vehicle ?

Introduce yourself in the Newcomers Section

 

[bigskybob]

Not a bad price at all.

 

[squire]

Just be aware you will need a MPPT controller to use them.

 

[Redbearded]

yeah, I'm planning on 6 panels on the trailer for 1800w and a nice victron controller (still deciding on 3 sets of 2 or 2 sets of 3) tied to a 24v tesla battery pack. Should be under 4k for the whole setup

 

[B and C]

I vote for 3 sets of two. If you get shading on one panel you only lose a third of capacity instead of half.

 

[bullfrog]

I was just looking at a video where they were putting a Tesla battery in an RV looked like to me keeping it happy and working out of the car required a lot of depending on heating and cooling systems as well as an exppensive charging controller. Pretty neat to be able to get 1,000 amp of battery for around $1,200 but could be really bad if something fails.

 

[Redbearded]

I'm hoping to not need a charger for it. I'm planning on having enough solar to be able to keep it filled without the need for a generator or shore power So no expensive charge controller needed, just let the mppt keep it topped up and have a low voltage cut out when/if it needs it. Also for keeping the battery warm I'm planning on a circuit to monitor that and keep it above a threshold temp.

 

[Redbearded]

I'm going to have them mounted something like

so if I do 3 sets of 2 they will be at different angles to the sun. If I do 2 sets of 3 they will all be facing the same direction and inclination. If I was going to mount them flat then I would do 3 sets of 2 as you suggest but with random angles and shading I thought it best to work with similar orientation

 

[B and C]

Even if angled as shown, shading from a random tree branch will cut your production in half. You can set them up just like this and still be 3 sets of 2. It is all in the wiring.

 

[Redbearded]

I'm wondering if I shouldn't just do all 6 in parallel as the voltage is high enough to minimize the losses and then let the controller figure it out, lol.

 

[B and C]

Shading wouldn't be as much of a problem. I don't know what size cable you would have to use after the combining though. Make all connections on the roof and penetrate with one pair of sufficient size.

 

[John61CT]

I would bring the individual panel wires inside if at all practical,

Flexibility for extracting maximum watt-hours per day output, Victron SCs give lots of options, but also, may want to change later on.

 

[Redbearded]

My thinking right now is to use a weatherproof combiner box with a din rail inside and some cable glans to keep it dry (sorta like how this is ). Then have a single pair of at least 4 gauge cables (peak amperage looks to be about 85 amps with a peak voltage of 70) coming down from the roof into a breaker to shut it off for repairs.