Specific questions about a 24v setup

[HappyTrails]

Greetings!

I've been in construction nearly a decade. Primarily home remodeling, am proficient on most aspects involved... but it is with some deal of humility that I admit, solar power is kicking my butt! I bought Will's book (which is fantastic) but I still feel like there's some details I'd like some feedback on. I am humbly asking for your help.

After watching one of Will's videos, I came to realize that there would be benefits to running a 24v vs a 12v system. That's where my problems start.
Setup:
12ft box on a Express 3500 van.

Renogy 40A CC

(2) Trina 380w panels:

Trina Solar 380W Tallmax Perc Monocrystalline Solar Panel

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www.solartechdirect.com

Giandel 3000w 24v inverter:

Amazon.com

And 32 of these cells:

Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

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for a total of 400Ah 24v.

Everything in my build is electric. 110v fridge rated at 297kW a year. 1800w induction cooktop. Lesser draw appliances are a toaster oven and a hot water heater for a recirculating shower (obviously not all running at the same time).

Questions I have are 1) Should I wire these panels parallel or series? With there only being 2 of them but still bringing in 760w, I'm confused. The 40A Renogy CC is rated to 100v (I believe) but the open voltage of the two panels comes to 97.6v. Too close to max to run them in series? From what I've read it would be ideal to run a combination of series and parallel, say if I had 4 or more panels. However, that does not apply here. If series is optimal, do I need to add a second identical charge controller?

2nd question: how do people wire circuits off an inverter... from the outlet receptacles? Do you use an extension cord? I'm lost on this portion of the system.

Thanks in advance for any advice! I really do feel like a solar dunce, heh.

 

[snoobler]

1) Parallel due to the lack of margin at the peak voltage. This has another advantage of making your system less sensitive to shading. Shading affects all panels in the series string. If they are all in parallel, shading on one panel won't affect others.

2) the inverter has lugs for L N and G AC output. Ideally, you would wire this to a distribution panel which would then send the power to the plugs.

In the absence of a distribution panel, it might make sense to have a quality power strip attached to those lugs since that's the only way you'll get 3000W out of anything. I didn't see the specs, but most conventional plugs on an inverter are limited to 15A.

You would then plug into the power strip or inverter plugs as you like.

 

[HappyTrails]

Thanks for the info snoobler! Parallel is what I had figured.. but if wiring series has the drawback of partial shading decreasing output of the whole string, why would anyone ever wire series? Would it only be used to increase the Volt output of a panel array to match a battery bank? I'm still trying to understand the appropriate application pros/cons of each.

A distribution panel for the AC circuits is something I hadn't even considered. That's brilliant, and frankly, should have been obvious to me, heh. I'm running just a few things 12v, so I was planning a distribution block for those circuits as well.

If anyone else has thoughts or input on the system feel free to add it here. I'm doing my best to read other posts on the forum, but while I feel like I'm getting some of the basics down, much of it just isn't clicking in my head so far

 

[snoobler]

If shading isn't an issue or only a small concern, then there are other reasons for series, including the one you mention.

In my case, I have a 3kW array that will eventually be 6kW on top of a shipping container. I wanted to fit it on one charge controller. By doing 3S6P, I was able to stay within the limits of my 100A charge controller (48V system) and only lose about 200W of potential peak output.

Another solution for vehicle mounted systems is to have a split system, i.e., you have the mounted array and a "mobile" array. You can park in the shade and deploy your mobile array out to the sunshine. Alternatively, if you can quickly mount/unmount your panels quickly, that accomplishes the same end result.

 

[chrisski]

For my build on my 35 foot RV, once I did the DC voltage calculator for six panels, my wiring needed to be pretty thick. To get runs of 30 feet with a 1% loss, I need to wire my panels in 3S2P with 10 gauge wire. I think I came up with 6 or 8 gauge wire for the same six panels put in parallel. Also, the charge controller had a no thicker than limit of 6 gauge. 10 Gauge MC4 plugs were about all I could easily find, and thicker than 10 gauge, the price of the crimping tools for MC4 plugs go up drastically.

I'm trying to keep losses as close to 3% as possible when I add up the solar panels to combiner, combiner to battery, and battery to inverter. If I stuck to 3% at each of those legs, I could lose 9% total.

One thing I found out that really crippled me where I could place the panels on my roof were 2 air conditioners, 2 sun roofs, 3 vents, and perhaps four to eight pipe vents. I could probably fit 8 panels total on my roof before I start running out of room to walk.

 

[John Frum]

Why not wire your panels in serial?
What is the max voltage your solar charge controller can accept?

 

[chrisski]

For me my charge controller is limited to 100 volts, 50 amps, and six panels with the Open circuit voltage of about 20 would exceed the 100 volt limit.

For the OP, his is 100 Volts and 40 amps, and both panels together come up just shy of that.