New Build Ele Design

[im_L0r3]

Hi Experts,

Owned a 40' many, many years ago. Havent had one in a very long time. About to pull the trigger on a 40'. Weeks of research and reiterations have ended up in this drawing version.

Are there any major design flaws here?
What am I missing?
Minor issues?
Suggested improvements?

Bus will be lived in by our family of four, for potentially weeks to months a few times a year. Power needed for all the standard comforts of home.

[rffffffff]

I would definitely add a battery monitor with a shunt. With this setup I would look at a smartshunt that’ll plug into your cerbo. Gx touch 50 is a little expensive but would make a nice interface for the cerbo if the budget is there.

I’m assuming batteries have a BMS built in?

Lastly I think you’re gonna end up wishing you doubled your solar panels on every cloudy day, and definitely look into wiring them in parallel, not series. If you shade one cell in your current configuration the whole thing will crash, where parallel will leave you with most of your power still. You can prolly get away with a lower voltage (cheaper) mppt controller too, a 150v unit.

Hope that helps!

[im_L0r3]

Thanks! This is the kind of input I was looking for.

Yes, will get batts that have BMS in them.

Ill rethink my number of panels and series vs parallel.

Going with a bigger controller so I can expand if/when needed in the future without having to replace.

The shunt is the one mystery piece for me still. If you have a moment, can you tell me a lil more? In the mean time, Ill google.

Again, thanks. Much appreciated.

[rffffffff]

The shunt actually measures power going in to the battery and out of the battery, the only real way to measure how you’re doing. It’s still
kind of a guess based on capacity and charging efficiently but it’s the best way to measure what’s going on with everything.

The smart shunt by victron will interface with the cerbo and provide a real state of charge number on the display that’s not just a guess like most are. It seems like it may be optional, and it is, but toast your batteries once and you’ll wish you had it. It’s the best teaching tool.

As far as parallel vs serial, parallel creates more and fatter wires but a shaded cell on one panel doesn’t matter much, as opposed to serial where it does and can take out a whole bank of solar just from a little shadow. Unless you’re in the desert with no clouds all the time parallel is vastly superior, especially on a skoolie. On a house it matters less depending on trees and things but skoolies that move need parallel panels.

Lastly, with a flat roof and no tilt you’re not going to achieve full solar potential of your panels probably ever… you can hook up more panels than you think and not overload the charge controller, and if you do it’s usually not a problem. A cloudy day with not enough solar, on the other hand sucks ass. Having way too much solar will make those days a breeze and your life sooo much easier. It’s hard to describe until you’re in it but it’s definitely worth it because it protects your batteries so much and gives you peace of mind. If you wanna go on a hike for a day and it’s cloudy you don’t want to have to worry about whether or not your fridge is wrecking things at home or if you’re gonna have to fire up the generator when you come home at midnight. It’s not worth the stress at all.

[im_L0r3]

If Im understanding this, looks like I would need 1 SmartShunt per set of parallel batts?

Or is it really required for each battery?

Thank you again!

[rffffffff]

Just one. It goes between the negative battery terminal and everything else essentially, so all devices in and out connect through the shunt.

Just make sure you get one rated for the total amp capacity of the system. I think they make a 500a unit that covers almost everything.

[im_L0r3]

Got it. They make 500, 1000, and 2000 amp ones.

[rffffffff]

Sounds right. If you’re going above 500a on a skoolie, however, I would strongly consider increasing system voltage until you’re not!

[Rucker]

Originally Posted by rffffffff

Lastly, with a flat roof and no tilt you’re not going to achieve full solar potential of your panels probably ever…

Regarding tilt, I did some searching on this a while back and shared in a separate post here:
https://www.skoolie.net/forums/f13/l...tml#post409207

Up to 25% loss, especially if you are on the top band of states in the US (or that latitude anywhere). Rather than tilt, my conclusion was it is better to over build solar.