diy solar

diy solar

Trying to start a set up in my bus

Andrew904

New Member
Joined
Apr 11, 2024
Messages
2
Location
Jacksonville Florida
I am starting to build out my 24 foot school bus and have watched way too many videos about the solar set up. All I’ve done is confuse myself more lol. I am currently planning on buying 4 200 watt solar panels and a 12v 430 ah battery. But with that being said I now am questioning if I should build a 12v or 24v system. Im not sure what other components to buy with the system other than they should be victron for the purpose of their quality. I don’t know the size of inverter or solar charger and what not, so if I could get any recommendations from you guys please shoot them my way.
 
am questioning if I should build a 12v or 24v
What do you expect your inverter size and max loads to be?

Consider 3000W / 12.8V = 234A and is essentially unmanageable.

And 4x 200W = 800W
800W / 14V charging = 57A this is manageable but at 28V it would require simple wiring and fusing.
 
I’m not 100% sure what everything will pull yet but I was hoping to keep it smaller. I’m only going to be charging phones and computers, have a water pump & heater, dometic 12v fridge, and cooktop. I do have an a/c that I would hope to be able to run for a bit off grid too. Do I need to figure out exactly what they will pull before getting anything? I don’t have an issue trying to bump up on solar but the most I could fit would probably be 1000w of solar but mayyyybe 1200w
 
I’m not 100% sure what everything will pull yet but I was hoping to keep it smaller. I’m only going to be charging phones and computers, have a water pump & heater, dometic 12v fridge, and cooktop. I do have an a/c that I would hope to be able to run for a bit off grid too. Do I need to figure out exactly what they will pull before getting anything? I don’t have an issue trying to bump up on solar but the most I could fit would probably be 1000w of solar but mayyyybe 1200w
The heater and cook top can be pretty big draws. Plus, you say 'I am only going to be..." now, but plan for the growth that you are going to want. I have a buddy that put in a system who gave me two pieces of advice:
(1) Use quality parts. You and your family are sleeping within a few feet of this equipment and you will be on the middle of nowhere and need as much reliability as you can get.
(2) plan for the system that can (eventually) do all you want. If you build a system can only ever handle what you think you "can get by with", you will be disappointed. If you cannot afford that now, it is better to build a system that can grow with you.
He said he wasted thousands of dollars and, even worse, suffered through a lot of crap from his wife because he originally put in a system that couldn't handle all that they needed. On the other hand if he had put in a system that didn't handle all they needed now but could later, his wife would have been supportive of his adventure in RV DIY.

In planning my system, getting feedback from some friends, the amazing members of this site, and taking with a Victron Ambassador, it seems the sweet spot for a many mobile applications is 24v.

A lot of RV products are 24v. That voltage means fewer bms's and smaller wiring than 12v while still being able to handle all the loads and amps required for most systems (unless you have something insane like 6 A/C units - yes I talking about you @justinm001 ;)).
For me, the battery size for 24v also hit a sweet spot. I felt 48v batteries were to big and heavy to work in the confined spaces of an RV.

Using a 24v system also allows using a the Victron Orion 12v to 24v charger from the bus' engine so you can charge your lithium system while driving and not damage your alternator.
 
Cart before the horse. Instead of deciding between 12v and 24v, you really need to do an audit (as was already mentioned) of your loads. Then design from there. Now is the time to do the homework, ensuring success.
Seat of the pants, 800w of PV and 5.1kw of battery is not going to get you far by any means.
Why 200w panels? Already have? With a schoolie you have a clean roof line, excellent for solar. If it were me, I would be looking at 400w panels minimum. These days, 400w panels can be cheaper than 200w panels from Amazon with minimal shopping.
 
Never seen one. Please educate.
Very very popular on commercial coaches, busses and semi/trucks. About 80% of my chassis is 24v including bay lights and other things. Prevost busses and coaches have an option for a 24v 225k btu massive HVAC system.

24v is that sweet spot where almost every fuse and breaker system works and you can't really feel getting shocked. Voltage drop isn't a huge issue like 12v either.
 
Prevost being the exception, it is a bus after all. :) Probably the only one.
Heck even my King Aire is 12v. Including start.
Id bet a lot of the super Cs are 24v or at least have 24v components in the chassis. Like 95% of RVs are made by 3 companies and they are 5-10 years behind in everything.
 
Elkhart is not known for their brilliance and innovation over there. Until they can find a way to save a nickel, it will still be 99.9% 12v.
I don't think it's the money because they would save. It's the fact they need to make a change and that requires retraining and completely new techniques. On top of this likley they're concerned if they make any electrical changes it'll require them to be a bit safer when running wires... And maybe not put them next to AC, comms, and water.

Long term 10 years out I really think they're just gonna get leapfrogged by higher tech RVs and they'll be a race to the bottom. We're watching this now in the auto industry with EV cars. Tesla is dominating as is Rivian and Hyundai. Ford sells the most popular pickup by far and couldn't get their lightening to sell. Idk what GM is doing as they keep delaying their platform and the Hummer RVs are an engineering joke.
 
retraining and completely new techniques
They could start with using screws instead of short staples.
next to AC, comms, and water.
Did an install on a 1 month old Brinkley earlier this year. Suppose to be a higher end 5th. Had to spend about 3 or 4 hours cleaning up their cables.
We are talking about companies that will not spend the time to cut tie wraps to save time.
 
Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

1a: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

2: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

3: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. :) Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

4: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

5: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round :) ) and help figure out which parts and pieces you're going to want to get.

Well that's the thing about solar systems, there is no 1-Size-Fits-All answer. Your system will need to be designed to fit YOUR needs. When you design and built the system, it's not going to be the perfect system for me, or Will or 12vInstall or anyone else, but it Will be the right system for You and that's the goal.

As for where to get started, let me throw my standard blurb in here to help point you in the right direction. There's going to be a lot of math and research involved, but that's going to be a LOT cheaper than just buying parts off of someone's list and finding out that it doesn't do what you need.

Don't panic on the Power Audit, you'll actually be doing that a few times. When you do the first pass put in ALL the Things that you might want. AirCon? Sure. Jacuzzi? Why not. MargaritaMaster-9000? Go for it.

The second pass will be the "I Absolutely Need This To Survive" list that isn't going to have much on there.

The third pass will be the "This is what is realistic" audit that you'll use to design the rest of the system.

The Power Audit is going to tell you 3 primary things: 1: How big does your inverter need to be to power your loads? 2: How much battery bank do you need to last $N number of days with krappy weather? and 3: How much solar panel will I need to install to refill those batteries in a 4 hour day (the average usable sun hours rule-of-thumb).

Once you know what you Want and what you Need and what your budget can Afford there will be somewhere in that Venn diagram where those three things meet.

After that, THEN you can start looking at parts.

Yes, it's a long drawn out process, but it's worth it in the end. Not every house has the exact same floorplan, not every vehicle is the same make & model, and not every solar system is designed the same.
 
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