Solar overwhelm :(

[Lil&Frankie]

Hi y’all!

We recently purchased a vintage International bus that has been gutted and conversion started. The person we bought it from was planning on using it minimally, but we’ll be living in it. She had already purchased 2 100w solar panels from grape solar, an inverter and charge controller. From what I’m reading that likely won’t be enough to run everything we need and I’m not sure if I can buy two additional random panels or need the same ones? How do I figure out the breaker box, outlets, etc? I’ve watched tons of videos and feel like I get the gist, but am still boggled when it comes to actual specs. Help? Thanks

[john61ct]

If the controller will be handling the added panels, best they match.

If you will leave the old set as is nd buy a new controller then buy panels that will maximize Watts per roof space, ideally higher voltage (Voc over 30V) with a good MPPT controller like Victron SmartSolar.

You need to build an energy budget in Ah / day at 12V to ballpark guesstimate "enough", if you carry a genset or stay at powered locations every few days then can start small (800W) and expand later.

[PNW_Steve]

I would suggest that you figure out what you need to run from solar then size your solar to fit your needs.

Your 200watts of solar is pretty minimal. If you are going to add panels you need to look at your charge controller and batteries and make sure that you stay within its specs.

To give you a comparison, I have 300watts on my travel trailer. I run the generator for about an hour each morning in order to run the coffee maker, microwave and hair dryer as well as getting a headache start on charging my batteries. The solar plus an hour of generator run are enough to meet my daily needs.

I have 2400watts of solar for my bus. I am hoping to eliminate daily generator run and have the ability to run my 9k BTU mini-split occasionally without having to run the generator.

[dzl_]

If you post the specs of:
(1) your charge controller (A: max input current B: max input voltage C: max output current)
(2) your panels (A: Voc B: Isc which can be found on the back of the panels or the spec sheet)


I'm sure I, or someone else, would be happy to take a peak and give some advice on how to proceed

[Lil&Frankie]

We have no batteries yet, but the 2 100w panels from GrapeSolar, an Xpower by xantrex inverter 450, and a Grapesolar Comet PWM charge controller so far.

[kazetsukai]

If you fill in your user profile to include your rig make/model and location you might find some folks nearby you that can help as well.

[dzl_]

Originally Posted by Lil&Frankie

We have no batteries yet, but the 2 100w panels from GrapeSolar, an Xpower by xantrex inverter 450, and a Grapesolar Comet PWM charge controller so far.

So the good news is that the system is really undeveloped enough that you sortof have a blank canvas and can go whatever direction you want.


The less good news is the components you do have already from the previous owner (with the exception of the panels) aren't that great (PWN controller and Modified Sine Wave inverter), and in my personal opinion, probably are not worth designing your system around. Xantrex is a decent company but modified sine wave is best avoided these days.


Without knowing more details about your system, there isn't much more I can say beyond generalizations


In regards to your question about adding more panels, that will depend on the controller spec's.


But Generally speaking, if you add more panels in parallel (which you would with a PWN controller) you want to make sure that the voltage is as close as possible to the panels you already. This will be listed on the back of each panel. The two figures you want to look for are "Voc" and "Vmp" (or Vmpp). If possible its best to buy identical panels.


Some details on the basics of solar panel wiring can be found here or here

[Ronnie]

Hello I have a 71 International. Great bus , love it. What engine and transmission do you have?


On the solar, I have 400 watts with a MPPT controller all by Renogy. Does well for us. You really need the energy budget first and will likely find you need more. I would be inclined to start fresh. Maybe do a temperary set up with what you while you work on just because it is there. I used a 200 watt harbor freight setup because I had it. This gave me lights, and enough power for circuit testing, fans etc. as I got closer to having it on the road then I changed the controller and panels. So I did wire(with heavy enough gauge wire) everything for my intended system. The value for me was learning a bit about solar from a practical application, and it helped spread out costs, as it took about a year to build the bus.


By the way the harbor freight panels I simply set on the roof and bungy corded them as we did not drive the bus yet, so no time wasted on mounting what I knew was not going be used long term.

[ACamper]

I would buy a couple of batteries and hook them up. It would give you a better idea of what you want and need. Might get you over the overwhelmed part.