Couple new to solar and skoolie.net

[procrastinator-SKO]

Hello everyone !

My name is Austin andI’m over a year in and we have finally started purchasing some electrical things. I’ve read many threads on here and I know everyone’s build is different but I’m having trouble sizing/figuring out how to put mine together.

We have 16-200w solar panels
4-270 ah battle born batteries
No other electrical has been bought

We are planning on running the solar panels in parallel and the batteries in series parallel .(not sure if this is correct for my application)

I’ve spent the last 2 months researching PV solar and the electrical that surrounds it and by the life of me I just can’t get a good feel for it . I understand terminology and how the system itself works for the most part. Now how I get this all to work is where I’m confused.

I’ve done all my electrical calculations that I think I needed to do but something is just not adding up correctly . My total daily watt hours is 29,147 which seems extremely high, but i am just going on what others have said on here .(I have pictures attached and can draw more and do more if needed)

Attached to the drawings I have some appliances and things that will be used daily.including 12v 120v and 220v appliances .Will my 24v 540ah battery bank be able to handle these efficiently ?

I really would love if someone could help me with this as I just cannot grasp the concept . I’ve tried calling a few electricians near me and nobody wants to do a consultation of the system . We are willing to pay for someone to give us advice on how to move forward .

So I guess the question to this thread is

-will wiring my solar panels all in parallel be fine for this application and if so how many charge controllers needed?
-if yes and two or more charge controllers needed , will this be fine going into a 24v battery bank
-please explain why
-after the battery bank what size inverters,converters etc will I need for the bus.

-how do I wire this all correctly in the correct order ie. solar-charge controller -fuse-battery -inverter etc to each different style of voltage ie 12v 120v 220v .

I know this is a heap load of help needed . I also know most people are going to tell me to just look these up and it’s dependent on what we’re doing. But I’ve tried and am running out of options . What I would like is pictures, diagrams and maybe a phone call . Id learn much better hands on and being able to draw as I go . If anyone can help it would be amazing . We’re willing to be helped on this thread or over zoom/FaceTime/etc and we will pay for the right knowledge if someone has it . We will greatly appreciate any help anyone has to offer . Also if anyone needs any help on woodworking or general construction I can help with that ‘

Attached are some photos and drawings.
The third photo is what I would like my diagram to eventually look like if possible . Thanks so much

 

[DeMac]

Welcome

Hi, Procrastinator. Welcome to Skoolie.Net. We love photos, load 'em if you've got 'em.

You have come to the right place. There are alot of helpful folks on this forum. We can probably help you to better understand.

I commend you. Most folks skip alot of steps and just buy a bunch of unmatched gear & devices. You did well to log-in and ask for help.

Might be best to break it all down into parts. Probably start with the expected demand for each of the separately derived systems (12vdc, 120vac...).

With a broad long question, you will recieve a variety of unrelated answers, which may add to your confusion. Stick with us, we are all a little nuts, but stay persistent and learn the details.

Glad you are here!

 

[Tejon7]

Good on you for trying to figure this out before going shopping. It IS tough, but keep at it and eat this elephant just like all the others: one bite at a time.

I got caught up on the first item in your energy budget list. The mini fridge consumption looks too high. 15 amps might be the startup draw, but it should normally use far less current. Best way to track AC power usage is with a kill-a-watt meter, but for fridges and other appliances you can look up the Energy Star yearly estimate to get an idea. A new dorm-room sized mini fridge should use somewhere around 300 kWh/yr, or around 800 Wh/day.

 

[Jono14]

Initial thoughts

-will wiring my solar panels all in parallel be fine for this application and if so how many charge controllers needed?
-if yes and two or more charge controllers needed , will this be fine going into a 24v battery bank
-please explain why
-after the battery bank what size inverters, converters etc will I need for the bus.
-how do I wire this all correctly in the correct order ie. solar-charge controller -fuse-battery -inverter etc to each different style of voltage ie 12v 120v 220v .

Some initial ideas:
1) For the solar panels, you will need to look at the 4 values Voc, Vmp, Isc, Imp to plan the best parallel vs series strategy. Lets pretend that the voltages are 20 and current is 10 amps (20V x 10A = 200W panel).
If you do all 16 panels in parallel, you will end up with just 20 volts (low) and 160 Amps (very high). If you make one 16 panel series string, you will be up to 320 volts (very high) and 10 amps (quite low). So neither of those plans works very well with most SCC setups.
Something like 4 parallel strings of 4 series panels each ("4P4S") could work. You would have about 80 volts and 40 amps heading into the SCC.

2) Either way, you have a total of 3,200 watts of panels, and so leaving the SCC into a 24V battery bank (and say it is low at 22 volts) you need 145 amps, and maybe more on cold days. I am not aware of SCCs >100 Amps so you probably need 2.
If you choose a 48V battery bank, a single SCC might do it (like 85 amps) because the higher voltage allows lower amps for the same watts.

3) I wonder about your battery bank size. I agree with @Tejon7 that the fridge estimate may be high and a kill-a-watt can help. Things like your coffee maker might also use much less than 1 hr a day and can be measured.
However, just the AC alone for 6 hrs uses more than your batteries have stored. 220V x 4.5 A = 990W x 6 hrs = 5,940Wh x 2 units = 11,880 AC Watt-Hrs - But inverters are often only 90% efficient so you need 13,200 Wh of DC power to create 11,880 AC Wh
Your entire battery bank holds just 12,960 Wh which does not quite cut it.
You do have a ton of solar coming in so if some of those 6 hrs of AC need are on bright days, the solar may be able to keep up. But hot, gray days will be tough on the system.
I'll be interested to see what others think. - Might be an argument for a larger battery 48V system.
Personal decisions like "Oh I actually only need AC for 4 hours, one or the other" would make a big impact on energy needs.

4) Inverters get sized on the total max concomitant AC load. If your refrigerator is more like 450 watts, then your max AC load looks to be about 5,000 Watts - Because you have 240V needs, that will narrow the options.

5) You will need a DC converter from 24 or 48 V down to 12V for lights, pumps etc and the same calculation of needed watts can be applied to the subset of items that the converter will power. These are pretty cheap and might work well to have more than 1. You can run the higher voltage the length of the vehicle (less loss and thinner wiring needed) and then position the converter next to a fuse block that drives the needed circuits.

Best - Jon

 

[TucsonAZ]

My brain is mostly fried most of the time but I don't think this has been mentioned so I'll add it.

1) What can you fit on your roof? For me, I can doe 12 - 410 watt panels and had to pay a premium for those versus smaller panels I couldn't use as efficiantly.

2) Run your batteries/system at 48V, always use 48V when that is an option. 24V is fine, 48V is the way to go.

3) Your inverter or ideally hybrid inverter will have a max voltage and a max amps for the MPPT side of things. That's going to determine everything. You'll max one or the other and sometimes with a lot of watts still on the table but I'm guessing you're going to be limited to 4 or so panels per bank.

4) I have 4 of the 3,500 watt MPP Solar Hybrid inverters, I don't need 4 but I have them for a reason. They're a great value and you can get them via MPP Solar directly from Taiwan on Alibaba, ask them to send you a Paypal invoice, they're quick, easy, and safe to deal with. Like I said, I have four in 3 separate orders and they're great.

I also noticed you're wanting to run 240V Split Phase, so you would need two of these for that which will also help with the MPPT and solar side of things. You can also use 3 with one side allowing for more amps, this way you have the option of split phase and a heftier side for the day to day basic 120V loads which is what I'm doing.

Shout if you think of any other questions and sorry I couldn't offer more, I'm too tired to think details today.

 

[HamSkoolie]

Our 2 bedroom, 2 story home only uses an average of 12kWh/day.


Your calculations are the right way but the wrong data. For instance the fridge is going to use WAY less juice. Our 22 CuFt home fridge uses about 1kW per 24 hours as measured with a Kill-A-Watt.


Speaking of the Kill-A-Watt, as mentioned, GET ONE. It's insanely difficult to find the power usage information we need on a given device. We either get that it needs a 15A wall plug or it pulls XAmps (but that's the max), and other issues. The Kill-A-Watt gives you precise and useful info.


Those 220VAC mini splits could be dropped to 120VAC units and while it won't be as efficient, it will remove the need for a 220 capable inverter and the extra cost associated with it. Also, if your bus is decently insulated, that 6 hour figure is too high. The AC will cycle on and off once the temp reaches the set temp. When cycled off the power usage is significantly less and you will be using way less power than your calculations indicate. One of our (okay her demand) specs was 24/7 AC availability. I've chosen two 120VAC mini splits with a 12,000 BTU unit in the front over the driver and a 9,000 BTU unit in the bedroom. The 9000 unit alone should be able to cool a 400 SqFt room with 8 foot ceilings. Our buses have 6' ceilings and even a 40' bus has only about 250 SqFt. The only reason we want two units is the difficulty of getting cool air the full length of the bus with just one unit. Plus, the one in the bedroom, with that small section closed off, will use substantially less total power even in the hottest of nights (or days) while sleeping.


Your number of lights seems extreme. 22 lights in the bedroom?



And finally, two TV's and two hours per TV for a total of 4 hours of TV per day? Perhaps if you have kids but it seems like a lot.


I'm working on a spread sheet of typical electrical draw for components and an accompanying calculation sheet where you just plug in the data and it spits out a total including adjusting for inverter inefficiency. It's not yet done but I am working on it as I get time.