Originally Posted by Hippyhaven
We need help figuring out what the best options for parts are in our solar setup. We have 1050 watts of solar, 6, 175 watt panels. I was planning to connect them in parallel. From there we think we decided on a renogy Rover 100amp charge controller and now I do believe I need a 1000 watt inverter and not to sure on the battery situation and wiring as well. We are just a couple rookies trying to not blow up. Any advise or help would be appreciated! Our largest power consumption would be our AC when we decide to put it on ( 984watts) and our fridge which will be on all day and is only 75 watts (300 starting watts). We need to know our best route to take to start getting power in our bus! Thank you for reading!
Before I start let me explain a few things about me that will help you to get the most out of my post.
#1. I live in the real world of off grid solar. Ruth and I have been full time off grid since the early 2000s. We did it on the cheap, building and scaling when we can.
#2. I have Aspergers. I may come off a bit blunt. That has left some who have read some of my posts feeling disparaged. I assure you that is far from my intent. I responded to you because I truly believe our experience can be helpful to you.
Lets talk about your needs first and foremost. If you think you will eve want to run your 1killowatt (approximate) air conditioning on your off grid system your inverter needs to be pure sine wave and minimum 2500W continuous/ 5000W surge. We used a Low Frequency Powerjack 5KW inverter for nearly a decade before it needed parts. Unfortunately parts were coming from China. We ordered in February and didn't get them till June. In the interim we purchased a really cheap Full Sine 3000W/6000W HF inverter from vevor.com
We figured it to be a temporary fix but ended up liking it so much we bought 4 more. 2 as backups and 2 for other systems we are building.
It turns out this very inexpensive inverter is very efficient(not by their claims but by our measurements.)
It is fan cooled but the fan is variable speed and very quiet.
It powers our whole system without a hiccup. We have a 14000BTU inverter heat pump we just installed that uses between 350W and 1750W. We run a 7.5CF deep freeze, a 10CF refrigerator, a compressor cooler fridge and various other appliances like our 50" tv all at the same time.
We do put the AC in fan mode if we want to run the microwave or convection oven.
In order to do that when the sun is not shining or obscured by clouds, you will need some hefty batteries. We moved from lead acid batteries in 2019 and have never regretted the decision. Because we are in a mobile situation, things like vibration and sudden changes in direction have to be a consideration when designing your battery bank.
We went with Lithium Iron Phosphate chemistry for a couple of reasons. Energy density and stability. You will find a lot of Youtube videos of people building power walls with Lithium Ion batteries. But this is a bad idea in a bus. I have one word you never want to hear in your bus. FIRE.
Lion batteries can be unstable. While their energy density may be a little better than LiFeP04 batteries, their potential for catastrophic meltdown is far higher.
How many batteries do you need? That depends on how much you are going to demand of your system.
We live in the dessert. Our battery bank is designed solely aground the regular need to run our air conditioning all night.
In our case we look at the worst case scenario. The air conditioning can require 1750W. The total refrigeration can require 300W. The TV, lights,sound bar, phone chargers, computers...another 400W. Now we add the wattage up to arrive at 2450W or 2.5KW. Mutiply that by hours of sustained usage (the time that you will be using and not charging) and you know how may KWhours of storage you need to sustain sacrifice free solar living. By sacrifice free, I mean not having to turn things off so that you have power for other things.
In our case we calculated that our daily needs could be as much as 30KWH
That's your kilowatts time the hours per day of use without replenishment. We calculated using winter hours of full charging in our area. In the late winter we can count on 4.5 to 5 hours of full sun charging. Leaving us drawing power with less than full assist from the panels for 19 plus hours in a 24 hour period.
Here is a kicker that many who are just trying to not blow themselves up don't calculate in their equation when determining their solar system specs,
when the sun is running your appliances it also needs to be charging your batteries. How hard does it need to be charging those batteries? The answer is how much di you deplete them last night? This is another beauty about LiFeP04 batteries is that you can charge them fast. In order to do so you need to be drawing down from the sun, much more energy than you are using.
I know this is getting wordy and might be filling you head up, so maybe cut and paste it to a document and then break it into usable chunks.
Here's what we did for batteries: 6 220ah 24V batteries in parallel. This gives us over 30KW available usage. For the best part this allows us to run the Air Conditioning all night long and then turn it off at about 8 am and back on at 1pm. This allows our batteries to charge from 30% to 80% really fast. Then top slowly as the rest of the day progresses.
Here is where the rubber meets the road. There is no way to do this without a sizable array. Even if you manage to get the rated value out of your approximately 1KW of solar panels (you won't) you'll only be able to pull 40 amps during full sun. That might run your fridge, and put some charge in you batteries but if you fire up the air conditioning you will be running a deficit even in full sun.
Ruth and I were amazed when we got to SkooliePalooza this year, (our first time) , not at the number of busses, (a lot), but how few solar panels on even the most extravagant builds.
Ruth and I agree, Put as much solar as your real estate will allow and you will be happy with your decision.
We have 12 325W Monocrystaline panels on the roof for a best case scenario of 3900W. We have the potential to charge out batteries at as much as 90A, while running the air conditioning. We actually see that potential sometimes.
The reality lately is that most of the time our hottest days come during monsoon, our cloudiest season. So even though we have nearly 4KW of panels we see 2KW to 2.5KW during the sunniest part of the day.
We are building an additional array on a trailer to plug into our system when we get lots of clouds. That additional array is larger than what you are suggesting you want as your primary array.
Charge controller: If you plan a tiny array, why a 100A charge controller? Your puny array will never make it worth the money you spent on the Renogy 100A controller.
Here are the things to look at when sizing your controller(s) :
What is the VOC of your array. Realize if you put panels in series you will be more affected by partial shading, even by passing clouds.
Your controller will have a max PV Voltage based on the battery bank voltage.
It will also have a max PV wattage based on the battery bank voltage.
For example: We use PowMr 60A Controllers. 1 Controller per 4 327W Panels in a 24V system. Our panel VOC is 60V
The charge controller Max voltage for a 24V battery system is 105V The max PV wattage for a 24V battery system is 1400W
Our system is broken up into 3 arrays comprised of 4 panels in parallel, each with it's own controller. When we bought the controllers in 2019 they were about 90 bucks each. So cheap that we bought backups that we have never needed.
Our system allows us to live like we are connected to the grid most of the time. Last year we only had to run the generator o total of 72 hours in 365 days. This year our plan is for that to be zero.
If the reason you are going with the 175W Panels is that you have them, then use them for some other solar project. If it is to save money, solar panels are cheap per watt compared to just a few years ago. Think of it as filling a water tank. You have a limited amount of time to run the water each day and so you want to fill the tank as fast as possible.
Depending on where you are located your Premium tank fill hours will be 3-6 hours a day. If you use more thn that many KW the night before you end up with a deficit.
New SolarEver 455W 144-Half Cell Mono Solar Panel
Six of those is nearly 3KW.
What you need for a solar system:
Start at your batteries and work from there. Size your battery bank to your needs plus 2/3, bare minimum.
By the way, the temptation to build a 12V system seems to be prominent. Avoid this. The 12V system is fraught with limitations. Heat production and therefore waste being the biggest one.
We went with a 24V system for a couple of reasons. It is much more efficient than a 12V system and 24V won't knock you on your tush if you place your hands right on the main buss terminals. If you have the perfect storm of conductive situations, you may get a tingle, but it won't end your life. A 48V system can light you up. Anything higher than that can be downright deadly if you make a contact mistake. (when you touch stuff you shouldn't). 48VDC is high enough to overcome your bodies internal resistance and give you a painful or even dangerous jolt. I'm not saying its a bad idea for a bus, just for me.
Panels: Get the most wattage your real estate will allow.
Controllers(s) You can spend big money on solar controllers if you like but the PowMr 60A Mppt controller is not only inexpensive but gets the job done and our experience says they are dependable.
Cabling: From your panels to your controllers, and from your controllers to your batteries, from your batteries to your inverter.
Fuses and disconnects, between your panels and controllers, between you controllers and your batteries, and between your batteries and your inverter.
From your inverter to the rest of the house, you wire it like it is a regular house.
Shunts: These allow you to monitor your power usage and production.
We use two Victron smartshunts. One to monitor the batteries and state of charge, and one to monitor solar production.
You can build your own LiFeP04 batteries. You do take the risk of getting counterfeit cells and other quality control issues, but if you are handy you can save money here on the most expensive part of your solar system.
we ought our batteries used from a solar farm that was swapping out. Our batteries tested out at their nominal rating. We saved a lot of money here.
We are planning a new even larger battery bank in the future and will be using these batteries: https://signaturesolar.com/eg4-lifep...ery-24v-200ah/
Our current system allows us to live like we re on the grid most of the time, but we are working to make that always with a fail-safe.
Our current system:
6 24V 220Ah batteries in parallel for 31.6KW
3 MrPowr 60 Mppt controllers
12 327W Sun Power E series panels in 3 groups of 4 parallel panels
We ran 6 gauge stranded copper cable from the panels to the controllers.
From the controllers to the battery bus, romex 10 gauge wire X 2. That is 2 10 gauge positive leads per controller and two 10 gauge negative leads per controller.
From the battery bus to the batteries 2 gauge stranded copper.
From the battery bus to the inverter 2 gauge stranded copper.
Our inverter is currently 1 Vevor 3000/6000W HF that we purchased for 239.00 in February. We are planing to put the air conditioning on its own inverter and the cooking circuits on their own inverter. soon. This will avoid the possibility of overworking the inverter by running too much at one time by accident.
We have had the air conditioning on full blast and run the 2KW convection oven at the same time without a problem, but we don't want to push it.
Just a final note: Back in the early 2000s we bult our first stationary solar system. We went 48 Volts. We had two Magnum 5500W Split Phase inverters, at about 4500 bucks apiece. We had 24 280W solar panels and 4 Morningstar 80A solar controllers that I think we paid 1500 each. Our battery bank was Lead Acid Trojan renewable 2V Batteries (48 of them) at about 350 bucks each.
That whole system ran us around 30K and work only as well as what we have now for much less money.
As far as dependability, I think the low cost PowMr 60A controllers have proved themselves. Our used BYD batteries are still performing as well as the day we bought them. And the powerjack inverter that just failed in February was a spectacular buy even if it never worked gain after almost a decade of service. I think we paid 350.00 bucks for it in 2011. The Vevor inverters are yet to prove themselves, but so far are spectacular for less than 300.00 for 3KW continuous.
The one clear lesson that time has taught us is not to skimp on storage or the ability to refill the storage.
We often call our build a hillbilly bus build, held together with baling twine and fence wire, but it gits er dun, when it comes to sheltering us in reasonable comfort and keeping our food safe to eat. That's important to us.
Figger out whet your goals are in terms of comfort and food storage and build yer system from there.