Newbie needs expert advice, please.

Fly · March 2019

Hello Guys!

My name is Vince. I live in SE Arizona. I am an A&P. Nice to meet you all.

I would appreciate your input on my potential inverter and storage battery choice, please :).

I am constructing a small 120 volt only off-grid home system. Total instantaneous load <3600 watts/ <20,000 watts per day.

A Solar well and pressure pump systems are already completed and independent from the house electrical needs.

I now have: (20) 285 Watt = 5700 Watts in Trina Panels and an FM80 Controller.

I have been looking for a 48 VDC 4000 watt or so 120 volt off-grid inverter/charger for use with Li-Ion batteries.

I have a 3600 Watt Generator for recharge/cloudy days.

A friend has been using a Chevy Volt Li-Ion battery (~18.5 kWh/~$3500.00 used) with an Outback FM80 and an Outback 3000 watt inverter/charger locally for years with success.

I think that I need a minimum of a 48 VDC 3600 Watt/120 VAC Inverter (Outback VFXR3648A-01 looks good), preferably 4000 watts or more. I think that I want a used Volt or Tesla Li-Ion battery also. I travel for work and can't do battery maintenance for months while I am away, but am open to suggestions. Budget does play a role for me.

Again, your help is very much appreciated!

Thanks! - Vince

mcgivor · March 2019

The first thing I would recommend is studying the different lithium chemistries, there are differing levels of safety and reasons why some are used in particular applications, in EV light weight along with high performance is a prerequisite, most use thousands of small cells to achieve capacity and high discharge capacity, offgrid requires endurance, so the opposite of EV.

Lifepo4 are probably the safest choice, but the cost per Kw comparison is something to consider as well, new verses used is another, my personal thinking is its better to start with a known quantity.

The loads mentioned 20Kwh, when are these loads mostly used, if during the day the PV can be increased to support them as well as charge the batteries, if at night the batteries need to do the work, so capacity would be key. Everyone has differing needs, my particular situation requires overnight loads, so the battery capacity is sized at double the demand, the logic is a battery bank that is less stressed will last longer.

You are correct in assuming 48V nominal would be the best, given the load demand, however conservation will greatly reduce needs, anything that heats or cools should be the target, use gas wherever possible for heat, natural or propane, for cooking, water heating, cooling is different, there are some very energy efficient choices available, research is necessary.

Whatever the choices, take the time to research all avenues, it's extremely hard to get it right the first time, experience will teach you more, but alas experience is gained over time, so pay close attention to comments, many are reflecting on experience gained over time, which will be valuable. No two systems are identical, so be patient, don't rush into anything, thats the best advice I can offer at this time, take the time to digest information.

Fly · March 2019

Mcgivor, Thank You! I am learning so much here from gurus such as yourself and others.

I agree that differing battery chemistries have different advantages. Point well taken! I prefer new, but budget is directing me to look at good, used Li-Ion EV batteries. And I have a local friend with a history of good success with a Chevy Volt battery. I will read every entry that addresses this issue in the forum here.

My thought is that my greatest load (cooling in the AZ Summer) will primarily be during the day. I am purchasing a high-efficiency mini-split system @ 1920 watts max to address that. And high r-value insulation as well. Hopefully, the power passing into the system from my panels during the day will primarily go to run the A/C, with some spillover to keep the batteries charged for lesser loads at night.

If I need to purchase additional PV panels to support that, I will absolutely do it. And your hard-won tips on conservation and using propane in any way possible are wise, also. Excellent advice.

As you pointed out: "Time is the best teacher." Unfortunately, she kills all of her students...;).

I can not encourage you and the other experts here enough to continue to help me.

You are saving both my time and money.

And you are all appreciated.

Sincerely,

Vince

DaangeroussDan · April 2019

I am no expert, but I have been sub contracting all my life and am very familier with how electricity works and how to back a system up with redundancy and isolation, which most "experts" don't really do. This is a new age and I believe demands new thinking.

I would go the inexpensive route and use a 12 volt battery bank of AGM (no risk of shock to kids or animals), with 3 or 4 separate 1500 watt inverters on separate breaker boxes. Throwing all ones eggs into one basket seems silly to me (an exceedingly expensive), and no need to be concerned with high battery bank voltage because of line loss since you can have your AGM battery bank in the home with climate control (not recommended with LI) for max performance, and a series of inverters running 120 ac bypasses any line loss you might be considering. Like this,https://www.youtube.com/watch?v=GO_d9Ek5nXg but on a much grander scale, I run only 1,200 watts solar and 800 watts wind into 900 AH AGMs. But I'm always expanding and find much security in knowing that if one inverter goes out, who cares, I have another to get me by until the problem is solved. But I have not ever had a problem in the past year . This inverter is amazing and efficient for the money (180 bucks) https://www.ebay.com/b/3000-Watt-Pure-Sine-Wave-Inverter/58020/bn_7023224038

and you can buy many. This Chinese "MAKE SKY BLUE" mppt charge controllerhttps://www.ebay.com/str/MakeSkyBlue has stole my heart with amazing performance for a year now, and is only 100 bucks. Look at this performance on a cloudy day on 800 watts of panels with 12 volt battery bank https://www.youtube.com/watch?v=4pHUt2x46Xw

Running 5kw array at 12 volt battery bank means you'd need 5 of them, but at 48 volt battery bank you'd only need 2. But the cost of the high voltage inverter will destroy any savings and leave you with no backup should old man doom come calling. Redundancy in off grid is critical to never being caught off guard, and this is how I do it, at half the cost, with an enormous safety net. But, its a bit more work. I recommend AGM batteries based on cost practicality and hazards; https://www.youtube.com/watch?v=ycjrC-3A79E

Try not to forget how sensitive LI is to heat, and your home insurance (fire) rates can be effected because of LI batteries. This is the battery I have chosen and comes with very high ratings https://www.ebay.com/itm/UPG-12V-100Ah-SOLAR-WIND-AGM-SLA-DEEP-CYCLE-VRLA-BATTERY-12V-24V-48V/381117629892?hash=item58bc6185c4:g:OYIAAOSw9uFW9XRj

at 170 bucks per 100 AH , its not cheap, but very safe and no maintenance.

BB. · April 2019

Dan,

Last warning. Please stop with the EBay links. For example, our host NAWS has the same battery for less than $1 more (list price).

https://www.solar-electric.com/unba100amagm.html (the EBay vendor does have free shipping, which can be a good deal for smaller orders)

This is a sponsored forum and all this posting to competitor's sites that have never supported our forum here (either volunteering time to helping with questions, or paying hosting/software development)... Please cut way back on the links. The EBay vendors do not deserve to have free advertising paid for by our host.

If you want to say how great something... Just say you love Universal Battery products like the UB121000 AGMs. And leave it at that, or a link to the Mfg's website for further information.

http://www.upgi.com/products/product-by-category/?cat=SLA

For your videos, if you want, just make a signature to your Youtube account such as "see my video on Tree Mounted solar panels, my Youtube homepage is in my signature:--And put the link in your signature:

https://www.youtube.com/channel/UCl-G3EJMjjdCKJkJdPTvkgg/videos

https://forum.solar-electric.com/profile/signature/ (link to edit your own signature)

I am pretty easy going here, and I appreciate that you are quite into off grid solar power and want people to see that is can be done without spending lots of $$$$$$.

However, you need to respect the forum and forum members here--I am getting lots of spam flags for your posts now and I am trying to educate you on our forum's etiquette.

I do disagree with some of your suggestions and links. They are not what I (and other here) would recommend doing. And a few are downright dangerous.

-Bill "Moderator" B.

Tecnodave · April 2019

BB,

I agree......

MrM1 · April 2019

Thanks BB. Seems DaangeroussDan is trying to build a YouTube Subscription Following to monetize his channel. I watched a video. Suggestions seemed Dangerous indeed.

DaangeroussDan · April 2019

https://forum.solar-electric.com/discussion/comment/396930#Comment_396930

OH damn,, I did not realize your a store, I am so sorry. My passion to get the world to clean energy made me obtuse. Was wondering why all the hate I just found. Thought this was just an open community forum. Won't happen again.

BB. · April 2019

I am not a store... The forum is funded by a store (Northern Arizona Wind & Sun)--And is open to all.

I have never had a phone call or email from the "mothership" about the editorial content of the forum. Just keep it business like (this reflects on their business) and free & open discussions. I do not censor comments that I don't agree with (you want to do ABC and I think ABC is stupid and everyone should do EFG always).

I am here to learn too. And if there are issues, I (and others) will post our concerns and reasons why. And I am not always correct (ask my wife).

We are all pretty easy going here. And are big on communications, not fire and brimstone. And i was not going for hate--Just communications.

No problems and welcome to the forum Dan,

-Bill

bevans · May 2019

Fly said:

Hello Guys!
My name is Vince. I live in SE Arizona. I am an A&P. Nice to meet you all.

Hi Vince,

Where are you in SE AZ? I'm in Tucson, but soon relocating further south to our property where I'm building an off-grid system similar to yours. Perhaps we can be in touch. I'd love to see what you have going.

Cheers,
bevans

Newbie needs expert advice, please.

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