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Solar Newbie Check ...

thetimbo

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Mar 19, 2022
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Newbie here, building a small off-grid backup housed in a outdoor shed. Will's book. Hours on the forums. A quick check would be much appreciated.

MPP solar 1012LV-MS 1kw 40a MPPT from Watts24/7

Two 100ah 12v LiFePO4 batteries wiring in parallel.

Four 100w panels each Voc 22.1V and Isc 5.86A, wiring 2s2p with standard 10g wire for a 15ft run at 44.2V

The 1012LV will be 2ft from the batteries.

My questions:

1. Watts24/7 included two sets of copper lugged welding wire with the batteries. A 2awg and a 4awg set, both 4ft long (8ft run?)
Which set should I use from bank to inverter? Maybe they're too long for my application anyway?

2. Should the short parallel battery jumpers be the same awg as my bank to inverter wire?

3. After the ?awg welding wire is chosen, what fuse rating is recommended to protect it?

4. I'd like to switch/break the panel array for servicing purposes. Can anyone recommend one?

Watching you guys talk/argue/hash it all out is an educational experience.

Thanks in advance for your help.
 
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.
 
Newbie here, building a small off-grid backup housed in a outdoor shed. Will's book. Hours on the forums. A quick check would be much appreciated.

MPP solar 1012LV-MS 1kw 40a MPPT from Watts24/7

Two 100ah 12v LiFePO4 batteries wiring in parallel.

Four 100w panels each Voc 22.1V and Isc 5.86A, wiring 2s2p with standard 10g wire for a 15ft run at 44.2V

The 1012LV will be 2ft from the batteries.
Looks good so far, will that be enough power for your needs or are you going to be pushing the limits of the inverter? Do you have any thoughts on future upgrades to the cabin that might push it over?
My questions:

1. Watts24/7 included two sets of copper lugged welding wire with the batteries. A 2awg and a 4awg set, both 4ft long (8ft run?)
Which set should I use from bank to inverter? Maybe they're too long for my application anyway?
Batteries to the inverter will be your heaviest load so put the 2AWG there, and you might want to trim those down, but 4ft between the inverter and the batteries isn't bad at all.
2. Should the short parallel battery jumpers be the same awg as my bank to inverter wire?
Best practice yes. If you decide to trim down the larger cables you'll have plenty of excess left over for the batteries.
3. After the ?awg welding wire is chosen, what fuse rating is recommended to protect it?
The fuse will be the inverter max * 1.25, so 1000a / 12v = 83.3a * 1.25 = 104a so you could use a 100a OR a 125 and be just fine. Make sure you get a good Class-T in there, ANL fuses have issues with LFP batteries. Remember, Fuses are cheaper than fires! so don't cheap out there.
4. I'd like to switch/break the panel array for servicing purposes. Can anyone recommend one?
Make sure you get a quality disconnect rated for DC voltage. The tube-type "Automotive" breakers are notoriously flakey so skip those. Links are examples only. :)
Watching you guys talk/argue/hash it all out is an educational experience.
Prepare to have your mind overstuffed with details and minutia. Don't let the Victron fanboys overwhelm you either. :)
Thanks in advance for your help.
Welcome to the forum!
 
Thanks so much for your reply. I've already bought the 1012LV, panels, batteries and PV wire, so I have to live with this limited capacity.
Thanks for your advice, I'll buy some 2awg lugs and a crimper and use the excess to make my jumpers, as well as a class-t fuse.
The T-Tocas disconnect you linked to https://www.amazon.com/Tocas-Circuit-Breaker-Manual-Waterproof/dp/B01F76VJT2/ shows an illustration
with the battery bank connected to the upper lug, and the load to the lower. Would this need to be mounted "upside down" if the batteries were
beneath the inverter? Or would it not matter?
Thanks for the welcome!
 
Newbie too... Just started thread asking if the deal at watts247 for this 1012LV-MS with 2-12V 100AH batteries would be a good place to start. Tips here from Rednecktec are good, as I was questioning the capabilities of building Will's Milk Crate for my first back up system.

I want to begin by powering a AC after sun goes down here in Phoenix area. I had grid tie system installed last year, but have not seen enough savings to pay for panels. I want to charge batteries during the day, SRP charges me to export energy, and go "off-grid" at night. My first thought was the 50AH battery I purchased for Milk Crate would not be big enough to power the Midea window unit I want to buy. Also, I have an old, 15 year old window AC unit I want to use in garage during summer and will need more battery anyway. Working in garage during summer is rough!

I also want to power "Beer" fridge in garage 24-7 with batteries!

Thanks All!
 
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