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diy solar

Summer/winter Cabin advice

Scoutmaster

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Joined
Jul 20, 2022
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Quick question if anyone would help i would be super grateful.

My cabin sits off grid at 7000ft and is poorly insulated. In the mountains…I only visit 2-3 days per week and often the inside temperature is way below 32 degrees in the winter.
My lithium system didn’t work very well last winter but seems to be adequate this summer so far. I would love more power year round.
I can run lights and a coffee maker and Tv.
I would love to upgrade to a slightly bigger system but intimidated. I get decent sun during the summer but only 3-4 hours in the winter max.


I currently have a very basic DIY system.
2 -Sok 12V 100ah batteries,
4x100w Solar, Renogy Solar Controller
Krieger 2000w inverter.
Back-up 4000w generator &
Back-up 2000w generator

I would love to run a small fridge 24/7 and also be able to maybe run more lights and charge my eBike. I run my generator to use the microwave and when the cabin is to cold for the lithium.

What would be the best plug and play system?
Looking at the
LV2424
4x400w solar panels
What batteries?

Any better options?
 
The obvious choice for below freezing applications is lead-acid. When kept charged, they can go below -40C without freezing. Go to Costco and get four of their 6V golf-cart batteries that are running 99$ right now. Wire them in series for 24V.

You can fully charge the Li batteries, then disconnect them from the system when freezing weather approaches. As long as they are not receiving a charge, they can sit below freezing with no problems.

Shop on Craigslist for some cheap grid-tie panels. Right now I am seeing 240-260W panels for 65-75$. Wire your four 100W panels in series. I'd think that each one has a Vmp of ~18, so four in series would be ~72Vmp. You could get some 300W 72cell panels that put out ~36V. So, two grid-ties in series would be ~72V, and then the two grid-ties could be wired in parallel to the string of four 100W panels. That would work out to be (600W + 400W)/25Vcharging = 40A. In the real-world that's likely to be ~35A. As long as lead-acid gets full charging, they will give you many years of service. Don't skimp on charge amperage. That is what spells death for lead-acid.

Keep a gallon of distilled water available, because you'll want to top off occasionally. Check monthly at first, but I typically go 3 months between water additions. You can then reconnect your Li batteries come spring.
 
Thank you for the reply.
I was thinking about picking up some different batteries for winter. Inside the cabin gets down to 5-10 degrees when I’m not there. I’ll pick up some lead acid for this winter.

I’ve been very tempted to buy one of the all-in one systems and connect it to my batteries. Any thoughts?

MPP LV2424 or 2724LV-MR or Gro-watt 3000
Just to clean up all the cables and add an easy way to switch to generator and charge batteries easily.
 
AiOs are OK if all you want to run is stuff like lights, TV, and items with low surge demands. For things like power tools, air-conditioners, compressors, ect, startup requires high surge currents which the AiOs typically can't supply for more than 10-20 milliseconds.

So, for the items listed, you're better off getting a low-frequency transformer-based component model, with Brand/model names like Evo, Magnum, Outback, and Schneider. They are typically a lot heavier, more expensive, but can supply starting surges for 5-60 seconds. So, if you want to watch TV, get the MPP. If you want to power your well-pump, get the Schneider.

The better component inverters can be paired to "electrical panels" that are brand specific. They are boxes designed to line up with the input/output ports of the inverter to make a seamless integrated system without wires hanging out. They are designed to hold all the breakers and stuff needed to connect it all together. I got those for both my systems to keep the spaghetti from spilling out.

I think the lead-acid batteries would be a good choice for your situation. Remember though that lead-acid dies from chronic undercharging, so I'd also install the extra solar at the same time that I had outlined above. I don't think 400W is going to be enough for winter.
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thinking out loud and taking a cheaper route -
but can you disconnect the lithiums while away, when you get there, run the generator to supply heat to the batteries to get them warmed up, than you can start topping them off/using them. I was under impression that lithium is ok below freezing so long as you don't charge them. I thought discharging was ok ? I have read where ppl will insulate the batteries and state the discharging alone keeps them above 32.
What that discharge rate is though I don't know. Or insulate the heck out of them, and rig a incandescent bulb to turn on and off at a set temp.
If done right I think you could keep them always above 32 in that situation.
 
Good point.
I have a big wood stove and large propane heater with 250gallons of propane.

Normally on a very cold day it takes 3-4 hours to warm the cabin to 45 degrees and after 12 hours I get to 60-65.

I normally start the 4500w generator or 2000W immediately when I show up for 30-45 minutes so I could easily have a small heater kick on to heat the batteries up. I have some propane lights I can run until the batteries warm up and other options if the generator is on.
Another option might be a few lead acid hooked to the current 400watt Solar to run the lights etc. Then upgrade the solar to 1000-1600w and hook that up to an “ALL in one system” with 400ah lithium. Since it has a battery charger I can cycle on the generator when the snow is covering the panels or it’s dark. I don’t mind running the generator but it gets annoying sometimes.

Maybe 2 different systems and a generator back-up. It sounds like spaghetti, but it could be the cheapest option since I already have 50% of it.

I can easily run my 400w solar current system on some new lead acid for just the lights etc. Then after a few hours kick on the other system for everything else. During the winter I normally just use lights, TV, Coffee Maker and charge electronics. I’m normally skiing and by myself with my dogs so it’s not fancy.

-Buying some lead acid is a good and reasonably cheap additional option. $400
-Insulation and a heater for my lithium is virtually free.

Last year I ran the generator exclusively and only spent $150 in gas. If I had a better battery charger and ignored Solar I might be able to run off this system again. My generator will run 14 hrs on 2 gallons. Most 2-3 days excursions I only used about 2 gallons. I have snowmobiles so gas is normally available. My smaller generator runs on propane so hypothetically I could run it very cheaply and never run out.

Buying an all-in-one Growatt/Mpp, 1600w Solar, and 2 more Li batteries will be $2500.

Makes be wonder if just running the generator, insulating my lithium, and some lead acid back-ups might be the cheapest option?
 

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Buying some lead acid is a good and reasonably cheap additional option. $400
-Insulation and a heater for my lithium is virtually free.
I live full time with 8 marine lead acid batteries from walmartha and two parallel 400W arrays. I’m in Vermont. I made it through the winter last year with minimal supplemental charging.
I haven’t read anything where lithium is of any great advantage to you. The Costco batteries are appealing imho
 
It might be worthwhile to look into improving your cabin's insulation. It would be easier for you to keep warm that way.
 
I’m definitely going to experiment with some lead acid and insulating my SOK’s this winter.

I have a new massive wood stove I’m putting in this winter which should help with the heat when I am actually at the cabin. I anticipate being able to get it over 70 degrees.

Insulating the log cabin is going to be a multiple year project and definitely on my dream list. Currently I have some vermin and mice…and some serious structural problems to fix before I can really tackle insulation on a big scale. I can plug holes and chink small sections, but it’s a piece of Swiss cheese right now. I’m a total novice at construction so my progress is slow. I’m attempting to find a balance between recreating at the cabin and working. I enjoy working on it, but I don’t want the cabin to become my only hobby.
 
Here is what I would do. Get a marine either/or switch and wire two parallel battery banks, the lead-acid for winter, and the Li for summer. You can charge up the Li in the fall, then switch over to LA for overwintering.

Then, when you arrive in the winter, you'll have power from the moment you walk in the door, but can switch over to Li once the cabin has adequately warmed.
 
some serious structural problems to fix before I can really tackle insulation on a big scale. I can plug holes and chink small sections, but it’s a piece of Swiss cheese right now. I’m a total novice at construction
Log cabin repair is not done in “small sections” because they are built of… logs. Covering/filling/chinking holes doesn’t solve the problems it just makes you feel like you’ve done something.
You need to get some logs dimensioned like yours and replace the rotted sections. Plunge cutting with a chainsaw, a socket slick, a couple 20-ton bottle jacks and you’ll probably have less time into repairs than the bandaids will take. Ya, I’ve spent time a log cabin crew, and had customers with rotted cabins.

You can usually find a way to make a pyramid cut out and take out larger sections do repairs without structural concerns. 1” steel pins let you use the bottle jacks to hold things if a window or door makes a pyramid cutout not safely possible. A quart-tube caulking product like “log builder” or 10.2oz polyurethane window and door caulking will let you seal up the repair.
 
Great advice. It’s hard not to try and bandaid repairs when you are 1 amateur lumberjack. I wish I had the money to hire a crew and do this project properly.
Last year we had to Jack up the entire cabin to level it and replace some rotten logs. It was definitely a learning experience. We fixed some of the problems and crested
a few new ones. I hand mixed several tons of concrete just to make new footers and support it.

I still have some major log repairs to tackle. Last winter I worked right up to the first big winter storm storm…just to get doors and windows back on. I had most of the cabin just wrapped in plastic for the winter.

Solar and Power are still secondary concerns but getting more important as winter is coming again quickly.
 

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So those logs are Lincoln-log laid, not splined together? That makes it easier for sure.
 
Not splined or pinned.

The logs were just stacked and held only at
the ends like corn on the Cobb.
I don’t think any support or rebar vertically.

The snow load has crushed the logs making them wiggle in and out. Mixed with the front foundation had sunk 9-11 inches.
Overall the cabin is in good shape but needs to be supported and straightened.
 
I think I need to jack up the roof slightly to take off the pressure… and then sandwich the walls with some sort of 2 x 6 or 4x4s using threaded rods to try to get the logs all back in a row…. Similar to a vise.
Then shoot some timberlocks to hold the entire mess together. Similar to these metal supports. My cabin is the 3rd shot you can see the logs are all over the place.
 

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jack up the roof slightly to take off the pressure
That might help. That’s how you fix floor joists in a camper trailer RV

But you’ll need at least 3/4 threaded rods imho, and steel plates over the 2x8s, cuz those logs are going to be wicked uncooperative ?‍♀️
 
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