Lake mini-cabin, all-in-one or manual build?

[porkchopexpress]

I've been in design mode for my lake cabin bunkhouse project... objective is to build a 12x12 tiny cabin which will supplement my lake cabin and provide extra sleeping/relaxing space for visiting family members. I thought it would be cool to have it run by solar.

Powered items will include some LED lighting, a ceiling fan, and an energy-efficient TV/DVD combo on the wall. Plus outlets which may see occasional use for charging phones and laptops. Making use of online calculators has indicated that a 2400W system will get it done.

One system that seems to match my needs is the MPP LV2424. I'd opt to shop around for the batteries and bring it to 24V 200ah, maybe leaving enough room to go to 400ah at a later time.

I like the idea of the all-in-one system because it seems easier to deploy for a novice (myself.) Also seems to have the option to plug into a generator or regular grid power if there are overcast days and the batteries aren't charging.

However, I wonder if I am selling myself short, or paying more than I need to, by not manually piecing a system together myself? Would it be more cost-effective to shop separately for the charge controller, inverter, panels etc. even though it will involve more of a learning curve?

 

[Bluedog225]

For the things you listed, I’d put it together myself. And I’d run it all at 12 volts. Saves you the inverter money.

That stuff is all readily available from the camping//RV world. Panel, fuses, charge controller, battery, outlets. Done.

You can add 12 batts in parallel “later” if you need more juice. I think battle born says up to 2 years. Not sure about others. And if you get 4, you could always convert them to 48 if your needs change.

 

[12VoltInstalls]

That stuff is all readily available from the camping//RV world

….and a lot of that stuff - identical- is available online for 50-80% less money than RV dealers.
My bright 12V 2-zone 12V LED ceiling lights were $19 when I got them versus $45 at the local RV shop, and mine have nice 1/0ff/2 rocker switches not sliders that wear out or break quickly, for example.

Would it be more cost-effective to shop separately for the charge controller, inverter, panels etc. even though it will involve more of a learning curve?

It depends. A 2400W system seems big for your listed requirements, but components can often be cheaper than an aio on lower-tier systems, or about the same on top shelf products.
Personally I’d look at the 12V MPP-Solar 1000W AIO for what you described. That would seem plenty of out put, but panel input at 2400W is a bit more than its design

1012LV-MS. 40A solar charger controller- so 5-600W array. But with three different facings I could conceive 900-1200W overpaneling could be fine.

FWIW I went ~April through fall 2021 with 400W of panels facing two directions totally off-grid running all my daily needs including a 5CF fridge. November or so I went to 800W

 

[Rednecktek]

I've been in design mode for my lake cabin bunkhouse project... objective is to build a 12x12 tiny cabin which will supplement my lake cabin and provide extra sleeping/relaxing space for visiting family members. I thought it would be cool to have it run by solar.

Hell yeah! Go for it!

Powered items will include some LED lighting, a ceiling fan, and an energy-efficient TV/DVD combo on the wall. Plus outlets which may see occasional use for charging phones and laptops. Making use of online calculators has indicated that a 2400W system will get it done.

That seems really high. Are you penciling in something really heavy like a water pump or AirCon or something, or just giving yourself a LOT of room to grow? Are you going to have space out of the elements to put the unit and batteries? With 2400-3000w of system, it's an advantage to go to 24v to keep the wire and fuse sizes down.

One system that seems to match my needs is the MPP LV2424. I'd opt to shop around for the batteries and bring it to 24V 200ah, maybe leaving enough room to go to 400ah at a later time.

Paralleling in more batteries is easy enough. Is this going to be in a location where it gets below freezing? Sub freezing temps and LiFe batteries are not good friends and you may have to look at going with FLA or AGM's instead. I actually opted for the Growatt 3Kw/24v version just to get that little extra overhead for not much more money. I think if MPP made a 3Kw 24v I would have bought that instead.

I like the idea of the all-in-one system because it seems easier to deploy for a novice (myself.) Also seems to have the option to plug into a generator or regular grid power if there are overcast days and the batteries aren't charging.

Those are definite pro's to an AIO. Cons to be considered are high idle draw (need more batteries and panels just to exist) and single point of failure for the system. If that's not a major concern then they are really easy to work with.

However, I wonder if I am selling myself short, or paying more than I need to, by not manually piecing a system together myself? Would it be more cost-effective to shop separately for the charge controller, inverter, panels etc. even though it will involve more of a learning curve?

Well, if you have internet access, you can just make a list of the comparable parts and see what a mid-tier copy would cost. Since the panels and batteries are common, all you really need to find is a SCC of comparable amperage/voltage and an inverter/charger that can take input from a generator, and a decent shunt/monitor to keep an eye on it all. If you can do that for less than the cost of an AIO, then you just have to decide how much your time is worth doing the separate pieces rather than the AIO.

When figuring time it doesn't seem that much different as you're still spending the same time running wires and screwing down panels and crimping ends, so kinda negligible IMO.

 

[porkchopexpress]

That seems really high. Are you penciling in something really heavy like a water pump or AirCon or something, or just giving yourself a LOT of room to grow? Are you going to have space out of the elements to put the unit and batteries? With 2400-3000w of system, it's an advantage to go to 24v to keep the wire and fuse sizes down.

Leaving some room to grow, I suppose. Estimating the ceiling fan at 100 watts and a TV/DVD combo at another 100, so figuring what if the ceiling fan was running for 10 hours and the TV for another 4. Plus some lighting and maybe charging of phones/laptop.

Paralleling in more batteries is easy enough. Is this going to be in a location where it gets below freezing? Sub freezing temps and LiFe batteries are not good friends and you may have to look at going with FLA or AGM's instead. I actually opted for the Growatt 3Kw/24v version just to get that little extra overhead for not much more money. I think if MPP made a 3Kw 24v I would have bought that instead.

It gets cold during winter months although we're usually not there. Is the cold bad as in "batteries will be inefficient till they warm up" or as in "batteries will be damaged if left in the cold"?

Well, if you have internet access, you can just make a list of the comparable parts and see what a mid-tier copy would cost. Since the panels and batteries are common, all you really need to find is a SCC of comparable amperage/voltage and an inverter/charger that can take input from a generator, and a decent shunt/monitor to keep an eye on it all. If you can do that for less than the cost of an AIO, then you just have to decide how much your time is worth doing the separate pieces rather than the AIO.

It looked as if that LV2424 on its own was comparable to buying similarly rated components separately, but of course it is important to me that I have a good understanding of what the components are doing. Things could change as I brainstorm more and as I move my projects further along...

 

[Rednecktek]

It gets cold during winter months although we're usually not there. Is the cold bad as in "batteries will be inefficient till they warm up" or as in "batteries will be damaged if left in the cold"?

As in batteries will be damaged beyond saving if charged below freezing. Bigger downside is that FLA's or AGM's only have a 50% DoD so you need twice as many batteries for the same usable power. On the plus side, FLA 120Ah batteries from WallyWorld are about $100 out the door.

 

[porkchopexpress]

As in batteries will be damaged beyond saving if charged below freezing.

Got it. In theory, if it's November/December and I'm winterizing to shut down for the season, could I just disconnect and leave the batteries in place or in a shed? (Meaning, in the below freezing temperatures.) Or, would I want to grab the batteries and haul them back to Chicago with me to keep in my (heated) house?

Bigger downside is that FLA's or AGM's only have a 50% DoD so you need twice as many batteries for the same usable power. On the plus side, FLA 120Ah batteries from WallyWorld are about $100 out the door.

Are you sure on that figure? I found those to be more in the area of $200, do you have any links?

When I looked at this, it was kind of a wash, getting to 24v/200aH lithium seemed about the same as 24v/400aH with regular batteries... in which case it would make more sense to focus on taking up less space.

 

[Rednecktek]

Got it. In theory, if it's November/December and I'm winterizing to shut down for the season, could I just disconnect and leave the batteries in place or in a shed? (Meaning, in the below freezing temperatures.) Or, would I want to grab the batteries and haul them back to Chicago with me to keep in my (heated) house?

As long as they're disconnected and not charging they should be fine. Your only worry at that point is when the sun hits on that crisp winter morning and your batteries start taking a charge below freezing. Storage OK, charging not.

Are you sure on that figure? I found those to be more in the area of $200, do you have any links?

I buy a LOT of the WallyWorld 122Ah 29DC batteries and after tax and core charge they're almost exactly $100 ($99.92) out the door.

When I looked at this, it was kind of a wash, getting to 24v/200aH lithium seemed about the same as 24v/400aH with regular batteries... in which case it would make more sense to focus on taking up less space.

The cheaper Chins/AmperTime/BobBattery are pretty much the same price as an AGM, but the FLA's are much cheaper. Yes, watt/cubic inch you can't beat the LiFe's. If freezing isn't an issue then they're the best bang for the buck any way you look at it. The ONLY thing that the acid based batteries excel in is cold weather survival.

But yes, to get 24v/180Ah usable at my camp cost me $600 in FLA batteries. If it weren't for the weeks-on-end-below-freezing-unattended nature of the location I'd be throwing LiFe's in there in a heartbeat.

 

[Smokin]

Your not going to learn much ordering an All in ONE. When it breaks you get to keep both halves.
Build you own battery. Install a bms. Learn as you go. Nobody watches DVD's anymore. Everybody watched their phone.
Slap a charge controller on it and some panels. Get a non PFC power supply to charge off generator.
Oh wait just use a 1200 Champion Generator. It will run all day on 1.2 gallons. Build a box for it so it's quiet. All good.
Install a Diesel Heater for Winter.

 

[Rednecktek]

Your not going to learn much ordering an All in ONE. When it breaks you get to keep both halves.

True. How much is the convenience worth over just using multiple pieces. That's something to noodle.

Build you own battery.

Order from Amy and make sure you get a BMS with low temp protection. That'll mitigate the charging-while-freezing issues AND cost less than a pre-built. I've heard of people getting a Not-A-Yeti cooler and mounting their batteries in there. It insulates really well, easy to cut into for your wiring holes, weather resistant, and CHEAP!

Slap a charge controller on it and some panels. Get a non PFC power supply to charge off generator.

In a pinch any modern battery charger with an AGM preset will get you 98% of the way there, or get something like an Aims inverter/charger that can take the input from a generator and charge the batteries while under load.

Oh wait just use a 1200 Champion Generator. It will run all day on 1.2 gallons. Build a box for it so it's quiet. All good.

Propane or Gasoline, pretty darn quiet, not a bad idea. I'd look at a 2000w range version though just to get the extra amperage out of it to charge faster if needed.

 

[Smokin]

I make my own batterys and I make my own chargers and I have a Ham Shack 450 watt transmitter that runs all day every day on the setup. I make 30 AH Lifepo4 batterys with $20 bms. Cost per battery under $100. Place them in Plastic Amo Boxes from Walmart. I use cheap charge controllers for charging safety. I set the $10 solar charge controller between the charger and the battery for an extra layer of protection. And these cheap charge controllers let you set manual profiles. Setting form 14.6 to 12.6 is super easy. 12.6 being for the 3s Lithiun ion packs. They also have a tap for led landcsape light. This can also be programmed to comeon for how ever many hours you want. Kinda Cool.

I also have 2 Walmart inverters. $10 one and a $40 one. These are fitted with XT60 plugs that connect to the battery/s. A flyaway setup.
My Solar pannels go on a trailer but I don't bother in Winter to deploy them. Not enough Sun to justify. In Summer all that changes.
In the winter if I loose power no much happens. The Diesel Heater connects to one of the batterys and it can run 24 hours on the battery. The outhe battery is fitted with an inverter for the Internet and router. Then the generator cycles to light up the whole place and charge the batterys run the fridge and furnace.
It's a modular setup and is transportable.
Keeps me busy tinkering.

 

[Koldsimer]

Estimating the ceiling fan at 100 watts

Thats pretty high even for a cheap fan. Get yourself a dc motor ceiling fan and they can run on as little as 3 or 4 watts and still move lots of air. I have three in my off grid house. They sip energy and allow me to really circulate the air from my mini splits.

 

[12VoltInstalls]

WallyWorld 122Ah 29DC batteries and after tax and core charge they're almost exactly $100 ($99.92) out the door.

If you take care of them they are a good value. At the time I bought 4 or 5 I picked the grp27 size because per amp hour they were less money. But the 27s went up a lot recently and 29s are probably a better choice for $/Ah
AGMs are a lot more money- I’ve never bought AGMs but others only get a couple years on them cycled daily. FLA marine batteries can go 3, 4 years- or more. (I don’t know how much more yet but I will)

Cost per year if you call LiFePo 10 years could be 1/2 price for FLA. The way I looked at it initially is I could afford the walmartha batteries up front. My view now is they are worth it if they go 3-4 years; anything after that is “free.”
(Though in my case jumping to LiFePo isn’t practical without a bunch of changes as my batteries live in well below freezing temps and they’re working so I’m comfy with the walmartha batteries. When I build permanently I’m going to seriously have to consider LiFePo batteries, probably a whole new system with big panels will make the most sense)

 

[porkchopexpress]

I buy a LOT of the WallyWorld 122Ah 29DC batteries and after tax and core charge they're almost exactly $100 ($99.92) out the door.

Awesome... that page also showed me a sponsored ad for this: Walmart 200aH lithium battery

A little better than the pricing I was seeing on Amazon and elsewhere, anyway...

 

[porkchopexpress]

Thats pretty high even for a cheap fan. Get yourself a dc motor ceiling fan and they can run on as little as 3 or 4 watts and still move lots of air. I have three in my off grid house. They sip energy and allow me to really circulate the air from my mini splits.

I will have to look into that. My 100w figure is just very rough based upon googling, I'm sure that won't be the final number.

Is it more energy-effective to do DC? As in, does power get "lost in the translation" from DC to AC?

 

[12VoltInstalls]

does power get "lost in the translation" from DC to AC

Yes, mostly in heat by the components that perform the operations

 

[Rednecktek]

Awesome... that page also showed me a sponsored ad for this: Walmart 200aH lithium battery

A little better than the pricing I was seeing on Amazon and elsewhere, anyway...

Just be aware that like the AmpreTime and Chins, those don't have low temp charging protection. Remember that whole "charging below freezing" thing? Yeah, these things fall into that category.

Still, $20 less than Amazon... Hmmm...

 

[Frank Enstine]

For the things you listed, I’d put it together myself. And I’d run it all at 12 volts. Saves you the inverter money.

That stuff is all readily available from the camping//RV world. Panel, fuses, charge controller, battery, outlets. Done.

You can add 12 batts in parallel “later” if you need more juice. I think battle born says up to 2 years. Not sure about others. And if you get 4, you could always convert them to 48 if your needs change.

Bluedog, I’m in a similar scenario as the original poster. I just received 2 12v 100Ah LiFePo4 batteries. I had already DQ’d the all-in-one (was considering the LV2424, as well) for a diy as you suggested. I get 2-5 hours peak sun so I was guessing I would need 800-1000 watts in the winter. I plan to buy half soon (for summer) and the balance before winter. I will have 100’ of wire between my panels and a warm spot for my batteries.

Where you told the original poster to go 12v, would 24v be a better option in my scenario? Thanks in advance for your perspective

 

[Bluedog225]

For me, the 10,000 12 volt things for the camping and RV world are where it’s at.

Something like 50 Ryobi tools and a 12 volt charger. All the auto stuff.

100’ run may change everything. I’m12 volt and will graduate to 48 volt.

 

[12VoltInstalls]

100’ run may change everything.

At panel voltage if in series that may not be a factor of consequence.