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Small Cabin Forum / Off-Grid Living / Thoughts on my solar idea.
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# Posted: 10 May 2021 13:46

New here (obviously) and just looking for input.

I'm building a small cabin on my land in Hawaii, going to live my remaining years out there in peace (am from the island originally). So without going through too much filler text here is what I have to power and what I'm looking to power it with.

Your average "dorm fridge" (215kWh/yr), Internet router & Arlo Cameras (0.5kWh/day), Television (0.15kWh), Pedestal Fan (0.07kWh), Radio for sleeping music (0.03kWh), and a couple of LED bulb lamps of the evening.
I also have a laptop, tablet, and phone that I'll be charging when necessary.

I may add a small chest freezer (219kWh/yr) or just upgrade to an upright freezer/fridge combo in the future if I have the juice to run it.

OK, with that out of the way here is what I plan on getting:
This solar kit from Grape Solar
And two of these batteries (actually maybe 3)
This inverter (with charger) 1500c-12/

OK, so now some filler text.
Getting stuff shipped to the island is slow and expensive. That kit I can get ordered from Home Depot and not have to pay additional for shipping.
The batteries are from Costco and are almost always in stock.
That Samlex inverter has a built-in charger, so if it's too cloudy or wot-not I can just plug my generator into it to keep everything going and charge up... just hoping not to do that too much.
I know I'll be using a 12v water pump for my outdoor shower, and probably a few smaller power things from time to time - but it's easy enough to use those just during the day time.

So what are your guy's/gal's thoughts on this? Am I thinking too small here? I'm a simple guy and apart from a blender, stereo, and ceiling fan I don't have any more electrical equipment than what was mentioned above.

# Posted: 10 May 2021 14:15 - Edited by: Steve_S

This is NOT the route I would go. Grapesolar is a consumer plug & play product which is 3X the cost because of it.

I use Samlex and am an Offgridder in the North. You ONLY want a Pure Sine Inverter, NOT a Mod Sine ! Pure Sine is clean smooth waveform whereas Mod Sine is choppy and no good for anything with a motor (fridge AC compressor etc) and not very nice with Fine Electronics (everything else you listed).

The amount of battery energy you require per day is determined by the amount of loads you will be feeding with them, plus any reserve for sunless non-charging days. Once you know that and what type of battery & their capacity, then you can figure out how big of a solar controller you need to charge that battery assembly and how much panel it will take to deliver that charge capability.

NOTE: Any Lead Acid / AGM flavoured battery can ONLY be taken down to 50% Depth of Discharge (DOD) any further and the lifespan is being cut & quickly too. Proper DEEP Cycle batteries for Energy Storage have much heavier plates & are larger, Golf Cart batteries work BUT are not designed for this.

A simple system such as below may just be the ticket without having a power use assessment.
- 1000 W of Solar Panel 3x350W ?
- Samlex EVO 12V Pure Sine Inverter/Charger
- 1 or 2 Battleborn 12V/100AH LiFePO4 batteries which can be used to 90% ($1000 USD ea +/-)
EPEver 50A Solar Charge Controller.
Eaton/Bussman fuses & Breakers (no knock offs).

Now if you want simpler & easier, I would suggest you consider an "All In One" Solar Charge Controller / Inverter / Charger. The components are modules and exchangeable/repairable. These simplify a LOT and solves having to buy some of the Balance of System gear that goes with solar. As well, the monitoring & Control software is most handy to tweak and monitor the systems health & status.

Have a look HERE for some ideas regarding basic plans and how to's related to this topic. Also feel free to use our Forum there to bounce ideas & things off...

EDIT: BTW if your curious, here is a link to my "About my System" page which at the moment is slightly out of whack as I have to add in another new config change. There are more links and tips there as well as in my signature on that forum, including how to assemble your own battery packs and more.
About my System on DIYSolar

# Posted: 10 May 2021 14:34

Steve is the man...

A cabin in Hawaii, man that sounds good. Make us jealous with some pics.

# Posted: 10 May 2021 14:40

You cant go buy the KWH/yr rating of these appliances. No where near accurate and you need accurate numbers to size a system.

# Posted: 10 May 2021 15:14 - Edited by: gcrank1

Unlike many of us you wont have much for heating issues
Imo, the most you want to go on an inverter size with a 12v system is 1000W (they peak at more) because the wire size is pretty big and gets huge after that. Consider that driving that inverter with 12v at the 1000 with just simple math means 100+ amp fuse/circuit breaker.
When you want to have stuff like 'fridge and freezer, air conditioning, elec water/space heater, etc. the power requirements stack FAST; waayyy to fast for me and my fixed, and rapidly declining in purchase power, income.
My choice last year was to go simple on my solar, 12v inverted to 120vac for LED lighting, small fans, usb ports, radio, tool chargers, etc (ie, light loads). YES, go Pure Sine Wave inverter Only.
We use a heavy duty cooler with ice for what Must Be Refrigerated. But we have a source for re-freezing my ice-packs for rotation.
For 'short term high loads' I start the inverter generator; things like the microwave, toaster, 30 cup electric coffee pot that is my easy water heater, etc. Whenever the gen runs so does my charger to bump up the bat-bank. Btw, we do not run the gen for hours on end (who want to listen to that) but only about 1/2 hr every day or two....or three.
I do not have thousands of dollars 'invested' and it works fine for our 'de-tuned from the grid' life at the cabin. It is a get-away,but we could long term it with the infrastructure Ive built.
Be aware that to be your own power company is not cheap, and for many not easy (power goes down, who do ya call?) and the more stuff you want to power the higher the price quickly goes up.
Some of the best advice I was given early on was,"FIRST do energy conservation".
Works for us, ymmv. I know some want their place to run just like a 'grid house' and that is fine too, just be prepared to pay.

# Posted: 10 May 2021 22:26

Imo, you would do well to check out the good info over at:
They entertain visitors so you can learn a lot even if you dont join, but then you wont be able to post.

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