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Small Cabin Forum / Off-Grid Living / Cabin lighting: how many lights/lumens?
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# Posted: 29 Jan 2021 19:34

I'm going to be building a cabin, powered by solar. I already have a thorough understanding of electrical systems and solar power. What I'm less clear about is how much LED lighting I need to adequately light a cabin. You know, how many light fixtures, how many lumens for each. I need to get at least a ballpark estimate in order to determine important questions like do I want 12 or 24 volts, and how much battery capacity I need. Is there a rule of thumb, e.g., so many lumens per square foot?

# Posted: 29 Jan 2021 20:41

What will be your cabin size?
How many rooms?
Height of ceiling?
Is there a loft?
Do you mind expounding?

# Posted: 29 Jan 2021 20:52

I would say 'it depends'....on your eyes and the kind of light you are used to and want. For instance, If I want to read I want good light but different than I want for brain surgery (lol). For a cabin do you want mainly soft, warm light more like the old school kero lamps or lit up like your home.
And how big a cabin/space to light?
Nice thing about led's is you have nice real light, superbly energy efficient and inexpensive bulbs these days. My preference is 60w equivalent but 40w equiv is far better than my old cabin wide wick kero lamps.

# Posted: 30 Jan 2021 07:22

One thing I will suggest is, if possible, use more light fixtures and more switches. This gives you the option to turn on more lights when extra is needed but less when not needed. Rather than two or three fixtures on a single switch split them up. More of a hassle wiring but gives you the flexibility.

# Posted: 30 Jan 2021 08:16

Agree with raz. All mine are on pull switches. Turn lights on where you want/need them, not everywhere.

LED lights 13w are 100w equivalent and work great for me.

# Posted: 30 Jan 2021 08:52 - Edited by: gcrank1

Re-reading your query I see I had focused on the lighting issue about 'adequate lighting/lumens' and missed the last part about you want that to determine solar voltage and bat-bank size.
In the old days that would have been much more of a 'need to know' than in these led days. Example, my old '83-84 off grid cabin was lit (for 1x 12vdc 100ah battery elec) with two 25w and one 50w Edison base RV bulbs (look just like household bulbs but 12vdc) on 12ga. Romex, std light fixtures with pull chain integral switch (my pref too).
Watts/volts=amps so those 3 bulbs total of 100w had a draw of 8.33amps (I round up on draw so call it 8.5a), use those 10 hrs and it pulled the battery down by 85amps. Not so good when a typical 'marine' deep cycle 100ah bat has only a 50ah max to use (much better to only use 25-30ah for battery health and life).
I killed a few batteries thinking that I could really 'deep' cycle those! NOT. I ended up using only one 25w most of the time (-20+ amps over 10 hrs) so I could get through a weekend stay. Longer meant light the kero lamps.
But now we have the marvelous led lights. Three 60w equivalent/9w draw bulbs use only 2.25/2.5 amps For All, 10 hrs use is 25amps not 85amps for more lumens and no hurt on the battery. And I usually only have one bulb on in our current 16x24 anyway, though I have 5 fixtures on demand.
What Im saying is that unless you are trying to light a cabin up like a shopping mall on a tiny LA (Lead Acid) battery the amps draw for led lights is so minimal that it is almost out of consideration.
On the voltage to use; for small scale 12v is Ok but knowing what I do now, and wanting to 'do more', I would be better off if I started with 24v, and for a bigger operation 48v.
One old rule of thumb was for each 100w of solar panel run 100ah of LA battery, 4 x 100w array = 4 x 100ah 12v bat's, but it is bad to parallel more than 2 12v batteries! Much better at 24v, you parallel 2 and series 2 and you have better bat health/life.
Game changer! LFP batteries. Instead of a max (MAX!) 50% dod (depth of discharge; ie, only get to use 50% of the rated battery amp hrs) you can use 80-90% on LFP! They recharge faster, unload faster to power up something with a heavy start up draw ('fridge, ac), have 2000+ true deep cycles vs 400-500 on a typical LA, dont off-gas (can use and store in the living quarters BUT cost 4x as much up front. However, that is not as big as it sounds because 1) those many more cycles(longer life) and 2) much more amp hrs of use in each cycle. Basically it means you get the equiv of 3 x 100ah LA batteries in 1 x LFP 100ah bat.
This means a Much Better Value/More Cost Effective for your dollars spent.
Starting today Id have better quality 24v panels, MPPT charge controller, LFP battery(s), 24v to 120vac pure sine wave inverter and have a better system geared to upgrade in the future.

# Posted: 30 Jan 2021 09:35

As others have said, need more info...

But in our 1 room cabin, I have 3 pendent lights hanging down the length of it. Each has a 60 watt equivalent LED bulb in it. They are on 1 switch. They are good for 85% of light needed- dressing, games, eating... For things like working on a small part at table or reading fine print, I used a small bright LED lantern. We also have a reading light at the head of our bed.

# Posted: 1 Feb 2021 15:23

Quoting: gcrank1
Game changer! LFP batteries.

I'm aware that it's inadvisable, with lead acid batteries, to combine new and old batteries. So you can't really go "Oh I need more battery capacity" and add another battery after a year or two. Does the same hold true with LPF batteries? With LAs, it wouldn't be that big a deal to intentionally go oversize in the first place to leave room for future upgrades, but with the cost of LPF, that's less practicable.

# Posted: 1 Feb 2021 15:41

Color of light is very important as well. The higher the K the whiter the light....ambiance is eveything inside a cabin, so you probably want to stay in the 3-4k range for light color and maybe get a floor lamp or something for a reading light with a higher K color.

# Posted: 1 Feb 2021 16:37 - Edited by: gcrank1

Last I heard/read on LFP age compatibility it is not as near narrow as LA; ie, within a year mfg but matching the voltage more important. Iirc you can add in different ah capacity LFP's also. Im sure someone else here can comment with more certainty.
Im really leaning toward the RhinoVoltz 100ah which will equal about 3 100ah LA. It would improve my bat-bank from the 2 old, tired LA by a lot and Id be pretty well set to add another whenever my wants/needs required more capacity.
But....if I was starting anew and all I wanted was to run a couple of good LED lights, run a few things off usb ports and maybe a cig-lighter socket I doubt I would build a whole system again.
Id go:
1)A 'solar-generator' (what a misnomer) or, more likely for me an LFP battery of about 50-60ah c/w a usb, cig-ltr soc, and voltmeter
2)A set of solar 'Edison' base looking portable bulbs that come with their own very small but totally adequate solar panel (I have a 3-set now, $30ish off Amazon, its way cool). Unplug, switch on, hang where ya want/multiples if you want more lumens at that spot
3)Maybe a 100-200w portable solar array but that LFP 'pack' could be charged off your vehicle or take home between trips.
No muss, no fuss, almost too easy. Really.

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