# Convert AC wired barn to DC lighting



## downsized (Aug 28, 2012)

I have a barn this is wired for 110 AC with AC fixtures, but I've killed that account, so there is no AC to it now. I'd like to convert this to a DC system using the exiting lighting fixtures.

I found these light bulbs: 75W LED Bulb LED.BULB-75W



> LED.BULB-75W
> Sale: $28.95, Regular Price: $58
> 
> This 75W bulb is design as a direct incandesent light bulb replacement. Uses 7 X 1W High Power LED emitters from Bridgelux, offering long life, 85% energy and cost savings, *consumes 7.6W of power. *Width of 2.1" and Height of 3.8". Operates at 110VAC, standard edison E27 screw base.
> ...


The barn will be running about 15 max at one time (that would be isle lights and stall lights all turned on at once). That would be a rare occasion, like I'm working on something major in the barn. On average, 5 lights would be run for a max of 5 hours each day (two feedings and both are taking longer than usual for some reason). So, I'm using a 10 bulb/day to over size the battery.

So, I'd like to size the system for 7.6W x 10ea x 5hr / day

I can mount the panel(s) near the barn (20 feet from edge of barn) with an over head wire back to the barn, in an area that will get sunlight for most of the day (shaded for last hour before sunset). 

I'm located near Youngstown, OH. 

The barn is not heated at all, but I was thinking about storing the batteries with the solar panel(s) in a passively heated 'case' (think of a small insulated wood structure with a clear side that heats a brick heat sink during the day to maintain some heat for the batteries at night).

Can someone help me figure out how possible this is, size the panels and describe how to attach the AC wire ( white-black-bare ) to the battery (or batteries?).

Any help or advice would be really appreciated.


----------



## downsized (Aug 28, 2012)

Okay, I just realized that bulb is for AC. So I need recommendation for a DC version of that bulb.... looking for one now


----------



## downsized (Aug 28, 2012)

Okay, so swap in this light bulb: 12V DC 25 Watt CFL Bulb - Cool Spiral

This spiral shaped compact fluorescent light is ideal for most household tasks and reading. It gives a bright white light equivalent to a 100 watt incandescent! It has a lifetime of up to 8000 hours and uses the standard medium Edison screw base. These spiral fluorescent lights are very popular! Perfect for use with solar, wind, micro hydro, and marine systems that use a battery.


> Specs:
> Voltage: 11-15 Volts DC
> Watts: 25
> Amps: 2.08
> ...


So, I guess that is:

25W x 10bulbs x 5hrs = Sized for 1250W/day ?



Although I'd really rather LED than CFL.

Also, I'm not opposed to a 24v system (assuming I can find bulbs) if that will make the wiring work better.


----------



## wy_white_wolf (Oct 14, 2004)

First thing you need to check is how much amperage you installed wiring will handle at 12 or 24VDC. That will determine what you can run for lights.

WWW


----------



## downsized (Aug 28, 2012)

Thanks, I'll get the specs off the wiring in the morning when it's daylight out.


So using this calculator ( Off Grid Calculator ) I need:

Battery Bank Capacity: 9509 watt hours (20deg lowest temp)
Battery Bank Capacity: 397 amp hours
3 String Configuration: 133 amp hours per string

Using Cleveland as the city, The total wattage of Solar Panels that I need is:
889.5 Watts, or 0.89 kilowatts

Using this solar panel: Suntech STP285-24/Vd 285W 24V Solar Panel 

I need 4 panels and a 48 amp Solar Charge Controller

Where's that big eyed "WHAT?" smiley with the jaw dropping?

Then I look at this "1800W system" for $1300 ( 1800 Watt Solar Generator-1800SG at The Home Depot ) 

I'm sooooo confused, but I'd really like to have lights in the barn again.... gerrrrr


----------



## ||Downhome|| (Jan 12, 2009)

um might be silly but why not just get a inverter and not change anything?

lets assume you go with 10 x 20 watt compact florescent =200 watts x 5 hours = 1000 watts hour

I'm going to assume you could get by with less. probably half ?

you would need at least 2, 100 ah batteries. 100ah x 12 volts = 1200 watts hour x 2 = 2,400 watts hour

depending on charge controller, lets assume the most efficient. you need to replace 1000 on your heaviest day, so 1000 / .66 = 1516 watt hours is what you need in panels.

lets say at max 3 hours a day peak 1516 / 3 = 505.33 wh.

I would go for 2-175 watt panels.

ya confusing isn't it.

I really think that system you listed is over kill for what you want to do.
Good price for the claims but over kill.

Kind of wonder what the gurus think of it?

edited-never mind I take it back that things grossly under powered. they kind of miss lead you with the inverter rating.
and I think it a bit over priced.


----------



## downsized (Aug 28, 2012)

||Downhome|| said:


> um might be silly but why not just get a inverter and not change anything?


I appreciate any input because I'm in a learning phase on this, so I'm going to go through your comments and explain my thinking (who knows, maybe others are learning too?)

I'm avoiding the inverter because I think I will loose power with it (to the conversion process) and all I really need are lights. I want to use my already installed 120v wiring, so that's why the specific light bulbs designed to use DC voltage, but fit AC fixtures. (I'm like 99% sure that my existing wiring is going to be for 15amp service, currently it is a single run down the center of a 50' long barn isle. I'd like to add lights over each of five stalls and am not sure how to do that -- it's between a split at the front of the barn where the 'service line' enters and a branch down each side of stalls or individual switched lights for each stall)



> lets assume you go with 10 x 20 watt compact florescent =200 watts x 5 hours = 1000 watts hour


This is an interesting question. If I do use the inverter then I can use the LED bulbs that I posted earlier that only use 7.6W so that would be:

7.6W x 10 bulbs x 5 hours = 380W / day 

So... that makes the inverter interesting again. Going back to the off grid calculator... and playing around with it, it seems like I could get away with just one of the solar panels that I linked above, but it still says I need a "3 string" battery bank with Battery Bank Capacity: 3219 watt hours

BUT! If I could find DC LED lights that use the existing fixtures... then I'd be back to "why use an inverter?"




> I'm going to assume you could get by with less. probably half ?


I admit that I'm over sizing from what I truly expect to do, but I'd rather over size than run into a situation where I have an animal that I need to deal with and no lighting. That may happen only once in a blue moon... but who knows, maybe I'll put outside floods on a switch, so I can kill them if I know that I'm going to need inside lights for longer during the night.




> you would need at least 2, 100 ah batteries. 100ah x 12 volts = 1200 watts hour x 2 = 2,400 watts hour
> 
> depending on charge controller, lets assume the most efficient. you need to replace 1000 on your heaviest day, so 1000 / .66 = 1516 watt hours is what you need in panels.
> 
> ...


Yup... that block above all kinda went woooshhh to me.


----------



## downsized (Aug 28, 2012)

Okay, so figured out the base is called an Edison base. 

Here is a DC LED light: 12 volt LED light bulbs, LED spot lights, LED PAR lights, LED globe lights, LED strip lights, quantity discounts



> Bulb 9 Watt LED Soft Daylight E26 12V
> 
> Voltage: 11-15 Volts DC
> Watts: 9
> ...


So, that gets me to:

9W x 10 lights x 5 hours = 450W/day

So according to that calculator site, I'd be just an itsy-ween tad bit over the capacity of 1 of the solar panels, but still need 3 batteries.


----------



## downsized (Aug 28, 2012)

Okay, so figured out the base is called an Edison base. 

Here is a DC LED light: 12 volt LED light bulbs, LED spot lights, LED PAR lights, LED globe lights, LED strip lights, quantity discounts



> Bulb 9 Watt LED Soft Daylight E26 12V
> 
> Voltage: 11-15 Volts DC
> Watts: 9
> ...


So, that gets me to:

9W x 10 lights x 5 hours = 450W/day

So according to that calculator site, I'd be just an itsy-weeny tad bit over the capacity of 1 of the solar panels, but still need 3 batteries.


----------



## 12vman (Feb 17, 2004)

Forget the thought of running low voltage D.C. through your existing wiring. That's not going to work.

Don't forget the conversion factor with using an inverter. The battery demand(s) will differ with different D.C. voltages. A 7.6 watt demand through a 12 volt inverter will be 76 watts to the battery. @24 volts.. 38 watts. @48 volts.. 19 watts. (not including inverter losses) A 24 volt D.C. system with an inverter would make sense in this case..

Design the system to work in the middle of December and add ~20% in battery and panel and it should work all year round. Your battery will decrease in efficiency ~20% when cold..

Sounds like a nice project. Keep us updated.


----------



## ||Downhome|| (Jan 12, 2009)

downsized said:


> I'm avoiding the inverter because I think I will loose power with it (to the conversion process)


Yes but with Dc,more so a low volt setup, you will more then likely have comparable line loss. But I suppose i did not factor the conversion loss in my
last post. so you would need to redo the math.



downsized said:


> 7.6W x 10 bulbs x 5 hours = 380W / day


How many lumens will these put out. the 20 watt CF put out around 1670 lumen per. then whats the price factor. good leds are pricy. cheap ones not so much. need to way apples to apples. you can get lower watt or higher watt CF. maybe have several types low for utility and a few high for work.



downsized said:


> but it still says I need a "3 string" battery bank with Battery Bank Capacity: 3219 watt hours


its not far off of my calculation, they are padding in some storage for those not so sunny days. Batteries only have so much in them. they have a finite number of charge cycles. taking them under 50% capacity shortens the life. besides the extra juice when you come up short on a cloudy day it also buffers you drain to keep you at that 50% mark.



downsized said:


> BUT! If I could find DC LED lights that use the existing fixtures... then I'd be back to "why use an inverter?"


Line loss, think of wire like a pipe, only so much can go through.
then friction comes into play. In the case of electricity that comes in the form of heat. Long Dc runs need to have thick wire.
higher the volts less wire diameter needed. still meaty compared to AC. 

Quote:
you would need *at least* 2, 
100 ah (that translates into 1 amp for 100 hours or 100amps for 1 hour. batteries. 
100*AHx* 012 *volts=* 1200 *watts hour* x 2 =
2,400 total watts hour

depending on charge controller, lets assume the most *efficient*. you need to replace 1000 on your heaviest day, so 1000(this is your daily load or juice used) / *.66 (efficiency factor)* = *1516 watt hours(what you need to produce total to replace your daily load in the bank)* is what you need in panels.

lets say at max 3 hours(total production from panels) a day peak *1516(what you need to produce)* / 3(total hours of production) = 505.33 watt (hours) needed in panels .

I would go for 2-175 watt panels.

ya confusing isn't it.


----------



## 12vman (Feb 17, 2004)

I had a 50' mobile home and wanted to do the same thing that you want to do. I connected a 12 volt battery to the fuse box in an attempt to use the existing wiring for some 12 volt bulbs. 2 rooms down from the fuse box, the voltage drop was so bad that the bulb would'nt hardly light up! I had to run new wiring throughout.. F.Y.I.


----------



## wy_white_wolf (Oct 14, 2004)

12vman said:


> I had a 50' mobile home and wanted to do the same thing that you want to do. I connected a 12 volt battery to the fuse box in an attempt to use the existing wiring for some 12 volt bulbs. 2 rooms down from the fuse box, the voltage drop was so bad that the bulb would'nt hardly light up! I had to run new wiring throughout.. F.Y.I.


That's what I was thinking. At 50'+ the voltage drop will be so high it won't work. If they used 10AWG wire they might get away with using 12VDC. Most likely they wired with 12 or 14AWG.

WWW


----------



## Jim-mi (May 15, 2002)

I would bet those existing lights are daisy chain wired with 14ga. wire . . .
So no way are those 12vdc lights going to work.........

You will be in for a big 'shock' when you find out what the big wire will cost to "rewire" for low voltage.


----------



## Jim-mi (May 15, 2002)

With all this wizz-bang figuring for what you think you need for ONE day . . . .that system will fall flat on its keister once the clouds, rain, snow come along.

Small one day supply batterys are a waste of time and money.......


----------



## downsized (Aug 28, 2012)

Okay, the barn is #10 wire (that makes sense because the run for that barn actually starts in the garage, and runs another barn's lights/heaters before it hit the barn I'm talking about. From the fuse box to the end of the barn was about 300 feet in total length.) 

There are only 4 lights in the center isle (not five).

Ref the mobile home. The LED light linked above is rated at .75 amp. If you used a bulb that needed higher amps, then that would really reduce the distance that a smaller wire could cover? I'm I getting that right? 

Since I have the Watts down using LED lights (I want something equivalent to a 60W bulb, so I've been looking for at least 800 lumen, but the 9W LED listed above at 720 lumen is the closest that I've been able to find so far. ) I'm not against the inverter or as set on running DC.

Jim-mi - actually in the linked calculator that I've been using, I've been setting it to factor for 2 days without sun. As I posted above, the calculator is recommending three batteries and a pretty sizable solar panel. Given that (a) I'd have to pay the power company a base $45/mo even if I never draw a single watt of power and (b) I have three other barns that are too far out to wire for electric, I find the idea of solar lighting valuable. But I appreciate your input.

This project is definitely not cheap, but the other barns are 150', 200' and 400' BEYOND this barn. To get electric to my 100x65 main barn, I was told that I'd have to put in a new line with a transformer. And this is so that I can have lights at night in the winter? I already have 220v in the garage and I don't run (need) bucket heaters. I have a generator that can run tools. I just would like to work at night without wearing a head lamp and what ever I learn in this little project will translate over so that I can light my main barn that is 400' out.

Thanks again for any input.


----------



## 12vman (Feb 17, 2004)

*"Ref the mobile home. The LED light linked above is rated at .75 amp. If you used a bulb that needed higher amps, then that would really reduce the distance that a smaller wire could cover? I'm I getting that right?"*

Yep.. The fuse box was in the rear bedroom, at the far end of the mobile home. The bathroom and a second bedroom was on the right of the hallway. I was in the second bedroom with just the bathroom between me and the fuse box. I screwed an Edison base 12 volt 50 watt incandescent into the ceiling fixture and... A candle woulda made more light.. 

I figure the wire was 14 Ga. solid copper from the fuse box to the bedroom.. 2Ga. multi strand stinger cable from the battery to the fuse box.. Slightly over a 4 amp draw, less than 15 ft..

I didn't test the voltage at the bulb but I figure it dropped well below 6 volts. I found out quick that this wasn't gonna work.. Plan "B"..

I re-plumbed and ran 3/4" copper pipe (hot and cold) on the ceiling, the whole length of the place. Did my water taps with plastic to the spigots and everything. Connected my battery to the pipes. (hot = pos./cold = neg.) Tapped power from the pipes to my outlets and whatever I needed power for. Worked fine, last long time.. 

I don't believe the 10 Ga. will do much better at low voltage. I'd consider an inverter with some standard flourescent lighting. They give you the best bang for your buck overall for area lighting, IMO..


----------



## Jim-mi (May 15, 2002)

We don't know what area you are in and so we have no idea of your sun time.
But a 2 day battery is still far to small and will lead to over discharging and short life for said battery.


----------



## downsized (Aug 28, 2012)

12vman said:


> I re-plumbed and ran 3/4" copper pipe (hot and cold) on the ceiling, the whole length of the place. Did my water taps with plastic to the spigots and everything. Connected my battery to the pipes. (hot = pos./cold = neg.) Tapped power from the pipes to my outlets and whatever I needed power for. Worked fine, last long time..


So.... that's a bit scary. Did you ever tell any building inspectors about this? Am I right in thinking that the water would have also carried a charge, so if you put a hot and cold hose in a bucket and let them sit to fill it up, you could have blown your battery bank up?


----------



## downsized (Aug 28, 2012)

Jim-mi said:


> We don't know what area you are in and so we have no idea of your sun time.
> But a 2 day battery is still far to small and will lead to over discharging and short life for said battery.


I posted in the first post, I'm near Youngstown, OH. In the calculator, I'm using Cleveland, OH because that is further north from Youngstown, but similar weather pattern.


----------



## downsized (Aug 28, 2012)

12vman said:


> I don't believe the 10 Ga. will do much better at low voltage. I'd consider an inverter with some standard flourescent lighting. They give you the best bang for your buck overall for area lighting, IMO..


Since I found 120v LED lamps, I'm going with the inverter and the combination gets me down to the one solar panel that I've linked above. 

I ran CFLs before (actually, they're still in there) and they weren't too happy in the cold. It took them a REALLY long time to come on. Initially, I'll have the main isle lights (only 4) and I'll probably just work my way through replacing them with the LEDs. My other issue with my CFLs is that in my experience, they have great life span (I was getting 8-9 years out of them), but when they go, they all go at about the same time (probably because they were all installed at the same time). 

I'm thinking the LEDs will be pretty much permanent lights that won't require me to drag out a ladder and juggle everything while I'm trying to change bulbs. And when I move to working on the the main barn, there are 120V 2200+ lumen LED lights (intended for use as street lamps) that run only 28W/.25amp.


----------



## 12vman (Feb 17, 2004)

downsized said:


> So.... that's a bit scary. Did you ever tell any building inspectors about this? Am I right in thinking that the water would have also carried a charge, so if you put a hot and cold hose in a bucket and let them sit to fill it up, you could have blown your battery bank up?


Naa.. 12 volt D.C. doesn't travel through water very far. Never had an issue..

Building inspectors aren't interested in an outbuilding..


----------

