Garage lighting

[kylemoul]

Hello all.

I am looking for advice on lighting for my detached garage.
It is maybe a 1 1/2 or 2 car garage. It has 2 windows and gets light during the day. It has no electric run to it.

What I am looking at is a panel of some sort maybe like this? that can charge a battery, and then I can hook up lights to that battery and thus light the garage.

First, I would be looking to power lights only, with the possibility of a small radio (maybe). I am not looking for bright white florescent performance, but something that will have decent light so I don't trip over my lawnmower or something, and maybe use the lighting for 4-6 hours if company comes over (we like to sit in the garage and drink beer).

I have some troubles trying to piece together the wattages of the lights and solar panels. I have found some cheap lights on amazon that are 8W~ or so and was thinking of mounting 4 of them.
Is there a way to calculate what the draw would be and how long a charge would last?

[inetdog]

Hello Kyle and welcome to Solar Panel Talk!

Can you just run low voltage landscape lighting wire from a transformer at the house out to the garage?
It would be a lot less expensive and probably give more light.

Your idea of four 8 watt landscape lights would take a total of 32 watts. It is that simple.

If you run them for 4 hours, that will be a total of 128 watt-hours. (Watts are a unit of power, or energy per unit of time, watt-hours are a unit of total energy.)
The panel that you linked to will produce 18 watts under ideal conditions. Since you did not say where you are located, I will guess that during the winter you get the equivalent of 3 hours of full sun.
So the panel will give you 54 watt-hours of energy each day. Less than half of the 128 watt hours you will use drinking beer.

Assuming that the lights you are looking at run off 12 volts, you would need a 12 volt battery that is rated at 50 amp-hours or more to power your lights and radio. And you would need a 50 watt or larger panel to keep the battery in good condition.

If you only have friends over once a week or so, you could get by with a 20AH battery and your 18 watt panel would be OK.

There is an off grid system sizing calculator in a sticky thread in the off grid forum that will help you compare alternatives.

[kylemoul]

Hello Kyle and welcome to Solar Panel Talk!

Can you just run low voltage landscape lighting wire from a transformer at the house out to the garage?
It would be a lot less expensive and probably give more light.

Your idea of four 8 watt landscape lights would take a total of 32 watts. It is that simple.

If you run them for 4 hours, that will be a total of 128 watt-hours. (Watts are a unit of power, or energy per unit of time, watt-hours are a unit of total energy.)
The panel that you linked to will produce 18 watts under ideal conditions. Since you did not say where you are located, I will guess that during the winter you get the equivalent of 3 hours of full sun.
So the panel will give you 54 watt-hours of energy each day. Less than half of the 128 watt hours you will use drinking beer.

Assuming that the lights you are looking at run off 12 volts, you would need a 12 volt battery that is rated at 50 amp-hours or more to power your lights and radio. And you would need a 50 watt or larger panel to keep the battery in good condition.

If you only have friends over once a week or so, you could get by with a 20AH battery and your 18 watt panel would be OK.

There is an off grid system sizing calculator in a sticky thread in the off grid forum that will help you compare alternatives.

Thanks for the response. I am in Missouri, and the roof gets a good 6+ hours of sunlight a day. I was not sure how the Wattage fit in with the solar panel, since the solar panel is just charging the battery.

Friends would only be over every 2 weeks or more. It would not be used a lot. I don't even go into the garage weeks at a time.
I will look at that sticky. Do you have a link for the landscaping wire? I am not familiar with that.

[Shockah]

Calculator inetdog mentioned <<<


Landscape wire @ amazon.com <<<

I've done many lights for garage and shed.

The best combo I have found for our December 3.5 hour insolation geographic is:
Instapark 20watt panel from Amazon.com
3amp Charge Controller with dusk-to-dawn light control from j2led on ebay.
3watt LED E27 bulb (the sunnier side of the island can go up to 5w)
22ah agm battery.

just mounted a "post" model above iconic Diamond Head Crater yesterday...

0404041104.jpg

or it can be roof, eve or wall mounted

shed.jpg

0104041437.jpg

[kylemoul]

Calculator inetdog mentioned <<<


Landscape wire @ amazon.com <<<

I've done many lights for garage and shed.

The best combo I have found for our December 3.5 hour insolation geographic is:
Instapark 20watt panel from Amazon.com
3amp Charge Controller with dusk-to-dawn light control from j2led on ebay.
3watt LED E27 bulb (the sunnier side of the island can go up to 5w)
22ah agm battery.

just mounted a "post" model above iconic Diamond Head Crater yesterday...

[ATTACH=CONFIG]4005[/ATTACH]

or it can be roof, eve or wall mounted

[ATTACH=CONFIG]4006[/ATTACH]

[ATTACH=CONFIG]4007[/ATTACH]

Awesome, I will defiantly look at those.

[kylemoul]

Also, where does the 20AH come into play in this equation?

[inetdog]

Also, where does the 20AH come into play in this equation?

Simple:

Your beer day usage is ~120 watt hours of energy. At a nominal 12 volts that would be 10 amp hours of battery capacity.
If you do not want to run your battery down below 50% on any given day, and then can spend a day or two charging it back up again, that means you can use a 20 amp hour battery.
In practice, if you end up draining the battery at the 8 hour rate (half of its capacity in 4 hours --> 8 hour discharge rate), you will not get the same capacity as you would at the standard 20 hour rate at which batteries are characterized. (Google "Peukert") So you would really need a larger battery. Say 25-30 AH.

[kylemoul]

Simple:

Your beer day usage is ~120 watt hours of energy. At a nominal 12 volts that would be 10 amp hours of battery capacity.
If you do not want to run your battery down below 50% on any given day, and then can spend a day or two charging it back up again, that means you can use a 20 amp hour battery.
In practice, if you end up draining the battery at the 8 hour rate (half of its capacity in 4 hours --> 8 hour discharge rate), you will not get the same capacity as you would at the standard 20 hour rate at which batteries are characterized. (Google "Peukert") So you would really need a larger battery. Say 25-30 AH.

So I have been doing some numbers. Hopeful you can scrutinize my math and make sure I am using your explanations of calculations correctly.
I am looking at this panel, which is a 20W panel.
I have planned 7 3W light bulbs for a total wattage of 21watts. I will estimate running these for 4HR a day, 2 days a week (probably less but for this calculation ill say 2 days) which would equal 84WattHours per day that I run it. Divided by 12 (nominal) for voltage comes to 7Amp hours.

So those 7AmpHours, does that relate to the total number of amps that is drained from the battery per hour for all of the lights running in that 4 hour period?

Depending if the above is correct, this panel shows an "MPP Current" (I don't know what that means, max current?) of 1.14A. does this mean that the panel is able to flow 1.14amps max back to the battery per hour?

Thanks again for explaining this to a novice. Trying to learn something.

[Wy_White_Wolf]

Look at it as:

Amps = flow
AmpHours = Volume

7Ah would be the total used in 4 hours. The hourly rate would be 1.75 Ah (7/4).

1.14 Amps is the amount it can flow to the battery. 1.14Ah is the volume it is capable of putting in in 1 hour.

WWW

[kylemoul]

Look at it as:

Amps = flow
AmpHours = Volume

7Ah would be the total used in 4 hours. The hourly rate would be 1.75 Ah (7/4).

1.14 Amps is the amount it can flow to the battery. 1.14Ah is the volume it is capable of putting in in 1 hour.

WWW

Ok, I got it. That's what was brewing in my head. Makes sense.

[Shockah]

I am looking at this panel, which is a 20W panel.....

Coincidentally, I put together a light today with the exact same panel.

0508141657.jpg

At about 2pm, I took a reading of the panel only... with moving it around to position it perpendicular to the sun, I got a high of 1.38amps.

[kylemoul]

I think I have the setup I am getting. Should give me the runtime when I need it for 3-4Hrs on LED lights with a day to charge the battery back up.

On my detached garage is where I will be installing it, I will screw it directly on the roof. Do you normally put any rubber washers between the mounting brackets and roof/shingles or anything to prevent leaks?

[inetdog]

On my detached garage is where I will be installing it, I will screw it directly on the roof. Do you normally put any rubber washers between the mounting brackets and roof/shingles or anything to prevent leaks?

What kind of roof do you have and is it flat or sloped?
A rubber washer may not do enough to prevent leaks if you drive a screw directly through the layers of shingles on a shingle roof.
You may need to waterproof the penetration through the inner layer of singles, not just the top one. Roofing cement will probably do better than a washer.
A proper installation will use flashing to divert water around the screw penetration and bracket. Or you can lift the top shingle and drive the screw through the ones underneath.

Roof penetrations are a little too complex for me to cover in both great generality and great detail here.

[kylemoul]

What kind of roof do you have and is it flat or sloped?
A rubber washer may not do enough to prevent leaks if you drive a screw directly through the layers of shingles on a shingle roof.
You may need to waterproof the penetration through the inner layer of singles, not just the top one. Roofing cement will probably do better than a washer.
A proper installation will use flashing to divert water around the screw penetration and bracket. Or you can lift the top shingle and drive the screw through the ones underneath.

Roof penetrations are a little too complex for me to cover in both great generality and great detail here.

It is sloped. It is an overhang so not the end of the world if something does leak. I'll have to look into the flashing part of it., unless a picture would help

[kylemoul]

Capture1.jpg

It is sloped. It is an overhang so not the end of the world if something does leak. I'll have to look into the flashing part of it., unless a picture would help

Might be hard to see, but the detatched garage is in the back yard, kinda covered up by the red marker.
It is sloped parallel to the road (westish/eastish).
I was thinking of pointing it a little south on the east part of the detached garage.