Bright, simple, cheap, durable, rustic dome light!

[gyroguy]

One thing to remember is that an inverter that is lightly loaded can be pretty inefficient. I wouldn't be surprised if the total current draw for the fluorescent lamp on the inverter isn't about the same as the 12V incandescent. P.S. Here's a link to some LED lights I made:
http://home.comcast.net/%7Ebdosborn/tea ... htBar.html

Thanks for kind comment on measuring light output. My light meter is more objective than I am, I'm trying to stay within the spirit of this forum, which is to be helpful instead of argumentative. This forum helped me a lot when I was building the Crocodile Tear, and it's payback time.

I estimated the inverter would draw 10 percent of the amperage. That could be 10 percent of the 13-watt load with one fluorescent bulb or 10 percent of its 130-watt output capability. Or 60 watts, as Bruce speculated. Opinions ar cheap. Regarding the amperage a small inverter uses -- has anybody measured it and is willing to post it here?

Bruce -- I went to your website and looked at the LED light bar you built. Nice job! From one of your night camping photos, I got the impression that it puts out less light than any of the three lights I tested. What is your impression: your LED light bar vs a bright single-bulb 12V dome light?

Not to hijack my own thread -- but Bruce, that's one beauty of a teardrop you've built! The build pix on your website show excellent craftsmanship. I liked the use of window sash locks for cupboard doors and drawers and the use of the 90-degree steel angles to attach bows. (I simply made shelves and put everything in Rubbermaid boxes. My bows fit in slots and were glued and screwed to the sides.) Your inclusion of solar panel, DVD, TV tuner, pre-amp, Direct TV dish, and speakers is impressive. (I thought a CB radio with weather band and a transistor radio were hot items!)

[dwgriff1]

Don't have a 12v battery in my tear, don't plan to add one.

Right now I am using an LED pistol grip flash light for internal lighting. In time I hope to find 9v LED dome lights, or something similar. Those touch lights that are advertised all over the place would be wonderful if they were LED.

Someone makes them. Right?

dave

[bdosborn]

I estimated the inverter would draw 10 percent of the amperage. That could be 10 percent of the 13-watt load with one fluorescent bulb or 10 percent of its 130-watt output capability. Or 60 watts, as Bruce speculated. Opinions ar cheap. Regarding the amperage a small inverter uses -- has anybody measured it and is willing to post it here?

The efficiency varies with how heavily the inverter is loaded. If the inverter is carrying close to its rated load they're typically about 90% efficient for a good one and less for a cheap one. The efficiency goes down as its loaded less. I generally assume about 80% efficiency so a 13W load woud draw 13/0.8=16.25W. But, I haven't ever measured the draw of my inverter.

An LED isn't as bright as an incandescent light and doesn't have as good of color rendition either. But its about half the current draw so I use them. We spent 10 days in the trailer this summer and never ran out of juice. The charge line from the truck had a blown fuse so we went 4-5 days with just the solar panel to recharge the battery. I didn't find the blown fuse till about 3 months later. The LED lights are a big part of maximizing battery life.

Thanks for the compliments on the trailer. You can hijack threads any time you want.
Bruce

[bledsoe3]

Don't have a 12v battery in my tear, don't plan to add one.

Right now I am using an LED pistol grip flash light for internal lighting. In time I hope to find 9v LED dome lights, or something similar. Those touch lights that are advertised all over the place would be wonderful if they were LED.

Someone makes them. Right?

dave

Like these?
http://www.harborfreight.com/cpi/ctaf/d ... mber=94254

[dwgriff1]

Yea.

Thanks. I'll pick up a set.

dave

[Airmad]

Hey Gyroguy:
I'm a little confused about the numbers you used. For the flourescent light you said the draw was 0.1 Amps. This is correct, but only for 120 Vac. If using a 12V converter, it would be 1.08 A for the bulb alone (at 12Vdc), and a little bit extra for the converter, so for backwoods use, I would think that the LEDs are the way to go. I just checked the current draw on my LED flashlight. 6 LEDs at 4.5Vdc was 36 mA Thanks. Roy

[Et Cetera]

I picked up a 3 pack of LED touch lights (they look like white hockey pucks) for $9 at Big Lots. The brand is Sunbeam and they all come with batteries. We used them during our recent power outage and they are great!!!

I think these are the same as the Sylvania Dot-it push lights that now come in a variety of colors. I've seen them at Home Depot.

[bledsoe3]

I saw a lady coming out of Costco with a pack of these types of lights. You might check there.

[gyroguy]

Hey Gyroguy:
I'm a little confused about the numbers you used. For the flourescent light you said the draw was 0.1 Amps. This is correct, but only for 120 Vac. If using a 12V converter, it would be 1.08 A for the bulb alone (at 12Vdc), and a little bit extra for the converter, so for backwoods use, I would think that the LEDs are the way to go. I just checked the current draw on my LED flashlight. 6 LEDs at 4.5Vdc was 36 mA Thanks. Roy

Smart guy, Airmad!

My Mom used to tell me that if I screwed up, 'fess up! So here it is, my case of blindness on electrical stuff, exposed for y'all to see... When you use an inverter to change 12VDC to 120VAC, it will (Duh!) take just as many amps to run the lamp! The law of conservation of stupidity... oops, meant the law of conservation of energy... DOESN'T say the same bulb that draws 1.08 amps at 12VDC can use 0.1 amps from a 12VACto 120VAC inverter.

So, here's what I figure. A 15-watt 12VDC incandescent domelight bulb will draw 1.25 amps. A 13-watt fluorescent bulb on a 12VDC ro 120VAC inverterwill draw 1.08 amps, plus 20 percent to run the inverter, or 1.296 amps. Both put out approximately the same amount of light, according to my photographic light meter. So it's your choice, dome light or fluorescent bulb, for an inside light. I'll take the softer light of the fluorescent bulb and the 10,000 hour bulb life.

Airmad, check me on this, plez. From what I can find out, LEDs produce about twice as much light per amp as an incandescent bulb. So if I had 0.625 amps worth of LEDs at 12VDC, I'd get about as much light as the incandescent dome light or the fluorescent bulb. I don't know how many LEDs that would take, but it looks like a big handful of LEDs would be needed to get the same light output. At 50¢ each, that's a big handful of money, too.

For backwoods use, the LEDs ARE most efficient. I just can't afford enough of them to read comfortably! Can anyone find me a white 60 LED array that costs $2 and works on 12VDC??