# 12 v DC light question



## City Bound (Jan 24, 2009)

I have found 12 volt light bulbs online that screw into standard size lamps. Can I take a standardized lamp, cut the power chord near the end, attach alligator clips to the ends of the wires, attach those alligator clips to a car battery, and then have the lamp run on DC without any danger?


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## Bearfootfarm (Jul 13, 2006)

Personally, I'd want larger wire than a standard lamp cord


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## City Bound (Jan 24, 2009)

why bear? 

What do you think of using jumper cables as a chord?


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## 12vman (Feb 17, 2004)

What kind of bulbs are they? (Standard incandesent? LED?)

Most run-of-the-mill screw in 12 volt incandesents that I've seen are ~50 watts. That's about a 4 amp draw. A standard length cord "should" handle that load as long as you don't lengthen it.

*Don't forget a fuse at the source! Ya never know..


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## Jim-mi (May 15, 2002)

Unless you have an "easy / cheap" way to charge the battery, stay away from those screw in incandesents . . . . . .they use so much current that your bat will get sucked down real fast . . . . . . . . .NOT the thing for a "grid down" time . . . . . .

Put your efforts into finding LED bulbs . . . . . .yes they are still pricy but that same battery could 'last' for two weeks compared to one of those incan's wiping out a bat charge in one night..................

The other day I took the time to look at what Home Despot is offering now in LED's
That industry is growing fast.........I was impressed...........


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## oldasrocks (Oct 27, 2006)

We use the 50 Watt 12V RV bulbs with good success. In 77 during a blizzard we found they provide safe light for up to 10 hrs hooked to a car battery. To recharge we carry the battery outside and hook to a vehicle to recharge.

They are a lot safer than any flame lamp or candle. I have several lamps we bought at garage sales for a buck and strip off the end and put clips on it.

I leave an extra battery on a 1 amp charger in the tornado shelter.


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## artificer (Feb 26, 2007)

oldasrocks said:


> We use the 50 Watt 12V RV bulbs with good success. In 77 during a blizzard we found they provide safe light for up to 10 hrs hooked to a car battery. To recharge we carry the battery outside and hook to a vehicle to recharge.
> 
> They are a lot safer than any flame lamp or candle. I have several lamps we bought at garage sales for a buck and strip off the end and put clips on it.
> 
> I leave an extra battery on a 1 amp charger in the tornado shelter.


If instead of the 12v incandescent lights, you went with a small inverter and LED's, the battery could last 10x as long. If you have 12V led's, its even better.

Our off grid chicken coop had the LED christmas tree lights (8.4 watts) on 16 hours a day, and it was powered off of 3 old 80amp-hr AGM batteries at freezing temperatures. They would last for more than a week without being recharged. I'm a big fan of the christmas tree lights since they're 110V, and provide diffuse light.

You can get 12V LED bulbs in a wide variety of styles. Either automotive replacement lights with bayonet ends, or screw in type. Unless you want to use a normal light fixture, it doesn't make too much sense to convert the fixture to just use 12v bulbs.

Michael


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## City Bound (Jan 24, 2009)

Jim-mi said:


> Unless you have an "easy / cheap" way to charge the battery, stay away from those screw in incandesents . . . . . .they use so much current that your bat will get sucked down real fast . . . . . . . . .NOT the thing for a "grid down" time . . . . . .
> 
> Put your efforts into finding LED bulbs . . . . . .yes they are still pricy but that same battery could 'last' for two weeks compared to one of those incan's wiping out a bat charge in one night..................
> 
> ...


I want a screw in led bulb but they are $25 each.

Right now I have standard table lamp, CFL bulb, an inverter, and a 12 volt marine?rv battery. I have have been using it at night for about three weeks now and it is still going strong. I was thinking that 12v bulb and going DC would make the battery last three times longer.


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## City Bound (Jan 24, 2009)

12vman said:


> What kind of bulbs are they? (Standard incandesent? LED?)
> 
> Most run-of-the-mill screw in 12 volt incandesents that I've seen are ~50 watts. That's about a 4 amp draw. A standard length cord "should" handle that load as long as you don't lengthen it.
> 
> *Don't forget a fuse at the source! Ya never know..


15 watt

This is them: http://www.amazon.com/Camco-41313-1...ref=sr_1_1?s=hi&ie=UTF8&qid=1328250440&sr=1-1


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## 12vman (Feb 17, 2004)

CB..

Nice choice! Just be very careful with polarity. Connect them wrong (Reverse Polarity) and you'll fry them in a second! 

With D.C. you're either 100% right or 100% wrong! ANY bulb that uses a ballast must be connected correctly the first time or you will have an expensive paper weight..


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## City Bound (Jan 24, 2009)

thanks 12. they are not cheap, but they are a better price then most that I saw on line.


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## rickfrosty (Jun 19, 2008)

artificer said:


> If instead of the 12v incandescent lights, you went with a small inverter and LED's, the battery could last 10x as long. If you have 12V led's, its even better.
> 
> Our off grid chicken coop had the *LED christmas tree lights (8.4 watts) on 16 hours a day, and it was powered off of 3 old 80amp-hr AGM *batteries at freezing temperatures. They would last for more than a week without being recharged. I'm a big fan of the christmas tree lights since they're 110V, and provide diffuse light.
> 
> ...


*LED christmas tree lights (8.4 watts) on 16 hours a day, and it was powered off of 3 old 80amp-hr AGM *

This sounds good, but batts hooked up parallel for 12 v, right ? And which of the old plug prongs was pos/neg ? (I know, I should know that ). Or maybe it doesn't matter ?


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## artificer (Feb 26, 2007)

rickfrosty said:


> *LED christmas tree lights (8.4 watts) on 16 hours a day, and it was powered off of 3 old 80amp-hr AGM *
> 
> This sounds good, but batts hooked up parallel for 12 v, right ? And which of the old plug prongs was pos/neg ? (I know, I should know that ). Or maybe it doesn't matter ?


Sorry, should have been more explicit.

Circuit is: bank of 3 batteries. 12V timer that turns on battery power to small inverter. 200' of extension cords to the coop, with the LED lights on the far end.

Michael


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## Jim-mi (May 15, 2002)

No your bat will not last "three times longer"......

Basic electricity current/voltage here..........

If you were to get a 12vdc LED lamp then yes . . . .your bat would last many times longer . .and be far happier . . . .

I have a 12vdc LED light with may be 25 LEDs in it (standard screw in) shining on the ceiling (night light good for walking around) . . .it has been ON continually for 4 or 5 years . . . . . .I forget to turn it off in the day time . . . . . .

Yes I paid a pretty buck for it . . . . . But to me it is well worth it............


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## artificer (Feb 26, 2007)

City Bound said:


> I was thinking that 12v bulb and going DC would make the battery last three times longer.


I'll add a followup to Jim-mi's response: 

The reason you would have more battery time with a 12V LED is that you don't have the losses of the inverter. My big Xantrex inverter has a 9watt standby loss. If you have a 9 watt LED, then you're only at 50% efficiency. You also have losses going from DC to AC, and back to DC. Switching from this large inverter and a 120v AC LED to a 12V one will double your battery life, everything else being equal.

If you have long runs of 12v wire to power the LED's, you'll lose some of the efficiency gains. I wouldn't want to think of what the losses would be in my 200' run of small gage extension cord wire if I tried running 12V DC instead of AC.

With a small/efficient inverter, I don't see you getting 3x the life by going to DC. Maybe a little better, but for me the convenience of AC outweighs the slight improvement in overall efficiency. Since you wanted screw in bases anyways...

Michael


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