About a year ago I built myself a portable power station thanks to the build your own portable power station thread and I have put it to good use recently. I went through about a seven day stretch where the electricity in my area was out almost every evening for 3-5 hours. After suffering the first blackout for a few hours with just flashlights I plugged a table lamp into the inverter in my power station and man was it a relief. I ended up plugging my modem and wifi router into it as well and passed the time watching youtube clips and streaming videos. (Yes, I do have a generator and lots of fuel that I could have used but chose not to because I didn't want to winterize it again unless I absolutely had to).

Anyway, I decided that plugging a 120 volt AC table lamp into my inverter isn't the most efficient use of my 12 volt DC electricity and I went looking for a 12 volt DC table lamp with an efficient LED bulb. I needed a 12 volt table lamp with a cigarette lighter connector because I wired a cigarette lighter plug into my battery box. To my surprise I didn't find very much in the way of 12 volt LED table lamps. There were a few options but I decided to just built one myself by converting a 120 volt AC lamp to 12 volt DC lamp.

I am no electrician so I don't know if what I did is technically electrically safe. I'm just a dude on the internet and this is what I did. So take it for what that is worth.

Parts:

E26 MEDIUM to 1 Pin BAYONET Base Light Bulb Socket Converter Adapter - $10.95
Roadpro 12V Fused Replacement Cigarette Lighter Plug with Leads - $3.28
GRV Ba15s 1156 1141 High Power Car LED Bulb 24-5050SMD DC 12V Warm White Pack of 2 - $11.20 (In terms of light this LED is about equivalent to a 40 watt incandescent. I picked it because it only uses 2.5 watts and enough light for a bedroom)
Cheap 120 volt AC lamp from Target - $20.00
Wiring connectors (I used Anderson power poles)

Here are the parts that I used:



I just cut the 120 volt AC plug off the end of the cord and wired in the cigarette lighter plug (I used Anderson power poles but you could just use wire nuts or whatever). This is the only step that required me to be a little careful, paying attention to polarity. I read that some LED's will burn out if you wire them in reverse polarity. I don't know if this is true (someone with more experience can clarify that) so I played it safe and made sure to keep the polarity consistent. The standard E26 120 volt AC light bulb socket has the hot wired into the very bottom center of the socket and neutral wired into the side screw portion of the socket. Using my multimeter and its continuity setting I determined which wire in the lamp cord was wired to the center of the light bulb socket and made sure to wire that to the red wire of my cigarette lighter plug.


After the cigarette lighter plug was wired in I simply screwed in my light bulb adapter and my 12 volt DC LED bulb and plugged it into my battery box.


If you are interested I measured the current (amps) drawn by this LED and found it to be 233 milliamps on a fully charged 12 volt battery.


That's it! If my math is correct I can run for almost 18 days straight with this 12 volt LED lamp using a 100 AH battery. I hope this is useful to someone out there. Again, I'm not an electrician so try this at your own risk.

Good project!

Cool. Didn't know they made 12V screw in adapters like that. And it never occurred to me to convert a 120V lamp. A 12V RV light fixture would have been cheaper but a lot less fun, plus table lamps are more convenient than RV fixtures, which are designed to be permanently mounted.

I have an 1141 LED bulb that only draws 0.13 amps @ 12V. I assume it puts out fewer lumens than the ones you have, but still pretty bright. 12V LEDs are crazy efficient.

Your math is right, but only if you run your battery down to 0% (i.e., kill it dead permanently). So 9 days if run down to 50%, which is about as low as you should regularly run a deep cycle battery.

cool

Where did you get the Anderson PP in the third pic?  I need some for adding a power circuit to my tractor for a sprayer.

Thanks,

just google anderson power poles and you should be able to find a load of links. ebay and amazon are also good options.

I bought them here: http://www.powerwerx.com/anderson-powerpoles/

But mylt1 is right, you can buy them from a lot of places. I found out about them from people on this form and the ar15 ham radio forum.

You'll also need a tool for crimping: http://www.powerwerx.com/powerpole-accessories/tricrimp-crimping-powerpole-contacts.html

Nice write up

Good motivation!

LEDs are fun!