TheSamba.com :: View topic - Convert your old 120v Christmas lights to 12v- pics included

Thu Dec 18, 2008 12:41 pm

Well, it's Christmas again . . . Time to celebrate by lighting up the bus!

Not everyone knows that your old strands of 120v Christmas lights can be easily adapted to run on 12v (or 6v !) without any additional cost or parts. Best of all, you don't need a power inverter. Why make 120v when your lights can run straight from the battery (well, the 12v fuse panel) ?

This makes good use of those old non-working strings and frees up a little money for the rest of the Christmas budget. Heck, put some more gas in the bus and drive through town making people smile!

I drew up the following diagram of how to re-wire your lights . . . Hope it helps! Also included some pics of our bus all decked out in 12v glory!

Merry Christmas, from our house to yours!!!

-Klauss

Thu Dec 18, 2008 12:59 pm

That's a handy tip for awning owners who want to light up their awning while camping as well. Nice bus--I like the interior (custom?) too!

Thu Dec 18, 2008 1:22 pm

Nice! What kind of seats are those?

Thu Dec 18, 2008 2:30 pm

Dude! is there a microwave in there!?!?

Thu Dec 18, 2008 2:58 pm

Thanks for the comments . . .

- Yeah, the interior is custom. Hand-built from free stuff.

- The seats were from a minivan, the two center captains chairs. Cut off the bases and welded up mounts.

- Of course it's a microwave, Dude!!!

-Klauss

Thu Dec 18, 2008 11:09 pm

i'm a stock-bus kind of guy, but that microwave is bitchin!!!! :twisted:

Fri Dec 19, 2008 12:10 pm

With a name like "Let There Be More Light", are you planning to rewire a few strands yourself? I think there could also be a lot of possibilities for some cool permenant interior lighting using this method . . . :-k

Now if I can just figure out how to convert the microwave to 12v !?!

-Klauss

Fri Dec 19, 2008 12:46 pm

I am amazed to see this mostly unsafe AC device.
In case it gets cut you get a full 120 volt AC to kill somebody. The bulbs will not lower this 120v significantly.
They sell them too in countries where AC is 220v. I think there is a warning, not to use outdoors, but who reads instructions ?

Converting to 12 volt is a nice idea and, then it becomes perfectly safe.

I will never have such a thing hooked on main AC with children and pets around.

Sat Dec 20, 2008 1:27 pm

Now I know what to do with all those light strings that don't work. cut'em up and hang'em on the bus...cooooool info!

Sun Dec 21, 2008 1:40 pm

akscooter,

That's exactly what I did - I was gettin ready to throw them out. Got tired of climbing up on the roof every time the wife said part of the string was out. We bought new ones for the roof, old ones are now for the bus!

Doesn't matter if they worked or not since you hack them up and reassamble to go 12v. You know, I think our bus was built mostly from other junk that didn't work . . . Yeah, that is cooool!

-Klauss

Fri Dec 20, 2019 4:38 am

Hey, man. Could you repost the pics for the lights adaptation? Original ones are down from photobucket.
Thanks!

Fri Dec 20, 2019 7:02 am

I don't know for sure what the OP did, since the pics and discussion was originally posted 11 years ago...

However, I can tell you what I did when I was in high school.

Not fully understanding at the time the differences between alternating current and direct current (though it doesn't matter much in this instance), but understanding that a typical Christmas light string was 100 lights, and 12v was 10% of the 120v that our house ran on... I cut down some old strings and twisted the wires together to make several short strings of approximately 10 bulbs.

To power those lights in the ancient Chevy Celebrity that I drove in high school, I simply twisted the wire from each side of the light strings to the map light socket, having removed that bulb. So I just had to tap the button to turn the lights on!

I had several of these mini strings of lights going around the headliner of that car. I also wired up a set and tucked them in around the windshield of a Beetle I had at the time (and once got pulled over because, apparently, blue lights aren't legal on a civilian car).

In retrospect, 20-odd years later, the typical non-LED Christmas light string in the US actually has two or three circuits of 50 lights each, so one could probably make longer strings and have them light up on 12v.

Using a string of LED bulbs, you may well be able to make much longer strings and have them light up. I'm not totally certain how all that works with the resisters and such that make an LED string work properly.

It would be fairly simple to do a little experimenting with a strand of old lights and a 12v battery. Just cut the plug off an end, strip a wire, and touch each end to the posts on the battery and see what happens!

Typing this out makes me want to do some experimenting with some strings of lights that I happened to save for some kind of project after a rat got in the attic and chewed them. I just threw the longer chunks in a plastic bag thinking I would come up with some possible use for the LEDs.

Total side note: One of my favorite roommates I ever had was from Venezuela. I tried to get him to bring me back a capybara when he went back to visit family one time.

Fri Dec 20, 2019 9:47 am

After writing out that last response, I got curious and did some googling...

Found this:

https://michaelbluejay.com/batteries/dc-christmas-lights.html

About 3/4 of the way down is a section called, "Rewiring Christmas Lights to Run off of Batteries."

That should tell you (and me, I guess!) what you/we need to know!

The calculations are based on 12v, though your car likely is running at closer to 13.5-14v if everything is totally up to snuff, so you can adjust your number of bulbs accordingly. With old school bulbs, all that would really happen if you had one or two too many is they'd be a little more dim.

Fri Dec 20, 2019 10:45 am

One thing to be aware of: when these lamps burn out, there's a little fusible device inside that effectively "shorts" out the dead bulb, which keeps current flowing to the rest of the string. Not a big deal when running lots of lamps on 120 vac, but starts to get significant when running a few lamps on 12 volts. Each burned out bulb increases the voltage on the remaining lamps a bit. Best to replace burned out bulbs ASAP to avoid cooking the remaining lamps...

Fri Dec 20, 2019 11:03 am

telford dorr wrote: One thing to be aware of: when these lamps burn out, there's a little fusible device inside that effectively "shorts" out the dead bulb, which keeps current flowing to the rest of the string. Not a big deal when running lots of lamps on 120 vac, but starts to get significant when running a few lamps on 12 volts. Each burned out bulb increases the voltage on the remaining lamps a bit. Best to replace burned out bulbs ASAP to avoid cooking the remaining lamps...

my 120v grain of wheat lamp strings lose 1/2 the string when a bulb goes.

Fri Dec 20, 2019 11:24 am

Maybe check at an RV outfitter and see what they have on their shelves.