12v to 6v voltage droppers?

I have some 6 volt lights that I want to run in a 12 volt system. They are

25w. Do most FLAPS have just run-of-the-mill voltage droppers? Or do I need something more specific?

I couldn't find anything listed at the Autozone, Advance Auto, etc. websites.

JC Whitney (I know, I know!) lists two different ones:

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The 6/8 amp version should work for what I want to do, correct?

Or would this one be better?:

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Thanks for any help.

Reply to
Scott H
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You will need droppers specific to your load, esp since they are lamps.

Each 25W lamp needs a 1.5 Ohm dropping resistor, rated at 25 watts.

IOW, *each* lamp will waste an additional 25 watts beyond what the lamp draws. Your genny will have to make all that loss up.

A few possible sources:

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eBay

Speedy Jim

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Reply to
Speedy Jim

If you are running *pairs* of lamps, simply connect two in series. No dropper required! It does require that the bulb sockets _not_ be grounded.

Jim

Reply to
Speedy Jim

Scott,

Why not just replace the lights with 12v, and have better visibility? After all this is the least expensive part of the upgrade to 12v. You can also get H4 adapters that install directly into headlight inplace of sealed beam. Those make a world of difference.

Ant> Speedy Jim wrote:

Reply to
anton

Thanks for the help, Jim.

Before I saw your second message, I had asked an electrical engineer at work about this. As he was explaining something that sounded to me like a cross between quantum physics and ancient Greek, I was able to sheepishly mention your dropping resistor suggestion. He had an enlightened look and said that was an even better idea. :-) He gave me a rig with some resistors to try but I haven't had a chance to fool with it yet.

It is one pair of lamps.

If I understand your second message correctly, I can rig the lamps like this:

12v positive>>>> +6v lamp- >>>> +6v lamp- >>>>12v negative ... with no resistors at all.

Correct?

If you need to explain it further, pretend you're talking to a 3-year-old and then dumb it down from there. :-)

Thanks,

Reply to
Scott H

Thanks for the input, Anton. This isn't an upgrade to 12 volt, the car _is_ a 12v car. The reason I'm asking about this is because I already have the 6v lights. They're sealed beam and I like they way they look. Best of all, I think they're "kewl". ;-)

Reply to
Scott H

Yes, your diagram is correct.

Best of all....no waste!

Jim

Reply to
Speedy Jim

Thanks, Jim. You're the best.

Reply to
Scott H

"Speedy Jim" wrote ...

I had time to fool with this today and it worked perfectly (as if there were any doubt :-)

Thanks again.

Reply to
Scott H

"Speedy Jim" wrote ...

Ok, I'm back for more abuse, er, I mean, advice. :-)

With some coaching and advice from the EE at work, I've learned enough about using a meter to be really dangerous.

With the meter, starting at the battery, here's my diagram again with the values I've found in parentheses:

12v positive(12.4v)>>>> +6v lamp-(5.8v) >>>> +6v lamp-(5.7v) >>>>12v negative

I also checked the amperage between the lamps and got a value of 3.5amps.

1) With these values am I correct in using a 4amp fuse in this circuit? 2) Do I place the fuse between my power source and my switch? If not, where? 3) Is there a specific rating for the switch I need? 4) Using an ampacity chart as shown here:
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it looks like 14ga wire will do, correct? 5) Also, I'd like to wire these lights into the circuit that shuts off the headlights when the ignition is turned off (this is a '72 Super). Would that work if I pulled the power from the black/yellow wire that goes from the ignition switch to the fuse box, then to the light switch, as shown here?:
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6) Is this too much load to add to my system? ('72 Super with stock generator)

7) Is this enough questions? ;-)

Thanks for any help.

Reply to
Scott H

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.. it looks like 14ga wire will do, correct?>

1) Yes/No. Let's splurge and use a 5 Amp :-) 2) Yes. 3) 10 AMp would be a common rating. 4) Yes 5) Yes 6) No 7) Maybe 8) You're welcome...
Reply to
Speedy Jim

Once again, thanks Jim.

Reply to
Scott H

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