Tapping Power Outlet Wires

[hayze]

Hello.

I was wondering if it is safe to tap the power outlet wires in my car (the red/black wires that power my cig lighter) with some kind of LED. LEDs dont use a ton of current, so i dont think i'll need a relay.

I could imagine that the power outlet wires can handle some current, so a few 5-8mm leds (without relay) shouldn't overdraw the wire, right?

The leds I'm looking at draw 21 milliamperes if i rememeber correctly.

let me know what you think.

and thank you

 

[Lynx_Arc]

wired properly it shouldn't be a problem at all if a circuit in the car can handle the current you could add whatever you wanted to. I have tapped into the ignition circuits and wired stuff up so it only ran when the key was on. I do recommend you make it to where you can shut it off as any power drain over time can drain your battery down if it is not recharged periodically.

 

[buickid]

Check your owners manual for the fuse rating for the Cigarette Lighter/Accessory Outlet. It should be something like 10 or 15 amps.

 

[hayze]

Okay I just checked. The combined power rating for both outlets is 120 watts (10 amps).

The 5mm LEDs I plan to use draw 20 milliamps, so I should be able to wire 3 or 4 of these, right?

 

[LukeA]

Okay I just checked. The combined power rating for both outlets is 120 watts (10 amps).

The 5mm LEDs I plan to use draw 20 milliamps, so I should be able to wire 3 or 4 of these, right?

You should be able to wire 3 or 4 hundred.

 

[Illum]

You should be able to wire 3 or 4 hundred.

heh...if I understand you right, sure...but FUSE IT!
its like setting a 470Ω + 5mm LED to the 12V terminals on your jumper chords...it'll light up telling you that your clamps are live, but it doesn't seem to affect anything. now if the LED's pins touch...hehehe

instant melt-through of the contact legs...and expect plenty of light while its at it.

I'm sure TigerhawkT3 would agree that even a small 12V 3AH battery can vaporize 14 gauge copper braid like its a rubber band...so FUSE IT OR GET BURNED when something FAILS

 

[hayze]

heh...if I understand you right, sure...but FUSE IT!
its like setting a 470Ω + 5mm LED to the 12V terminals on your jumper chords...it'll light up telling you that your clamps are live, but it doesn't seem to affect anything. now if the LED's pins touch...hehehe

instant melt-through of the contact legs...and expect plenty of light while its at it.

I'm sure TigerhawkT3 would agree that even a small 12V 3AH battery can vaporize 14 gauge copper braid like its a rubber band...so FUSE IT OR GET BURNED when something FAILS

Are you referring to an inline fuse, or something else?

If the LED pins touch, will the inline fuse prevent damage to my car?

Also, what are the LED pins? Do you mean the two contacts the come out of the back of the bulb? There is a rubber sheith around them on the wired LEDs I have. Shouldn't that protect it?

 

[65535]

99% of the time all 12 volt power taps are on circuit branches with a 10A inline blade type fuse, normally found in the fuse box of your car. You really can't do damage to your car through those plugs. I wouldn't worry too much about fusing it any more than it already is.

You have 12 volts and 10 amps at your disposal. You can power hundreds of 5mm led's or a dozen or so MC-E/P7 LEDs.

 

[Ken_McE]

I was wondering if it is safe to tap the power outlet wires in my car (the red/black wires that power my cig lighter) with some kind of LED.

Yes.

LEDs dont use a ton of current, so i dont think i'll need a relay.

Correct

I could imagine that the power outlet wires can handle some current, so a few 5-8mm leds (without relay) shouldn't overdraw the wire, right?

Correct.

If the LED pins touch, will the inline fuse prevent damage to my car?

Yes.

Also, what are the LED pins? Do you mean the two contacts the come out of the back of the bulb?

I expect he does.

There is a rubber sheith around them on the wired LEDs I have. Shouldn't that protect it?

It should, but who knows what the assembler was doing when they got to that particular unit back in China somewhere? Adding a fuse is easy, and we all screw up from time to time when wiring things. The fuse makes for easy fixes if you miss something.

Are you referring to an inline fuse, or something else?

I expect he was. Any fuse would work though.

 

[QualityAir]

Use a 1 amp (or smallest you kind find) fuse to the LED's to prevent a fire if the LED's or wire short or ground, the wire used to the LED's may not be rated at the same amperage as the main fuse in the auto's block.

 

[hayze]

First, thanks Ken McE for the reply.

Use a 1 amp (or smallest you kind find) fuse to the LED's to prevent a fire if the LED's or wire short or ground, the wire used to the LED's may not be rated at the same amperage as the main fuse in the auto's block.

Are you saying that the LED wire may not be able to handle the power supplied by the car? Are you also saying that a defective or damaged LED can cause a fire? If so, is the 1 amp inline fuse guaranteed to prevent damage in these 2 events?

Many people with the same exact car as me do the same exact tap to the power outlet wires and to the storage unit light's wires. And their LED wires have held up without problems. Maybe this proves that the LED wires can handle the car's power supply???

Also, if I wire the 5mm LED to a 9V battery and let it shine for an hour or two, does that prove that the LED itself won't screw up in my car?

Thanks everyone for the replies.

 

[hayze]

I'm back. i have a friend who tried to tap his cubby light with an LED, but when he cut the red wire, he blew some electrical box under the hood. Just simply cutting the red wire caused this damage. How could this have happened? Do you think it was because he didn't disconnect the battery before cutting?

I can't reach this person to ask him directly, but what do you think? If you disconnect the battery, then nothing should short out while cutting wires, right?

 

[buickid]

Yes. Its recommended that you disconnect the negative/black/ground cable from your battery whenever you work on your car, unless of course you need the car to have power. (Of course common sense will dictate that some tasks such as changing wiper blades or checking the oil level don't require this precaution, but then again, common sense isnt all so common :duh2

Also, perhaps your friend let a wire slip and touch part of the car's metal frame. The entire frame is a ground point, so any +12V wire can cause a short to the frame

 

[hayze]

I see,

I think it also could have been just because he touched the live wire with his hand. Can't your body also hold a ground charge if you're touching a piece of metal elsewhere?

I also wanted to ask this: if i tap a few wired LEDs (22 ga.) to a 30 gauge light wire, is the gauge discrepancy a problem?

 

[LukeA]

I also wanted to ask this: if i tap a few wired LEDs (22 ga.) to a 30 gauge light wire, is the gauge discrepancy a problem?

Not a problem. 30ga can still carry more current than you're passing through it.

 

[hayze]

^^so the amperage is what matters, not the gauge?

 

[LukeA]

^^so the amperage is what matters, not the gauge?

Right, as long as the gauge can handle the amount of current passing through it.

Here's a chart, see the "Maximum amps for chassis wiring" column.

 

[hayze]

special thanks

this chart is very useful

Let me just confirm that I interpreted it correctly:
The column states that the max amperage for 30 gauge is 0.86 amps or 860mA.

This means that if the already existing light that the wire supplies draws 36mA, then I can wire the following number of 20mA LEDs:

((0.86 * 1000) - 36) / 20 = 41.2 LEDs

haha, not that I'm going to actually use 41 LEDs... more like 5 or 6.

I just want to make sure I calculated it right.

 

[LukeA]

special thanks

this chart is very useful

Let me just confirm that I interpreted it correctly:
The column states that the max amperage for 30 gauge is 0.86 amps or 860mA.

This means that if the already existing light that the wire supplies draws 36mA, then I can wire the following number of 20mA LEDs:

((0.86 * 1000) - 36) / 20 = 41.2 LEDs

haha, not that I'm going to actually use 41 LEDs... more like 5 or 6.

I just want to make sure I calculated it right.

That would be correct if the supply voltage and the voltage in the car were the same, but your calculations are correct for current (You just forgot voltage). In reality, you could have 41.2 parallel strings of LEDs each drawing 20mA, or about 160 LEDs total in a 13V automobile.

 

[hayze]

^^cool thanks

I'm not understanding the voltage part though.

Could you explain how you estimated 160 LEDs? I just want to understand how the chart shows you that.

And what do you mean by parallel strings of LEDs?

Anyway, using 41.2 LEDs is safe (with regard to current and voltage) for the 30 gauge wire that already has a 36mA LED, right?