Install cigarette lighter plug

jmeny

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Sep 11, 2007
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So I'm not gonna pretend to be an expert on electrical, I'm not. Years ago I hooked up a switch panel to a few accessories (lights, bilge, etc) but that's about the extent of what i've done myself.

I wanted to add a cigarette lighter style power outlet to charge my phone for gps purposes. The attached diagram shows how i tried to hook it up (i didn't include the other accessory connections as those still work fine). Obviously i did something very wrong, both negative and positive wires going to the outlet immediately melted and started smoking with nothing plugged into it. Really need some advice here, feel like there's something simple i missed.

Would it be better to just run a positive and negative wire direct from the battery to the outlet? I was hoping to not have to do that, which is why i bought the positive bus.

Thanks,
Joe
 

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batman99

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For my Boat, I ran an aux outlet (aka: cigarette lighter outlet) for our 12 volt cooler via direct thick 10 gauge black wire to "-" post on battery. I then ran a thick 10 gauge red wire to the "+" post of the battery. Within 12" of "+" battery post, I also installed a properly sized ATC fuse within a protection rubber cap. Fuse size is calculated via load (surge) in watts / 12 volts. For example, 90 Watts draw / 12 = 7.5 Amp. If fuse size not available, then round up to next available size. For example: 95 Amps for 7.9 Amp load (use 10 Amp fuse instead). If one splices into existing factory wiring and its wire is thin 14 gauge or too small size fuse, it will blow. And, blow other things that might need that factory thin wiring area.

Hope this helps.
 
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alldodge

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So I'm not gonna pretend to be an expert on electrical, I'm not. Years ago I hooked up a switch panel to a few accessories (lights, bilge, etc) but that's about the extent of what i've done myself.

I wanted to add a cigarette lighter style power outlet to charge my phone for gps purposes. The attached diagram shows how i tried to hook it up (i didn't include the other accessory connections as those still work fine). Obviously i did something very wrong, both negative and positive wires going to the outlet immediately melted and started smoking with nothing plugged into it. Really need some advice here, feel like there's something simple i missed.

Would it be better to just run a positive and negative wire direct from the battery to the outlet? I was hoping to not have to do that, which is why i bought the positive bus.

Thanks,
Joe

Joe

You wired it correctly, my guess is something was bent and caused the + and - to connect together. Only thing missing in you drawing is a 20 AMP fuse on the + side to the center conductor.
 

jmeny

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Batman, thanks for the advice on the main fuse, i had thought about putting one in but it's a small boat and figured the minor amp draw from my accessories wouldn't be a problem. I might reconsider that though. As for running the 10 gauge wire direct to the battery, i'm still concerned there's some other issue at work here since i'm connected via the bus terminals...

Alldodge, good suggestion on the 20 amp fuse, i just knew i wouldnt be doing anything with the outlet other than charging a cell phone, but obviously bad things can still happen unexpectedly. Your idea that the positive and negative could have connected made me question the unit itself, since no wires were touching. I attached an image of the one i have...if this is an all metal unit, how is it possibly separating the + and -? I don't see any possible way they are buffered from each other?

Thanks for the quick responses, I appreciate it.

-Joe
 

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alldodge

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Alldodge, good suggestion on the 20 amp fuse, i just knew i wouldnt be doing anything with the outlet other than charging a cell phone, but obviously bad things can still happen unexpectedly. Your idea that the positive and negative could have connected made me question the unit itself, since no wires were touching. I attached an image of the one i have...if this is an all metal unit, how is it possibly separating the + and -? I don't see any possible way they are buffered from each other?

Don't see how It could have happened, but the only way you get a short is if somehow the wires connected together, there is no other way. All I can suggest is look real close to what managed to get the two wires/connections together
 

StarTed

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Always fuse for the wire. The fuse should be as close to the source as practical. In this case to the + bus. You could put a smaller fuse in for the device but never greater than for the wire size. The only exception is for the starter which is not fused.

Where I worked before retiring we once tested fuses to determine characteristics and verify the manufacturer's claims. Tests are a one time event but it is amazing how much current a fuse can carry for a short time. One has to be able to carefully control the current in order to perform such tests. An example is a 10 amp fuse can carry 50 amps for a few seconds. Then there are all kinds of fuses, slow blow ones for devices that need protection and have starting surges and semi-conductor fuses that will blow at the rating in 1/4 cycle AC. Fusing is a trade in itself but manufacturers are usually very knowledgeable and are very helpful when asked.

AllDodge has some good advise as usual.

To add to batman99's advise. Fuses are designed to carry amperage. Wattage can be used to calculate the amperage but has no affect on the fuse other than for the calculations. In the boating world we're usually talking 12 VDC so we can divide the wattage by 12 to get amperage to select the minimum size fuse. The maximum size is determined by the wire size. For most wires one can consider 10 A for 16 AWG, 15 A for 14 AWG, 20 A for 12 AWG, 30 A for 10 AWG, etc. The voltage doesn't matter as long as the fuse is rated for higher voltage than your use. You can use a 600 volt rated fuse on a 12 volt circuit with no ill effects except maybe to your wallet.

That said, it is best to use fusing designed for your application. Automotive fuses are fine as long as the holder is designed for marine applications due to moisture probabilities.

I wonder if the cigarette lighter plug might have gotten somehow connected backwards and was mounted in a metal panel. Just a thought.
 

NYBo

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The only explanation is a dead short in the socket or wiring.

You should use a fuse no larger than the rating of the socket or the wiring. Most accessory sockets are rated for 10 amps.
 

Silvertip

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That power outlet has an all metal shell. If you inadvertently wired the +12 v feed to the terminal that is really the ground side of the outlet you have a direct short. That is provided the outlet is mounted to a metal part of the boat. Even though the battery negative terminal is not connected to the hull directly, the hull generally gets connected to the battery via the engine mounting bolts. If that's not the case, there is a problem with the outlet itself. Disconnect the wires and use an ohm meter across the two terminals. Should read open circuit. If not, you have a bad outlet.
 
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alldodge

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Ya, know I just had a brain fart, ouch, but if the pos was connected to the outer case and not center post you would get a short if it was grounded to the panel it was installed in
 

gm280

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jmeny, with all the expert advice already posted on this, all I have to say is, make sure you replace the melted and burnt wires before trying again. Don't try to reuse those wires now. It will cause troubles either now or down the road. JMHO!
 

jmeny

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Thanks for all the suggestions everyone, will have to look into this some more. It is mounted in a wooden dash, not metal. Either way will be replacing the wires, they are shot and it's only a couple bucks to replace them. Unless the instructions were backwards and the hot was supposed to go to the ground and vice versa i'm thinking the outlet might be bad, but an ohm meter is a good idea.
 

gm280

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Thanks for all the suggestions everyone, will have to look into this some more. It is mounted in a wooden dash, not metal. Either way will be replacing the wires, they are shot and it's only a couple bucks to replace them. Unless the instructions were backwards and the hot was supposed to go to the ground and vice versa i'm thinking the outlet might be bad, but an ohm meter is a good idea.

Just wire up the next one with the positive going to the center terminal and the negative (ground) going to the shell of the lighter. You should have no problems...unless there is a defective cigarette lighter.

I have actually installed two such lighters in my boat. And both are not for cigarettes either. One is setup with a USB port adapter to allow my wife to charge her phone if she wants.
 

tav

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i have a fuse panel on my boat and just wired the hot to a (i forget) 10 amp and the white to the ground buss bar. waalaa.....power.
 

Silvertip

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Every power outlet has a maximum current rating normally printed on the package. Use a wire gauge and fuse that appropriate for that rating, not what you might plug into it.
 
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