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Old 09-01-2008, 02:25 PM   #1
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Default car cigarette lighter watts??

i want to put an adapter that allows me to plug in outlets through the cigarette lighter in my car. If i used a (120 V~60Hz) 38W guitar amp (connect with the outlet adapter), would it kill my car battery (optima red top) or blow a fuse somewhere?
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Old 09-01-2008, 02:53 PM   #2
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Default Re: car cigarette lighter watts?? (uses0ap)

How many amps is this amp drawing?
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Old 09-01-2008, 02:55 PM   #3
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Default Re: car cigarette lighter watts?? (Haleiwa-Brando)

Quote:
Originally Posted by Haleiwa-Brando
How many amps is this amp drawing?
it all depends on the amps that its' drawing. well mostly
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Old 09-01-2008, 04:43 PM   #4
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Default Re: car cigarette lighter watts?? (uses0ap)

for my CL the fuse is 10amp but that is 2 outlets so usable wattage is max 120W
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Old 09-01-2008, 04:45 PM   #5
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P (wattage) = I(amps) x E (voltage)

If you know any two of those you can figure out the 3rd. Just plug in numbers and use simple 4th grade algebra.
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Old 09-01-2008, 05:57 PM   #6
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Default Re: (IslandSi)

Quote:
Originally Posted by uses0ap
i want to put an adapter that allows me to plug in outlets through the cigarette lighter in my car. If i used a (120 V~60Hz) 38W guitar amp (connect with the outlet adapter), would it kill my car battery (optima red top) or blow a fuse somewhere?
They do make inverters that can handle this much power, they will need to be hard wired to your battery, and used with the car running. Nothing that plugs into a cigarette lighter will work... at least safely.
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Old 09-02-2008, 12:30 AM   #7
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While the amp is rated for 38W, I'm sure that the actual draw from the outlet is a hell of a lot more than the .3A posted above. Post the manufacturer and model # of the amp and I can do a bit of googling to find the technical specs for you. Something just doesn't seem right. I mean, my cell phone charger pulls .2 amps. No way that an amp is only drawing .3A.
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Old 09-02-2008, 12:33 AM   #8
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Default Re: (IslandSi)

Quote:
Originally Posted by Haleiwa-Brando
How many amps is this amp drawing?
You can figure that out from his post.

Quote:
Originally Posted by Cypher0117

it all depends on the amps that its' drawing.
Which you can figure out from his post.

Quote:
Originally Posted by YeuEmMaiMai
for my CL the fuse is 10amp but that is 2 outlets so usable wattage is max 120W
This isn't a 12v device.

Quote:
Originally Posted by IslandSi
P (wattage) = I(amps) x E (voltage)

If you know any two of those you can figure out the 3rd. Just plug in numbers and use simple 4th grade algebra.
So why didn't you answer the question?

Quote:
Originally Posted by JDM_Ej

They do make inverters that can handle this much power, they will need to be hard wired to your battery
No

Quote:
Originally Posted by JDM_Ej
and used with the car running.
No

Quote:
Originally Posted by JDM_Ej
Nothing that plugs into a cigarette lighter will work... at least safely.
No


Quote:
Originally Posted by uses0ap
i want to put an adapter that allows me to plug in outlets through the cigarette lighter in my car. If i used a (120 V~60Hz) 38W guitar amp (connect with the outlet adapter), would it kill my car battery (optima red top) or blow a fuse somewhere?
P = I x V
38 = I x 120

∴ I(rms) = 317 mA


That is very low current. You'll be fine.
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Old 09-02-2008, 12:36 AM   #9
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Default

Nice ninja edit. But like I said in my above post, there's no way in hell an amplifier is only pulling a third of an amp.
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Old 09-02-2008, 12:39 AM   #10
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Default Re: (IslandSi)

Quote:
Originally Posted by IslandSi
While the amp is rated for 38W, I'm sure that the actual draw from the outlet is a hell of a lot more than the .3A posted above. Post the manufacturer and model # of the amp and I can do a bit of googling to find the technical specs for you. Something just doesn't seem right. I mean, my cell phone charger pulls .2 amps. No way that an amp is only drawing .3A.

That's because your phone is low voltage. If the amp was a 12v device, the current pull would be 3.17 A.


Quote:
Originally Posted by IslandSi
Nice ninja edit. But like I said in my above post, there's no way in hell an amplifier is only pulling a third of an amp.

You simply don't understand the direct relationship between voltage and current. But what do I know, I'm only an EE who designs and builds circuits all day every day.
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Old 09-02-2008, 12:46 AM   #11
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Default Re: (Legion_2)

Quote:
Originally Posted by Legion_2

This isn't a 12v device.
well duhhhhhhhhh.... Click the image to open in full size.

"i want to put an adapter that allows me to plug in outlets through the cigarette lighter in my car"

so I gave him typical wattage one can expect from 12V @ 10amp....in reality it is more like 14V @ 10amps when the car is running....... the adapter that he uses must draw LESS than 10 amps or 120W..

and D/C to A/C converters are not exactly the most efficient things out there you know.........

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Old 09-02-2008, 12:57 AM   #12
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Default Re: (Legion_2)

Quote:
Originally Posted by Legion_2
You simply don't understand the direct relationship between voltage and current. But what do I know, I'm only an EE who designs and builds circuits all day every day.
I understand the relationship just fine. It's just that .3A seems like a real low number for something like a guitar amp to be pulling.
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Old 09-02-2008, 01:00 AM   #13
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Default Re: (YeuEmMaiMai)

Quote:
Originally Posted by YeuEmMaiMai
and D/C to A/C converters are not exactly the most efficient things out there you know.........
They also create a lot of NOISE since they're basically creating a fake alternating current. Probably not the best thing to use in sound producing equipment.

They do make some real nice true sine converters, but they cost a hell of a lot more than the 40W plug in types the OP is referring to.
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Old 09-02-2008, 01:30 AM   #14
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Default Re: (IslandSi)

Quote:
Originally Posted by YeuEmMaiMai
and D/C to A/C converters are not exactly the most efficient things out there you know.........
That isn't worth mentioning. Compensating for losses isn't going to raise the 0.3A anywhere near the 10 - 15A fuse limit. 3% efficiency? I don't think so.


Quote:
Originally Posted by IslandSi

I understand the relationship just fine.

You clearly, clearly don't. Otherwise you wouldn't be saying stupid stuff like this:

Quote:
Originally Posted by IslandSi
They also create a lot of NOISE since they're basically creating a fake alternating current. Probably not the best thing to use in sound producing equipment.
I guess the OP better halt his plans for his in-cabin studio then.
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Old 09-02-2008, 01:37 AM   #15
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Default Re: (Legion_2)

Quote:
Originally Posted by Legion_2

That isn't worth mentioning. Compensating for losses isn't going to raise the 0.3A anywhere near the 10 - 15A fuse limit. 3% efficiency? I don't think so.

You clearly, clearly don't. Otherwise you wouldn't be saying stupid stuff like this:

I guess the OP better halt his plans for his in-cabin studio then.
lol you're not the only one who has a EE degree and understands about designing circuits.........personally I would not be using a noisy Inverter to power an audio amp.......but hey what do I know.........lol Click the image to open in full size.
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Old 09-02-2008, 01:50 AM   #16
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Default Re: car cigarette lighter watts?? (uses0ap)

Quote:
Originally Posted by YeuEmMaiMai
personally I would not be using a noisy Inverter to power an audio amp
Like I said, the OP had better cancel plans for his in-car recording studio. And everyone should probably throw away their tickets to his in-car performance this weekend.


Quote:
Originally Posted by YeuEmMaiMai
but hey what do I know.........lol Click the image to open in full size.

You know how to follow the GDD protocol:

1. Someone asks a question.
2. 9 people read the question and make worthless, un-helpful posts.
3. The 10th person answers the question.
4. Everyone else comes back to nitpick, split hairs, and post any extraneous info that is even remotely related to the topic in an attempt to seem useful, intelligent, or simply to "win."


Original questions:


Quote:
Originally Posted by uses0ap
would it kill my car battery
No

Quote:
Originally Posted by uses0ap
or blow a fuse somewhere?
No, although this would in fact be the worst case scenario if the amp draws too much current. Even shorting the circuit to ground won't burn the wires.


Click the image to open in full size.

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Old 09-02-2008, 07:01 PM   #17
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Default Re: (Legion_2)

Quote:
Originally Posted by Legion_2
That's because your phone is low voltage. If the amp was a 12v device, the current pull would be 3.17 A.

You simply don't understand the direct relationship between voltage and current. But what do I know, I'm only an EE who designs and builds circuits all day every day.
A 38W amp is probably going to draw ALOT more than 3.17A at 12V. The power rating of an amp is typically the OUTPUT, and NOT the consumption. Typically, amps are somewhere around 50-60% efficient. So, in order to be conservative about how well this will all work, we should probably assume that this amp is going to draw TWICE the amount of power that its output is rated at (76W). This means that the amp would probably draw about 6.34A at 12V (most appliances actually list the amp draw at 120V somewhere - multiply this by a factor of 10). Of course, these inverters are not 100% efficient. But after using them for quite a few years, I have come to the conclusion that they are actually not too bad efficiency-wise (even if your typical cheapo inverter CAN'T produce a good sine wave) - probably around 90% efficient. This brings current draw up to around 7A, which is well below the 10-15A rating of a typical cigarette lighter fuse.

A couple more things. I should add that I have used cigarette lighter inverters to run MANY things that draw AT LEAST this much power from the lighter with no problems. Just be sure that you use an inverter with a large enough power rating. Those dinky little things that have the cigarette lighter plug AND inverter in the same case that put out ~30-40W will not work. I would recommend 100W or more. Also, if this is something you are REALLY serious about doing ALOT, I would consider having wires going directly to the battery to run your inverter. Perhaps you could have a second cigarette lighter under the dash for just this purpose. The issue here is the size of the wires that supply power to a typical cigarette lighter: they tend to be VERY small (around #18AWG). And because of this, voltage drop between the battery and lighter will be significant. This will cause your inverter to sound the alarm fairly quickly. 10AWG or 12AWG would be a better size to use. Of course, direct wiring has the disadvantage that, once you hear the alarm with THIS setup, your battery might be too discharged to start the car.

Quote:
Originally Posted by IslandSi
They also create a lot of NOISE since they're basically creating a fake alternating current. Probably not the best thing to use in sound producing equipment.
Cheap inverters typically produce a kind of square waveform called a 'modified sine wave'. Unlike a true square wave, the 'modified sine wave' stays at zero for a time between Vmax and -Vmax. This brings the waveform a LITTLE closer to a true sine wave (in terms of reduced harmonics). But it can still lead to noise. But the amount of noise that you are likely to hear from audio equipment all depends on the quality of the filtering in that equipment. So the noise can be VERY significant if filtering is not good. However, even if this is the case, it may only be noticeable when there is no signal.


Modified by StorminMatt at 8:10 PM 9/2/2008
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Old 09-03-2008, 04:06 PM   #18
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Default Re: car cigarette lighter watts?? (Legion_2)

Quote:
Originally Posted by Legion_2
*un-subscribes*
wait wut? u subscribed to this thread? lol Click the image to open in full size. *


*disclaimer, I know you are just kidding........


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Old 09-03-2008, 04:17 PM   #19
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Default Re: car cigarette lighter watts?? (uses0ap)

Hook it directly to your battery. Well, avoid the cig. light.
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Old 09-03-2008, 04:52 PM   #20
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Old 09-03-2008, 05:13 PM   #21
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Default Re: car cigarette lighter watts?? (Legion_2)

Quote:
Originally Posted by Legion_2
You know how to follow the GDD protocol:

1. Someone asks a question.
2. 9 people read the question and make worthless, un-helpful posts.
3. The 10th person answers the question.
4. Everyone else comes back to nitpick, split hairs, and post any extraneous info that is even remotely related to the topic in an attempt to seem useful, intelligent, or simply to "win."
Click the image to open in full size. X 10 Best Laugh I've had all Day
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