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Author Topic: current rating of automobile cigarette lighter plugs  (Read 21297 times)
NO9E
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Posts: 439




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« Reply #15 on: March 27, 2013, 11:01:00 AM »

I ran FT-100 from cigarette plugs. Could run full power on US cars but only reduced power from Honda or Toyota. Very useful on rental cars or where one does not want any permanent changes. Never a problem.

With voltage conditioner MFJ-4403 that uses supercapacitors,  any cigarette plug in any car would likely supply enough power for any 100W rig. This is because the conditioner replaces 20 A peaks with about 5A average.

Ignacy, NO9E 
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W9MMS
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Posts: 121




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« Reply #16 on: March 27, 2013, 08:18:25 PM »

I ran FT-100 from cigarette plugs. Could run full power on US cars but only reduced power from Honda or Toyota. Very useful on rental cars or where one does not want any permanent changes. Never a problem.

With voltage conditioner MFJ-4403 that uses supercapacitors,  any cigarette plug in any car would likely supply enough power for any 100W rig. This is because the conditioner replaces 20 A peaks with about 5A average.

Ignacy, NO9E 

Ignacy, the scary thing about what you just wrote, is you believe it!

Please go back and revisit the principles of "Time Constant" in regards to Capacitor.


(((7))) Milverton.
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N4CR
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Posts: 1702




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« Reply #17 on: March 27, 2013, 09:33:57 PM »

I ran FT-100 from cigarette plugs. Could run full power on US cars but only reduced power from Honda or Toyota. Very useful on rental cars or where one does not want any permanent changes. Never a problem.

With voltage conditioner MFJ-4403 that uses supercapacitors,  any cigarette plug in any car would likely supply enough power for any 100W rig. This is because the conditioner replaces 20 A peaks with about 5A average.

Ignacy, NO9E 

Ignacy, the scary thing about what you just wrote, is you believe it!

Please go back and revisit the principles of "Time Constant" in regards to Capacitor.


(((7))) Milverton.

And regardless of that, peak current isn't what melts wires. Average current is what melts wires and that's not mitigated by a supercap. It's made worse.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
KM3F
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Posts: 526




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« Reply #18 on: March 27, 2013, 09:48:18 PM »

A 'capactor bank' at the radio will allow somewhat more power to be drawn on a mode such as SSB where the caps have a chance to recharge between audio drive signals but there is a limit to this.
This would be of little to no help on FM trying to extend the circuit's full current limit.
This is the same trick the auto audio high power boys do to feed the big amps when the lows are hit instead of trying to get it 'all' out of the battery and alternator but they use large gage wire.
Good luck.
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W9MMS
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Posts: 121




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« Reply #19 on: March 27, 2013, 10:40:23 PM »

I ran FT-100 from cigarette plugs. Could run full power on US cars but only reduced power from Honda or Toyota. Very useful on rental cars or where one does not want any permanent changes. Never a problem.

With voltage conditioner MFJ-4403 that uses supercapacitors,  any cigarette plug in any car would likely supply enough power for any 100W rig. This is because the conditioner replaces 20 A peaks with about 5A average.

Ignacy, NO9E 
Ignacy, this is not mean to attack you as a person, however lets go back and re examine ( for the benefits of others) some very glaring statements.

1) "I ran FT-100 from cigarette plugs. Could run full power on US cars but only reduced power from Honda or Toyota." <snip>
  Most cars uses wire size of 12 swg or less to power their Cigarette lighters.
  The Amperage required for 100 watts PEP is around 20 Amperes.
   12 to 13 volts with a peak current of 20 Amperes through a 12 swg wire will encounter massive voltage drop, which leaves the question to be asked.
  Were you actually getting 100 watts PEP form that FT 100 using the cig lighter?
   I'll skip over the potential fire hazard that could have happened to the vehicle electrical system.

2) Using a " Super Capacitor " or any Capacitor for that matter, will only multiply the potential danger to the Electrical system.
    Once discharged to whatever percentage, the massive inrush of current required by the very nature of a capacitor will increased the fire danger 10 fold.
My point is simply  V = IR  has not change since Ohm's Law.

PS.   There are many young operators who uses this forum to further their knowledge of the Hobby, and sometimes do take whatever is written here as the
GOSPEL.
We all ( Myself included ) should be very thoughtful of what we print here on the forum.


((((73)))) Milverton.   
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W8JX
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Posts: 6685




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« Reply #20 on: March 28, 2013, 05:29:12 AM »

  Most cars uses wire size of 12 swg or less to power their Cigarette lighters.
  The Amperage required for 100 watts PEP is around 20 Amperes.
   12 to 13 volts with a peak current of 20 Amperes through a 12 swg wire will encounter massive voltage drop, which leaves the question to be asked.
  Were you actually getting 100 watts PEP form that FT 100 using the cig lighter?

I love thins "massive voltage drop" theory. Assuming it is 12ga, 10 feet of it would drop a "massive" .3 volts at 20 amps and even 14 would only drop .5 volts. In realty the length of in a average car feeding lighter socket from main buss is less than 10 feet so voltage drop in wiring is not really a big issue at all.

   I'll skip over the potential fire hazard that could have happened to the vehicle electrical system.

Love this fire hazard thing.

2) Using a " Super Capacitor " or any Capacitor for that matter, will only multiply the potential danger to the Electrical system.  Once discharged to whatever percentage, the massive inrush of current required by the very nature of a capacitor will increased the fire danger 10 fold. My point is simply  V = IR  has not change since Ohm's Law.

Love this too. A capacitor will actually reduce average load on power lead during SSB operation. There will be a very brief surge draw 9less than a second) when a large capacitor is first charged from zero but then it will never as it feed radio for peak draws and recharges during low demand but can never discharge below voltage on power feed to it.  It is a great trick to use a large cap to stabilize voltage and reduce peak draw on a power feed. I have used it for many years. Again love the fire hazard claim

PS.   There are many young operators who uses this forum to further their knowledge of the Hobby, and sometimes do take whatever is written here as the
GOSPEL.
We all ( Myself included ) should be very thoughtful of what we print here on the forum.

I agree many seek knowledge here but also correct knowledge. One should try to base comments on direct knowledge of actual application rather than what they think might happened based on never have done it and a "theory". 

The weak link here is the plug in the socket not wiring in car. If it does not make excellent contact with socket, resistance can develop and plug can get hot and possible melt under prolonged very heavy loads. But as one poster stated based on his own experience when you use a large capacitor in circuit feed from socket the average draw on plug is reduced and it also runs cooler.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
N3QE
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Posts: 2426




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« Reply #21 on: March 28, 2013, 06:35:44 AM »

I might remind that the purpose of the original cigarette lighter plug is to get hot :-).

Tim.

resistance can develop and plug can get hot and possible melt under prolonged very heavy loads.
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N4CR
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Posts: 1702




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« Reply #22 on: March 28, 2013, 10:48:37 AM »

Love this too. A capacitor will actually reduce average load on power lead during SSB operation.

I'd love to see your proof of this. You have a load. You add a component and now the load draws less average power. This could be part of a perpetual motion machine if you could harness that magic component.

The rig draws x average current. Let's call that N electrons per second.

The capacitor draws only leakage current. Let's call the L electrons per second.

Now you tell us that L+N electrons per second is less than N electrons per second?
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73 de N4CR, Phil

Never believe an atom. They make up everything.
M0HCN
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Posts: 473




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« Reply #23 on: March 28, 2013, 12:26:09 PM »

Don't forget that heating in the wiring is proportional to average of (current squared) so a short term 20A at say 10% duty cycle produces much more heat then 2A continuous would.

If we assumed say 0.1 ohms loop resistance then during that 20A pulse we are dropping 2V in the wiring and dissipating 40W in the cables (For 4W average dissipation at 10% duty), the steady state 2A is dropping 0.2V and dissipating 0.4W for the same average current in the load. 

Fitting significant local energy storage may help, but how much strongly depends on how much voltage drop you have under load, and what the power back off ratio for the modulation mode in use is in terms of the current envelope (quite different to the RF power envelope with most simple minded PA designs).

In any case, lighter sockets are notoriously poor, better to use almost anything else (Speakon loudspeaker connectors are nice).

Regards, Dan.
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KB1GTX
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Posts: 463




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« Reply #24 on: March 28, 2013, 12:35:48 PM »

I tried to use one of those radio shack 2.5 amp power supplies on my hr 2510 and it would pop the breaker after a few seconds and the lights would dim on the radio, but with a 1F cap the radio runs perfect,, now this is on ssb only with just the alc compression that's in the radio that I speeded up a bit..  With the tests I ran it seems that you can "stretch" a power supply to 3to1 on an untouched ssb radio running normal limiting.
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W8JX
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Posts: 6685




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« Reply #25 on: March 28, 2013, 01:41:59 PM »

Love this too. A capacitor will actually reduce average load on power lead during SSB operation.

I'd love to see your proof of this. You have a load. You add a component and now the load draws less average power. This could be part of a perpetual motion machine if you could harness that magic component.

The rig draws x average current. Let's call that N electrons per second.

The capacitor draws only leakage current. Let's call the L electrons per second.

Now you tell us that L+N electrons per second is less than N electrons per second?

I meant to say reduce peak loads and maintain a more steady average draw on power feed and steadier voltage for rig. 
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
AD5X
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Posts: 1437




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« Reply #26 on: March 28, 2013, 05:06:00 PM »

Actually, the MJ-4403 works very well.  It works a lot like the Gamma HPS-1a power supply.  The Gamma uses a 5-amp 13.8V supply with a 5-farad capacitor bank across the output.  It does a good job of powering a 100 watt SSB radio, though I found that you needed to drop to about 80 watts on CW as the higher duty cycle on CW overwhelmed the 5-amp power supply at 100 watts CW. 

I ran a bunch of tests on the MFJ-4403 on the bench.  It places a large current limiting resistor in series with the capacitor bank (4.33 farads)  until the capacitor bank is nearly charged, then the resistor is shorted out by a relay - i.e. a step-start circuit.  That takes about 30 seconds or so.  Once that 4-farad capacitor bank is charged, it does a very good job of handling the current peaks for intermittent modes like CW and SSB at 100 watts.  Most of my on-the-air experience was with the MFJ-706 - always powered from the accessory socket in various cars.  The MFJ-706 is a package that includes a MFJ autotuner, a MFJ-4403 - and your IC-706.

Of course, wiring directly to the battery is cheaper and better.

Phil - AD5X
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N4CR
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Posts: 1702




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« Reply #27 on: March 28, 2013, 07:13:55 PM »

Love this too. A capacitor will actually reduce average load on power lead during SSB operation.

I'd love to see your proof of this. You have a load. You add a component and now the load draws less average power. This could be part of a perpetual motion machine if you could harness that magic component.

The rig draws x average current. Let's call that N electrons per second.

The capacitor draws only leakage current. Let's call the L electrons per second.

Now you tell us that L+N electrons per second is less than N electrons per second?

I meant to say reduce peak loads and maintain a more steady average draw on power feed and steadier voltage for rig. 

There is no doubt of that.

The interesting thing that comes along with averaging the current is that it also averages the voltage. So the voltage is never as low without the supercap, but by the same token, it's also never as high. Since we know that lower voltage feeding a regulated circuit causes more current to flow, the small gains in reducing the current surges are paid back in the slightly higher average current because of the slightly lower average voltage.

There's no free lunch.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
W8JX
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Posts: 6685




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« Reply #28 on: March 28, 2013, 07:29:18 PM »


The interesting thing that comes along with averaging the current is that it also averages the voltage. So the voltage is never as low without the supercap, but by the same token, it's also never as high. Since we know that lower voltage feeding a regulated circuit causes more current to flow, the small gains in reducing the current surges are paid back in the slightly higher average current because of the slightly lower average voltage.

There's no free lunch.

This is somewhat true as far as voltage but a slightly lower peak voltage when transmitting is more than offset by it being more stable and not sagging during voice peaks delivering higher average output and cleaner signal too (in theory) due to more stable voltage so there is indeed a bit of free lunch.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
N4CR
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Posts: 1702




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« Reply #29 on: March 28, 2013, 08:00:56 PM »

This is somewhat true as far as voltage but a slightly lower peak voltage when transmitting is more than offset by it being more stable and not sagging during voice peaks delivering higher average output and cleaner signal too (in theory) due to more stable voltage so there is indeed a bit of fee lunch.

If it's a fixed load, then voltage drop is the key to less current flowing. (light bulbs are not fixed loads)

If it's a regulated load, if voltage drops, more current flows and the same wattage is dissipated within reason.

If you mean less voltage sags is your free lunch, then yes. But that won't make your cigarette lighter wiring not catch on fire from too high average current.
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73 de N4CR, Phil

Never believe an atom. They make up everything.
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