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Author Topic: Yaesu FT-7800R power from cigarette lighter jack question  (Read 206 times)

K6RQR

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Hello All -
 I am curious as to how many amps I could expect to get from a cigarette lighter plu powering an typical 2/440 transceiver running at 30-40 watts output? I have a 2006 Ford Focus.  If I ope
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K6RQR

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #1 on: Yesterday at 07:51:03 PM »

 continued -
If I operated the rig at medium power I assume that there would be no problem. However one website stated that the voltage from the lighter jack might be as low as 10.2 vdc which would be too low. Any comments appreciated. Thanks

73,
Bruce  K6RQR
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K5LXP

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #2 on: Yesterday at 09:01:31 PM »

Cigarette lighter plugs generally suck as stable power sources.  You could prove that though by putting a load on it and seeing what it does.  They tend to float a bit above ground promoting current through the coax shield which can sometimes cause noise or weirdness.  Power ports on the other hand are sometimes better.  The cigarette lighter plugs themselves aren't usually anything to write home about either, offering minimal contact area and poor fitment.  By definition I recall the max current for the plugs is 10A but I've had them get hot and melt at less than that with sustained current.  I've run high power rigs using cigarette plugs on occasion but will turn the power down to minimize the issues.  If it's more than a temporary operation, do it right and run a wire to the power distribution box under the hood.

Mark K5LXP
Albuquerque, NM
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KE6SLS

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #3 on: Yesterday at 09:13:26 PM »

Hiya Bruce,

I am using my cig socket to power my dualband.  You're right, medium power is about all you can get without blowing the fuse, and/or damaging outlet. 

I doubt you will see such significant voltage drop as 10vdc.  Just know it's a poor way to power a radio.  The socket in it's best condition is a terrible conductor/connector.  You can't filter ignition and other noise etc. 

I think as long as you make sure you never go above mid power, you're rig should work fine.

73
Jaye
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K6RQR

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #4 on: Yesterday at 10:52:53 PM »

Greetings -
 Thank you for the helpful comments. An alternative to using the lighter socket as I was asking about would be for me to take a fused DC power cord that I have and try and find a place in the firewall where I can route it through and reach the battery itself. An advantage to that is that I could use the duo-bander at full power if I needed to.

73,
Bruce  K6RQR
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AE5SB

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #5 on: Today at 05:28:24 AM »

Greetings -
 Thank you for the helpful comments. An alternative to using the lighter socket as I was asking about would be for me to take a fused DC power cord that I have and try and find a place in the firewall where I can route it through and reach the battery itself. An advantage to that is that I could use the duo-bander at full power if I needed to.

73,
Bruce  K6RQR

That's the best way!
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K5LXP

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #6 on: Today at 06:05:08 AM »

Note, the connection you make under the hood wouldn't be to the battery, it's to the power distribution box and a frame ground near where the battery is grounded.  Connecting directly to the battery has a host of issues that are best avoided.

Mark K5LXP
Albuquerque, NM
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W9IQ

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #7 on: Today at 06:41:54 AM »

Greetings -
 Thank you for the helpful comments. An alternative to using the lighter socket as I was asking about would be for me to take a fused DC power cord that I have and try and find a place in the firewall where I can route it through and reach the battery itself. An advantage to that is that I could use the duo-bander at full power if I needed to.

73,
Bruce  K6RQR

For 8.5 amps, you can often find a suitable positive connection at the distribution/fuse box. You could reappropriate the circuit that feeds your cigarette/auxiliary power jacks if you have no other significant use for them.

With that being said, I regularly plug that type of radio into the vehicle OEM auxiliary power connector without problems. We do this in emergency vehicle ride-alongs as well.

- Glenn W9IQ
« Last Edit: Today at 06:46:25 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W7CXC

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #8 on: Today at 09:30:37 AM »

This comes under the heading of for what it is worth. For several years I ran a IC706MK2G using the lighter socket on my 96 F250. There were NO issues at all. Have since put in direct to the battery #6 , properly fused lines and do not notice any difference. The rig was run at 100w SSB. Do I think the direct lines are better? Yes, but that is just because most of what you read says it is better. In my experience they worked equally well. 73's David
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WA3SKN

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #9 on: Today at 11:26:07 AM »

The cigarette lighter, if fused, is normally fused at ten amps.
The FT7800r specs claim max power draw of 8.5 amps.  So in theory it would work.  However, you might want to measure actual current draw, or use a lower power setting.
You DO NOT want to melt a wire in the wiring harness!  And the wiring specs for autos is quite liberal, the wire gauge is small.

-Mike.
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K6CPO

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #10 on: Today at 01:20:23 PM »

Note, the connection you make under the hood wouldn't be to the battery, it's to the power distribution box and a frame ground near where the battery is grounded.  Connecting directly to the battery has a host of issues that are best avoided.

Mark K5LXP
Albuquerque, NM

It really depends on the age of the vehicle and how much it has in the way of on-board computers. I drive a 25 year old Dodge truck and I've had my my power coming directly from the battery since I put my first radio in it back in 2011. The same wiring has powered four different radios over the years. The only radios I've ever connected to my lighter socket are HTs.
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W9IQ

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #11 on: Today at 01:53:19 PM »

The primary issue with direct connections to the battery is the potential for defeating the SoC (state of charge) circuit which could cause the battery to go dead. The other issue to consider are potential ground loops when the power cord minus is not connected to the vehicle chassis.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KE6SLS

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Re: Yaesu FT-7800R power from cigarette lighter jack question
« Reply #12 on: Today at 06:11:42 PM »


Really good comments here.  I want to clarify my situation and highlight a few points:

I have a 2016 Honda Fit.  Two cig outlets(sockets.)  One in dash and one in center cubicle between seats.  They are individually factory fused with 20a sub-mini fuses.

Running an SSB rig @ 100w is VERY different than an FM rig @ 50w.  The FM rig is at 100% duty cycle, the SSB rig isn't, ever.  If it was, that poster would have then explained how much damage occurred to wiring, socket & plug.

I originally had an HT (5w) in my car.  I was talking to a ham and sending some APRS msg.  The HT went dead and I reached in to ensure plug was firm in the socket.  It was hot.  So hot is branded my hand!  The plug I had was a very cheap adapter, ill fitting in the socket.  The resistance on that poor connection, even at 5w was enough to literally cause the plug to burn me.  Had a short talk with god about that!

Ditto on the auto wiring.  No matter what you do, work on the side of safety and derate your fuse.  By derating, I mean use a smaller fuse that will blow sooner.  Better safe than sorry.  Keep a good stock of fuses in the glove box.

The Honda I own uses a battery one would think was made for a motorcycle.  Wiring direct is out of the question.  All my other vehicles I owned, I did run direct to battery, then a fuse > through a DC noise filter > radio.

What I need is an auxiliary battery, charged by a 5amp limited plug.  If I could, I would have a smart limiter, it would detect when I turned car off, and open the connection to the radio, but I'm dreaming out loud! 

A second option, have the folks at our auto-electric shop modify the socket in the console cubical to add powerpole outlet for me, but I fear the price tag.

Tnx for the good feed back.

73
Jaye
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