20A Cigarette Lighter socket

Discussion in 'Mobile Radio Systems' started by KC3U, Oct 3, 2013.

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  1. G4COE

    G4COE Ham Member QRZ Page

    Geesh.... 12 volts is nothing to a fleas whisker, but ya' don't wanna be fooling about with 10 amps let alone 20A.

    Either wire the rig correctly or not at all!
    Anything happens whether its related to the wiring or not the insurance folks will give you a hard time.... yeah I've seen the result at first hand with a hi-powered car stereo system. All the wires melted because of a wrong connection and a knackered stereo I refuse to touch....

    .... needless to say it wasn't fused at the right point, think about it - no explanation necessary, ever measured the current of a fully charged car battery when shorted?

    With high current sources you need to make proper connections or they become resistive, might be fine n' dandy on a test meter but might not be so for high current thus creating a voltage drop and producing heat.... and longer the wire run the thicker it needs to be.

  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Another thing to consider, The power point / cigar lighter shares power with the automobile system computer on many autos.

    OBD and such use this power connection.

    Don't blow the computer out.

    Good Luck.
  3. WA7KKP

    WA7KKP Ham Member QRZ Page

    Yers ago I used to run a Johnson Messenger II with a cig lighter plug . . . it drew about 5-6 amps continuous and it loved to melt down the plug from a not-too-solid connection (high resistance).

    If you want 20 amperes, you'll have to provide a much better plug/socket arrangement, and make sure you are using at least #12 wire; the bigger the wire size the better. Another good idea is to use multiple contacts in parallel. This also keep the contact resistance low; if one goes bad the others keep working. I used to use a cinch-jones 6 pin plug/socket pair with three pins paralleled for both positive and negative leads, and never had a problem.

    And keep the fusing correct. Use fuses designed for 12v; the common glass 3AG fuses are not very good at 20 amps. Again the culprit is any sort of resistance with a high current flow turns in to power lost and heat.

    Gary WA7KKP
  4. W0LPQ

    W0LPQ Ham Member QRZ Page

    If people would pay attention to the assembly of these stupid things, usually they would find that the spring is small gauge wire, obviously not meant for anything over a couple amps, let alone 20A. That and the small contact area of the mating area to the spring ... you mean you really want to push the current rating? Cig lighter plugs to me are the worst thing ever invented. They are a fire looking for a place to happen. As Gary says, they melt. That means it got hot. You want to put your finger on that thing ... as long as it is YOUR finger ... go ahead. Years ago I used one in a pinch with my TM-241A and at low power it got warm. At medium power ... it shut off ... not enough current available ... that and the voltage was less then 10V.
  5. KK6GMN

    KK6GMN Ham Member QRZ Page

    I really do not want to run wire to my battery for a number of reasons. The simplest way to go is with a metered battery charger and a med size (11-18AH) sealed battery. It can be stored in some inconspicuous place and the 1a charge can reload it. This way you also have an instant field battery ready for field day. Gordo does this in rental cars with a nice leather bag setup from DaySaver. I will be assembling my own, but similar idea.
  6. K0BG

    K0BG Ham Member QRZ Page

    Well, guess what? That doesn't work either. A one amp charge won't keep the battery up to its nominal charge level if the current draw is more than the charge rate. Low voltage relates to all sort of maladies such as premature shutdown, increased IMD, and a few others.

    Nothing you do in a mobile installation is more important than proper wiring. Almost any antenna mounted in almost any fashion will work to some degree. That's not true of sloppy wiring.
  7. KH6AQ

    KH6AQ Ham Member QRZ Page

    I looked at cigarette lighter socket and plug specs and it appears that while the sockets in vehicles are rated for 20 amps the plugs come in 2 to 20 amp versions.

    Were the damaged plugs mentioned in this thread not rated for the current drawn?

    Cigarette lighter sockets and plugs are specified by SAE J563 and comply with safety standard UL 2089.
    Last edited: Oct 21, 2013
  8. KK6GMN

    KK6GMN Ham Member QRZ Page

    While that is true, it is like a hole in a bucket. If the battery is large enough to handle the duty cycle. the 1amp charge will refill it all be it slowly as long as you are not in a constant transmit mode. And if in a nice case, if you run it too low, just pull it and charge it in the house over night. Essentlly you are running on a large batterypack. Very easy to monitor voltage with a simple alarm or meter....if it sounds, stop transmitting and charge a while.
  9. K0BG

    K0BG Ham Member QRZ Page

    You missed the point. If you use a nominal 18 aH battery, and you run a 25 watt transceiver (≈50 watts input), the battery voltage will drop. How far it will is a bit subjective without knowing more about duty cycles, etc. If it drops below about 11.7, most transceivers will just shut themselves off. You very well may get by with the lash up, but that doesn't make it kosher.

    There is another post here, by WA6MHZ. You could wire yours up like his too. But again, that doesn't mean it is the way to go.
  10. KK6GMN

    KK6GMN Ham Member QRZ Page

    I guess Gordo does not know what he is doing then. :(
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