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  • #31
    Originally posted by Frank DuVal View Post
    My turn,

    The essence is:

    The 6 volt battery has its positive terminal connected to the car chassis.

    If one was to set a 12 volt battery in the trunk and connect the negative terminal to the chassis, nothing would happen. Follow? The 12 volt battery has no connection to the existing 6 volt battery system, except for the chassis.

    They are two different voltage supplies. Nothing in common. Like when parallel parking (with chrome bumper cars) your positive ground car and the bumper touches a negative ground car. No sparks, no flash, no lightning! But you have just connected a positive ground chassis to a negative ground chassis.

    The box (DC to DC converter) creates a completely isolated (now, one does have to buy the box that is an isolated model) voltage supply, like another battery. The supply to make it work is positive ground. The output is like a separate battery, with the negative terminal connected to chassis.

    Just like on negative ground cars (12 volt Studebakers), the ignition system is STILL positive ground! Yes, the center electrode of spark plugs (exception the new waste spark systems) is negative with respect to the engine! The ignition coil provides a completely separate high voltage system with a positive ground.
    Sorry Frank, but when I hear this type of "logic" it completely explains why for every older vehicle I've restored - that had been electrically "modified," the wiring and electrical system had to be ripped out of it and new installed from scratch.

    In this case there aren't two different cars with differently grounded closed electrical systems touching each other, there aren't two different batteries or electrical circuits, there's one electrical system - one electrical circuit, all being powered by and grounded by ONE battery a singular closed system and closed complete circuit. And in the course of all this "magic" I understand how the voltage and polarity are changed, but it makes absolutely no sense to me about how this works on a single ground with power that is the same polarity as that ground - even though it does work, it makes no sense.

    And then again there's that word "isolated." It is, it isn't, it has to be, it doesn't have to be - blah blah blah.

    BUT.......

    For all the garbage I give him, all poking aside, Roy is about the sharpest electrical guy here, and despite the joy I get from tormenting him, he's usually 100% right. And if he says it will work, despite him not being able to make sense of it for me, I believe him. Love ya Roy, LOL!
    Last edited by Big Dan; 12-03-2022, 10:08 AM.

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    • #32
      It really is that simple. Ground is at zero volts. Zero has no polarity. The polarity of the circuit in question is taken relative to ground. You can have any number of isolated circuits sharing a common ground, even some with AC in them. It's when the hot sides of two circuits that are supposed to be isolated come in contact with one another that the magic smokes comes out.
      Gord Richmond, within Weasel range of the Alberta Badlands

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      • Big Dan
        Big Dan commented
        Editing a comment
        There's that word again - "Isolated." And your right, there's no voltage at ground. But your kind of mixing apples and oranges again - voltage and polarity. You don't get voltage, or amperage or consume watts until you have a completed circuit with FLOW. And yes, you can have different voltages flowing to a common ground - depending on your equipment limitations.
        Last edited by Big Dan; 12-04-2022, 08:21 PM.

    • #33
      To further illustrate this many of the computer circuits in new cars work on 5 volts, but are grounded to the same ground as the 12 volt system. What created heat, which is what a short is, is resistance. There is very little resistance in a ground circuit. And it doesn't matter to the power source how much "pressure/voltage" is returning as long as the amperage doesn't exceed the design parameters'

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      • Big Dan
        Big Dan commented
        Editing a comment
        Different voltages is not the doubt I have. It's having a ground that is the same polarity as power. Or as Gord explains it, power that is the same polarity as the ground. How is a circuit flow completed if everything is the same. If you pull the battery cable off the "ground" post. (Whether 6V positive on your Stud or 12V negative on your modern car) everything electrical stops working (I'm speaking in general terms here. Don't present the alternator on the running car situation just to be argumentive)and touch it to the power post on the battery - NOTHING WILL HAPPEN no power running things, no sparks. It's an OPEN CIRCUIT!
        Last edited by Big Dan; 12-04-2022, 08:15 PM.

    • #34
      Originally posted by Big Dan View Post

      Sorry Frank, but when I hear this type of "logic" it completely explains why for every older vehicle I've restored - that had been electrically "modified," the wiring and electrical system had to be ripped out of it and new installed from scratch.

      I do not think you ever followed any of my modifications, I understand electricity. I do agree, many people should not touch anything electrical!


      In this case there aren't two different cars with differently grounded closed electrical systems touching each other, there aren't two different batteries or electrical circuits, there's one electrical system - one electrical circuit, all being powered by and grounded by ONE battery a singular closed system and closed complete circuit.

      There is the issue! There are two complete separate circuits if the DC to DC converter has isolated input and output terminals. The output of the converter is isolated from the input, a 4 terminal/wire converter, with the case not part of the circuit. Just like if two batteries were sitting there, or like my analogy of two cars with bumpers touching. Two separately derived circuits that can share a common chassis.

      And in the course of all this "magic" I understand how the voltage and polarity are changed, but it makes absolutely no sense to me about how this works on a single ground with power that is the same polarity as that ground - even though it does work, it makes no sense.

      Draw the circuit is what I tell people. Notice there is only one connection common between the two isolated circuits.

      And then again there's that word "isolated." It is, it isn't, it has to be, it doesn't have to be - blah blah blah.

      Of course it has to be! Just like two batteries are isolated from each other.

      Set two batteries on a car chassis. Connect a positive terminal of one battery to the chassis. Connect the negative terminal of the other battery to the chassis. Run a wire from one battery's unground terminal to a headlamp, run the other headlamp's wire to the other battery's ungrounded terminal, with the other terminals of the headlamp's connected to chassis. Why do you not think both headlamps will light?

      The same isolated "separately derived system" is how 99% of transformers are used in our AC power distribution system.


      BUT.......

      For all the garbage I give him, all poking aside, Roy is about the sharpest electrical guy here, and despite the joy I get from tormenting him, he's usually 100% right. And if he says it will work, despite him not being able to make sense of it for me, I believe him. Love ya Roy, LOL!
      It seems I need to add more characters after the quote for this to work. The purple inserted into the quote does not count? OK computer people, explain this to me!

      Frank DuVal

      50 Commander 4 door

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      • Big Dan
        Big Dan commented
        Editing a comment
        Problem here Frank is that you simply aren't listening. There AREN'T two separate circuits with the box the OP has. It's a box that converts original power to a second power supply of a different voltage and polarity that powers the accessory, and then uses the SAME GROUND as the rest of the car. The power source and the ground being the SAME POLARITY. It's NOT a Second closed circuit, and it's NOT ISOLATED, RTFQ. You're entitled to your opinion. And while none of us are on the same page you're not even reading the same book. Repeating the same point and fielding all the unrelated responses has worn out it's welcome.

        So, the OP has the instructions Roy gave him, he's going to install the box, it's going to work, and the post can be closed. And for the rest of all of our lives we will all argue about electricity. But for now, let's just stop - I will if you will guys!
        Last edited by Big Dan; 12-06-2022, 10:18 PM.

    • #35
      It is not I who is not listening.

      It IS a second closed circuit.

      It IS isolated (hence why it can be a separate closed circuit).

      And That's what Radio Roy says along with other responses.

      Roy:
      It's probably got an isolation transformer inside and probably works like this.
      -A chopper converts -6 volts DC to about 6 volts AC.
      -A floating/isolation transformer bumps the 6 volts AC up to 12 volts AC.
      -A bridge rectifier converts 12 volts AC to +12 volts DC.
      -The polarity reversal is possible because the transformer secondary floats and acts as an isolation device and has no reference to ground.
      Frank DuVal

      50 Commander 4 door

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      • Big Dan
        Big Dan commented
        Editing a comment
        Unbelievable Frank! It cannot possibly be a separate closed circuit if it's using a COMMON (the same) GROUND! Perhaps we are not on the same page semantically with our terms?!?

    • #36
      A quick update, and perhaps vindication for RadioRoy. I installed the magic box, and it works. Much like Big Dan, I don't really understand it...but there are many things I don't understand. I wired it directly to the cigar lighter, and removed the heat coil on the lighter so I don't accidentally pull so much amperage to make the box explode. It works well enough to keep juice in my phone for navigation, and that's all I intend to use it for. So far, so good...but I'll visit again if things go badly.

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      • Big Dan
        Big Dan commented
        Editing a comment
        It's magic!

      • Frank DuVal
        Frank DuVal commented
        Editing a comment
        Yay! Science for the win. I was just saying Yay, but there is a 10 character minimum.

    • #37
      Originally posted by markindy View Post
      A quick update, and perhaps vindication for RadioRoy. I installed the magic box, and it works. Much like Big Dan, I don't really understand it...but there are many things I don't understand. I wired it directly to the cigar lighter, and removed the heat coil on the lighter so I don't accidentally pull so much amperage to make the box explode. It works well enough to keep juice in my phone for navigation, and that's all I intend to use it for. So far, so good...but I'll visit again if things go badly.
      That's outstanding. Glad it worked - and glad we are done with this discussion.

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      • #38
        It's solved

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