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Reasons why I should not do DC-AC-DC?

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  • Reasons why I should not do DC-AC-DC?

    I've been using a cigarette lighter AC adapter to power my carpc for the past six months or so and it seems to work fine. Is there any reason why I would want to use a DC-DC converter instead? Sorry mods of this is a repeat I wasnt able to find much through search. Thanks

    IHateMayonnaise

  • #3
    Sorry that I overlooked that; thanks for the link. From what I got from that, the answer is that I should if I really care about efficiency, but other than that I have no reason. Thanks again

    IHateMayonnaise

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    • #4
      so from
      Inverters are a cheap and easy way to power your computer. An inverter takes DC power from your car and converts it to 120 volt AC power, just like in your house. To use the inverter, simply plug in your home power supply to the inverter. The power supply converts your AC power BACK into DC power that your computer can use. Naturally, converting DC power to AC just to convert it back to DC is inefficient and the inefficiency manifests itself as heat. Many also report that inverters introduce noise in your audio lines, distorting the sound. In addition, the manner in which inverters convert DC power to AC power can be unacceptable to certain computers and they will not work with an inverter. In addition, automatic startup and shutdown of the PC by an inverter requires additional hardware such as a DSSC (see above).
      you only got the efficiency bit?


      Also having it plugged into the cigarette lighter on a long term basis is not a good idea, there are so many threads where people are having issues with their system and they have inverters or even DC-Dc connectors going through the cigarette lighter socket. Try and hardwire it, it is better in the long run.

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      • #5
        Also, it depends on whether your cigarette lighter is sufficiently wired for this. Some can handle 120 watts or so but if your system isn't a low power one, you may be over drawing the wiring. If it isn't fused properly, this can lead to a fire.
        Originally posted by ghettocruzer
        I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
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        • #6
          Something to watch out for:
          Inverters kill batteries. I'm not talking about the car battery, I'm talking about a charger plugged into the inverter charging a battery. So, don't plug an ipod into the computer if you're powering it by an inverter.

          For the most part, a computer will run fine on one, but inverters make "dirty" power. The issue I had with running a computer off the inverter was that I would get a constant hum/buzz our of the speakers.

          I also recommend not hooking into the lighter socket.

          Also, check the inverter's output voltage. I had one a while back that put out 90 volts rather than 110-120. This is fine for some electronics and some power supplies but not for others. Some things are lenient and expect anything from 80 volts to 260 volts. Other things aren't and expect a tight 110 - 120 volts. Check the inverter and check the labels on any devices getting plugged in.

          Also, check the temperature of the inverter. If it's hot to the touch, it's poorly designed/underrated for what you're using it for.
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          • #7
            not to go against anyone with way more knowledge than me on this matter, but i think that you should go with whatever you have. What follows is my opinion.

            You said its been working for 6 months?
            why change it? it works!

            dirty power this, and better efficiency that.... just look at the post in this forum alone. there are more people with problems with their m2 atx or opus not working as anyone with an inverter. if you don't believe me just look at titles.... my opus is broke or why won't my m2 output 5V.

            if your car computer lasts as long as a year without you messing with it by upgrading or something else, well then great. If it doesn't, prices and spare parts will be cheaper and you can fix it. You will have learned something, and know how to do it better (and maybe try the other one).

            There is no reason to not have a dc-ac-dc connection. For every person that can give an example of an inverter doing damage in a car, you can find one for a person with a dc-dc converter. (The world is full of smart people doing stupid things.) will either system last two years? maybe. but that is a lifetime in terms of computing and carpc's especially. at least you would have enjoyed it for that time (it was probably due for an upgrade anyway).

            If you choose to use an inverter, just do it right. that is the main problem half the people in this forum have. make sure you have an adequate buffer of power (120 watt inverter is not usable with a 110 watt system) and like other have already said, make sure it is a reliable brand (some of the cheap stuff is outright lies in capability).

            The point is that either system is good and RELIABLE if it is done right. Don't worry about the amount of heat from the inverter, just plan for it and know that it needs airflow.

            Now that I'm done ranting, just get it into your car and enjoy the system, NOW. whatever you have.

            I'm not trying to start a battle, but this question is asked too often and for the wrong reason. Again, this is just my two cents, for what it is worth.

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            • #8
              Originally posted by natemart View Post
              You said its been working for 6 months?
              why change it? it works!
              As long as it is properly rated for the power you are drawing. Did you use a power calculator to estimate the total system draw? Did you compare it to what the rating on your cigarette lighter is (you can often find this on a cover for the lighter or in the owners manual)

              Originally posted by natemart View Post
              dirty power this, and better efficiency that.... just look at the post in this forum alone. there are more people with problems with their m2 atx or opus not working as anyone with an inverter. if you don't believe me just look at titles.... my opus is broke or why won't my m2 output 5V.
              In general, DC-DC power supplies are much more popular than inverter solutions, thus many more people post problems with them. Not that there aren't problems with them, there are but it's the same reason you see a lot of issues with Lilliput monitors -they're more popular.

              [
              Originally posted by natemart View Post
              There is no reason to not have a dc-ac-dc connection. For every person that can give an example of an inverter doing damage in a car, you can find one for a person with a dc-dc converter. (The world is full of smart people doing stupid things.)
              I doubt you are trying to imply that people with DC-DC power converters are smart people doing stupid things, but that is what it sounds like.

              [
              Originally posted by natemart View Post
              ]The point is that either system is good and RELIABLE if it is done right. Don't worry about the amount of heat from the inverter, just plan for it and know that it needs airflow.
              Both systems can be good and reliable. There are more variables using an inverter (can introduce buzzing in the audio, don't provide auto-start signal, only certain ones provide true sine wave output). The heat issue needs to be addressed with proper fusing.

              The main problem with people using inverters is that they choose them for the wrong reason -price. Either they already have one or they have found one cheaper than a DC-DC power supply. The cheap ones are the ones that cause the problems, the buzzing, the dirty AC output. The solution is nearly always to either buy a well designed inverter which is usually more expensive, or to switch to a DC-DC power supply.

              Since you already have an inverter and it already works fine, just make sure you aren't overloading the cigarette lighter wiring. If you are, run dedicated wires for the inverter with proper fusing. If you're not, then great! Enjoy the car pc!
              Originally posted by ghettocruzer
              I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
              Want to:
              -Find out about the new iBug iPad install?
              -Find out about carPC's in just 5 minutes? View the Car PC 101 video

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              • #9
                nate, while i do agree on a couple of points that you have made, i think that the biggest reason for using a invertor is if you already have a inverter of good quality, on hand(in this case, every point you made is spot on). if you still need to go out and buy equipment, then a decent quality inverter is going to be near the cost for a dc-dc power supply, which will make a dc-dc option a better idea.

                it a inverter is like riding around the block 6 times everytime you arrive at your destination, or only take left turns the entire trip... sure you still get to where your going, but are taking the longer route, at the cost of efficiency...

                if you are using a inverter, are not having any problems, then there is no reason to change to a dc-dc option, other than possibly space constraints.
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                • #10
                  Thanks everyone for your input! Hopefully this thread will help some others

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                  • #11
                    sorry if it came out that way but im not implying that people who use dc convertors are stupid, what im trying to say is, think how many times you have done something even though you knew better (for example, plugged in something backwards or got cocky and didn't disconnect power only to blow a fuse?). the point is it doesn't matter if you have an inverter or converter, accidents happen and that is what a lot of people have problems with. you damage your stuff due to stupid mistakes. And yes, the forum is full of people like that, that is what makes this a fun hobby, we are "making things work" and "putting the circle in the square hole". we've all done it, and it doesn't matter if you have a m2, opus, or inverter, you're going to break something.

                    also my point was to reinforce that if his stuff works (i.e. six months) why change it? A problem with wiring, line noise, ground loop, overheating or inadequate power should have manifested by now. if he is enjoying his system with it working then good.

                    and to make sure that he is using a good quality inverter (which i totally agree that a quality one will probably cost as much as a dc-dc, but he already owns one). the heat i am referring to is the heat created from the inverter by transferring from dc-ac-dc. In other words don't put the inverter in the case with the pc or in an enclosed space without airflow.

                    i hate this post to feel like im defending myself, but if one person posted and misunderstood what i said, then there are 20 more who may have walked away thinking the same thing. Hope this clarifies my viewpoint.

                    i would hate him to fall into the old saying, "if it ain't broke, you can fix it till it is!" which is something this hobby has pulled me into many a time.

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                    • #12
                      There are a few primary reasons to use a DC-DC PSU over an inverter for a PC:

                      1 - Inefficiency. The conversion process wastes energy. Because of this you need an inverter that is capable of more AC power than the PC actually draws.

                      2 - Heat. The conversion process from DC to AC generates heat. If you've ever felt the PSU in your desktop computer (which does the AC back to DC conversion), it gets warm, as well. Heat is something you want to avoid with your PC. Two devices generating heat near your PC doesn't help matters.
                      Some inverters get so hot that they become a potential fire hazard if mounted with carpeting or upholstry around it.

                      3 - Size. Let's face it, a decent inverter is not a small piece. That added size is something else you have to compensate for when planning your install. A smaller car is tight on space as it is.

                      4 - Electromagnetic Interference (EMI). This is mostly due to low build quality in inverters. These aren't designed to power sensitive electronics in the first place. EMI can cause noise in your audio system and static on your video. I'm sure you want neither.


                      I agree that an inverter-based PC setup can work. It's been done many times.
                      However, if you are planning a new setup and can afford a DC-DC PSU, it is definitely the better way to go.

                      If budget is a concern and an inverter is available, I'd suggest using the inverter and planning to upgrade to the DC-DC PSU in the future, if at all possible.
                      Have you looked in the FAQ yet?
                      How about the Wiki?



                      Under normal circumstances, a signature would go here.

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                      • #13
                        Jeeze darque, you're up early. :P
                        Tidder

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                        • #14
                          Originally posted by Tidder View Post
                          Jeeze darque, you're up early. :P
                          Always!
                          Have you looked in the FAQ yet?
                          How about the Wiki?



                          Under normal circumstances, a signature would go here.

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                          • #15
                            Originally posted by DarquePervert View Post
                            There are a few primary reasons to use a DC-DC PSU over an inverter for a PC:
                            ...

                            3 - Size. Let's face it, a decent inverter is not a small piece. That added size is something else you have to compensate for when planning your install. A smaller car is tight on space as it is.

                            ...
                            .
                            And the added size of a standard ATX PSU, too... Wich mean one has to use a standard case, or scratch build a case to house this psu..... sometimes to power a mini-itx board.
                            Now Galileo is real. Muhahahahaha :p

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