Need help with some questions about car stereo set ups

Discussion in 'OT Technology' started by GT40, Nov 7, 2006.

  1. GT40

    GT40 lol

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    First off, I never have been big into car stereos. I'm in basic electrical class for automotive maintenance. I've decided to stop trying to be boy racer but instead get a automatic car that's comfortable with a nice stereo set up. :coolugh:

    I have an understanding of the basics to electricity from class and I skimmed through the basic info sticky. So onto my questions:

    Set up:
    Say I wanted to set up a car stereo with a computer, touch screen monitor, amplifier, subwoofer, and speakers. I would want to get an extra battery mounted in the trunk so I wouldn't drain the more important engine battery.

    Question set 1:
    To power the computer and monitor I need AC voltage. So I'd need an invertor, correct? Does the inverter ground back to the battery? If so would I want to ground directly to the battery instead of the frame since it may interfer with the main battery?

    Question set 2:
    With the amplifier, I'd hook the amp to the battery and the subwoofer and speakers off of that, correct? Couldn't I just hook the amplifer and inverter in parallel to each other?

    Question set 3:
    And because of the voltage drops across each resistor, how would the battery get it's charge back? Would the two batteries have to be hooked in parallel to each other so it gets charge back from the alternator? If so, could I/would I need a more powerful alternater if this is the case?


    That's all the questions that I've thought of so far since starting to plan this process. I do understand it may be confusing so just ask if you have any questions. I hope this is somewhat organized although I do understand it's long. :o

    And you must take this with a grain of salt since I'm only a couple weeks into this electricity class and am trying to run before I can crawl. Also, some of the basic questions are there just to make sure I'm understanding the idea correctly too. :o
     
  2. veonake

    veonake OnT poster, OT lurker

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    From your electronics class you should know that it will have to have a ground. If your question was just wondering if you need to ground directly to the battery rather than chassis ground, the answer is no. Most inverters you'll find run off a cigarette lighter adapter. But, of course it is still grounded. You may find it preferable to run a short length of cable to the chassis to provide a better ground, rather than running a long cable to the adapter or the battery itself.

    Ah, just read the 2nd half of the question. Still, the 2nd battery will still be grounded to the chassis, even if you are using an isolator (diode or solenoid), otherwise it would never be charged by the alternator. So, you can still use chassis ground but get your 12V+ source from the 2nd battery without draining your primary battery (this is the point of the isolator). In fact, an isolator is essential in your case if you don't want to drain your primary battery when running the stereo.
    If you mean you want to power the amp AND the inverter off the same source wire, then no, you can't. I mean, it would work, but not properly and it would be dangerous. You WILL be effectively wiring them in parallel (as far as a shematic would show), but they must have seperate power wires. The reason is the inverter will not use a very large gauge (small #) wire for its 12V+, probably something like 12awg. However, depending on the power output of your amp, it will require as little as 8awg to as much as 0/1awg. So, unless you run at LEAST as large wire as your amp will require to the inverter and use a distribution block you should run 2 seperate power wires, it's just easier and makes more sense. Plus, your ground wire for the amp should be no longer than 18 inches before it reaches the chassis.
    What resistor? Are you referring to the components in the system as resistors? I guess you could look at it like that (I believe there is an electronics analysis method that converts loads into one effective resistor, but I forget the name). Yes, they are wired in parallel and you will need to run an isolator like I mentioned (here is a diagram and explanation: http://www.bcae1.com/battiso.htm). You definitely can and probably should run a more powerful alternator if you are designing a stereo system that requires enough power to be running a 2nd battery. But, it may not be necessary. Tell us how many RMS watts you want to run.
     
  3. GT40

    GT40 lol

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    So the battery would get charged by the alternater even if they aren't directly hooked to each other? From a skim of that site it sounds like the solenoid would be a better choice although I don't understand each of the pictures in the schematics. But basically I'd hooked up the isolators so that running the stereo with the engine off wouldn't drain my main battery. But the extra battery would get recharged from the alternator after being turned on?

    Also about the invertor. I'd want one that doesn't plug into the cigarette light so it looks cleaner. They are available like this correct? :x: :o

    The first part is what I was trying to infer. I'm not too far into class to determine when one component requires a bigger wire so I can't talk too much about this yet :o

    I was referring to the components as resistors. I know how to calculate resistances between the different types of circuits. And RMS watts, I don't know :o To give an idea of everything I'd like to run would be a Mac Mini, a ~7" touchscreen off the inverter. The speakers wouldn't be too impressive, most likely in the 200-300W range for each speaker (probably around 6 depending on the car :o) I'm not sure about the subwoofer either since I've never looked into/compared anything about them. Of course both being run off the amplifer. Nothing top of the line which may sound odd with the amount of effort put into the system as a whole but enough to sound good while being reliable and safe.
     
  4. GT40

    GT40 lol

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    Thanks for the help too. Although there will probably be many more questions.


    Another question. :o
    Could I just save the time and energy and safely run the computer/monitor, amplifer/speakers/subwoofer off the main battery without draining my battery? I'm sure an alternater upgrade would be necessary. The system may be on a tab bit without the car running but not really too often.
     

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