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    ok, heres my problem
    my computer is running in my car, but lets say i try to turn on the air while my foot is on the brake, the puter turns off, while its in park i have to rev the engine, ok so last night i get some new fogs put in, and while backing up into a parking space the puter shuts off, so my question is how hard would it be to hook up another battery just for the computer, space doesnt really matter, i just need to know how simple it is,
    BTW i dont know what wattage the fogs are but i have hyper super duper plasma white or whatever, and i have plasma white as night lights so im kinda at a dead end here
    Music is the language, love is the message.

  • #2
    Well, this was covered in a lot of other hardware posts but.....

    You got some serious issues.

    Im guessing your using an inverter.

    Has the problem just started, or is it alwayse like this ? How much other stuff is running off your car ? ( CB, Amps, fog lights Etc. )

    Without the answers to those questions, I would say you have 2 possible problems .

    Your alternator is overloading. or your batery is just going bad.

    Take the car in and ask them to check the electrical system.

    If the electrical system checks out, and its still rebooting, your inverter just sucks.

    The thing about adding a batery is :
    In a 2 batery setup, you normally charge both bateries while the car is running, and run some sort of accessory off the AUX bat when the car is NOT running. If the car is having trouble charging 1 bat and runing the computer, I doubt it can charge 2 bateries and run the computer. Unless the second batery has a lot of amperage.... But I think you should have the alternator / exectrical checked first.

    Techonlogy on Wheels
    Techonlogy on Wheels


    • #3
      im running car, fogs, and computer, i think its the alternator, its a good car just alot of miles so a new will come right up thanks for your response.
      Music is the language, love is the message.


      • #4
        Hooking up a seperate battery for just the computer (or all electronics) is a bit tough. First you'd need a high output alternator to keep both batteries charged. Then you'd need to find space to mount the battery, plus run all new wires. You could probably keep the existing battery, just get a bigger, stronger alternator. Although it is possible that your current alternator is going bad. Bring it into pep boys, they test it for free.


        • #5
          Plus you'll also need a battery isolator otherwise adding a second battery won't do much other than load up your alternator more. With an isolator you can draw power all day from the secondary battery and not affect the rest of your car's electrical system. I know of someone with a late model BMW that has a setup like this with a 1000W inverter and a DJ amplifier running 2 15" subs!
          Jason Johnson
          Yorba Linda, California

          MPC Phase IV - *** PENDING ***


          • #6
            I had this problem too when I put my mp3 player in my new ride. As a temporary fix, I just had the inverter plugged into the cigarette lighter. At idle, it would squeal (low voltage/amps) and the player would die.

            I installed a sub and amp and ran a 4 gauge cable directly from the battery to a brass distribution block (made by Monster Cable i think) to power my amp and inverter. I've got a simple relay that turns on with the head unit that completes the circuit to the inverter. The distribution block and heavy gauge cable eliminated the low power issue altogether.


            • #7
              Wiring. That's all you need to know

              Use a heavy gauge cable from your battery to your inverter or DCDC and all your problems will disappear You have toooooo much of a voltage drop from your battery to the PC. The reason your PC stops at idle, is because the altenator is not up at 14.4V when you are idling, you may only have 13.0V available at the battery. When you then take this voltage off to your PC via tiny cheap cable, you may only have 10.5V at the inverter, (depending on what the current consumption is) and this will cause your inverter to stop, shutdown due to low voltage.

              This problem can also occur because your battery is getting old, and it can't keep up to the load of your car when you idle.

              Get your battery checked, and then proceed to installing at least 8 gauge cable (if your PC is in the back) and you'll be home free



              BjBlaster! Car MP3 & Carputer!

              "The solution to one problem is only the beginning of another"


              • #8
                Ok, Its late, Im board Im in "Picky *****y bastard mode" Cable size has nothing to do with voltage. You can run 300 volts over 24 Gauge wire. Its amperage.

                You cant push a lot of amperage through small wire.

                The voltage may be droping, and thats part of the problem, but the REASON for the voltage drop is something in the electrical system. the reason for a drop in amperage is the wire, but more likely again the electrical system.
                Techonlogy on Wheels


                • #9
                  There _is_ voltage drop down cable, gizmomkr. How much depends on the length and gauge of the cable.


                  • #10
                    Ok, there *IS* loss of anny signal over cable. but I PROMISE, If you get out the DVM, and hook it to the lighter socket, Its going the read the same damn number ANNYWHERE in your car!

                    The drop is tiny, miniscule, minute, - over that kind of distance.

                    Over a thousand feet of cable, you would probably see like .5 to 1 volt drop.

                    There is a formula for it. Cant remember right now.... attenuation.... resistance.... E=mc2

                    But I promise, you will never see a drop in voltage over a cable in your car.

                    One more time - A M P ' S

                    If you dont believe me, try this :

                    get 5 feet of cat 5. and five feet of 4 gauge wire.

                    Disconnect the + lead from your car to the battery. connect the 4 gauge wire to the battery. Test for voltage ( somewhere around 12V) hook the other end to the + wire from the car.
                    Crank the car.

                    now, disconnect, and place the cat 5 cable in its place. test for voltage - Guess what !, still 12v. now crank the car.

                    Let me know what happens.
                    Techonlogy on Wheels


                    • #11
                      Ah yeah, but what you don't seem to understand, is that what you are telling us isn't really all true. Sure if you get a bit of ****y gauge cable and mesure the voltage at the end, it will be the same for a chunky cable.
                      BUT if you then put away your 20,000R load voltmeter and add a 4amp load to the end of the cable, instantly you have a voltage drop.

                      When you load a cable of course it will loose voltage. The current drawn causes the voltage drop.

                      gee where did you go to school......
                      BjBlaster! Car MP3 & Carputer!

                      "The solution to one problem is only the beginning of another"


                      • #12

                        If you put a piece of cat 5 in series with your battery cable, and start the car, you will either start a fire, or the solenoid won't kick in as the current drawn from your starter will burn the thin cable instantly.

                        mind you the voltage at the other end of your cat 5 will be about 0.5 - 1V as the load is so great (200A or so on average) drawn from your starter, that the cable it basically shorted to the battery terminals. WRT the negitive term.

                        So in answer to this post, heavier gauge cable will prevent a voltage drop to your PC and therefore stop shutdown of the puter when you are cranking, or idling at the lights.

                        an average PC will use about 3.5A to 6A @ 12V. say it's 4A for an example.


                        if a cable has a resistance of 0.1R (ohms) per metre, and it's 4.5 metres from your battery to the puter, then the resistance of the cable is 4.5 * 0.1 = 0.45R.

                        Then the voltage drop over that piece of cable is....

                        0.45R * 4A = 1.8V

                        This means that the voltage at the inverter is 12V(battery) - 1.8V(cable loss) = 10.2V.

                        Not quite enough if you want to start your car as well.
                        BjBlaster! Car MP3 & Carputer!

                        "The solution to one problem is only the beginning of another"


                        • #13
                          Get a new alternator.

                          Aaron Cake
                          London, Ontario, Canada

                          Player: Cyrix 200, 32MB RAM, 10.2Gig Quantum HD, Onboard EtherNet/Sound/Video, Custom Lexan Case, Arise DC-DC, Win95 Kernal w/Custom Player
                          Car: '86 Mazda RX-7 w/Basic Performance Upgrades
                          Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
                          Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
                          "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."


                          • #14
                            I'm not disagreeing with what your saying BJ. Based on mc's description, I just dont think that was the root of the problem.

                            And no, I dont recomend using cat 5 as jumper cable. I guess you missed the sarcastic tone.
                            Techonlogy on Wheels


                            • #15
                              The problem is heat and resistance.

                              There is a bit of resistance over a length of wire, as a result the more current across it (Voltage is only potential, current is the actual flow) the more heat that must be dissipated.

                              Also for very long runs there is a loss in power due to the resistance built up over time. 1 foot of cable may not show any, but 1000' will.

                              In a car the distances are so short that cable length is negligible, however the big problem is the power (volts x current). Your fuse is a length of wire designed to take so much flow through it before it burns out 'blows'. Hopefully that amount is lower than the wires attached to it, or your wires will act as a fuse, getting hotter and hotter until they melt apart. probably after setting the interior of the car on fire.

                              Since cars are 12v systems, the only variable you need to worry about is Amps (current).

                              Bottom line. The more amps a machine is pulling, the thicker the wire needs to be, and the larger the fuse.
                              current projects