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  • Adding a second battery?

    I'm interested in adding a second battery to my car for running my amp and car PC alone (so it won't kill my car battery to listen when the car is off). I know it's not at easy as just adding another battery off the terminals of my regular car battery (I at least need an isolator to stop it from killing the main battery...) What else does it take to put together a little backup power system?

  • #2
    All you need is a battery isolator and the necessary cable.
    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."

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    • #3
      Just make sure your alternator can handle the extra load. Right, Aaron?
      ~m
      PII 266, 512 MB RAM, 10 Gig, 36x CD-ROM, 16x DVD, DeLorme GPS, 5.6" LCD Screen, Dschmidt power controller, Keypower ATX DC-DC Supply, PowerAmp Macro controller, Dauphin mini-Kbd.
      Sony Head Unit, Sony Unilink input selector, rear deck Kenwood 6x9's, stock door spkrs... All in my '96 Civic, of course :}
      BC ROCKS!!!

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      • #4
        Almost sounds too easy. My alternator is 110 amp (stock Camero).
        Where would I pick up a strong enough batery isolater (is it a Radio Shack part)?

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        • #5
          Originally posted by TheDingo:
          <STRONG>Almost sounds too easy. My alternator is 110 amp (stock Camero).
          Where would I pick up a strong enough batery isolater (is it a Radio Shack part)?</STRONG>
          You could use a diode!
          The MBR745 from fairchild semi or www.digikey.com would do the trick. Its only 65 cents. That way when your car is on, the battery is charged to 14 volts and the aux battery is charged to 13.6 volts. No current can flow back into the cars elect system when you start your car or turn it off, and both batteries won't discharge each other. Use more of them if you use a larger battery, each diode can pass 7.5 amps.


          Jeff_
          MPEGBOX - Plexiglass Computer
          www.mpegbox.com

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          • #6
            Originally posted by Jeff Mucha:
            Use more of them if you use a larger battery, each diode can pass 7.5 amps.
            Do not parallel diodes and expect them to each carry the same current. There is variation in the manufactur, and some diodes will carry more current than others. These diodes will blow, forcing the remaining diodes to carry even more current. They will then blow. So, you will have a bunch of blown diodes...
            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."

            Comment


            • #7
              Originally posted by dos4who?:
              <STRONG>Just make sure your alternator can handle the extra load. Right, Aaron?
              ~m</STRONG>
              True, true.
              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."

              Comment


              • #8
                With a second battery in parallel, could you not use the atx DC-DC converter from industrialpcs?

                i doubt there more than $180 from keypower.

                industrialpcs

                -MJR-

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                • #9
                  I meant series, but you knew that
                  -MJR-

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                  • #10
                    I found from old at-ps doublediode which can handle 30 amps!
                    It's MBR 3045
                    WINAMPCAR
                    Project almost ready

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                    • #11
                      Originally posted by embedded:
                      <STRONG>I found from old at-ps doublediode which can handle 30 amps!
                      It's MBR 3045</STRONG>
                      Digikey has the MBR4045WT-ND 40 amp diode for about 2 bucks. It has a forward voltage drop of only .4 volts at 10 amps! It is my guess that you could use this to charge just about any battery. And if your worried about over current problems, you can always put a 0.01 - 0.5 ohm resistor in series with it to limit the charging current.
                      MPEGBOX - Plexiglass Computer
                      www.mpegbox.com

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                      • #12
                        I have a 2nd battery (split charge relay)
                        shows schematics and pics http://oacar.mp3car.com

                        costs like $10+battery cost..
                        easy to do, 10 minute install job..

                        just make sure if u buy an acid battery to house it properly.
                        John McLear - [email protected]
                        http://www.205oc.co.uk
                        UK Mp3car slapnut
                        #mp3car - Efnet
                        Carplayer and Mediaengine *****
                        spank gemma.co.uk for holding my motherboard for so long. still no board, wood work nearly done :|
                        [-----------(90%)----] Completed :)
                        pics at: http://www.zcentric.com/~mitcht/gall...me=Convertable

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