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So Called Tank Circuit *NEED HELP PLEASE*

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  • So Called Tank Circuit *NEED HELP PLEASE*

    Ok, I can't seem to get this to freaking work and I'm getting really ticked. Please advise. My pc still shuts off when cranking.


    I have a 2000 Expedition. I have a 400 watt inverter hooked up to my 1 farad cap, then the cap it inline with a mbr3045 diode then the battery.

    the two outter pins on the diode are tied together going to the battery and the center pin is going to my cap. so it kinda looks like this:

    pc ---> Inverter ---> 1 farad Cap ---> mbr3045 (middle pin) ---> battery.

    I feel that the 1 farad cap alone should be strong enough to handle a inverter to stay running while cranking, but I guess I'm wrong. I've been reading all the threads about tank circuits and that's when I decided to go with the mbr3045, I bought the 1 farad cap off my buddy pretty cheap. What is going wrong here. It really does seem so simple to have an inverter stay running during cranking but this thing is causing me so much stress.

    Any help would be greatly appreciated.

    Thanks

  • #2
    What all is running on the inverter when you crank?

    How long does the car take to crank

    Mastero

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    • #3
      just my pc (it's a cappaccino tx1) and the truck I would say about 1 - 2 seconds.

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      • #4
        I may be wrong (most likely) but aren't the 1 farad caps designed to supply short bursts of power to amps?

        Just go buy a small sealed lead acid battery to replace the cap and you should be set.

        Comment


        • #5
          I had the same problem, the capacitor doesn't hold the voltage up high enough, long enough to stop a reboot.

          Like grahamrb said, a small (& cheap) sealed lead acid battery to replace the cap is the answer.

          Comment


          • #6
            But guys wont the small battery need to be charged ? .. then i guess it will be connected to the main car battery ..

            What about the small battery getting over charged..??

            Mastero

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            • #7
              This is the inverter I use
              http://shop1.outpost.com/product/3796786
              30 buck when they have it on sale.
              Battery: Autozone DuraLast Gold ** 800 COLD CRANKING AMPS (1000 CRANKING AMPS) (2 years old).
              No problem when cranking and my car can take up to 5 seconds on cold day to start. I run full size P3 system(150W PSU) + 2 amps. Well during cranking the amps are off so that doesn't count.

              No tank circuit or anything but I has 4 GA wire run directly from the battery to inverter.
              Oh it's the Supra not the Matrix.
              2004 Matrix XR A7N8X-VM/400 AMD XP-M 2500+, DS-ATX
              89 Supra Turbo P3 [email protected]/Abit BE6 II, Alpine M-BUS Car2PC.
              Y2K Accord Dell GX150
              RoadRunner is the best FE PERIOD
              EmoRebellion is a SCAMMER

              Comment


              • #8
                Yeah, the battery does need to be charged. It will charge its self automatically from the car. There are plenty of threads on tank circuits using lead acid batteries. You are suppose to hook the lead acid battery up to the alternator (through the mbr3045 diode) but this can get quite complicated. I would recommend just hooking it into the accessory (ie the cigarette lighter, still with the diode). By putting it on the accessory the battery can only receive power when the ignition is on. The diode stops the car from drawing current from the lead acid battery during cranking.

                A cars electrical system is designed to charge a 12 volt battery, therefore there is no issue with overcharging or anything like that.

                Comment


                • #9
                  topache,

                  I guess you missed this thread then :

                  http://www.mp3car.com/vbulletin/showthread.php?t=18537

                  I did post a calculation regarding how long this so called 1F capacitor can hold a charge. >>> Less 0.5 seconds which is useless anyway.

                  Heres my calculation from the thread above :

                  If we assume :

                  The PC drains 5A then we can say the load resistor = 12/5 = 2.4Ohms

                  So :

                  Battery supply = 12V
                  Minimum supply volatge = 10V
                  PC Load = 2.4Ohms
                  Capacitor = 1F

                  t = RC log[e] (Vi/V)

                  t = time ( how long it take to drop to minimum voltage )
                  R = resistor ( PC load, 2.4ohms )
                  C = capacitor ( Tank capacitor, 1F )
                  Vi = Initial Voltage ( Battery supply, 12V)
                  V = Voltage at time t ( Mimimum supply voltage, 10V )

                  Therefore :

                  t = 2.4 x 1 x log[e] (12/10)
                  = 2.4 x log[e] 1.2
                  = 0.44 seconds

                  I though poeple has given up on this idea?



                  MASTERO,

                  "What about the small battery getting over charged..??"

                  Sure you need to charge it first...same as the capacitor. Charge it at "TRICKLE" rate so it doeasnt over charge the battery. The battery can be charged even if the car is not running...this ensure your circuit will survive the crank...hence the name backup. Its abit pointeless if your backup is not charged up when you needed it

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                  • #10
                    "No problem when cranking and my car can take up to 5 seconds on cold day to start."

                    Interesting design...one question though.

                    Do you know the minimum operating voltage of that inverter? A crank can put your battery down to 8 volts which is more than enough to crash your PC.

                    Comment


                    • #11
                      "A cars electrical system is designed to charge a 12 volt battery, therefore there is no issue with overcharging or anything like that."

                      Yup, an optional limiting resistor can be put in series if needed. The typical 13.8V from the alternator ensure your battery can be fully charge as each cells need slightly more voltage than its output voltage.

                      Comment


                      • #12
                        Originally posted by Ricky327
                        "No problem when cranking and my car can take up to 5 seconds on cold day to start."

                        Interesting design...one question though.

                        Do you know the minimum operating voltage of that inverter? A crank can put your battery down to 8 volts which is more than enough to crash your PC.
                        This is the spec for the inverter http://www.xantrex.com/products/product.asp?did=788

                        My point is not really an inverter but the battery.
                        A good battery and big (capacity) will not drop the voltage that much during cranking.
                        2004 Matrix XR A7N8X-VM/400 AMD XP-M 2500+, DS-ATX
                        89 Supra Turbo P3 [email protected]/Abit BE6 II, Alpine M-BUS Car2PC.
                        Y2K Accord Dell GX150
                        RoadRunner is the best FE PERIOD
                        EmoRebellion is a SCAMMER

                        Comment


                        • #13
                          What i was wondering, if you have a motorcyle battery and a car battery.. wont the small battery get over charged...??

                          mastero

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                          • #14
                            Originally posted by Mastero
                            What i was wondering, if you have a motorcyle battery and a car battery.. wont the small battery get over charged...??

                            mastero

                            Shouldn't do, as long as it's a 12v battery and not a 6v battery.

                            Afaik, charge voltage for 12v lead acids is the same, regardless of capacity. As the baterry is charged to capacity, it should stop accepting charge current (especially when it is one diode drop away from the main charge voltage ).


                            Rob
                            Old Systems retired due to new car
                            New system at design/prototype stage on BeagleBoard.

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