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qucs battery component simulation

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Anonymous
2012-10-06
2012-12-15

  • Anonymous
    2012-10-06

    Hi all I'm a newbie of qucs. I'm trying to make a circuit simulation with a AA 1,5 battery. How can I add a battery component or create it? I have only current and voltage source. How can I simulate a 1,5V AA battery? tnx

     
  •  magneto98
    magneto98
    2012-10-06

    Batteries are quite good voltage sources. If you want to be more accurate you could add a resistor in series representing the internal resistance which depends on things like  battery type / aging / temperature and is probably about 0.3 to 0.1 Ohms

    http://en.wikipedia.org/wiki/Internal_resistance

    Cheers
    Carsten

     

  • Anonymous
    2012-10-06

    tnx, but if I have a voltage source of 1.5V and 500mAh can I use an internal resistance of 3 Ohm? It seem work it give me an output of 0,5A

     
  • @magneto98:
    Creating a true model for a battery is very difficult.  It is no simple task modeling the intricacies of the electrolyte with electrical circuits.  For example, Lithium batteries have a curve that is non-linear (http://johndayautomotivelectronics.com/?p=517) like the one in this link. Batteries have a complicated models where by the series resistance is more of a dynamic resistance which will change as a function of temperature and load current.

    This link (http://www.sciencedirect.com/science/article/pii/S0378775306018349) show a very crude model showing how to model a lithium battery.  This other link shows another approximation (http://www.sciencedirect.com/science/article/pii/S0378775309007873).  The bottom line is that modeling a battery is extremely difficult.  I have experimented trying to make a model, so I can simulate for a example a charging circuit and model the battery being charged and discharged.  I have never gotten close to predicting the behavior of a real battery to a simulated value.  Each curve is different for each chemistry, and determining the battery aging mechanisms is an insurmountable challenge.

    I don't mean to discourage you, but QUCS or LTSpice do not have the modeling of any a real battery.  As someone else mentioned, they are ideal sources which provide infinite current to any load.  They have zero resistance (unless you add one) and it is made of unobtainium material.

    I am not entirely sure what you are trying to do, but perhaps you can use LTSpice or QUCS and use look up tables to do different loading scenarios.  In the past I have measured the discharge rate of a Li battery and fed that data into excel and do different mathematical modeling of a circuit by doing table look up as a function of time.  Depending on the amount of time you need your circuit to run, you can find a battery voltage representative of the real battery and feed that to your system for performance. 

    I hope this helps!

     

  • Anonymous
    2012-10-07

    tnx so much. Do you know an irc chat where i can talk about electronics and qucs? sometimes forum ar not so fast for learning.

     

  • Anonymous
    2012-10-13

    tnx, but in general how can I simulate a source with a specific Voltage and Amperage?

     
  •  magneto98
    magneto98
    2012-10-13

    A source can be seen either as a
      voltage source with voltage and internal series resistance or a
      current source with a internal parallel resistance.
    This model of course neclects the finite energy capacity and other nasty details that rjrodrig6  mentioned.

    The specification 500 mAh of your AAA battery tells you about the capacity, not the internal resistance or what the short circuit current  is. Do you want to simulate the finite capacity of a battery? Could you be more specific about you want to simulate?

    Are you common with the definition of voltage / current sources? See for example
    http://www.allaboutcircuits.com/vol_1/chpt_10/10.html
    for "Thevenin-Norton equivalencies"

    I hope this was helpfull

     

  • Anonymous
    2012-10-14

    tnx for the info. Yes sorry, I confused mAh and mA. I mean there is a method in general to simulate a voltage source with a limited current. I mean an ideal source not so fair from reality with witch I can simulate a battery charger, a AA battery or a power supply.

    Another question is: i need to use a DC-DC stepdown like this

    http://www.ebay.it/itm/LM2596-DC-to-DC-Converter-Step-Down-Module-Power-Supply-4-40V-to-1-5-35V-/170918100512?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item27cb833e20

    to supply a circuit (that we can assume to be like a load resistor). I think that a step down circuit have a square output. How can I simulate a square output? There is an element like a customizable source of energy? For example qucs has particular source like power source and file based source.

     
  •  magneto98
    magneto98
    2012-10-15

    > with which I can simulate a battery charger, a AA battery or a power supply.

    some remarks:

    If you want to simulate a battery, as your source, the easiest is just a voltage source. The next step to reality is a series resistance, which simulates the internal resistance of your battery. With this setup, you already have a maximum current, that you can drain from the battery (in a short circuit situation), because the internal resistance limits the current.

    A battery charger on the other hand in the simplest case is a constant current source. There is additional circuitry, which stops the loading process on the base of specific measure values.

    What do you mean with "power supply" ?
    For example most of the lab power supply devices can operate in a constant current and in a constant voltage mode. They automatically switch between them.

    The step-down-module has already capacitors at the output to smooth the voltage. For many applications, you can assume, that it is a constant DC.
    Your module can supply 3A. For big load resistances (small load currents), it acts as a voltage source. If your load resistance is so small, that you hit the 3A limit, I think the module will switch to a constant current mode as a self protection method.