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Test Rig

Discussion in 'General Electronics Discussion' started by Phi, Sep 29, 2015.

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  1. Phi

    Phi

    3
    0
    Sep 29, 2015
    Hi all

    I'm looking for a little help in building a test rig to simulate a 6 cell lithium polymer battery. What I need to do create circuit that has 6 variable outputs between 3.2 to 4.2vDC but the circuit must act like six batteries connected in series. For example if one cell voltage drops by 1v the overall voltage drops by 1v.

    Any help would be most appreciated.

    Phil
     
  2. Minder

    Minder

    3,102
    664
    Apr 24, 2015
    Is there any significant current drawn from the various junctions?
    Li-Po cell is around 3.3 - 3.6, one way would be to string a number of rectifiers in series to provide a constant volt drop at the junctions, it may require some individual selection of diodes etc.
    And also depend on what you are doing with the junction voltage?
    M..
     
  3. Phi

    Phi

    3
    0
    Sep 29, 2015
    Thanks for your quick response. The junction current would be a couple of milliamps at most. I have designed a circuit to monitor the individual cell voltage of a multi-cell Li-Po pack to be used in RC models. Each cell voltage is fed into a PIC via a resistance divider (2k7 and 27k) the software in the PIC works out the individual cell voltages and deals with it accordingly. I can test the circuit by connecting a LiPo battery and discharging. This is a slow process and cannot simulate each cell dropping individually hence the need for a test rig.

    Thanks

    Phil
     
    Last edited: Sep 29, 2015
  4. Minder

    Minder

    3,102
    664
    Apr 24, 2015
    Is this for an academic exercise as the off the shelf ones are fairly sophisticated and Cheap!
    May not be worth the exercise to make.
    M.
     
  5. Phi

    Phi

    3
    0
    Sep 29, 2015
    Its for my own use and others in my club. The commercially available one's don't do what I want, they tend to rely on lights/sounders to indicate a low cell trip i'm doing something different with the speed controller. I've designed and had pcb's produced i just needed a quick way of testing them without discharging a LiPo each time .
     
  6. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    Have you considered using six variable resistors in a string driven by a constant current source? If each cell doesn't need to be discharged to zero volts, then each test cell resistance could be a variable resistance in series with a fixed resistance.
     
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