ultra-capacitor based battery for data acquisition system

Discussion in 'The Projects Forum' started by jimit5, Sep 18, 2017.

  1. jimit5

    Thread Starter New Member

    Sep 26, 2016
    17
    1
    yes are there any alternatives for comparator lm2231 and MOSFET pmv30un
     
    JohnInTX likes this.
  2. jimit5

    Thread Starter New Member

    Sep 26, 2016
    17
    1
    is i possible to use comparator ic lm358 for the same purpose ??
     
  3. wayneh

    Expert

    Sep 9, 2010
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    The LM358 is an op-amp, not a comparator, and not a good choice here because it requires at least 3V to operate. That's the absolute most your panel can output.

    I don't fully understand that circuit but the shown op-amp is a rail-to-rail type and I suspect that's important for that circuit. LM358 can approach the negative supply rail but it is not rail-to-rail. It cannot sense voltages within about 1.5V of the upper rail.

    You need a low-voltage, rail-to-rail op-amp.
     
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  4. jimit5

    Thread Starter New Member

    Sep 26, 2016
    17
    1
    Found this protection circuit can i make individual circuits for each capacitor and then connect them in series
     
  5. wayneh

    Expert

    Sep 9, 2010
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    5,160
    I think that's a better choice.
     
  6. jimit5

    Thread Starter New Member

    Sep 26, 2016
    17
    1
    thank you for all the help ill upload the final project files which might help others :):)
     
  7. mikewax

    Member

    Apr 11, 2016
    104
    4
    a while back i ordered some chips, the ALD8100xx. never ended up using them, but they are supposed to be your one-chip solution to balancing supercaps while charging in series.
    http://www.aldinc.com/pdf/ALD8100xxFamily.pdf
     
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  8. jimit5

    Thread Starter New Member

    Sep 26, 2016
    17
    1
    thank you for sharing but i have made the above circuit and it works perfect voltage never exceeds 2.69v.
    now that it works can i charge the capacitors with higher voltage coz they cannot over charge and will it increase the charging speed ??
     
  9. wayneh

    Expert

    Sep 9, 2010
    14,616
    5,160
    The answer is, "it depends". First let me point out that your capacitors will have a maximum current rating, and you don't want to exceed that.

    Your ability to supply current depends on the impedance of your power supply. Just raising the voltage might not increase the charging rate. You need to analyze your system to identify the bottlenecks before you can make smart adjustments.
     
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