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Cut off voltage lithium battery?

Discussion in 'General Electronics Chat' started by Rorut, Apr 30, 2016.

  1. spec

    spec Well-Known Member Most Helpful Member

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    No Probs Rorut.

    I dare say you have skills that I would be jealous of :D: music, singing, dancing, art of any kind, advanced maths, physics, chemistry, are examples.

    Oddly enough, this was the architecture I started out with but chose the other architecture because it was simpler and gave more voltage drive for the PMOSFET, which is the critical aspect.

    spec
     
    Last edited: May 28, 2016
  2. Rorut

    Rorut Member

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    Hi again, I have a question regarding my project that I think maybe is related to the circuit. If you look at my image (hope you can understand my drawings) and look where my arrow points between relay 3 and amp.

    If I connect ac/dc and turn switch 1 on and then off and measure where arrow is pointing I get around 3v that slowly counts down. I think this is wierd? Shouldn't I get 0v after power off? Is there any current staying that leaks down to the capacitor in the LVC?
    Same thing happens if amp is disconnected.

    Relay 3 activates on ac/dc on. Its normally on/closed for battery use.

    image.jpeg
     
    Last edited: Jun 11, 2016
  3. spec

    spec Well-Known Member Most Helpful Member

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    Nothing to worry about:

    There is always stray capacitance around that will store electric charge and as your digital multimeter has a very high input impedance it will take a long time to discharge the charge.

    The amplifier will certainly have some capacitors across the input lines which will store more charge, but the amplifier circuit will provide a discharge path in addition to the input resistance of the multimeter.

    Put a 100K resistor or so across the input to the multimeter and measure again.:happy:

    spec

    PS: Some electronic products, especially hifi amplifiers, have massive capacitors across the supply lines and will continue to operate for a few seconds after the mains power has been switched off.
     
  4. dave

    Dave New Member

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  5. Rorut

    Rorut Member

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    Thank you very much Spec. Now I feel more relaxed about it :). Next step maybe is to figure out how to change my three relays to mosfets :)
     
  6. spec

    spec Well-Known Member Most Helpful Member

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    No probs. Rorut

    After looking at your schematic/block diagram, I hope you don't mind me saying this, but I suspect you have three relays too many. Can you post a truth table to show us what you would like to achieve?

    spec
     
  7. Rorut

    Rorut Member

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    Thank you. No problem, appreciate it :)
    Only reason I have two of thoose relays is because my switches is small and only handle 1A. Third relay is switching between ac/dc and battery. That is why Im using that third relay.
     
  8. spec

    spec Well-Known Member Most Helpful Member

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    Shall I have a look at simplifying your set up?

    spec
     
  9. Rorut

    Rorut Member

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    :) you are to kind!
    This is how my mess looks at the moment. Dont know anything about how to do or draw schematics correct so it's possible things looks crazy. Sorry if it does not make sense! hope its not a problem going offtopic...

    image.jpeg
    19.5v DC is now a 16v, 5A DC psu
    4s BMS is a small balance charger
     
    Last edited: Jun 11, 2016
  10. spec

    spec Well-Known Member Most Helpful Member

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    No worry. I will have a go.

    spec
     
  11. spec

    spec Well-Known Member Most Helpful Member

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    Last edited: Jun 11, 2016
  12. Rorut

    Rorut Member

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  13. spec

    spec Well-Known Member Most Helpful Member

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    Yes, you have got it in one.:)
    If you can ever remove a relay or switch, it is best to do it because they are troublesome things.:eek:

    spec
     
  14. Rorut

    Rorut Member

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    Just wanted to share my boombox i have been working on. It sounds great!! :)

    image.jpeg
    image.jpeg
     
  15. spec

    spec Well-Known Member Most Helpful Member

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  16. Rorut

    Rorut Member

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    Thanks! Because of you I got last pieces together! Im very grateful
     
    • Thanks Thanks x 1

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