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The inside of an EDLC supercapacitor

TechEkspert 4722 5
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  • The inside of an EDLC supercapacitor
    Surprised by the damage to the supercapacitor, I described the repair of the fault in the topic: Damage to the EDLC supercapacitor (RTC hold). Reading the answers, I learned from @bestler that this is a standard fault and I overestimated the durability of supercapacitors supporting the operation of RTC systems in relation to traditional batteries and disposable cells, e.g. CR2032.

    @tmf pointed out that the EDLC can spill and destroy the PCB, @ritterx suggested that there are two series capacitors inside. We'll see what's inside the damaged capacitor.

    We remove the plug with the leads, you can see the electrolyte and the contact to the capacitor inserted into the metal housing, it is a "push-in" connection without additional welding or soldering.
    The inside of an EDLC supercapacitor


    The plug on the other side connects to the metal housing.
    The inside of an EDLC supercapacitor


    In the housing there is another element in a plastic cover.
    The inside of an EDLC supercapacitor


    They are two capacitors connected in series. The housing resembles a button cell. There is a spring-loaded conductive pad between the capacitors.
    The inside of an EDLC supercapacitor


    It's exactly as you predicted, inside there are two capacitors that have leaked. It's good that the whole thing is in an additional housing.

    I wonder if spercapacitors are used in a housing such as a button cell?

    If so, you can easily confuse such a capacitor with a disposable cell or a battery (unless it has a meaningful marking on the board or a print on the housing).
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  • #2 20427716
    Anonymous
    Level 1  
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  • #3 20428110
    1rycho
    Level 22  
    I have replaced many such capacitors in Mitsubishi motor encoders. After several years of work, the inside of the capacitors looked exactly like the pictures.
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  • #4 20431148
    austin007
    Level 17  
    They fail from hours worked (under voltage) or it doesn't matter if they are working or a lounger? How is the MTTF defined in the notes? Interesting demolition.
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  • #5 20431426
    TechEkspert
    Editor
    This capacitor has failed during live operation (buffer power / RTC backup).
  • #6 20431481
    Anonymous
    Level 1  
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