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What happens if we feed an electrolytic capacitor only positive voltages while keeping the negative pin voltage lower than positive. for example positive pin 20V and negative pin 5V.

Does it affect capacitor life?

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2 Answers 2

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The cap can only see the voltage difference between its two pins. When you say "positive pin 20V and negative pin 5V" you are implying these voltages relative to GND (0V), but the cap doesn't care because it cannot see GND. How can it? No pin is connected to GND. It can only see and care about the voltage difference between its two pins.

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  • \$\begingroup\$ So it doesn't matter if the negative pin voltage be higher than the positive pin? \$\endgroup\$ Feb 8, 2020 at 21:13
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    \$\begingroup\$ @ElectronSurf That does matter because it's a difference between the voltage at the pins. The capacitor can definitely tell which pin is higher than the other, especially a polarized one. Remember that A-B and B-A are both differences and have different numbers. \$\endgroup\$
    – DKNguyen
    Feb 8, 2020 at 21:14
  • \$\begingroup\$ @ElectronSurf, the negative pin voltage is not higher than the positive pin voltage \$\endgroup\$
    – jsotola
    Feb 8, 2020 at 21:58
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What matters is the voltage across the capacitor. In other words, from its negative terminal to its positive terminal. As long as that voltage is within the manufacturer's limits then the capacitor will be fine.

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