If I have a 100V rated capacitor, can I expose it to a 200V source as long as I cut off the source before the the capacitor is fully charged? For example remove the 200V source when the capacitor itself reaches 80V of charge.

Does it perhaps make a difference on chemistry/material as well? I was thinking of doing this with the electrolytic can type.

  • \$\begingroup\$ It can be done, but it's kinda tricky. 1.) Assuming you've got a hot 200 volt source and your box is connected to it and its output is sitting at at 0 volts, how long can you wait for the box's output to rise to 80 volts? 2.) How much current will your 80 volt load require? 3.) How much output ripple can you stand? \$\endgroup\$
    – EM Fields
    Oct 11, 2015 at 4:31

1 Answer 1


Capacitors are rated for the voltage across their terminals.

Be aware that in many cases it is desirable for reliability to derate capacitors so that they never get close to their max rating. Also the ratings may also be lower if the temperature is higher.

Why are you using a 200V supply if you are only going to charge the capacitor to 80V? You will be waking more than 50% of the energy.

  • \$\begingroup\$ I'm trying to avoid a step down transformer or something to provide a lower voltage power source for a small draw. I just want to pulse a capacitor bank with the 200V source as needed to maintain an approximate 80V on it. @Kevin \$\endgroup\$
    – RobC
    Oct 11, 2015 at 1:39
  • \$\begingroup\$ That idea sounds like either a charge pump (using a switched capacitor to supply a high-voltage, low-current load) or a switch-mode power supply (using a switched inductor)... either way, it's tricky enough that it's worth looking into these before trying to roll your own. \$\endgroup\$
    – MarkU
    Oct 11, 2015 at 4:03

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