True enough, but for electrolytic capacitors in series opposition, why would the voltage rating for the pair be twice the voltage of the voltage rating of the weakest cap?

Because the capacitors in series are a voltage divider just like resistors in series. It just made sense to me that each cap only sees the potential difference of half the applied potential. And without this effect, supercapacitors could not do much over 2.7V.

Here is a comment from a super capacitor manufacturer...
https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php

Voltage
Series connection: When placing cells in series the overall voltage is increased directly by the number of cells in series.
Example: 4 cells (rated at 2.7V each) connected in series will have a maximum voltage of 10.8V.

Do you see it differently?

 

Because the capacitors in series are a voltage divider just like resistors in series. It just made sense to me that each cap only sees the potential difference of half the applied potential. And without this effect, supercapacitors could not do much over 2.7V.

Here is a comment from a super capacitor manufacturer...
https://www.tecategroup.com/ultracapacitors-supercapacitors/ultracapacitor-FAQ.php


Do you see it differently?

Yes, quite differently.

First, the manufacturer's comment is directed toward connecting the capacitors in series aiding for use in DC applications, while the discussion in the thread is about connecting electrolytics in series opposition for use in AC applications where a non-polarized capacitor is required.

Second, while it's not an excellent analogy, an electrolytic capacitor can be likened to a rectifier with its cathode corresponding to the capacitor's positive plate. Such being the case, if two rectifiers with different breakdown voltages are connected in series opposition and subjected to a symmetrical AC signal, the breakdown voltage of the pair will be the breakdown voltage of the lowest rated rectifier.