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I've recently seen 8.4V stacked super-capacitors which advertise themselves as "not requiring any balancing". Namely, the 196HVC series from Vishay.

enter image description here

How can this be true? Even if the cells are extremely well matched, wouldn't wear and tear eventually cause a sufficiently large mismatch to require balancing after all?

EDIT:

I actually bought some of these to try them out, and it turns out the cells slowly discharge from 8.4V (maximum voltage) down to around 7.8V over the course of 12hrs or so. Afterwards, the voltage stays at 7.8V for a very long time (i.e. months). This most certainly points to an internally balancing mechanism, using SAB MOSFETs, clamping diodes, or something else.

The verdict is still out as to how these particular super-capacitors implement the balancing.

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  • \$\begingroup\$ Internal balancing/clamp diodes? \$\endgroup\$ – winny Sep 18 '17 at 21:03
  • \$\begingroup\$ Maybe SAB mosfets? aldinc.com/… \$\endgroup\$ – TRISAbits Sep 18 '17 at 21:04
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    \$\begingroup\$ If the leakage is proportional to voltage, that's equaivalanet to having a balancing resistor across each. If the leakage is proportional to a higher power of voltage, that's equivalent to having some sort of soft threshhold diode across each. It's possible, who knows? \$\endgroup\$ – Neil_UK Sep 19 '17 at 6:04
  • \$\begingroup\$ Are you sure that wasn't just dielectric absorbtion? \$\endgroup\$ – τεκ Jan 5 '18 at 19:18
  • \$\begingroup\$ @τεκ: My understanding of dielectric absorption is that a small voltage will develop in a discharged capacitor. What I've observed with these super-caps is a slight discharge to a fully charged capacitor. Does dielectric absorption work in this way? \$\endgroup\$ – TRISAbits Jan 5 '18 at 22:50

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