I read that the underlying technology (the dual layers) of ELDC super capacitors is limited to about 2.5 V. Yet I see 5 V (and 3.3 V and other) supercap packages on the market.
Also, it is well known to put such capacitors in series with balancing resistors, to prevent one of the two capacitors from receiving voltages beyond their 2.5 V limit. And there are IC's dedicated to charging series supercaps without balancing resistors, e.g. the LTC3225.
For example, the Cooper Bussman brand, part number PB-5R0H104-R. Rated 5 V max with max ESR of 4 Ohms. That supercap appears to be two cylindrical capacitors bound together.
Does that particular model of supercap have built in balancing resistors? In general, is that the case for supercaps rated over 2.5 V?
Are there any tradeoffs to using such a supercap? As opposed to say a Cap-XX brand, a model from the "GW 2" family (having two cells in series). That model has a "balancing" pin and the mechanical drawings at the bottom of the datasheet show its use with an external balancing resistor network. (And a note "Please contact Cap-XX for further information.") When would you want to design your own balancing resistor network, or use a dedicated IC to charge, a series supercap?