Super Caps - Fascinating Electronics

John, If you can find 2 identical Caps, why can't you find 4?  From a technical document I found you don't really need protection on just 2 caps.  Once you move up the # of caps above 2 zeners are recommended.

I seriously doubt they are measuring and matching caps to make the 5V version.

The are just the 2.7V one internally connected.   G

George, they're taking them from the same manufacturing run, and I'm guessing they assume they're characteristics are identical.  You might be able to do the same thing with separate caps, who knows.  I suspect there has been enough testing and analysis to make the manufacturer believe that they are closely matched.  I didn't say they were measuring every set, just that they insured they would be closely matched.

I used to buy sets of resistors for avionics that were matched to .01% for critical bridge circuits. so it's obviously possible to match components.

Absolutely, but you paid for it. Difference between the .05cent resistor and the .45 cent one.  G

Actually, there were more like $20, but I get the point.  In reference to the battery, I think the assumption is, doubtless tested to some degree, that the same batch of batteries have close enough characteristics to not need balancing components.

It was a little more involved.  It also includes the charging supply.  It was a neat article.  It made sense that 2 charging would not get so imbalanced, if so one of the caps was defective anyway, but as you increase the number of caps, the charge time, the voltage, the need for the zener is necessary.

All this is based on using the 2.5V cap as the building block for 5V, 10V, 15V, etc... 

For our system, we are limited to 5V and current limited for charging so it is safe.    G