@Vernon Barry posted:Yes, this design with lack of zener diodes depends on the 4 super capacitors being perfectly matched and never going imbalanced.
The 5V caps used are two 2.7V caps in series with no balancing components. As long as you use capacitors from the same manufacturing lot, they should be well balanced. Obviously, if you're using different types of caps, you could have a balancing problem.
@Vernon Barry posted:It's not as bad a say that time I opened up a PS2 3V engine I bought at a show, and someone made their own supercap using only 1 2.7V rated supercap, and for reasons I'll never find out, also put a resistor in parallel across the capacitor. This had to be the worst misunderstanding of electrical components I've ever seen and the capacitor definitely failed, was ready to explode and one more time powering would have been the event. But that's why I inspect before testing- and this reinforced that.
Apples and oranges here. I actually bench tested the technique used by Peter and checked the balance of the two caps.
FWIW, the resistor across each capacitor is another balancing method, though the Zener diode is a better way to do the job. Of course, you need multiple caps to do this job, not to mention to have a reason to balance the charges. The resistor adds to the load and subtracts running time for the capacitor stack, the Zener only conducts when one capacitor approaches it's maximum voltage rating.
