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Supercapacitor cycle life, myth or reality?
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ZeroResistance:
I read this statement quite often on the internet

Supercapacitors can be charged and discharged millions of times and have a virtually unlimited cycle life, while batteries only have a cycle life of 500 times and higher.

But when I skim through the datasheet of a supercap, if find this:

Life Time: 1000 hours with rated voltage applied at 65°C
Life Cycles : 500,000 cycles
( 25°C) 1 cycle= Charge to WVDC
for 20s, constant voltage charging
for 10s, discharge to ½ WVDC for
20s, rest for 10s

So it seems there are a number of constraints for the "Life Cycle" parameter.
Are there any true, unlimited (read > 10 million cycle) supercapacitors?

Thanks in advance!
FotatoPotato:
500k cycles sure is a lot!  :scared: I think what the statement "Supercapacitors can be charged and discharged millions of times and have a virtually unlimited cycle life, while batteries only have a cycle life of 500 times and higher." means is that after all those charge cycles the super cap will still contain a good portion of its original capacity whereas a battery would be dead.

But I'm not capacitor expert, just a hobbyist so I'm not 100% sure.
ZeroResistance:

--- Quote from: FotatoPotato on September 24, 2018, 06:39:22 pm ---500k cycles sure is a lot!  :scared: I think what the statement "Supercapacitors can be charged and discharged millions of times and have a virtually unlimited cycle life, while batteries only have a cycle life of 500 times and higher." means is that after all those charge cycles the super cap will still contain a good portion of its original capacity whereas a battery would be dead.

But I'm not capacitor expert, just a hobbyist so I'm not 100% sure.

--- End quote ---

Agreed it seems a lot! However there a quite a bit of fine print linked to the "Life Cycle" parameter.
Eg. 1 cycle is considered when you dicharge the capacitor to 1/2 the WVDC value...
And I'm looking at it from a point of view of discharge application. Like a photo  flash.
How would a camera manufacturer ensure that the capacitor is discharged only to less than 1/2 the voltage and that too at a limited discharge current rate. But then I guess camera's won't be using super cap's due to these limitations, they might be using specially designed caps for the high discharge rate that they are subjected to.
SeanB:
Supercap would prtobably be discharged to half the energy, so to 0.7 of the rated voltage, and also charged to 0.9 of the rated voltage, giving a big increase in lifetime. Thus they could do a million cycles, and under the same situation a lithium cell can also do 2000 cycles.
David Hess:
Increasing the charge voltage by 0.4 volts decreases the life to 1/10th.  Increasing the temperature by 10C decreases the life to 1/2.

So life expectancy at 2.6 volts and 65C may be only 1 month while life expectancy at 2.0 volts and 35C could be 35 years ignoring other failure modes.
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