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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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