Author Topic: Polarised capacitor ̶m̶a̶x̶i̶m̶u̶m̶ minimum voltage  (Read 775 times)

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Offline RoGeorgeTopic starter

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Polarised capacitor ̶m̶a̶x̶i̶m̶u̶m̶ minimum voltage
« on: December 30, 2022, 05:34:12 pm »
Capacitors can be damaged if too much voltage is applied.
Can a capacitor get damaged if too little voltage is applied?

Yes.  ;D

There is a type of Li capacitors, a hybrid between a supercapacitor and a Li battery.
https://www.digikey.com/en/blog/lithium-ion-capacitors-can-help-you-provide-high-quality-power

They come charged, and become permanently damaged if discharged less than 2.5V or so, usually they should be kept charged at about 3.7V or so.  Often they come with a small BMS (battery management/protection), just like a rechargeable Li-Ion and alike use to have.

Found one a couple of years ago in a toy RC car, desoldered and charged it, and it was behaving about the same as a small Li-Ion battery.  Then soldered it back and forgot about the RC toy car in the scrapbox.

Now the "super Li capacitor" was measuring only a few mV, tried to charge it but it only heats and barely goes above 0.3V-0.6V open circuit after charging.  I've desoldered the battery protection PCB and pumped more voltage/current, but it only heats and started to bulge.  I guess the damage get from self discharging is fatal for Li capacitors.  :-\

Sometimes called capacitor battery or alike, usually with an associated number, i.e. 13250, like the 16850 Li-Ion cells (16mm diameter 450mm height).

To me it was a surprise to learn that Li capacitors have both a maximum voltage and a minimum voltage, and that they will be permanently damaged not only by overvoltage, but by undervoltage, too.  :scared:



Quote
Li-ion capacitors include a cathode of electric double layer capacitors and an anode of Li-ion batteries. They feature longer operation, higher power output, and higher safety than Li-ion batteries, although the capacity is smaller. Besides, compared with electric double layer capacitors, Li-ion capacitors have larger capacity and higher output voltage.

However, a Li-ion capacitor needs the same protection as Li-ion batteries, for it also overcharges or overdischarges.

You can use Li-ion battery protection ICs for Li-ion capacitors as well, for the voltage level to protect is the same as Li-ion batteries.
Source:  https://www.nisshinbo-microdevices.co.jp/en/faq/091.html

Offline AVGresponding

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Re: Polarised capacitor ̶m̶a̶x̶i̶m̶u̶m̶ minimum voltage
« Reply #1 on: December 31, 2022, 06:42:51 pm »
And I thought tants were a pain in the arse...
nuqDaq yuch Dapol?
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Offline Infraviolet

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Re: Polarised capacitor ̶m̶a̶x̶i̶m̶u̶m̶ minimum voltage
« Reply #2 on: December 31, 2022, 07:41:20 pm »
Those supercaps shouldn't really be thought of as caps but as batteries. Just the way an Li battery can die if drained too far, these supercaps die too.
 
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Offline RoGeorgeTopic starter

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Re: Polarised capacitor ̶m̶a̶x̶i̶m̶u̶m̶ minimum voltage
« Reply #3 on: January 01, 2023, 09:21:48 am »
Agree, though the words "super" and "capacitor" and the value "3.7F" all of them written in clear on it's body makes one think it's a supercapacitor and not a Li based rechargeable battery, or even stranger, a hybrid between a Li-Ion rechargeable and a supercapacitor.  :o

If it weren't for the small round PCB attached to it (the BMS), I would have never noticed that's not a 3.7F supercapacitor.  ;D


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