Can I apply a voltage higher than a capacitor's rated voltage

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Discussion Overview

The discussion revolves around the implications of applying a voltage higher than a capacitor's rated voltage, specifically in the context of using a 5.5V, 0.22F capacitor with a 6V LED for a school project. Participants explore the potential risks and considerations involved in this scenario, including the effects on the capacitor and LED performance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant considers using a 6V LED with a 5.5V capacitor, acknowledging the potential for minor damage to the capacitor.
  • Another participant explains that running a component at its rated voltage decreases its Mean Time Between Failures (MTBF) and warns that exceeding the rated voltage could lead to catastrophic failure.
  • A participant suggests testing the LED at 5V first to determine brightness before deciding to use 6V.
  • Concerns are raised about the risk of damaging the LED when connecting it to a voltage close to its maximum rating.
  • One participant mentions planning to use a 220 ohm resistor to limit current to the LED, referencing a separate thread for further discussion on resistance calculations.
  • Another participant confirms that a 220 ohm resistor should be adequate, although they note a lack of earlier details about the project.
  • Questions arise regarding the type of capacitor being used, with some participants speculating it might be a supercapacitor rather than a ceramic capacitor.
  • One participant suggests running the LED at 5.5V instead, noting that the capacitor's voltage will drop when the LED is connected, unlike a battery.

Areas of Agreement / Disagreement

Participants express differing views on the safety and feasibility of using a voltage higher than the capacitor's rated voltage. There is no consensus on the best approach, and multiple competing perspectives remain regarding the risks and methods of operation.

Contextual Notes

Participants have not fully clarified the type of capacitor being used, which may affect its performance and reliability under higher voltage conditions. Additionally, there are unresolved questions regarding the appropriate resistance for the LED circuit.

stephenkohnle53
I have a 5.5v .22F capacitor and I plan on using a 6v led on it for a project. Since I am not going to need to use it much and I am willing to do minor damage to the capacitor could I do that. By the way its for a school project so I will likely use it once or twice then keep it but never use it again.
 
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When an electrical component is run at exactly its rated voltage, it will have a certain MTBF (Mean Time Between Failures). The MTBF decreases quickly as the voltage increases. At some voltage, it arcs over / fails / explodes / melts immediately. You will probably have no problems putting 6 volts on a 5.5 volt capacitor if you only do it once or twice. Any damage, however, will not be minor. The capacitor will either still be good, or it will be destroyed.
 
Alright that is what I thought would happen, I think I will see how bright the led is, at say 5v and if it is bright enough then I will use that, otherwise I will use 6v. I got the capacitor from salvaged electronics so I can always get a new one if it gets damaged.
 
Typically connecting a LED to 5.5 V (or 6 V) is an almost sure way of killing it.

You need to protect the LED from too high current.
 
I was planning on adding a 220 ohm resistor. I did not calculate the ohms needed, I read that, that is a good resistor for it. I made a thread about the project here https://www.physicsforums.com/threads/how-to-wire-an-emergency-flashlight.934421/#post-5902730

I put this as a separate thread so others can see this for other projects instead of getting the information from a thread devoted to a flashlight rather than whatever someone else might be searching for. If you want to discuss the resistance needed please go to the other thread as for other protections needed feel free to put that here or the other thread
 
Yes, with 220 Ω it should be OK, you have just not mentioned the other info earlier.
 
Yeah, I have been up far later than I should disassembling things, so I am a little forgetful. Any way after school I will gather some switches then post the supplies I have scavenged in the other thread.
 
What is the function of this capacitor?

If it is a ceramic capacitor, the likely effect will be that it will have only a fraction of its nominal 0.22uf of capacitance.
 
My bet is that OP means not 0.22μF but 0.22F supercapacitor.
 
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  • #10
Borek said:
My bet is that OP means not 0.22μF but 0.22F supercapacitor.
Thanks,
Didn't notice that...
 
  • #11
Why not just run the LED on 5.5V? It will stay alight at a much lower voltage than that.
Remember that, if you plan to use a Capacitor as a power source, its voltage will start to drop as soon as you connect the LED. (Unlike a 6V battery)
What is the current drain of the LED?
 

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