Super Caps 50F: Charge, Discharge & Heat Info

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Discussion Overview

The discussion revolves around the charge and discharge characteristics of supercapacitors, specifically focusing on their charge and discharge times, heat generation, and related parameters such as equivalent series resistance (ESR) and power dissipation. The context includes theoretical calculations and practical implications of using these components in applications.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Some participants inquire about the charge and discharge times of supercapacitors and their heat generation during operation.
  • One participant suggests checking the datasheets for specific values related to charge and discharge times and maximum current ratings.
  • A participant proposes a calculation for heat generation based on the formula P=R*I^2, indicating that this would provide power loss but not the heat dissipation capabilities of the capacitor.
  • Another participant mentions that certain datasheets indicate a discharge capability of 38A for one second, noting the internal resistance and potential voltage drop at that current.
  • Concerns are raised about the longevity of the capacitors under high current conditions, with references to cycle life and temperature effects on ESR and power dissipation.
  • Some participants express uncertainty about the equivalent series resistance (ESR) and its importance in calculations.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the specifics of charge and discharge times or the implications of heat generation. Multiple viewpoints and calculations are presented, indicating ongoing exploration of the topic.

Contextual Notes

Limitations include the need for specific datasheet values for accurate calculations and the dependence on various operational conditions such as load and temperature, which are not fully resolved in the discussion.

marmstrong941
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I know they are low voltage that's fine. I want to find out charge and discharge time as well as heat from them.
 
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marmstrong941 said:
I know they are low voltage that's fine. I want to find out charge and discharge time as well as heat from them.
Have you looked at their datasheets?
 
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A good back of the envelope calculation for heat will be the ESR * your expected current draw squared

P=R*I^2

But that will only tell you power loss, not heat dissipation capabilities of the unit itself. If your power loss is greater than your heat dissipation limit, goodbye capacitor.

For charge and discharge time that will be dependent on your load and other properties (look up RC time constant), or are you talking about maximum. the mins and maxes can be found on the datasheet.
 
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Some...
http://cdn-reichelt.de/documents/datenblatt/B300/VEC3R0506QG.pdf
..say you can discharge at 38A for a second.

The internal resistance is around 10mOhm so there will be an IR voltage drop of perhaps 380mV at that current. The I2R power dissipation would be large 382* 0.01 = 14W.

I don't think they would last very long if abused like that. They give a life of 500,000 cycles (at 25C). If cycled every 2 seconds that would be about 12 days. Over the lifetime the ESR and hence power dissipation could also double. The general rule for some capacitors is that the lifetime halves for every 10C increase in temperature.
 
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I don't have r yet?
12 days would be great
 
marmstrong941 said:
I don't have r yet?
12 days would be great
Look on the spec sheet for the capacitors. you're looking for the ESR
 
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