How long to charge and discharge 50F supercapacitors and how much heat?

[marmstrong941]

I know they are low voltage that's fine. I want to find out charge and discharge time as well as heat from them.

 

[berkeman]

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?

 

[donpacino]

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.

 

[CWatters]

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.

 

[marmstrong941]

I don't have r yet?
12 days would be great

 

[donpacino]

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