Does a battery exert energy keeping a capacitor charged?

[berkeman]

Sure they do, AC currents are conducted by the changing electric field.

 

[Piotr R]

Sure they do, AC currents are conducted by the changing electric field.

The current doesn't pass between the plates though, if that's what your saying

 

[berkeman]

The current doesn't pass between the plates though, if that's what your saying

https://en.wikipedia.org/wiki/Displacement_current

 

[Piotr R]

"However it is not an electric current of moving charges, but a time-varying electric field"

 

[Clark Magnuson]

IIRC Lithium batteries leak less than Aluminum electrolytics, but other than that, batteries self discharge more than capacitors leak.
After 30 years of designing battery chargers and power supplies for many companies, and reading the customer like I was playing poker, it seemed that a circuit that lost less than a micro Amp when not in use was ok. Designing a circuit that leaks less than a uA but can stand up to lightning, takes some work.

 

[Piotr R]

what material do you use for dielectric in the capacitor?

 

[berkeman]

what material do you use for dielectric in the capacitor?

Who are you asking, and what do you mean?

There are a number of common dielectrics used. Is this a separate topic you want to ask about, or related to your electrolysis questions somehow?

 

[Piotr R]

Who are you asking, and what do you mean?

There are a number of common dielectrics used. Is this a separate topic you want to ask about, or related to your electrolysis questions somehow?

i'm asking Clark Magnuson, because he brought up designing circuits, so i assume he has experience building capacitors, and yes the dielectric is relevant to electrolysis, because water in a capacitor acts as a dielectric with coefficient value ~80.4, and I am wondering if there is anything he knows that he can tell me about the properties of water, and/ or dielectrics in general in capacitors.

 

[berkeman]

i'm asking Clark Magnuson,

Ah, it helps to remove ambiguity when you want to ask someone if you quote part of their reply. That makes it clear who you are asking. You can do that by clicking "Reply" in the lower right of a post, or just click-drag to select part of a post and click Reply to quote just that part of the post.

I'll tag @Clark Magnuson in case he doesn't have auto-notification of replies enabled in his account.

 

[Clark Magnuson]

I never designed capacitors other than ones I did not want. That was the 10pF /foot of parallel wires or traces. Multiply by 2pi for coax shield.

I have anecdotes from designing with commercial capacitors. Some of the things we look at are:
1) ESL effective series inductance. The leads or wires to the capacitor are 1uH/ meter that adds to the cap's own problems.
2) ESR effective series resistance. For high frequency this is more important than the value of the capacitor in Farads.
3) Maximum RMS current. Must get the heat out of the capacitor.

If there is an electrolyte, it can leak and cause end of life. I test the capacitor with an oscillator, hooked up to an amplifier, hooked up to transformer, hooked up to a DC bias, hooked up to the capacitor under test in an oven. I weigh the capacitor before and after testing. I pick up the capacitor with tweezers, as my finger prints weigh more than the amount of Hydrogen outgassing I am trying to measure.

Some of the best capacitors I have used are multilayer ceramic. They are available in a range of dielectric materials.