Capacitor Physical Size??

[DavezDesignz]

I have many capacitors of the same voltage and capacitance but the one I need to replace is larger in physical size .... why would a 16V 100uF cap be twice the size of anothe 16V 100uF cap? sorry I am still quite a noob to learning electronics but have been tinkering for many years.

 

[john monks]

There is no good reason. I noticed that old 20uF 150V capacitor made in the 1940's is much larger than the capacitors made today. I just think the processes are better today.

 

[DavezDesignz]

thank you john monks .... thats what i was figuring but wanted to make sure ... i'm a better safe than sorry type of person

 

[(*steve*)]

There are a number of reasons.

The first, as has been suggested is the age of the device. All other things being equal, manufacturing techniques etc have improved so that the same capacitor can be made smaller.

Other reasons include:

1. Different type (electrolytic, vs supercap, vs tantalum, vs paper)
2. Different ESR. Lower ESR capacitors are often larger.
3. Different in other specs (just like ESR, other specs may have a size impact)
4. Fake capacitor not really the voltage (or capacity, etc) marked

 

[Raven Luni]

There are a number of reasons.

Fake capacitor not really the voltage (or capacity, etc) marked

Why would anyone do that?

 

[poor mystic]

That betrays a happy incomprehension of greedy bastardry.
Don't change, O Luni - you are the hope of the world

PS
The best of modern materials are a good deal stronger and purer than what was available 50 years ago. That means dielectric can be made thinner without breaking down, and that means that more charge can be stored in the same amount of space.

 

[Raven Luni]

Oh I know all about greedy bastardry - so much so that I frequently wonder why the **** I was born into a human body.

But - something like marking a capacitor wrongly in order to profit - surely the consequences of that would be very immediate and quite profound. You make it sound like people are buying capacitors on the black market or something

 

[(*steve*)]

You make it sound like people are buying capacitors on the black market or something

They are. And they don't always know.

Read this. And this.

Bought any parts from eBay recently? Do you know their provenance?

Oh, capacitors specifically, this one (and this one and this one).

(Did anyone mention LEDs?)

 

[Raven Luni]

Dam - way to blow my innocence. I am nolonger the hope of the world

So thats where the capacitor plague came from. I had a motherboard that died from that. I'm going to check all my components before I use them now

P.S. I have never bought anything from ebay and never will

 

[poor mystic]

Something that tends to work in favour of the black market is that capacitors n power supplies tend to be over-engineered. So a designer often specifies a larger device than he thinks will be needed. This leaves room fot the gradual deterioration of the capacitor over the years. Hence the crappiness of the component is not always obvious.