Voltage rating of Capacitors.

[HellasTechn]

Good day to all !

Like most of us, i have come across various types of capacitors with many different voltage ratings.
strange thing is that on computer motherboards most capacitors are rated 6.3 Volts and that value i have only seen on computer motherboards. Isn't that strange ? anyone knows why ?

 

[davenn]

Isn't that strange ? anyone knows why ?

why do you think it is strange ?

they will be on either 3.3V or 5V rails

 

[Anon_LG]

They may be required to keep a ±25% tolerance. 6.3V-5V = 1.3V. 1.3/5 = 0.26. Close enough to 25%.

 

[HellasTechn]

Isnt 6.3 volts a very tight margin for 5 volts rail ?

 

[HellasTechn]

why do you think it is strange ?

they will be on either 3.3V or 5V rails

Well mostly because i havent seen theese in other circuits.

most commonly Circuits runing at 5volts use 10volts capacitors. circuits runing on 12 volts use 16 volt capacitors.

 

[davenn]

without knowing the specifics, the 6.3V ones may all be on the 3.3V rails

 

[HellasTechn]

It is spossible.

 

[davenn]

is what possible ?

 

[gorgon]

There is also a size problem for big capacitors vs higher voltages. Finally also a price problem, lower voltages are cheaper to make.

 

[HellasTechn]

It is possible that they are used on 3.3 volt rails.

 

[AnalogKid]

A general rule of thumb for capacitor reliability is to use a voltage rating that is at least twice the peak voltage the part is likely to see. In this case, a 6.3V cap is close for a 3.3V application. Not exactly following the rule, but motherboards are notorious for squeezing every micro- penny out of the BOM. The world consumes about 20 million motherboards a year. Every penny equates to $200,000.00.

ak

 

[cjdelphi]

I've been using a 16v 10000uf cap on a solar panel which supplies 19v/10w solar panel...

Not yet exploded (handles 19v ok lol) ...
Yet

 

[davenn]

I've been using a 16v 10000uf cap on a solar panel which supplies 19v/10w solar panel...

Not yet exploded (handles 19v ok lol) ...
Yet

well that is a little silly ... seriously

but on the other hand, it's probably not a 19V panel, that's probably its open circuit voltage
it's loaded voltage is more likely to be ~ 12 - 16V

 

[cjdelphi]

I measured 19v with full light...

And i'm happy to take the risk because when the panel is in use, the cap never reaches 19v under load..

Having said that, could i get away with 19v on a 16v cap... i bet i could, i just doubt it would make it's life expectancy...

Electrolytic caps really only explode if you pass more than a few volts higher than rated (3v higher (16>19v) could try this myself supply around 30v) or you reverse polarity on them...

 

[Anon_LG]

I've been using a 16v 10000uf cap on a solar panel which supplies 19v/10w solar panel...

Not yet exploded (handles 19v ok lol) ...
Yet

Have you seen electrolytic caps explode?! Search YouTube for "Russians explode caps in house", in the one I watched, they tested on their furniture and there was dust everywhere. The stuff pops out of the top and becomes airborne, I am guessing not so good for your lungs!

 

[BobK]

It is not a matter of exploding, it is a matter of degrading. Electrolytic capacitors essentially have material plated on a substrate. A voltage higher than the rating reverses this process and the material is removed, eventually causing failure.

Bob

 

[chopnhack]

I had one explode inside of my enclosure for my 'wired' wireless rain sensor project. Due to rms voltage rating not being taken into consideration! oops, rate your caps appropriately

 

[cjdelphi]

Indoors? (It's a portable solar panel)