Operating caps well below rated voltage

[Perry Babin]

I think this has been answered but I couldn't find the thread.

Someone asked me if it would harm a capacitor (10F [not a typo], 24v) if it was operated on nothing more than 12v.

So, I ask... Does it change any of the capacitor's characteristics/parameters/? in any way if it is never operated near rated voltage?

If operated for years at 1/2 rated voltage, does it accept full rated voltage like it would if it had always been operated at the higher voltage?

Or would it require reforming?

[andrewsawesomr]

Operating caps well below rated voltage is fine, however, over time the cap will need to be slowly risen up to its rated voltage if you want to use it at the rated voltage again.

[Perry Babin]

+1

[CapLeaker]

That depends on how much below rated value you go.

For shits and giggles let’s say you use a 200v cap and only have 12v on the rail, that is not a good idea. 25V cap on a 12V rail, is perfectly fine.

[sam_sam_sam]

That depends on how much below rated value you go.

For shits and giggles let's say you use a 200v cap and only have 12v on the rail, that is not a good idea. 25V cap on a 12V rail, is perfectly fine.

What is the best practices should you follow when using a capacitor voltage values because in rare occasions I will use a capacitor with a voltage of 50 volts on a 12 volt switching power supply circuit

I guess this is a valid topic to discuss with what would be an acceptable general rule of thumb to follow

[CapLeaker]

sam_sam_sam
I go by the rule of roughly double the voltage rating vs what the voltage rail is. However this doesn’t work 100% of the time, because of size etc… and also depends on what circuit.
A different problem is when you need caps in stock. Mostly I have 50V caps but I also have common capacities in 25V format. Then I got a very few odd 63V caps that I need occasionally. Primary filter caps I don’t stock period as they are rather expensive. Weird or large capacities I usually order. The brands I use are Panasonic, Nichicon, Rubycon and very seldom a 4th brand all are 105C rated and order them from a trusted supplier, not eBay or AliExpress etc. So far so good, never had a return of any of my capacitors that I put in fail yet.