Question about bipolar electrolytics

[Cap_search]

Good morning all,

Is it true that all the bipolar electrolytics are made/manufacturered of two "back-to-back" polar electrolytics in the - + + - configuration, and that would explain why they are usually larger than equivalent value of a common polarized electrolytic? (e.g. Muse UES)

N.B.: polarized Silmic II are also usually larger than common electrolytic, though.

[stj]

Re: Question about bipolar electrolytics

who cares, it's better to replace them with polyester or polypropylene anyway - just more expensive.

[Cap_search]

Re: Question about bipolar electrolytics

What about BP caps of 220uF or larger?

[stj]

Re: Question about bipolar electrolytics

never seen one.
they probably are very expensive and hard to find too - so still possibly a way to use foil instead.
specially as most BP caps are running below 100v

[Hitto]

Re: Question about bipolar electrolytics

Good morning all,

Is it true that all the bipolar electrolytics are made/manufacturered of two "back-to-back" polar electrolytics in the - + + - configuration, and that would explain why they are usually larger than equivalent value of a common polarized electrolytic? (e.g. Muse UES)

N.B.: polarized Silmic II are also usually larger than common electrolytic, though.

I think not. Bipolar electrolitics are also built as single capacitors with both the anode and cathode foils oxidized.

Back-To-Back vs. Single Cap. is more or less the same but purists swear that the second one has better characteristics. For sure there is less ESL if the capacitor is a single one and lower E.S.R. is also possible.

[Cap_search]

I think not. Bipolar electrolitics are also built as single capacitors with both the anode and cathode foils oxidized.

Back-To-Back vs. Single Cap. is more or less the same but purists swear that the second one has better characteristics. For sure there is less ESL if the capacitor is a single one and lower E.S.R. is also possible.

That's what I thought, too. Just wondered they are usually bit larger than normal polarized equivalents. Grazie.

[R_J]

Re: Question about bipolar electrolytics

Usually the non polarized caps that are larger in size handle larger currents, as an example are the ones that were used in the horzontal yoke section of monochrome tv's & monitors. I still have some Rubycon 6.8µf/50v (18mm x 40mm) I have seen people replace them with regular 6.8/50v nonpolarized and after a few minutes of running the cap heats up and removes itself from the chassis.

[petehall347]

Re: Question about bipolar electrolytics

I have seen people replace them with regular 6.8/50v nonpolarized and after a few minutes of running the cap heats up and removes itself from the chassis.

nearly fell of my chair laughing then ... and of course higher voltage ones are bigger . strange thing i once used a polar cap for testing something that should have had non polar fitted .seem to remember it was starting a motor or something .it worked just fine on AC .

[R_J]

Re: Question about bipolar electrolytics

Higher current ones "of the SAME capacity and voltage" are a lot bigger.
I've seen other shops/customers replace the cap with the type normally found in cheap crossover's
IE: 10µf/50v (6mm x 12mm) for the one I described, and they can't handle the high current. They would look at the capacity and the voltage and figure it should work. They would think there must be a fault somewhere else, They would eventually bring it to our shop and after seeing what they did I would install the correct cap and that was it, fixed.

[redwire]

Re: Question about bipolar electrolytics

I think physically bigger electrolytics have higher ripple current rating because they can get rid of the heat better.

One problem using two polarized electrolytics to make a bi-polar one, is the two capacitors are always mismatched i.e. 9uF and 11uF so the smaller cap can end up seeing reverse voltage, if low frequencies get passed through.
The midpoint is supposed in theory be zero but you get voltage there, and the cap eventually causes distortion and then shorts. So I don't make them this way anymore.

Lately, I always change out bi-polar electrolytic caps for film caps.

[mockingbird]

Re: Question about bipolar electrolytics

Someone on this forum mentioned once that they eventually become polarized.

Mr. Carlson on Youtube also has a video on how film caps really are actually polar caps.

I guess the only real non-polar caps are ceramic.

Every time I come across an NP cap in a circuit, I wonder to myself if it would be possible to re-design the circuit without the need for one. They're very common on modems.

[stj]

Re: Question about bipolar electrolytics

the film caps that are uncased that have a stack of layers with end terminals - the silver ones.
those wont be polarised.

[redwire]

Re: Question about bipolar electrolytics

Mr. Carlson talks about (wound) film caps being "polarized" as far as the outside wrap and a marking stripe on the case.

It's desirable to have the outside wrap connected to the output of a stage (not input), kind of acting like a shield. But this is only for high-impedance tube gear from days long ago.