330V Flash Capacitor Question

[Gryphon]

If i were to wire two of these flash caps in series and them apply 600~660V to them would they charge equally? That is, will each of the caps charge to 300~330V.

I know that in rechargable battery packs where rechargable cells are wired in series and charged in series, each of the cells take on a nearly identical charge, im wondering if these flash caps will do the same. What i don't want is one cap taking 500Vs and exploding cause the other one only took in the other 100V.

Just a quick question that i hope can be answered without any headaches

 

[photonaholic]

Its not a common practice.

Electrolytic caps have broad tolerances usually +/- 20%

Further if the electrolyte in one or the other breaks down, it can cause a short allowing the full amount to go to the other cap.

I have always chosen caps that were rated above the working voltage of my project.

ever see one "pop"???

Batteries and capacitors are only minimally similar. they behave very differently.

 

[Gryphon]

Thats exactly what i needed to hear, i guess i'll just get some ~600V rated caps. I
have seen what happens when small electrolytic caps pop, its nasty! I only asked
cause i have dozens of these caps and thought it might be worth a shot.

Thanks for the advice!

 

[digital_blue]

I hope you realize that by putting two or more caps in series, you get less capacitance. It is similar to paralleling resistors; two same value caps in series= half the capacitance and so fourth.

You would normally put caps in series to archive a higher voltage rating. By putting the caps in series like you have done, you have doubled the voltage rating while halving the capacitance. If you want to get higher capacitance,you should put them in parallel...

 

[diachi]

As Digital Blue said, putting them in series reduces the capacitance as it essentially makes your two "plates" further apart.

 

[digital_blue]

I would also like to point out that charging 2 caps in series is going to be difficult. Capacitors can be considered short circuits as they are charging but become open circuits when they are fully charged, if either one of your caps charged before the other one, it would essentially stop the current flow through the network and your other cap(s) will not charge to capacity.

 

[photonaholic]

I think Gryphon has already figured out it's not the best idea.

So why keep flogging the horse? it's already dead.

 

[digital_blue]

I think Gryphon has already figured out it's not the best idea.

So why keep flogging the horse? it's already dead.

Since when did "giving a little more info" equate to "flogging a dead horse"? I've read and re-read my posts and I don't feel I'm being repetitive about anything...

 

[brtaman]

Gryphon: What do you need the capacitors for? Is there a strict 660V requirement?

If not, I have quite a few electrolytic caps, usually inverter grade in the 1000uF area 400V or 450V, if it is a decent project that doesn't require strict 660V i'll let them go for cost of shipping.

450V 1000uF KEMET|ALC10C102EL450|CAPACITOR, 1000UF, 450V, 40X80 | Farnell Republika Slovenija

400V 1000uF EVOX RIFA|PEH200VJ4100MU2|CAPACITOR, 1000UF, 400V, 50X95 | Farnell Republika Slovenija

The 400V one has nice screw down terminals, but is also quite a bit larger. Shoot me a pm, if you're interested.

 

[photonaholic]

Since when did "giving a little more info" equate to "flogging a dead horse"? I've read and re-read my posts and I don't feel I'm being repetitive about anything...

That was "targeted" at no one , I am very sorry if you felt I singled you out.

The additional info is educational to many, and I temporarily overlooked that.

It just seemed at the moment that once the decision was made not to do it, more posts saying it's not a good idea just kept popping up.

However the refresher course on basic electronics 101 is nice:beer:

 

[Hemlock_Mike]

Wellll --- A little old school here. 45 years ago, in ham radio, we often need filter caps for 2,500 volts. The big electrolytics we could afford generally were rated at 450 VDC. So we series 6 of them knowing that the effective capacity was 1/6 of the individual ratings. (Always the same rated caps for this) We also added "balancing" resistors across each cap. Usually 100 KOhms.

HMike

By the way -- these resistors acted as bleeder resistors -- highly recommended in HV power supply applications.