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Capacitor Charging? Answered

How do I charge a capacitor rated for 450v at 1150uf using 2 AAA batteries?
I tried using a mini transformer but it takes a very long time.
Is there a quicker solution?
Thanks in advance,
IndianHacker

Discussions

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icengverence

Answer 3 years ago

Skimmed it, good article Eric took some effort there.

I would worry that the 2AAA have enough to charge 465 joules with 1.6 watt-hours...

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icengiceng

Answer 3 years ago

Correction

Capacitave Energy = C*V*V / 2

E=.00115 Farads x 450v x 450v /2 = 116 Joules

Battery Energy = watt-sec = 3volt*.540AH*60s/h = 97 Joules (Carbon-Zinc)

Alkaline battery = 3v*1.2*60 = 216 Joules x .6eff = 130 Jouls

and the efficiency of a 3v to 445v DC to DC converter may only be 60% efficient .

So if you use a converter and two AAA Alkaline batteries you should charge your capacitor in one hour

IF

the AAA voltage maintains 1.5volts for the full hour.

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steveastroukverence

Answer 3 years ago

Alas, how many will read it ? Very nice article though.

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rickharris

3 years ago

2 AAA batteries = 3 volts. That's the maximum your going to charge the cap to. Just slap it across the batteries.

DON'T do this with higher voltages.

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steveastroukrickharris

Answer 3 years ago

He said he used a mini-transformer...you should read the question :-p

:-)

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Jack A Lopez

3 years ago

I am guessing the thing you call "mini transformer" is some kind of DC-to-DC converter,

https://en.wikipedia.org/wiki/DC-to-DC_converter

more specifically a boost converter

https://en.wikipedia.org/wiki/Boost_converter

This type of circuit is commonly used for charging the capacitor for xenon flash tube, for cameras.

This page,

http://www.talkingelectronics.com/projects/XenonFl...

was written by someone who took apart a bunch of camera flash charger circuits, and then he wrote this page to explain how those circuits work.

So, I think the answer to your question can be found by studying the converter you have. Use a voltmeter, with a full scale of 1000 volts DC, for to check if your capacitor is actually being charged. For example, if you discover the capacitor is only charging to 300 VDC, well, then there's some room for improvement.

You can also use a meter or two, to check voltage and current on the input side. Your converter circuit ?might? work better if you give it more voltage than that provided by 2 AAA batteries. Although too much voltage, might destroy your converter circuit.

But even if you did destroy it, then you would have the opportunity to replace it with something better.

By the way, the circuit you want is called a "DC-to-DC converter" . If you use that phrase when describing the problem to others; e.g. "How do I build a DC-to-DC converter?", I think you'll have better luck finding out how to do that. Although, I think the links I have provided are maybe enough to get you started in that direction.

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Josehf Murchison

3 years ago

Of course it takes a long time, I bet about an hour.

If you want to charge the capacitor faster use more than 2 AAA batteries.