Capacitors and Batteries

[calbiterol]

I have two questions and LOTS of time on my hands.

1. How can I make capacitors?
   
2. How can I make a rechargeable battery?
   

I'm not looking for incredibly efficient, just working.

 

Thanks in advance.

 

P.S.: If you guys have any other ideas about things I could make, along the lines of linear accelleration, power production, etc, lemme know.

[YT2095]

1. you don`t mention what Type of capacitor or rating?

but a simple way is to get 2 sheets of alu baking foil attatch a wire to each, get 2 sheets of plastic from a thick bag, making sure it`s a good inch bigger than your foil sheets, put the plastic sheet 1 on a flat table then a foil sheet then the other plastic sheet then the last foil sheet, so you have a layered sandwitch effect, and then carefully roll it up, making sure it stays as even as possible, then wrap some tape around this to keep it in position, you`ve just made a capacitor

 

2, get 2 peices of roofing lead sheets attatch a wire to each, put them in a plastic container 1 each side making sure they don`t touch, and pack in some fiberglass loft insulation between them so they don`t move about, then pour in a 30% sulphuric acid soln.

put that on to charge at roughly 2.5 volts, for an hour or so. there`s your rechargable battery

[5614]

I think that saltwater acts as a capacitor (but probably a poor one), the reason I say this is that when I was looking at cheap! tesla coil designs one website suggested using lots of saltwater for the capacitor (cap) bank!

[YT2095]

no it doesn`t.

the salt water only acts as one of the conductors, the Glass bottle acts as the dielectric.

[5614]

ohhh, that explains that! salt water is preferrable because its a better conductor than water and is very easily available.

[calbiterol]

I don't know too terribly much about types of capacitors and their ratings, so I didn't specify. I know the basic theory behind them, though. Can someone explain the ratings, types, and general theory behind capacitors to me?

 

Thanks.

[5614]

here's a lot on capacitors (aka caps):

http://en.wikipedia.org/wiki/Capacitor

 

any questions just ask, I thought I may as well give you that rather than type loads up and I probably wouldn't have included all of that anyway! If you have a question I will answer it though.

[calbiterol]

YT, what are "roofing lead sheets?" And could you give me a rough idea of the amount of power these will store?

[YT2095]

roofing lead sheets are just that, sheets of lead metal used for flashing on roofs, you`ll be able to get this from most large DIY stores, usualy sold in rolls.

 

as for the power, that all depends on how large and how many cells you make, the emf per cell is a constant in way of voltage, but the current alters with surface area.

[calbiterol]

Are there any other ways of making rechargeable batteries? Can I just use the same stuff that they have in commercial ones, if I can get a hold of it? Also, where could I get sulfuric acid soln? And does it have to be a 30% soln?

 

Thanks.

[swansont]

Are there any other ways of making rechargeable batteries? Can I just use the same stuff that they have in commercial ones' date=' if I can get a hold of it? Also, where could I get sulfuric acid soln? And does it have to be a 30% soln?

 

Thanks.[/quote']

 

Maybe an auto parts store would have acid for car batteries. Online, I'd try Fisher scientific.

[ed84c]

Are there any other ways of making rechargeable batteries? Can I just use the same stuff that they have in commercial ones' date=' if I can get a hold of it? Also, where could I get sulfuric acid soln? And does it have to be a 30% soln?

 

Thanks.[/quote']

 

Find a car battery by the side of the road. Since this idea was mentioned in a thread a couple of days ago, ive noticed no end of them, so it shouldnt be too hard, just keep your eyes open

[Guest hoichua]

Hi guys, I am new here. I had a 220VAC 1000 micro farad capacitor from Nippon Chemi-con. This capacitor started to leak out some yellowish liquid and lots of smoke prodcuced. This happen while connected to the power source of 240VAC at 50Hz. Please advise.

[YT2095]

it`ll carry 220vac through it, but not at infinate current, a dead short charge will kill the cap (it`ll basicly Boil). caps of that type are usualy used in conjunction with an inductive load for mains conditioning and spike supressors, not to be used alone in parallel to the supply, but rather in series with a load (for the AC types).

 

the yellow discharge is the contaminated electrolyte gell leaking out, be carefull as some caps have a rather toxic electrolyte.

[mmalluck]

Hi guys, I am new here. I had a 220VAC 1000 micro farad capacitor from Nippon Chemi-con. This capacitor started to leak out some yellowish liquid and lots of smoke prodcuced. This happen while connected to the power source of 240VAC at 50Hz. Please advise.

 

 

Well lets see.... It's rated for a maxium of 220vac and you decided to run it at 240vac. Not to surprising it died really....

 

I'm guessing this is an electrolytic and most (but not all) are polarized. This means one terminal needs to be keep positive and the other terminal negative with respect to eachother. Things like camera flash capacitors and what-not usually have a dark stripe with little negative signs to denote the negative terminal of the capacitor. Failing to hook it up right will end with a lot of smoke, goo, and possibly rupture.

[YT2095]

I read ir as 220v AC rating, in that case it`ll be fine with AC current, and the extra 20v won`t hurt it as there`s a good +15v per hundred overvoltage tollerance.

 

the problem will be shorting it directly across the mains! it`ll try and draw infinate current and just blow, it needs a resistive (or reactive, frequency matched) Load.

[Guest hoichua]

mmalluck, indeed it is polarized.

Well I am not too sure whether it is directly connected to the mains. I will check out the diagrams and come back to this as I found this forum pretty responsive, I like that.

 

YT2095, I am interested to find out more about this tolerance thingy. How do you know it's +15V? Mind sharing a little more to enlighten a newbie here?

 

Thanks in advance.

[MetaFrizzics]

Electrolytic caps have TWO ratings: a constant voltage rating, and a surge rating, about 20% higher than the normal rating. The idea of charging or using an electrolytic cap in a circuit and exposing it to more than its standard rating is bad advice. First of all the ratings are variable between manufacturers and are based upon statistical testing only. If they meant 240 v they'd have said 240 v, not 220 v.

 

(1) Electrolytic caps can never be reliably used in pure A.C. circuits. They work by having the charge that they hold help sustain an insulating film between the plates. In order for electrolytic caps to work reliably, they must be charged to at least 30% of their rated voltage.

 

(2) There are a few specialty caps made that are made out of pairs of electrolytic caps manufactured in one package. They work by placing two caps in series, one in reverse orientation (by tying the +ve leads together internally). These caps however usually have low voltage ratings ( < 120 volts AC) and low capacitance (100 MFD is large). They are made for light-duty audio circuits such as crossover networks inside speaker cabinets. They should not be used in power supplies.

 

(3) Most non-polarized caps have very low capacitance values (e.g., < 100 MFD) but can have higher voltage ratings, such as caps made with insulating mica layers.

 

The typical rule of thumb in building circuits is to OVER-rate the cap's requirements by 20-30% at the minimum. Thus for a full duty-cycle powersupply of 50 volts, it is sensible to use a cap with a 60-80 volt rating (100 v surge). But one should not use one with a rating higher than 150 volts in the same circuit, because the internal dielectric (insulating) layer would be insufficiently formed and there would be internal arcing and shorts.

 

While some (not all) electrolytic caps are 'self-healing', that is, if there is a short, it is momentary, and burns out like a fuze, this leaves the cap with a slightly lower capacitance overall, and too many such incidents will eventually cause the part to fail.

 

Caps should not be exposed to maximum voltage without a charging resistor in series to limit the current while the capacitor is charging up to operating voltage. This resistor can be switched out of circuit by a relay when the cap is charged and ready to go, thus preventing it from hindering the operation of the powersupply when in normal operation.

 

In sum, if you want large capacitance you need either electrolytics or home-made (very large) caps, built according to safety standards regarding fire/shock.

 

Electrolytics have to be charged to 30% of their rating to work reliably.

 

Electrolytics should not be operated higher than to 90% of their rating.

 

Electrolytics should have a charging resistor in series when powered up.

 

Electrolytics should not be used in pure A.C. circuits without special precautions.

 

Manufacturers' ratings should only be used with a safety factor tacked on.

[[Tycho?]]

How would one charge a homemade capacitor? Does one simply run a current throught it, does the time connected matter?

[YT2095]

impossible to determine without knowing the parameters of the cap, or what type of current you wish to use it with.

 

surface area, dielectric constant for the material used, dielectric thickness, plate spacing from edges etc...

[[Tycho?]]

impossible to determine without knowing the parameters of the cap' date=' or what type of current you wish to use it with.

 

surface area, dielectric constant for the material used, dielectric thickness, plate spacing from edges etc...[/quote']

 

 

Could you give an example case then?