Charging Supercapacitors

[KarlSchmaltz]

Hey Guys,

I recently ordered some Maxwell 350 Farad 2.7V Supercapacitors, but I have had some problems trying to charge them. When I put it on a normal battery it acts like a short and the wires will start melting. Probably because it's trying to charge it all at once. When I try to charge them on an SSG it acts like a short as well. This is probably a noob question but how do I charge a supercap on an SSG circuit? Has any one done it before?



Thanks.

[Ren]

Do you just use one? Or 8 or so in series? Are they 2nd hand or damaged? Super caps can be sensitive to input voltage, @ 2.7v per unit that doesn't leave much room for error. I hope you didn't connect 12v to the poor thing.

Try using a small battery, within the voltage range of the cap to charge the cap, then remove and measure the cap with multimeter. If it doesn't hold a charge it probably is shorted internally.

I have 6 x 3000F ultra caps here, out of the regen system on a bus. Biggest ones I've seen so far, but even putting 6 in series only nets about 18v worth of use @ 500F. Haven't been game to try them on any of my machines yet.

Regards

[BobZilla]

Not knowing about your machine I cannot say if it will charge them however I CAN say that Bedini tech in general will charge them.

I have a small Solid state energizer that I charge mine with and it works fine. My caps are IoxUs brand 2.7V 400 Farad.

My small SS setup is a single transistor setup with 21 AWG wire about 75 feet to give you an idea about it's size and capability. It is low output compared to a classic wheel. I built it specifically for small stuff like caps, 9v battery, AA battery etc.

.Also Ren is absolutely right about the voltage. We can use a Bedini device because it is high voltage but LOW Amperage. A 12 volt battery by itself is going to slam the hell out of a 2.7 volt cap with current. ---Bob

[Ren]

.Also Ren is absolutely right about the voltage. We can use a Bedini device because it is high voltage but LOW Amperage. A 12 volt battery by itself is going to slam the hell out of a 2.7 volt cap with current. ---Bob

Hi Bob,

Thats not exactly what I was getting at. I was pointing out that a single capacitor is limited by its voltage, in this case, less than 3 volts. If one wanted to use them with a 12v device there would need to be multiple caps in series to reach a suitable voltage range. Running above their voltage ratings will quickly destroy the dielectric material, leaving you with a short circuit. The cap should be able to handle all the current you throw at it, it can only store energy in relation to its capacitance, but the voltage is what it is sensitive to.

Regards

[BobZilla]

Yup I'm with you, I was not focusing on the voltage Level but rather if he connected a 12volt battery directly , think of the current that flows out. It's a combination of over voltage and current in that case.

That's why I mentioned the low current involved on an ssg, to demonstrate voltage doesn't melt wires, current does. An ssg is putting out 100+ volts.

He probably fried it on the first go at the battery and then it was shorted by the time he tried it on his machine. Like you said he can test it with the proper voltage and see if it takes on a charge.

People make the same mistake with LED's all the time, they don't put a resistor in the path and wonder why it fries.---Bob

[KarlSchmaltz]

Thanks for your responses guys. You are exactly right. I was trying to charge them with a 12V battery and that voltage is just too much for cap. I used a AA and the cap started filling up. I have only used one of those caps from the eight I ordered, and luckily it didn't break from the abuse I put on it. I'm learning from experience. Thanks guys.

[BobZilla]

Good to hear that you didn't damage it.

You can put at least 5 in series and charge from a 12v source or you should be able to put resistance in the path to charge just one. If you use about 50 Ohm 1/2 watt it should work. Just be prepared to unhook it quickly when you test. I tried it on one of mine and it was fine. I used two 100 Ohm in parallel. It will actually charge kind of slow, you could lower the resistance to speed it up but just use caution until you find what works.