Super Capacitor Series Circuit

In summary, this conversation is about a power bank that uses capacitors and the circuit is potentially dangerous. The person is worried about whether the circuit is safe and wants someone else to check it. They found some interesting Google searches related to supercaps in series and passive balancing of capacitors.
  • #1
emtae55
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TL;DR Summary
I'll make a power bank with capacitors and I made circuit of it. But I'm worrying about whether the circuit is safe, because it's dangerous to use capacitor.
I'll make a power bank with capacitors and I made circuit of it. But I'm worrying about whether the circuit is safe, because it's dangerous to use capacitor.
So, can you check the circuit i made??

pic2.png

My capacitor is 2.7V, 600F and the power bank circuit has "Charging current : 1A maximum, output current : 2.1A(5V) maximum, ouput voltage : 5V DC","http://www.11st.co.kr/product/Selle...%DB_PC_S_%BC%EE%C7%CE&utm_medium=%B0%CB%BB%F6"
I wonder if you understand this site because it's korean :(
Thanks. :)
 
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  • #2
Web site in Korean is useless here and I have no idea what it is that you think is unsafe. You seem to be working with very low voltage and very low current capability. What do you think is unsafe?
 
  • #3
phinds said:
Web site in Korean is useless here and I have no idea what it is that you think is unsafe. You seem to be working with very low voltage and very low current capability. What do you think is unsafe?
I thought whether the power bank circuit gives voltage to the capacitor that greater than 2.7V. Isn't it?
 
  • #4
emtae55 said:
I thought whether the power bank circuit gives voltage to the capacitor that greater than 2.7V. Isn't it?
Well, yes, if you are using a capacitor that is rated too low for the voltage you are using that could make the capacitor have dialectic breakdown. Why would you do that?
 
  • #5
emtae55 said:
I'll make a power bank with capacitors and I made circuit of it. But I'm worrying about whether the circuit is safe, because it's dangerous to use capacitor.
I'm not familiar with placing large value supercaps in series, but for more normal size capacitors in series, we generally would put large resistance value resistors in parallel with each capacitor, to help to equalize the voltage on each. But with such large value capacitors (600F !), I'm not sure that technique works...
 
  • #7
DOH_small.jpg


I clearly was not paying attention. Thought the caps were in parallel. @emtae55 you should be OK since each cap only gets 1/4th of the voltage, so about 1.25V per cap. Still, you should check equalization, as @berkeman pointed out.
 
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  • #8
Although I have not worked with super caps we do need to keep in mind what a capacitor is able to do. And that is accumulate a large quantity of charge from a harmless low current source. It may take many hours to charge a super cap or bank of super caps but by definition a capacitor can dump it's charge very quickly. This will depend on equivalent series resistance (ESR) but when it comes to safety I would assume the capacitor bank can dump its charge with NO ESR.
 
  • #9
emtae55 said:
I wonder if you understand this site because it's korean :(

If the translate got it right then this thing is for Li-Ion batteries. Current seems to be OK, but I'm not sure if it's for single or for double cell?
Quite wasteful to use that suparcap bank this way, but it's expected to be safe.

Though I would put a small fuse in series somewhere.

Ps.: wait, your circuit is actually four supercap in series :woot: Are you sure about that? It's safe up to 10.8V or so, but ... erm...
 
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  • #10
We're getting a number of similar questions recently. There may be some articles driving it. I imagine the application is mobile recharging of batteries for drones, scooters, hoverboards and the like. The advantage would be that the mobile charger could itself be recharged in a very short time from AC mains.

If any of our EE members know of a good tutorial article on mobile power banks, that would be welcome. As always, if you would like to write an Insights article on the topic that too would be welcome. What I would like to see most is a schematic for a commercial mobile power bank using supercaps.
 
  • #11
berkeman said:
I'm not familiar with placing large value supercaps in series, but for more normal size capacitors in series, we generally would put large resistance value resistors in parallel with each capacitor, to help to equalize the voltage on each. But with such large value capacitors (600F !), I'm not sure that technique works...
Passive balancing technique with resistors or ZDs is widely used and protection circuits are similar to circuits for series connection of Li-ion batteries . A colleague has written a paper with simuls included:
https://bib.irb.hr/datoteka/942041....balancing_using_resistors_T.Bari_pp_15-22.pdf
 
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  • #12
Um, guys, I tried to make a batteries, but it doesn't work. I used DMM but it displayed 0V when i measured the charging part.(The charging board's 'B+' and 'B-') I think it is because of the board, so i want to find another one.
The board's name is '864-KC v1.0'. Google it! and the circuit was like this. Thanks
2.png
 
  • #13
Any half-decent Li-charger board would need a bunch of different kind of protection circuits: likely against charging non-healthy (under-depleted, 0V) cells too.

I think you have to supply the initial charge of supercaps yourself, before the charger can kick in.
 
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  • #14
Rive said:
Any half-decent Li-charger board would need a bunch of different kind of protection circuits: likely against charging non-healthy (under-depleted, 0V) cells too.

I think you have to supply the initial charge of supercaps yourself, before the charger can kick in.
I tried it, but it didn't work. I charged the caps and tried to charge with the board, but i couldn't charge them
 
  • #15
emtae55 said:
I tried it, but it didn't work. I charged the caps and tried to charge with the board, but i couldn't charge them
83566975_165308411466635_161139996055568384_n.jpg
83617086_576837356200714_6872001261906952192_n.jpg
83094600_3441058965965106_5784204767316148224_n.jpg
 
  • #16
I'm in a project that make a powerbank with supercapacitor. I made it but it didn't work. Can you confirm it?? My circuit is here. The green one is a board (charging board, 864-kc v1.0). It gives 4.2V DC to capacitor.
2.png
83094600_3441058965965106_5784204767316148224_n.jpg
 
  • #17
emtae55 said:
Summary:: I'll make a power bank with capacitors and I made circuit of it. But I'm worrying about whether the circuit is safe, because it's dangerous to use capacitor.

I'll make a power bank with capacitors and I made circuit of it. But I'm worrying about whether the circuit is safe, because it's dangerous to use capacitor.
So, can you check the circuit i made??

View attachment 255083
My capacitor is 2.7V, 600F and the power bank circuit has "Charging current : 1A maximum, output current : 2.1A(5V) maximum, ouput voltage : 5V DC","http://www.11st.co.kr/product/Selle...%DB_PC_S_%BC%EE%C7%CE&utm_medium=%B0%CB%BB%F6"
I wonder if you understand this site because it's korean :(
Thanks. :)
So far, seems the circuit would work without balancing resistors. Super-capacitors typically have quite uniform Rseries and capacitance to connect them in series without balancing. Take care to equalize temperatures though (make a solid common heat sink) .
 
  • #18
The link you posted is in a language many of us can not read. Can you post a link for the English version?

The photo you show is for a USB power supply that will turn off if more than 1A output is needed (some will work to 2A).

Put a resistor in series with the power supply output for charging. A resistor value of 5 Ohms or more will limit the current to less than 1A. The power rating of the resistor must be 7 Watts or higher, otherwise it will get too hot and burn up.

If the power supply will really supply 2A, then the resistor can be 2.5 Ohms and 15 Watts or higher.

With a 5 Ohm resistor, it will take about 1 Hour to charge the capacitors to 2/3 of full. A full charge will take about 5 Hours. If you want a faster charge you will have to use a higher current supply and a lower value (or no) resistor. To charge in 10 minutes needs a 30A supply. These numbers are not exact but are probably within a factor of 2. (that means it might take twice as long or half as long)

Cheers,
Tom

(p.s. for those that are wondering about the above estimates, the charge time was estimated using the RC time constant. A Constant Current supply would speed things up but those cost more and are harder to find.)
 

1. What is a super capacitor series circuit?

A super capacitor series circuit is a type of electrical circuit that is made up of multiple super capacitors connected in a series. This means that the positive terminal of one super capacitor is connected to the negative terminal of the next one, creating a continuous flow of energy.

2. How does a super capacitor series circuit work?

A super capacitor series circuit works by storing electrical energy in the form of an electrostatic charge. When a voltage is applied, the charge is stored in the super capacitors, and when the voltage is removed, the charge is released. By connecting multiple super capacitors in a series, the total capacitance and energy storage capacity of the circuit is increased.

3. What are the advantages of using a super capacitor series circuit?

There are several advantages to using a super capacitor series circuit. Firstly, they have a higher energy density compared to traditional capacitors, meaning they can store more energy in a smaller space. They also have a longer lifespan and can be charged and discharged more times than other types of capacitors. Additionally, they have a faster charging and discharging rate, making them ideal for applications that require quick bursts of energy.

4. What are the potential applications of a super capacitor series circuit?

Super capacitor series circuits have a wide range of potential applications, including in renewable energy systems, electric vehicles, and consumer electronics. They can also be used in combination with batteries to improve their performance and lifespan. Additionally, they are often used in industries that require high power and quick energy delivery, such as aerospace and defense.

5. Are there any limitations to using a super capacitor series circuit?

While super capacitor series circuits have many advantages, they also have some limitations. One major limitation is their relatively low energy density compared to batteries, meaning they cannot store as much energy. They also have a higher self-discharge rate, which means they lose their charge over time even when not in use. This makes them unsuitable for long-term energy storage applications.

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