For example a 100 farad 2.7v super capacitor
if I were to charge with limited 1mA current with unlimited voltage
what would be the danger zone for voltage tolerance?
Should i stop exactly upon reaching 2.7v and add no further charge?
or charge to just under 2.7v for example 2.69v?
or is there a reasonable voltage tolerance slightly above 2.7v for a short time if the current is limited to a few milliamps and not forced at high rates?
for example if i were to keep giving it a charge at 20mA continously after reaching 2.7v
would the voltage keep climbing for a bit then level out?
or would it just keep climbing and climbing till the capacitor turns to mush and crumbles to ash from slow corrision or something?
I wanted to know these things because I wanted to get several 3K farad super capacitors and put 5 in series charged up to about 12v to 13v with some battery clamps to use as a car jump starter.
I found some for really cheap too. just 20$ a piece. was going to buy one per month. ending with a total of 5 of them.
if I were to charge with limited 1mA current with unlimited voltage
what would be the danger zone for voltage tolerance?
Should i stop exactly upon reaching 2.7v and add no further charge?
or charge to just under 2.7v for example 2.69v?
or is there a reasonable voltage tolerance slightly above 2.7v for a short time if the current is limited to a few milliamps and not forced at high rates?
for example if i were to keep giving it a charge at 20mA continously after reaching 2.7v
would the voltage keep climbing for a bit then level out?
or would it just keep climbing and climbing till the capacitor turns to mush and crumbles to ash from slow corrision or something?
I wanted to know these things because I wanted to get several 3K farad super capacitors and put 5 in series charged up to about 12v to 13v with some battery clamps to use as a car jump starter.
I found some for really cheap too. just 20$ a piece. was going to buy one per month. ending with a total of 5 of them.
I've played with supercaps. I suspect you may not have done the math for charging a 100F with 1mA - it gives you a rate of rise of voltage of 10uV/s. So to charge to 2.7V needs 270,000s (75hours) assuming there's no leakage current (and there always is).
I'd not worry about the voltage rating if the charging current is only a few mA, the leakage current will increase such that your cap no longer charges at all above a certain voltage. Its very unlikely you'll damage the cap.
Watch out for the ESR in high current applications such as car jump starting. When buying older caps, the ESR will likely be degraded compared to what's in the datasheet.
I'd not worry about the voltage rating if the charging current is only a few mA, the leakage current will increase such that your cap no longer charges at all above a certain voltage. Its very unlikely you'll damage the cap.
Watch out for the ESR in high current applications such as car jump starting. When buying older caps, the ESR will likely be degraded compared to what's in the datasheet.
1 mA charging 100 Farads will take 270000 seconds to reach 2.7V, so some 75 hours.
Rising charge current to 20mA it will now take 3.75 hours
Your capacitor will keep charging beyond 2.7V, until its loss current becomes also 20 mA
Just for argument´s sake suppose it reaches so at , say, 3.5V (reasonable to me as being 30% above rated voltage) and in that case it would be dissipating .02A*3.5V=70mW
Don´t know capacitor size, mass or thermal dissipation, but just guessing it shouldn´t rise more than 1 or 2 Deg C above room temperature, if that much, a very survivable "punishment"
So you won´t kill it by any means, but I very much doubt you can kisckstart your car with it, since we are talking hundreds of Amperes here, cap will discharge in a very short time, probably milliseconds.
I´ll let you calculate that, I already did the first part
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And since you can buy an already made jump start unit for under $50, it seems pointless anyway.
3-in-1 Portable Power Pack with Jump Starter
If you don't like Harbort Freight, there are other brands of jump start power packs. The mechanic at the garage I use uses one of them. So much more convenient that lugging a whole car battery around.
3-in-1 Portable Power Pack with Jump Starter
If you don't like Harbort Freight, there are other brands of jump start power packs. The mechanic at the garage I use uses one of them. So much more convenient that lugging a whole car battery around.
so as long as i'm not trying to shove a current limt of 2 amps into the capacitor with unlimited voltage access
it should be okay?
I have a 100 farad super capacitor at 2.7v
and i was charging at 0.75A and went to the bathroom and came back and it was at 3.00v so i unplugged it really quickly.
im hoping its not damaged in any way. didn't get warm or hot or overheated or anything.
The voltage didnt change when i took it off charge. still holding at 2.95v a few hours later
im afraid to use it now in case i damaged it severely.
ive seen a few spec sheets for similar capacitors saying 2.85v surge rating but im not 100% sure what that means.
it should be okay?
I have a 100 farad super capacitor at 2.7v
and i was charging at 0.75A and went to the bathroom and came back and it was at 3.00v so i unplugged it really quickly.
im hoping its not damaged in any way. didn't get warm or hot or overheated or anything.
The voltage didnt change when i took it off charge. still holding at 2.95v a few hours later
im afraid to use it now in case i damaged it severely.
ive seen a few spec sheets for similar capacitors saying 2.85v surge rating but im not 100% sure what that means.
I wouldn't be using a 100 farad cap to try to jump start a car
but five 3,000F caps would probably work as a jumpstarter.
and with a 100 watt solar panel they would charge quickly (i have a 100 watt solar panel)
so they would charge in a few minutes or less with a 100 watt panel
I wouldn't be charging them with 20mA of course the solar panel can output a lot more than that at 100 watts
and since their only jump starting the car rather than trying to keep it running i wouldn't have to worry so much of needing a 6th capacitor in series
I probably wont go through that though so i'm going to stick with a 100 farad 2.7v capacitor for now.
it was just an idea/concept.
but I found a neat idea for using my 100 farad capacitor.
I used a 10 ohm resistor to slowly drain it without overloading it from 3v to 2.75v
so i used it at 2.75v with my wireless mouse that would run on two NICD AAA's rated 200mAh that died in a few hours
and the super capacitor has been lasting all day and night.
and it still hasn't cut out when at 1.980v the LED on the bottom of the mouse is still lit
and its still working. pretty good for a cheap 6$ 100 farad super capacitor from amazon
its samwha brand which isnt whats on the photo and looks like its been used but it works.
but five 3,000F caps would probably work as a jumpstarter.
and with a 100 watt solar panel they would charge quickly (i have a 100 watt solar panel)
so they would charge in a few minutes or less with a 100 watt panel
I wouldn't be charging them with 20mA of course the solar panel can output a lot more than that at 100 watts
and since their only jump starting the car rather than trying to keep it running i wouldn't have to worry so much of needing a 6th capacitor in series
I probably wont go through that though so i'm going to stick with a 100 farad 2.7v capacitor for now.
it was just an idea/concept.
but I found a neat idea for using my 100 farad capacitor.
I used a 10 ohm resistor to slowly drain it without overloading it from 3v to 2.75v
so i used it at 2.75v with my wireless mouse that would run on two NICD AAA's rated 200mAh that died in a few hours
and the super capacitor has been lasting all day and night.
and it still hasn't cut out when at 1.980v the LED on the bottom of the mouse is still lit
and its still working. pretty good for a cheap 6$ 100 farad super capacitor from amazon
its samwha brand which isnt whats on the photo and looks like its been used but it works.
They're the same caps I bought, except here about $1 a piece. I noticed on one or two the snap-fit pins become a bit loose from the rivets - as the rivet's making the electrical connection this raises the ESR substantially.
https://item.taobao.com/item.htm?spm=a230r.1.14.39.T3yW4L&id=534159938975&ns=1&abbucket=18#detail
https://item.taobao.com/item.htm?spm=a230r.1.14.39.T3yW4L&id=534159938975&ns=1&abbucket=18#detail
You could use a blob of solder to fix the rivets in place. just cover that portion with some flux dabbed on a little bit then place a blob of solder on neatly. not overdoing it but enough to keep it in place and from moving around. Solid connection and probably will never wear out.
I wish I could order the capacitors from that website.
i bought mine for 6$ from amazon with free shipping no tax. took a week or two to get here.
I could buy 10 of those from that website easily no problem as long as the shipping and tax dont factor in.
I would much rather get one of these modules.
https://world.taobao.com/item/53888...a312a.7728556.w12046059-16028651036.39.6cMo1O much better option too.
I could use 3 or 4 regular diodes in series soldered in parallel to each capacitor to act as a balancing circuit. then I wouldn't have to worry of overcharging at all.
I wish I could order the capacitors from that website.
i bought mine for 6$ from amazon with free shipping no tax. took a week or two to get here.
I could buy 10 of those from that website easily no problem as long as the shipping and tax dont factor in.
I would much rather get one of these modules.
https://world.taobao.com/item/53888...a312a.7728556.w12046059-16028651036.39.6cMo1O much better option too.
I could use 3 or 4 regular diodes in series soldered in parallel to each capacitor to act as a balancing circuit. then I wouldn't have to worry of overcharging at all.
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If I bought a good module or good set of beefy 3000F capacitors. used diodes to limit the voltage and balance automatically.. and used ultra heavy duty beefy cables on them.
I was thinking 6 in series with diodes to prevent overcharge and balance them.
I found some for really cheap about 5$ a piece on a website but i dont remember the link..
I could buy 10 of them and get a discount for half off on it!
if I had two sets of 5 in series and paralleled them thats super overkill.
I was thinking 6 in series with diodes to prevent overcharge and balance them.
I found some for really cheap about 5$ a piece on a website but i dont remember the link..
I could buy 10 of them and get a discount for half off on it!
if I had two sets of 5 in series and paralleled them thats super overkill.
Right click. translate this page to english manually.
You will see all the specs and info about this super capacitor.
https://world.taobao.com/item/53415...=a230r.1.14.39.T3yW4L&ns=1&abbucket=18#detail
It says 8 amps continous with 61 amps max draw current
Possibly more than 61 amps if at full charge and your only pulsing it on for a very short period of time like 20ms or something.
The thing is.. I charged it up to 3.2v by accident.. I immediately took the charger off when i saw it hit 3.2v because i wasn't quite paying full attention.
I was only charging with 0.75A
It didn't drop in voltage or anything. It was still cold to the touch.
Kept its voltage over 3.1v for 30 minutes after the charge was removed.
I guess theres quite a bit of over voltage tolerance.
I've taken 35v capacitors up to 50v with no damage whatsoever at all..
I guess capacitors are significantly more resilient to overvoltage than i previously thought..
They are enormously more susceptible to reverse charge damage though.
Ain't testing that with a super capacitor for sure though. yikes.
Well obviously dont use these super capacitors. they aren't the ones you want.
I did see someone manage to do it with six 400F super capacitors though!
Another person did it with six 3,000F super capacitors (or 4,000F I couldn't quite read the value from the camera but its probably 3,000 or 4,000F)
which last long enough to run a huge power inverter and run a heavy load like a shop drill mill.
I did see someone manage to do it with six 400F super capacitors though!
Another person did it with six 3,000F super capacitors (or 4,000F I couldn't quite read the value from the camera but its probably 3,000 or 4,000F)
which last long enough to run a huge power inverter and run a heavy load like a shop drill mill.
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