defective supercap? - Page 1
Forum section: electronics / beginners

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 18, 2024, 01:01:51 am
content: err... I need help. I bought these 10F 3V supercaps made by Cornell Dubilier off Mouser. on my first time testing one, my circuit shorted out. I checked the circuit, but nothing was wrong. the circuit is supplying 2.3v, at 1.5a max. and the supercap polarity was correct. so I checked that supercap with my meter on a 2v conductivity test. it gave me the "short circuit" signal. and then, I ran it through resistance mode, and it shows the resistance between the supercap's + and - is 10Ω. yep. 10Ω. so I thought maybe that specific capacitor was faulty. I grabbed another supercap and conductivity then resistance. same thing. but I think, since these are all-new and haven't been used before, maybe it's just a "sleepy dielectric". what do you think? if it is a "sleepy dielectric", how can I "wake up" the dielectric without frying my MOSFET or voltage reg? plz be gentle

author: Kim Christensen
author_rank: Super Contributor
timestamp: April 18, 2024, 01:32:03 am
content: Your ohmmeter is going to take a very LONG time to charge up a 10F super capacitor... During that time, its going to read as a very low resistance if it started out fully discharged.Charge it via a resistor to limit the current. Or use a power supply with current limiting that can handle a continuous short.

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2024, 01:44:36 am
content: You can use a 3V incandescent bulb to limit the current when charging and provide an indication of the charging progress.

author: wraper
author_rank: Unknown
timestamp: April 18, 2024, 01:45:19 am
content: So do you expect it charging in milliseconds? If circuit has no charging current limit, supercapacitor will basically cause a short circuit.

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 18, 2024, 01:59:09 am
content: that "circuit" wasn't my ohmeter

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 18, 2024, 02:01:37 am
content: what do you mean "has no current limit"

author: wraper
author_rank: Unknown
timestamp: April 18, 2024, 10:58:05 am
content: Quote from: BrainyCapacitance on April 18, 2024, 02:01:37 amIt means you connect it directly to constant voltage power supply. If it's a switch mode supply, most likely it will just go into protection, try restarting, go into protection again.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 18, 2024, 11:28:53 am
content: charging a supercap can take a very long time, in some case it will appear as a dead shorti usually use them in clock related stuff or clock backed up mcu etc ... i use an resistor to drop the inrush it create, sure it create a time constant, a simple diode and a resistor on the clock ic ....for an 1.5 farad at 5v it take at least 15 mins to charge it, and keep 1 week of clock10 farad is a lot ... i mean a lot lollfor sure you don't use that to filter out an psu ??

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 18, 2024, 02:31:47 pm
content: BTW, here is the schematic of "the circuit" that shorted out because of the sleepy Supercap:I am just a starter at electronics, so please tell me if this circuit is bad gently

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 18, 2024, 03:19:18 pm
content: Quote from: Kim Christensen on April 18, 2024, 01:32:03 amokay, so something like This?

author: wraper
author_rank: Unknown
timestamp: April 18, 2024, 06:24:05 pm
content: Both circuits are totally nonsensical. No surprise it doesn't work.

author: Gyro
author_rank: Super Contributor
timestamp: April 18, 2024, 06:27:22 pm
content: Just FYI, the OP is a 16 year old.

author: bdunham7
author_rank: Super Contributor
timestamp: April 18, 2024, 07:32:42 pm
content: Quote from: BrainyCapacitance on April 18, 2024, 02:31:47 pmWhat do you want the circuit to do? The easiest way to charge your supercap is to use a voltage supply and then a series resistor to limit the current. For a supply putting out 2.3V, a 10-ohm resistor would limit the current to 230mA maximum. Your supercap will take a bit of time to charge.

author: CaptDon
author_rank: Super Contributor
timestamp: April 19, 2024, 02:20:49 am
content: You got parts delivered to Antarctica from Mouser?? It's a pain in the ass to get them to Iceland! When first applying a voltage to any capacitor it will appear as a dead short if it is in an energy storage type circuit. You have to current limit the charge with a simple resistor.

author: BrainyCapacitance
author_rank: Contributor
timestamp: April 19, 2024, 03:45:27 pm
content: err... I'm not ACTUALLY in Antarctica. I just chose it for "safety reasons". I hope you can understand