Vishay Supercapacitor Odd discharge Pattern - Page 1
Forum section: electronics / projects

author: peotra
author_rank: Newbie
timestamp: June 06, 2024, 08:03:17 am
content: Hello,I have this supercapacitor from Vishay MAL219690111E3:https://eu.mouser.com/ProductDetail/Vishay-BC-Components/MAL219690111E3?qs=NEWnq6vH5LfL%2FyoS5veEWQ%3D%3D.When I try to discharge it, I see a very odd behaviour. The supercapacitor instantly goes close to 0V.(Graph Attached)When I stop discharging it, it starts surging back up at a slow pace.(Graph Attached)I'm also unsure if it even discharges much at all, I tried shorting it for hours yet it still stabilizes back to a Voltage close to the one before I attempt to discharge and it doesn't produce heat like other supercapacitors I have shorted.Anyone knows why this happens?

author: CosteC
author_rank: Regular Contributor
timestamp: June 06, 2024, 08:20:22 am
content: I think you might be interested in phenomena of dielectric absorption:https://en.wikipedia.org/wiki/Dielectric_absorptionFor reasons you mentioned, large capacitors are always supplied with terminals shorted - to avoid danger of voltage appearing on seemingly discharged capacitor.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 06, 2024, 08:28:30 am
content: Check the current ratings.Usually:* Supercapacitor is the type which has large capacitance but can supply very little current, maybe just microamps. Used to power real-time clock, back-up SRAM circuitry etc.; typically discharged within days or months* Ultracapacitor is the type which has large capacitanceandcan supply a lot of current, possibly in hundreds of amperes; typically discharged within tens of seconds. Can be used for stuff like storing regenerative braking energy in a train or something.

author: unseenninja
author_rank: Regular Contributor
timestamp: June 06, 2024, 09:14:04 am
content: From what you describe, I would guess that you have ruined this capacitor.The data sheet is quite clear that you should not:o Charge the capacitor at more than 1.5A and ideally charge at less than 1Ao Exceed the capacitor's maximum voltage during chargingo Discharge the capacitor at more than 3Ao Continue to discharge the capacitor below 2.4VThe capacitor in question is a hybrid ultra/super capacitor. The data sheet's limitations as to how it may be charged and discharged have to be respected to avoid damaging the capacitor. Permanently shorting the capacitor is not allowed either.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 06, 2024, 09:38:17 am
content: They really need to stop calling this class of components as supercaps. Call it superbattery or something.

author: unseenninja
author_rank: Regular Contributor
timestamp: June 06, 2024, 09:43:14 am
content: Quote from: ArdWar on June 06, 2024, 09:38:17 amVery true. The list of limitations that I posted could come straight from a battery data sheet.

author: wraper
author_rank: Unknown
timestamp: June 06, 2024, 09:47:44 am
content: Quote from: Siwastaja on June 06, 2024, 08:28:30 amThere is no such clear distinction, all are supercapacitors (double layer capacitors). Some may call them an ultracapacitor but that's about it. Old supercapacitor types all were low current, very high ESR as you mentioned. You really need to look into the datasheet of what you buy to see of what type it actually is.

author: wraper
author_rank: Unknown
timestamp: June 06, 2024, 09:48:30 am
content: Quote from: ArdWar on June 06, 2024, 09:38:17 amThey are not a battery and do not act like a battery.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 06, 2024, 09:55:42 am
content: Quote from: wraper on June 06, 2024, 09:48:30 amHybrids are practically a rechargeable battery tho. It doesn't work like supercaps at all, or capacitors for that matter.In any case there should be distinction between the mode of operations. A better distinction than inferring from EDLC v Hybrid alone.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 06, 2024, 02:47:10 pm
content: Relevant:https://electronics.stackexchange.com/questions/713096/why-is-my-super-capacitor-self-discharging-so-fast