Supercapacitor charging methods from 0 V. - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 25, 2018, 07:39:44 pm
content: So I have a supercapacitor bank that I like to play around with for tab welding to ups/inverter testing etc...The problem I've been having is no power supply with a short protection will charge the bank up from 0 potential since the internal resistance of the capacitors is too low and would need to draw huge amount of current so they just shutdown.The only way I can see this working is by using a CC power supply.I've managed to charge them up decently with a Buck converter and a high power 24V DC power supply but the buck converter is limited in terms of power and needs around 5 minutes to fully charge.I'd rather not use a car battery to charge them up since I have no control over the rate at which they are being charged at and don't want to harm the battery by doing so.What would be the best way to charge them up quickly?Would a 600W power supply meant for LED's work? They work in CC mode so I believe this can work...

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2018, 07:55:51 pm
content: Quote from: drummerdimitri on February 25, 2018, 07:39:44 pmYou mean something like PS-MW-600-12 ? They are for LEDs, but still constant voltage supplies, with some short protection. In short: it will not work. Short protection will just choke supply and it will not output any power. You really need purpose-built CC hi-power supply. Don't confuse LED supply with LEDdriver.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 25, 2018, 08:07:50 pm
content: I was thinking something like the Meanwell HLG-600H-15 LED driver.Works with CC and CV modes not sure if it will read a short at 0V though...

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2018, 08:15:53 pm
content: Quote from: drummerdimitri on February 25, 2018, 08:07:50 pmExactly. In case of short it can act different way. Unfortunately datasheet is not that specific. Could be so that short protection differs from CC mode at nominal output voltage. We can only guess here. BTW you can try to contact MW support and simply ask them.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 25, 2018, 08:18:50 pm
content: Quote from: ogden on February 25, 2018, 08:15:53 pmSo will it work? I can always try it before I buy it...

author: The Soulman
author_rank: Super Contributor
timestamp: February 25, 2018, 08:28:33 pm
content: Most cc led psu's I've came across have a fold-back current limiting below a certain load voltage so probably wont work,but if you have the ability to try it, why not..Just out of curiosity, what size capacitor bank are we talking about and how fast do you want to charge it and to what voltage?

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 25, 2018, 09:47:54 pm
content: Quote from: The Soulman on February 25, 2018, 08:28:33 pmI am using 6 2.7V supercapacitors of 2000F each and would like to charge them to 12-15V.The faster the rate of charging the better of course without harming the bank (pun intended).

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2018, 10:00:01 pm
content: Quote from: drummerdimitri on February 25, 2018, 09:47:54 pmFor series supercaps you definitely need application-specific (supercap) charger/supply. They must be balanced similar way as series li-ion batteries.

author: jbb
author_rank: Super Contributor
timestamp: February 25, 2018, 11:27:21 pm
content: Quote from: drummerdimitri on February 25, 2018, 07:39:44 pmI suggest a bigger buck converter. Or several in parallel. You might be able to come up with one that hasinputcurrent limiting which will make maximum use of your 24V supply.Also, Ogden is dead right about needing some balancing between caps.By my calculations you have some 30kJ or more on hand. That’s alot, so be careful! Eye protection is a must, because you don’t want hot chunks of metal in your eyes. Ear protection is probably advisable as well. And gloves to protect you from hot chunks of that-used-to-be-my-good-spanner.Finally, remember to fit some discharge resistors so that this bank will eventually reach 0V on its own (rather than wait for weeks and surprise you).

author: digsys
author_rank: Unknown
timestamp: February 26, 2018, 12:20:58 am
content: For our huge EV capacitor banks, we have a permanent power resistor in series, for charge and discharge. Then a settable LV circuit that switchescontactors IN/OUT. Our Tyco Kilovac / Gigovac breakers are rated up to 1000A @ 1000V, and provide safety OFF as well. They have a huge rangeof smaller sizes.

author: texaspyro
author_rank: Super Contributor
timestamp: February 26, 2018, 06:31:26 am
content: The Maxwell super cap modules that I have (58F/15V, BPAK0058 E015) have 6 caps in series. They sell two versions... the low standby discharge ones use op-amps and interconnecting cables between modules to do balancing. The standard ones just have resistors (270 ohm?) in parallel with each cap in the modules. They came out of wind turbines and had 20 modules (300V) in series. Check their app notes for balancing info.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 26, 2018, 09:21:21 am
content: I forgot to mention that my bank has active balancing circuits made by Maxwell.I have a 12V 1500W power supply and if I can add some type of resistance in series I should be able to limit the current to the max rated power output of my power supply.Problem is finding a resistance that will handle the load and not glow red hot and melt!

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: February 26, 2018, 03:14:55 pm
content: So I tried using my 500W 0.2 Ohm resistor bank and although it worked, the charging time is still quite slow since the current draw decreases rapidly as the charge of the capacitors goes up.I am now convinced I need a CC power source that switches to a CV algorithm midway to get the fast charging I need.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: February 26, 2018, 03:18:01 pm
content: Why not CC all the way?

author: ogden
author_rank: Super Contributor
timestamp: February 26, 2018, 03:18:59 pm
content: Quote from: drummerdimitri on February 26, 2018, 03:14:55 pmYou want to have supply which switches to CV *only* when nominal voltage reached - basically at the very end of the capacitor charging.

author: station240
author_rank: Unknown
timestamp: March 02, 2018, 03:52:04 am
content: Quote from: drummerdimitri on February 26, 2018, 03:14:55 pmHave you tried using a contactor to bypass the charge 0.2ohm resistor once you reach a certain voltage.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: March 02, 2018, 09:33:14 am
content: Quote from: station240 on March 02, 2018, 03:52:04 amNo since I don't know how to make that work...Ideally some kind of voltage regulated automatically variable high powered resistor would be perfect for this. It would start out at 0.2 Ohms of resistance and slowly decrease it's resistance in a way that more of the power supply's power can be dumped into the supercaps. Not sure if such a thing exists!

author: Bendba
author_rank: Regular Contributor
timestamp: March 02, 2018, 02:45:59 pm
content: Automotive light bulb in series? Relatively high resistance when high current goes through, resistance drops when it get close to charged. Just choose the wattage depending on your charging rate.

author: ogden
author_rank: Super Contributor
timestamp: March 03, 2018, 10:07:53 am
content: Quote from: drummerdimitri on March 02, 2018, 09:33:14 amSimpler and much more effective solution is "generic" supercapacitor charger which is based on buck converter. Instead of inventing exotic chargers, better look at supercapacitor as high current battery with discharge voltage equal to 0V.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: March 03, 2018, 03:06:53 pm
content: I found a 600 W power supply capable to delivering a constant 50A to the bank from 0V and starts dropping when the bank's voltage near 14V.I am now capable of charging them in under 2 minutes!Model is a Mean Well PSP-600-12.

author: r0d3z1
author_rank: Regular Contributor
timestamp: July 22, 2019, 06:52:56 am
content: Quote from: drummerdimitri on March 03, 2018, 03:06:53 pmthanks, this suggestion is really useful for me.Could you confirm me that the feature "Constant current limiting" allow the SMPS to act like a CC-CV charger ? My doubt is how does the PS discern between a short-circuit and a discharge capacitor ? Are there some documentations about the short-circuit protection from meanwell ?

author: digsys
author_rank: Unknown
timestamp: July 22, 2019, 07:34:48 am
content: Quote from: r0d3z1I can add support that Meanwell as an excellent manufacturer, as I used to contract to a distributor and met one of the designers. BUT, that unit is not actually a constant current P/Supply ! and you can't use it as such !QuoteWhat it is saying is - the current goes above 105% and below 135%, it will limit the current and commence voltage reduction or foldback. Not sure what the V/I profile is "exactly" with that unit, but once you try to exceed 135% it will go into full shutdown ! If I can find my tech docs, I'll see if they have a "real" CC version.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: July 22, 2019, 08:55:37 am
content: Quote from: r0d3z1 on July 22, 2019, 06:52:56 amThere is no way you could short this unit out as by nature CC power supplies will not try to generate larger currents that what they're rated for. I tried to with a very large gauge wire and when I turned it on it would pass 60A of current through that wire at whatever voltage it comes out to be (Ohms law).Hope this answers your question.

author: Psi
author_rank: Super Contributor
timestamp: July 22, 2019, 09:08:12 am
content: One dirty hack you can do to get past the problem of triggering short circuit protection is to put a light bulb in series with the load and also add a high amp relay across the light bulb to short it out.Power the relay coil from the capacitor so that once the voltage gets high enough the relay automatically removes the bulb from being in series.

author: Kjelt
author_rank: Super Contributor
timestamp: July 22, 2019, 09:23:02 am
content: Check the posts of tatus1969.For his tab welder he designed a pcb that converts some 12V server PSU's to a supercapacitor charger. He also sells them.

author: r0d3z1
author_rank: Regular Contributor
timestamp: July 22, 2019, 10:05:57 am
content: Quote from: drummerdimitri on July 22, 2019, 08:55:37 amyour answer is very clear, thanks.However, it is not consistent with the digsys comment. Have you ever been able to trigger an overload condition as reported by digsys ?

author: digsys
author_rank: Unknown
timestamp: July 22, 2019, 10:36:18 am
content: Quote from: r0d3z1No one can answer that question, nor will having FULL waveform data from the Meanwell. The reason is -howandwhenthe Meanwell reacts to an "overload" depends on thedurationandintensityof the over-current (short cct) pulse !! So, a 1mS pulse of say even 200-300% overloadmayget through without any reaction, but a 1.5mS pulse of the same overload valuemaytrigger an immediate foldback and shutdown. We (you) have no way of knowing the supercap inrush current profile in ALL conditions ie cold / dead flat / under load etcYou can greatly minimize this by inserting a small series resistance, as others have advised, but again - how small and how much effect will it have?drummerd is saying - you can't blow up the P/Supply, but will that 60A inrush pulse trigger the Meanwell's protection circuits? If it does and you don't mind pressing reset a second time, it should work. The only way to find out for sure is to hook the 2 up and run actual tests. Make sure you account for worst case - ie Supercaps totally dead and cold.

author: BravoV
author_rank: Super Contributor
timestamp: July 22, 2019, 12:55:36 pm
content: Alternative cheap solution, suggesting to look for local listing for used LED driver, usually thrown away or sold as scraps as LED signage in retail business tends to upgrade a lot, bought few while ago at really-really dirt cheap price, decent brand ones like Meanwell usually are pretty robust and long life.Had similar situation, not for supercapacitor though, but for charging quite big capacitors in parallel for 36V target voltage, used a Meanwell CV+CC LED driver to charge them at 5A, works flawlessly. For my particular model (photo below), the voltage is adjustable from 33 to 40V and current 2.6 to 5.2A.Bought these last year, the price is too embarrassing low that I won't say it.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: July 22, 2019, 10:02:33 pm
content: Quote from: r0d3z1 on July 22, 2019, 10:05:57 amNever been able to trigger an overload even when charging supercapacitors from a few millivolts .

author: r0d3z1
author_rank: Regular Contributor
timestamp: July 29, 2019, 07:18:23 am
content: Quote from: BravoV on July 22, 2019, 12:55:36 pmgood to know, indeed I am also considering the HLG-600H-36.

author: r0d3z1
author_rank: Regular Contributor
timestamp: August 14, 2019, 04:42:24 pm
content: After some test on HRPG-600-36 I can say that it can't work in CC. Here is the picture of current and voltage on a 1ohm load. As you can see, it is like an overcurrent protection with hysteresis between 15A and 26A. Also the top and low current value are not reported in the DS anywhere.