Most DANGEROUS battery charger circuit I've ever seen. - Page 1
Forum section: electronics / general

author: snipersquad100
author_rank: Frequent Contributor
timestamp: November 06, 2014, 09:09:50 pm
content: I just seen this video on you tube.Would you build this???

author: lewis
author_rank: Frequent Contributor
timestamp: November 06, 2014, 09:20:18 pm
content: Jesus fricking Christ! I suppose it's on that wimpy Yank mains, but still!

author: snipersquad100
author_rank: Frequent Contributor
timestamp: November 06, 2014, 09:31:07 pm
content: Can you imagine plugging that into UK mains.DC Mains voltage, that could give you a bad day.

author: mrflibble
author_rank: Super Contributor
timestamp: November 06, 2014, 09:33:27 pm
content: Dunno. I hate slow 2 minute videos that convey the same amount of information as a single page I oculd scan in 10 seconds max to see if it's crap. And that factor of 12+ is why I won't even watch this or similar videos.So judging by lewis' reaction it is a direct mains connection? If yes then no I would not build it myself. Spare transformers in the junk box are cheap, electrocuting yourself ... well, is actually also cheap but not that desirable.I zapped myself with mains voltage more than a few times as a kid, but it's probably not recommended as a survival strategy.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 06, 2014, 11:50:01 pm
content: It was originally discussed on an EV website so it's probably intended for high voltage batteries, lead acid or NiMH. Obviously for testing and balancing, not everyday use.

author: richard.cs
author_rank: Super Contributor
timestamp: November 07, 2014, 09:36:12 am
content: I own two similarly "dangerous" non-isolated battery chargers that run off UK mains:1) 100W filament lamp, 1n4007, croc-clips. - Gives a pulsed current-source for desulphating lead-acid batteries, can also trickle charge healthy batteries. It's safe so long as you make the connections and give them some kind of insulating cover before switch-on. Generally you connect it to a dead battery that won't take charge, over the next 10 minutes or so the bulb slowly lights as you bash the lead suplhate off the plates and it starts to draw current. After a while the battery is clamping it to whatever it's nominal voltage is and you can put it on a standard charger.2) Motor run capacitor and bridge rectifier heatshrunk into the middle of a cable (8:1 glue-lined heatshrink is amazing stuff) with a connector on the end to mate with the 4 Ah 10-cell NiMH pack I used to use for my bike lights. When loaded by the battery you get 400 mA constant-current charge, a perfect C/10 "standard charge" rate. Again make the battery connection before applying power. I would normally use either a bench supply or a homemade charger to charge the pack at home but the capacitive one was really lightweight and could be carried on my bike.Both are dangerous if used incorrectly, neither has as much exposed live conductor as in the video. As EEs we understand the risks and make such things for our own use but I wouldn't want anyone else to use either of these chargers and if I had children they would be locked away.

author: Shock
author_rank: Super Contributor
timestamp: November 07, 2014, 10:26:32 am
content: http://www.evdl.org/docs/bonn_charger.pdf

author: SeanB
author_rank: Super Contributor
timestamp: November 07, 2014, 06:45:21 pm
content: I had one I used for rejuvenating NiCd cells. Was not exactly safe, but worked well with the 300V pulse into the short to open it. Would give about a month before it needed a zap again.

author: SirNick
author_rank: Frequent Contributor
timestamp: November 07, 2014, 07:46:59 pm
content: Quote from: snipersquad100 on November 06, 2014, 09:09:50 pmNot me, I know when I'm too far in over my head -- and this would be such a time.But, if I were neighbors with richard dot cs, I would head over to his garage with a dead battery and a pack of good beer, stand waaaaaaay back, and let him do his thing.

author: SeanB
author_rank: Super Contributor
timestamp: November 07, 2014, 07:59:04 pm
content: I have some dead batteries, but that will not work with them, they were cooked to death rather well.

author: wagon
author_rank: Frequent Contributor
timestamp: November 07, 2014, 10:37:57 pm
content: I have a big box of various 'widow makers' under my bench. My kids know not to touch it. Also, I'm in the habit of joining the A & N together if the wires are exposed, so if it is plugged in and turned on the breaker outside should pop.

author: snipersquad100
author_rank: Frequent Contributor
timestamp: November 07, 2014, 10:41:50 pm
content: How does this pulse then?

author: VK3DRB
author_rank: Super Contributor
timestamp: November 08, 2014, 09:13:38 am
content: At least it will prevent Cousin Goober from breeding. What a moron.

author: German_EE
author_rank: Super Contributor
timestamp: November 08, 2014, 09:55:37 am
content: Famous last words "Hey Bubba, watch this!"The Darwin Awards website have been notified.

author: G7PSK
author_rank: Super Contributor
timestamp: November 08, 2014, 10:05:20 am
content: I once went into an old rural garage that had a charger on the wall for lead acid batteries of various sizes and types. It was all open copper bars, carbon filament bulbs and bare resistance wires and wood handled knife switches on a large piece of slate. It was still in use despite being originally made for a DC mains in the 1920's sometime in the 50's or 60's it had been fitted with a metal oxide rectifier.The owner reckoned that it worked better than the modern unit he had.I would love to have one on my wall for decoration.

author: rob77
author_rank: Super Contributor
timestamp: November 08, 2014, 10:31:43 am
content: yet another stupid kidbtw... didn't those guys noticed that a transformer is cheaper nowadays than such a big ass capacitor ? and a side effect of using a transformer is safety to some extent

author: Psi
author_rank: Super Contributor
timestamp: November 08, 2014, 11:32:50 am
content: I'm more worried about the lack of a discharge resistor on the capacitor than any thing else.Could easy end up with a charged 60uf mains cap lying on your workbench.Charging a battery using a capacitor based psu isn't unsafe per se, it just has a lot of dangers that need to be handled correctly.It's certainly not a good idea for the general public to be building that.But really, it's not a good idea for the general public to be playing around with mains in general.

author: Psi
author_rank: Super Contributor
timestamp: November 08, 2014, 12:56:37 pm
content: I only said it wasn't a "good idea"

author: richard.cs
author_rank: Super Contributor
timestamp: November 10, 2014, 09:47:33 am
content: Quote from: snipersquad100 on November 07, 2014, 10:41:50 pmIf you're asking about my first charger it pulses because it's only half-wave rectified.

author: Psi
author_rank: Super Contributor
timestamp: November 10, 2014, 11:14:44 am
content: Quote from: GEuser on November 08, 2014, 01:13:31 pmI also said "playing around with" implying unneeded tinkering.

author: Arlen moulton
author_rank: Regular Contributor
timestamp: November 10, 2014, 07:43:46 pm
content: I thought it was that thing with the UK plug on one end of the wire and an american one on the other and a transformer unit in the middle but that is bloody suicidal!!!!!!!!

author: nctnico
author_rank: Super Contributor
timestamp: November 11, 2014, 01:41:39 am
content: Quote from: snipersquad100 on November 06, 2014, 09:09:50 pmA couple of months ago I ran into an adjustable battery charger which basically consisted of a mains powered variac (non isolated) and a rectifier. It did have a 300mA GFI though

author: dannyf
author_rank: Super Contributor
timestamp: November 11, 2014, 02:17:15 am
content: That's a prime example of Mother Nature at work: natural selection.Thanks to that, we are where we are. and we could use more of it still.

author: GEuser
author_rank: Frequent Contributor
timestamp: November 11, 2014, 02:24:22 am
content: Quote from: Psi on November 10, 2014, 11:14:44 amLOL , one actually did not "SaY" anything , one typed it as I cannot hear what your saying at all , but apart from sounding Ha Ha Ha like a politician i'll leave you with your semantics right here ...

author: fubar.gr
author_rank: Unknown
timestamp: November 11, 2014, 03:12:01 pm
content: Here's a similar charger:http://screwdecaf.cx/dp2.htmlAnd a demonstration of the device in action:It IS quite dangerous, but also useful. I once had a car battery connected to a typical charger for three days straight before it would even start drawing any current. With a charger like that I guess it would start drawing current much quicker.

author: nctnico
author_rank: Super Contributor
timestamp: November 11, 2014, 03:14:57 pm
content: A lab power supply which can be set to 30V is much more useful. Still don't expect to get any useful capacity from a lead acid battery which was discharged too deeply.