PC ATX power supply for Lipo battery charging. Not working. Faulty? - Page 1
Forum section: electronics / beginners

author: akujiwar
author_rank: Newbie
timestamp: December 22, 2014, 06:02:54 pm
content: HiAnd greetings from Norway. This will be my first post here. Apoligies in advance if my english is not up to scratchI've recently attempted to convert an ATX PC power supply in order to power a high power lipo battery charger. However i'm having little luck. I have earlier done this with success using an older 200w supply, but needed more power and bought a new 950W one. On paper it should be capable of 64A on 12V which suits my needs just about right.But this is what happens:Firstly, when i plug it in, ( or flick the mains switch, whichever results in powering it, but not starting it) most of the time, it will overload the fuse and im left fumbling around in darknessGot 220-230V in my outlets and have tried powering it through an otherwise unused 10A fuse ( or mains circuit? whats the word?). Infact i tried all my outlets and blew all the fuses just to make sureresetable fusesHowever, on accation the fuse will hold, and i can get on with testing. I then connect green wire to ground in order to start the supply but all i get is a short flash of power ( fuse holds ) before it shuts down again. The cooling fan will spin one revolution at the most. I can do this as many times as i like but the same things happens.I have tried adding various loads to all the outputs, ranging from about 4-100w (but never above specs), but makes little to no difference. In one case the psu would keep flashing as if i were playing with the switch. Otherwise, nothingAm I missing something, or is the supply faulty, perhaps?

author: Simon
author_rank: Unknown
timestamp: December 22, 2014, 06:06:05 pm
content: sounds like it's faulty. Also more modern supplies have a brown feedback wire that goes to the 3.3V, make sure it's connected.

author: ovnr
author_rank: Frequent Contributor
timestamp: December 22, 2014, 06:38:01 pm
content: Post which supply it is, please.As for it blowing your fuse: If they're old resettable breakers, you might find that anything with an exciting amount of inrush current (esp. cheap supplies with no limiting) will blow them. I had to cobble together some NTCs in a box to keep from blowing my breakers.If it is as awful as I expect it is, it probably trips on an output overvoltage fault due to there being no load on the 3.3v and 5v rails. Make sure you loadallthe rails at the same time. If it still happens, throw it at the seller's head.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 22, 2014, 07:00:06 pm
content: That behavior is consistent with a short circuit on the DC output. Check and make sure that there are no loose/broken/crossed wires or connectors that could be shorting.

author: akujiwar
author_rank: Newbie
timestamp: December 22, 2014, 07:14:22 pm
content: Awesome quick replies hereQuote from: Simon on December 22, 2014, 06:06:05 pmYes, i forgot to mention, brown is connected to orange (3.3v) like it was originally in the motherboard plug. I assume it doesnt matter which one of the orange leads? got mixed up after i cut the plug. Atm is only connected to one of them.Quote from: ovnr on December 22, 2014, 06:38:01 pmThe supply is a MS-N950-VAL from MS-tech. Yes i admit, cheapest i could findNTCs? Negative temperature coefficient (NTC) thermistor? Had to google thatAs i understand it those are commonly used for reducing inrush current. First beeing cold with high resistance but then heats up and resistance goes away while fuse survives? I'm unfamiliar with such components. What specs would i need for this purpouse i wonderAnd yes, I have put load on all outputs at the same time, to no avail.Quote from: Phaedrus on December 22, 2014, 07:00:06 pmWill have to get back to you on that

author: akujiwar
author_rank: Newbie
timestamp: December 22, 2014, 09:08:21 pm
content: Checked and, and checked again. No shorts. No joyI now got the followling resistive loads, mostly power resistors, attached, from color to ground.-purple, 6 ohm-red, ~1 ohm-yellow, 5 ohm-orange and brown, 3 ohm-blue, 33 ohmgreen is connected to ground through a slider on/off switchgrey is not connected anywhere.

author: Simon
author_rank: Unknown
timestamp: December 22, 2014, 09:16:47 pm
content: Which one is purple be careful you don't overload some of the rails that provide low power although from memory purple is standby 5 V

author: akujiwar
author_rank: Newbie
timestamp: December 22, 2014, 09:34:37 pm
content: Quote from: Simon on December 22, 2014, 09:16:47 pm5V standby. rated at 2A

author: ovnr
author_rank: Frequent Contributor
timestamp: December 22, 2014, 10:04:33 pm
content: Well, some quick googling suggests it's pure and utter shit. Since you're in Norway it looks like you paid ~450 NOK for it ($61 or so); a proper 950W supply is going to be 3-4 times that.Ignoring the obvious issues (such as "it doesn't work"), it'd erupt in an exciting display of smoke and flame if you tried running it at 950W for extended periods; realistically, it's probably a 300-400W unit with a fancy sticker.I'd just send it back; try to just get your money back as opposed to a new unit. Then buy something that's not hilariously bad. Protip: If the only people selling it are the cheap&nasty stores (Multicom, Amentio, Deal.no, Proshop, Supersmart.no, etc), it's a load of shit and/or old stock someone stumbled across while cleaning out the fridge. Don't even bother.

author: Phaedrus
author_rank: Frequent Contributor
timestamp: December 23, 2014, 04:49:47 am
content: Such cheap high-wattage PSUs are typically fraudulently or deceptively labeled. Your 950W probably delivers less power with worse regulation and ripple than a US$60 Corsair CX500 or equivalent.

author: Kappes Buur
author_rank: Regular Contributor
timestamp: December 23, 2014, 05:31:55 am
content: Take a look at this videoMight be helpful.Although I am not that thrilled with the guy's soldering job, he does show how to load up the rails for proper operation.

author: akujiwar
author_rank: Newbie
timestamp: December 23, 2014, 01:05:56 pm
content: Quote from: Kappes Buur on December 23, 2014, 05:31:55 amAye. That video got me started on converting supplies in the first place. Tried more loads in the hopes that it could still help. Guess i will just have to accept its broken and move on. On the plus side, seller has offered me a refundand i learned a lesson about cheap suppliesAny suggestions for non fuse blowing alternatives that can handle 60A on 12V for up to 1 hour?