ATX Power Supply for Charger 12v - Problem

[TWINSET]

Just finished converting an ATX PSU into a 12v power supply for running a charger off.

Got 12v coming off the relevant sockets but, with the PSU powered up (top fan spinning), when I connect charger or turn charger on, PSU shuts down for a couple of minutes.

If I connect the charger first, turn in on the power up the PSU, the setup works - What's up?

[Yonez]

Computer PSUs don't turn on unless they have a load. Did you include a power resistor in your conversion to always burn some power?

[TWINSET]

No, no resistors were fitted, I followed this; http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/?ALLSTEPS

The fan's running off 12v - is that no use?

Connected green to a black as per;
The green wire is what tells the power supply to turn on from stand-by mode, we want to just solder it to a ground (black) wire.

Put some heat shrink on this so it won't short out on anything else.

This will tell the PSU to be constantly on without a computer.

but otherwise all same-colour wires straight to terminal posts

The PSU turns on fine, it just switches itself off when I turn my charger on

If I plug the charger in, turn it on and then power up the PSU, it all springs into life

[pizzachaude]

How many amps can your power supply deliver on 12V? Should be written on the label, unless its a very cheap one

[TWINSET]

[pizzachaude]

In my opinion, your power supply is going into overload protection. No offense but that is a pretty inexpensive unit, and the amps printed on the label are probably pretty far from reality. I replace these things all the time in computers and have seen 430W Enermax power supplies power on powerful gaming computers that cheap 600W PSU couldnt. It kinda works like speakers, where we all know that really cheap speakers and amplifiers will have say 600W music power, in reality its likely 50W RMS at something like 10% harmonic distortion. Any power supply that has such a marked difference in the +5V and 12V+ amps , in this case 38A vs18A, is a pretty good indicator, as computers use very little amps on the 5V, the 12V is the most important when it comes to todays CPUs and graphics cards.

You should try your setup on a quality power supply from Antec, Enermax, or Cooler Master, should work. You should also get one that has the 12V supplied on a single 12V rail, your PSU supplies the 12V on 2 rails, hence the 2x18A

I've been thinking of modding a PC PSU for a 12V charger, just havent had the time to do it yet, but I will check that link you put up.

It could also be that your PSU is simply tired and on its way out

[MetBoy]

Have you tried it with another charger?

Could it be that your charger does something on startup that is, even momentarily, overloading the PSU?

I agree, it does sound like a poly fuse or something is being tripped due to overload.

If you startup the arrangement in the right order to get it going, can you charge as per normal? If so, then, maybe just make sure you always plug it in before you turn it on.

I have used old PSU for various things in the past, but one thing I learned to do the hard way, was to always keep testing everything before and during my hack to make sure it does exactly what I need it to do! I have filled many a rubbish bin with things I have blown up!

C..

[WillyChang]

PC PSUs might not supply clean 12V when under unbalanced load.

Chargers run better off 13.8V; some will take up to 24V and we feed them 15-18V.

[TWINSET]

No offense but that is a pretty inexpensive unit...

None taken, the PSU was in my bits box so I thought I'd have a play. No idea how old it is, must have been in the box for a couple of years though as I thought I knew where they all were

I'm driving blind into this, it just looked like an easy way to save £16 on a dedicated power supply

I found another site today suggesting a resistor on GND/5V so I'll pick one up tomorrow and report back - it'd be cool to get it to work even if it's not totally up to the job

Will report back...

[dyahipfakta]

You should be able to combine the 2 12 volt rails with no problem and will hopefully stop your overload issue. I have done this hack before on a generic 200w power supply with no issues at all.

[TWINSET]

Inside the box I have all the yellow wires (25 odd) bound to one post - is that what you mean?