Discussion Made my own 12V Supply and it sucks

[ov10mech]

I bought a brand new 450W computer power supply thinking I would save some money. Its not the best brand (echostar) but its rated for 450W Max /14A at 12V.

http://tekgems.com/Products/et-11182...star-450-n.htm

I wired it up and hooked up my Electrify Polycharge 4. Basically I crossed a green and black to get it to stay on all the time then took a yellow and black lead for my positive and negative.

If I put a load on the thing any more than 2A, the low voltage alarm goes off and the PS voltage drops in the 10V range. Is this just a crap supply or do you think I did something wrong?

[yangster]

Originally Posted by ov10mech

If I put a load on the thing any more than 2A, the low voltage alarm goes off and the PS voltage drops in the 10V range. Is this just a crap supply or do you think I did something wrong?

Must be a crappy power supply. I did the same to an old 300 watt power supply I have and it works super. I'm able to power up and easily charge up to 5amps (max of my charger) just fine. I have 2 extra power supplies (I use to be a computer geek). PM me and I'll see if I can send you one.

[JohnMuchow]

Typically, you need to add a load to the 5V line to get the 12V line to regulate. Without that load, the 12V line can drop in voltage when it's used. Do a search in this forum and you'll find lots of examples of power supplies being modified for use with a charger. Some great tips there!

John

[jeffs555]

On PC supplies, you generally need to put a load on the +5v wires to get good regulation on the other voltages. Not sure how much load you will need, but you can use power resistors or light bulbs.

PS seems like John is faster on the keyboard than I am.

[JohnMuchow]

Originally Posted by jeffs555

PS seems like John is faster on the keyboard than I am.

Nah, I probably just got the msg a bit earlier.

[JohnMuchow]

Originally Posted by yangster

Must be a crappy power supply. I did the same to an old 300 watt power supply I have and it works super. I'm able to power up and easily charge up to 5amps (max of my charger) just fine. I have 2 extra power supplies (I use to be a computer geek). PM me and I'll see if I can send you one.

You didn't add a load to the +5V line? Almost every computer power supply I've seen requires that for good regulation on the +12V line, no matter how how high quality the unit is. Perhaps older units don't require it?

IMHO, ov10mech's power supply is plenty good enough to get the job done and just needs that load.

John

[quigley257]

Try checking your wiring setup against the suggested wiring and resistor setup shown here... http://web2.murraystate.edu/andy.bat...OWERSUPPLY.HTM

--quigley

[ov10mech]

Thanks guys. Found an auto brake light bulb here in the basement and wired that into a the 5v wires (red/black). I have 3 lipos charging right now @ 2a each. It chokes on the 4th lipo port but 3 should be ok. Voltage is maintaining around 11.41 with a 6A load.

I can see the power trying supply kicking back up the voltage now on the volt meter when a new pack is added. This bulb is kind of big and runs hot and will have to find something else to put a load on it. What do I tell the rat shack guy I need as far as a resister?

[ov10mech]

Never mind.. the link sent explains the resistor

[Poli]

Hallo. Sorry for bad english buth you need (10 Ohm\ 10W) resistor or automotiv bulb. Buth I think then this is just crapy supply.. And main problem is low 12 Volts when in load about 11,45 - 11,75V.

http://www.flyinggiants.com/forums/f...er-supply.html

http://web2.murraystate.edu/andy.bat...Y.HTM#POWER_OK

http://www.wikihow.com/Convert-a-Com...b-Power-Supply

Good luck. Bye

[Poli]

Ohh im too slow.

[JohnMuchow]

ov10mech,
If your supply still drops down to that 11.4V under a 6A load, be sure to try a second resistor (or bulb) to see if that "stiffens up" the 12V line a bit more. Sometimes you have to increase the load on the 5V line to get the 12V line to maintain its voltage well enough. That 0.6V drop is a bit large IMHO and can be reduced....hopefully.

John

[ov10mech]

I'll hit the shack tommorow and pick up a couple of those sandbars and report back! Then maybe I can change the thread title to "Made my own power supply and it works!"

Originally Posted by JohnMuchow

ov10mech,
If your supply still drops down to that 11.4V under a 6A load, be sure to try a second resistor (or bulb) to see if that "stiffens up" the 12V line a bit more. Sometimes you have to increase the load on the 5V line to get the 12V line to maintain its voltage well enough. That 0.6V drop is a bit large IMHO and can be reduced....hopefully.

John

[HoaRC]

http://www.youtube.com/watch?v=2Uxp6Vn2KdA

[ov10mech]

I wired in two 10-Ohm / 10watt resistors today.

I pretty much have the same voltage drop after a couple of amps of load. I appreciate all the suggestions. The supply will be useful, just not for high draw applications.