need power supply help

[princew]

Sorry I didn't know where else to ask about powersupplies so I thought I'd ask in the charger thread. I am looking for someone that knows about electronics and powersupplies..

My problem is this. I have two chargers; A Triton (v1), and a polycharge 4 so that I can charge 5 batteries at the same time. The problem seems to be I can't get a powersupply to hold a high enough voltage to run both chargers at the same time. I've tried two powersupplies so far. One was something I ordered on ebay that is a 12V 10Amp powersupply. The other is a PC powersupply I converted to use for my chargers. It's a decent 300w PC powersupply and the writing on the side says that +12V should be able to handle 15Amps. So I can't figure out why I can't run my chargers on this thing because it's losing so much voltage.

Any help or recomendations would be greatly appreciated.

[WayneBrown]

Your voltage is simply dropping below the threshold as your PS outputs are going to drop voltage as your demand increases.
I've cheated a bit and paralleled two 12V 7A gel cell type batteries inline between the PS and chargers for the extra 'Omph'..
My converted pc PS is a 500W Antec, idle voltage is 12.38vdc, as soon as I connect a charger and charge a 6S pack, the voltage drops to 11.8vdc.
As neither charger you are using needs 'clean' filtered DC to function, look at an auto battery charger of 20A or so. The idle output voltage is 14.7vdc, and under a 20A load will drop to around 13.2vdc.

[princew]

Cool thanks for the help. Turns out the powersupply I ordered is working perfectly. At first I thought it was broken, but it ended up being the input power volt selector was set to 220V instead of 110V.. duhh. Never thought to check that heh.. Also the small flat style power supplies conveniently usually have a pot which you can use to alter the voltage usually up to 14V or so. So with that dialed in correctly I can power up just about anything now :). I ordered a small led voltage display I am going to put on the banana plug power strip I made to show the current voltage in case I ever need to tune it on the powersupply.

[falconea45]

To get more voltage out of the 12v on the PC power supply you need to load the 5V lineas you increase the 5v load the 12v voltage will creep up and not sag so much when you load it up. But a power supply like the one you got from Ebay is a better idea.

[princew]

To get more voltage out of the 12v on the PC power supply you need to load the 5V lineas you increase the 5v load the 12v voltage will creep up and not sag so much when you load it up. But a power supply like the one you got from Ebay is a better idea.
That's cool I didn't know that. Thanks for the tip. I did have a 10 watt, 10 ohm wire wound load resistor (sandbar type) on the 5 volt line, but apparently that wasn't enough heh.

[falconea45]

Just make sure the wattage of the resistors you use is a high as you can get without going mad. You can get resistors like the one you are using in 25Watt and they will run much cooler

10 ohms at 5v= 0.5A = 2.5watts you should probably go down to about 2 or 3 ohms.
2 ohms at 5v= 2.5 amps =12.5watts.
I have one with 0.3 ohms at 5v= 16.6 a = 83.5 watts so I use 3 X 1 ohm at 40 watts each=120w so they run at about 69% of capacity heat wise and do not get too hot.
Good luck experiment and see how low you need to go to keep the 12 v line up to 12v with your load.