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computer Power supply

Old 02-18-2006, 07:08 PM
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Viper 15
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Default computer Power supply

I was wondering if a computer power supply could be made to work to power a standard dc battery charger like an ICE or 969. If so what kind of specs should I look for(as I don't want it to be 2 powerful) Thanks
Old 02-18-2006, 07:30 PM
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Dr1Driver
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Default RE: computer Power supply

[link]http://www.rcbatteryclinic.com/[/link]

Dr.1
Old 02-18-2006, 07:30 PM
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Default RE: computer Power supply

This web page has a section about it.
Look toward the bottom left I think.
http://www.rcbatteryclinic.com/
JLK
Old 02-18-2006, 09:10 PM
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Default RE: computer Power supply

Thanks guys
Old 02-19-2006, 05:24 PM
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Default RE: computer Power supply

Hey Viper,

The power supply should be rated at 10 Amps on the +12V output at least, but the higher the better. You can only have too little current available, not too much.
Good Luck,

Pete
Old 02-19-2006, 05:40 PM
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Default RE: computer Power supply

hmmm...
Curious about the 10amp requirement.
I have an old Dell PC power supply that is labeled 4.5 amp on the +12v output and I have another flatscreen power supply that says 4amp. I run one or the other with two chargers as follows:
I am able to run my Hobbico Fast Field Charger MKII with both outputs set at 1 amp and my Sirius Pro Plus running both outputs for both a 900mah RX pack and the OEM TX pack in a Futaba 9CAP transmitter. If the input to the Pro Plus drops below the required level for either the TX or RX a red light will come on...it never has.
Why does he need a minimum 10amps?
JLK
Old 02-19-2006, 06:00 PM
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Default RE: computer Power supply

Hi jlkonn,

Just being conservative in that recomendation, what you just described would work fine from now till doomsday, but if you are going to fast charge large packs you will go over 5 amps real fast. Also too, consider when using a computer P.S. their is not much filtration, as most of the caps. are on the MoBo. I guess my main point is that if you are going to the trouble to recycle an old P.S. find one that can handle a heavy load.

Regards,

Pete
Old 02-19-2006, 07:31 PM
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Default RE: computer Power supply

Also too, consider when using a computer P.S. their is not much filtration, as most of the caps. are on the MoBo.
While I agree there is additional filtering on the motherboard I've yet to see a PC supply that has a lot of noise or ripple on the 12 VDC output line. These supplies seem admirably suited (cheap) to be used for powering our chargers.

Just my opinion,
John
Old 02-20-2006, 11:54 AM
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Default RE: computer Power supply


ORIGINAL: jlkonn
Why does he need a minimum 10amps?
JLK
He needs a minimum of 10 amps because he is considering using the DuraTrax IntelliPeak ICE Charger which is a 10 amp charger.
I bought a new 500W ATX PC power supply from Comp USA for $19.95 (after rebates) and converted it for use with my ICE charger. See photo below.
I connected banana jacks to three of the positive voltage outputs, 12v@18a, 5v@36a, and 3.3v@22a. I also added a green LED pwr-on indicator. The power supply has a power switch on it's case.
It provides smooth, well regulated, quiet (quiet fan) power to my ICE charger.
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Old 02-20-2006, 12:43 PM
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Default RE: computer Power supply

Your pix didn't come thru.
Could you retry?
I would love to see your setup.
Not to split hairs but it says 10amp discharge and 8amp charge.
I imagine that is it's capability not all time requirement.
But I don't know.
JLK
Old 02-20-2006, 01:20 PM
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Default RE: computer Power supply

Hi,

One thing you may want to consider is to adjust the power supply voltage to 13.6 volts, not 12 volts, usually the power supply will allow you to adjust for this. Car batteries run at 13.6 volts and this is what most chargers are expecting.

Example, if you are charging a 3 cell LiPo pack, the charge expects to bring them up to 12.1 volts (sometimes a little more), if the supply to the charger is only 12 volts, it can't get to full charge and you may experience problems which you may blame on your charger.

Something you may want to consider.

Fly4Fun,

Wayne Miller
Old 02-20-2006, 02:55 PM
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Default RE: computer Power supply

ORIGINAL: Wayne Miller

Hi,

One thing you may want to consider is to adjust the power supply voltage to 13.6 volts, not 12 volts, usually the power supply will allow you to adjust for this. Car batteries run at 13.6 volts and this is what most chargers are expecting.

Example, if you are charging a 3 cell LiPo pack, the charge expects to bring them up to 12.1 volts (sometimes a little more), if the supply to the charger is only 12 volts, it can't get to full charge and you may experience problems which you may blame on your charger.

Something you may want to consider.

Fly4Fun,

Wayne Miller

Rspectfully your statement could be totally wrong if it is a new chargers using a switching power supply in design. Look at the specs for the Triton. It can run on Input Voltage: 10-15.0V DC and put out 1-24 Nickel Cadmium cells (1.2- 28.0V NiCd). You do not have to have 13.8 VDC to run many of the new chargers. ICE or Elite. My PC supply only puts out 11.6 VDC and I have no problems with it.

John
Old 02-20-2006, 03:07 PM
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Default RE: computer Power supply

Hi John,

Thanks for information, I wasn't aware they were using switcher power supplies. I can't seem to find this info in my Hobbico MK II spec sheet, but it makes sense to me.

I do know some people charging LiPo's, on power supplies at 12 volts, sometimes have LiPo failures, therefore I always crank the output up on all my supplies and have never had a failure. As you pointed out, this may not be necessary.

Thanks for the insight.

Fly4Fun,

Wayne
Old 02-20-2006, 03:36 PM
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Default RE: computer Power supply

ORIGINAL: JNorton
While I agree there is additional filtering on the motherboard I've yet to see a PC supply that has a lot of noise or ripple on the 12 VDC output line. These supplies seem admirably suited (cheap) to be used for powering our chargers.

Just my opinion,
John
I agree with John on this one. I use three different surplus computer power supplies in my shop, one rated at 5A continuous output, the others a bit lower. None of my chargers has a problem with these power supplies; an Astro 110D, Schulze 330-6 (or whatever it's called, going from memory), and a Triton. They work no differently than on a battery source, and I don't get errors like I used to on my Astro or Schulze when using another power supply that was not so smooth.

As to requiring a 10A power supply, that is only true if the charger needs to draw that much for the task at hand. If the maximum output is lower and the required input current is less, then as long as the power supply is up to the demand for whatver you are doing it should be fine. However you are of course limiting your maximum charge rate. On the subject of inpout voltage, many chargers do indeed use switching power supplies internally and are therefore not sensitive to input voltage of 12V or 13.6V. That's how you can charge higher voltage packs from 12VDC input.

MJD
Old 02-20-2006, 03:40 PM
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Default RE: computer Power supply

Wayne,
I probably could have worded it better. It is easy to know if your charger uses a switching supply. If it can output greater than the input it is a switching supply. Just check your specs. I do not believe the Hobbico MKII uses a switching power supply.
John
Old 02-20-2006, 03:42 PM
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Default RE: computer Power supply

ORIGINAL: JNorton

ORIGINAL: Wayne Miller

Hi,

One thing you may want to consider is to adjust the power supply voltage to 13.6 volts, not 12 volts, usually the power supply will allow you to adjust for this.
<snip>

You do not have to have 13.8 VDC to run many of the new chargers. ICE or Elite. My PC supply only puts out 11.6 VDC and I have no problems with it.

John
John and I have had a running discussion over voltage levels for converted PC power supplies and we both agree that folks many times are trying to drive the output voltages higher than are needed for their chargers to function properly. While some PC supplies have internal trimmer pots to control output voltage, the majority I've opened do not and the only recourse is to tweak voltage levels with resistive preloads. It is possible to raise voltages by applying higher loads (lower resistance) to a certain extent, but as long as your charger functions, there is no gain in increasing the load and certainly no advantage in using any resistance below 2 ohms. I start with 10, drop to 5 then possibly to 2 if needed -- on occasion, I have needed over 12 volts for foam cutting, but as John said, most of the newer chargers will function with input voltages in the 10.5 to 11 volt range.


Input voltage specifications for the Hobbico Mk II is 10 to 15v, but the instructions state further down that 11v is the minimum required for proper operation.
Old 02-20-2006, 03:47 PM
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Default RE: computer Power supply

Hi John,

Thanks for your help, its greatly appreciated. I'll know what to look for in the future.

Fly4Fun,

Wayne
Old 02-20-2006, 03:48 PM
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Default RE: computer Power supply


ORIGINAL: jlkonn

Your pix didn't come thru.
....................
Not to split hairs but it says 10amp discharge and 8amp charge.
JLK
The manual says the ICE can do a motor break-in at 10A constant and 30A surge.

Can you see my power supply photo yet? Can anyone see my photo?
Old 02-20-2006, 04:11 PM
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Default RE: computer Power supply

Hi Rocketman_

I see the photo and have a question, what is the "Load in/out"? Is this the load needed to bring the power supply up? Typically, I put a bulb on that load.

Fly4Fun,

Wayne Miller
Old 02-20-2006, 04:36 PM
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Default RE: computer Power supply

Yep...
I see the pix now.
Looks alot like the power supply I got out of the old Dell.
JLK
Old 02-20-2006, 04:55 PM
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Default RE: computer Power supply


ORIGINAL: Wayne Miller
.... what is the "Load in/out"? Is this the load needed to bring the power supply up? Fly4Fun,
Wayne Miller
Yes it is a 10 Ohm, 10 Watt switchable load but the power supply powers up to 12.120V without the need for a load and the load raises it a little to 12.253V.
When connected to the ICE charger it will charge a Thunder Power 3-cell 2100mah Li-Po to 12.5 volts.
Old 02-21-2006, 08:21 AM
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Default RE: computer Power supply

FYI: (quoted from ICE manual)
To achieve Ice’s absolute maximum output power capabilities the DC power
source must be capable of delivering at least 15 amps of current while
maintaining 12 volts DC (although 12.5A will be enough for most functions).


High cell counts at high charge rates may take more current than a 10A supply can handle. I know when i was charging 8 cells at 5A, the charger was drawing ~7-8A iirc.
Old 02-21-2006, 01:21 PM
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Default RE: computer Power supply

I won't be charging any thing over 7 cells.
Old 02-21-2006, 02:34 PM
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Default RE: computer Power supply

Hi guys,I'm looking for 2 25 amp 1 ohm sandbar resistors to load my power supply instead of a bulb. I was told they were Radio Shack items but my local RS says no got and not listed on their computer. Any idea where I could get them or another sulution would be appreceiated.
Butch
Old 02-21-2006, 04:02 PM
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Default RE: computer Power supply

ORIGINAL: BUTCHMAN

Hi guys,I'm looking for 2 25 amp 1 ohm sandbar resistors to load my power supply instead of a bulb. I was told they were Radio Shack items but my local RS says no got and not listed on their computer. Any idea where I could get them or another sulution would be appreceiated.
Butch
Go to Radioshack.com and search for part number 271-131.

What you are looking for is a 1 ohm 10 watt wirewound power resistor, sometimes called a sandbar or ceramic resistor. Try [link=http://www.radioshack.com/product/index.jsp?productId=2062290&cp=2032058.2032230.2032267&allCount=102&fbn=Type%2FPower+Resistors&f=PAD%2FProduct+Type%2FPower+Resistors&fbc=1&parentPage=family]this link first[/link], if it fails, then do the search on RatShack.


I would suggest using a single 10 ohm 10 watt resistor first. If your voltages are sufficient, then there is no need to load the PS any further.

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