RE: How to convert an ATX power supply to rc use  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> RE: How to convert an ATX power supply to rc use
Page: <<   < prev  1 2 3 [4]

Login
Message << Older Topic   Newer Topic >>
RE: How to convert an ATX power supply to rc use - 2/29/2008 7:35:57 AM   
mrasmm


 

Posts: 4412
Joined: 1/9/2007
From: Sometown, Northern Utah, USA
Status: offline
quote:

ORIGINAL: Tusken

Im having a problem with my power supply shutting off when i try to charge 4s packs. The psu is out of a compaq pc and is rated 8 amps at 12v. It works fine charging 3s and im getting about 12.6v under the charge load. Does it take that much more juice to charge 4s packs? or ??

Allso I had the same problem as edwal07 on page2
""and the 5v sense to the 5v. In this configuration I had voltage but no current. I removed the 5v sense and it latched on perfectly. ""

I had 12v+ but it wouldnt power anything until i disconnected the grey and red wire.

This is the charger im using if that matters. http://www.allerc.com/etecchargers.htm

Thanks
Rob


it all depends on the conversion efficiency of your charger, but yes it will take considerable more power, about 33% more assuming a 100% efficient conversion factor. If it's a compaq PSU, it's likely not very good, infact most cheap PSU's are only good for about 50% sustained draw of what they are rated for.

The simplest fix would be to just charge at a slower rate, and see how that works

basically the math of it is: max voltage of 4s lipo pack is 16.8v, at 2.5A. I assume an 80% conversion efficiency, so if you do the math you end up with 16.8v x 2.5A / .8 = 52.5w required, and if you figure your PSU, you'll need basically 4.5A sustained current @12v

In your case you run into a problem because your PSU probably just puts out 12v, and if you load it up around 4A, then the voltage drops below 12v, as soon as that happens your charger shuts off to prevent an undervolt that would fry it.

_____________________________

I don't always check every thread I respond to, so feel free to PM me

(in reply to Tusken)
       Post #: 76

RE: How to convert an ATX power supply to rc use - 3/1/2008 12:07:53 AM   
Tusken



Posts: 2
Joined: 6/25/2004
From: Fresno, CA, USA
Status: offline 		Thank you mrasmm for the help. Does anyone have a recomendation for a good off the shelf psu i could convert to be able to charge 4s.

Thanks

(in reply to mrasmm)
       Post #: 77

RE: How to convert an ATX power supply to rc use - 3/1/2008 5:52:07 AM   
mrasmm


 

Posts: 4412
Joined: 1/9/2007
From: Sometown, Northern Utah, USA
Status: offline
quote:

ORIGINAL: Tusken

Thank you mrasmm for the help. Does anyone have a recomendation for a good off the shelf psu i could convert to be able to charge 4s.

Thanks


sure thing. FSP group makes a good PSU for about 40 or 50 bucks that would be able to put out what the label says. If not, I'd just look for something that's more along the lines of 16 to 18A or higher on the 12v rail. if you are getting one for RC only, you may want to get a single 12v rail PSU. If I remember right the dual PSU's have a different setup process, and there would be other concerns with them as well.

Basically a simple rule is, better quality PSU's weigh more per watt they are rated for. Look for something in the 4 to 5LB range.

_____________________________

I don't always check every thread I respond to, so feel free to PM me

(in reply to Tusken)
       Post #: 78

RE: How to convert an ATX power supply to rc use - 3/1/2008 6:12:28 AM   
Andrew


 

Posts: 1850
Joined: 2/4/2003
From: Murray, KY,
Status: offline
quote:

ORIGINAL: mrasmm
<snip>..... if you are getting one for RC only, you may want to get a single 12v rail PSU. If I remember right the dual PSU's have a different setup process, and there would be other concerns with them as well.



If you're referencing the standard dual rail ATX 12v PSU with the 4 pin motherboard connector, it will convert the same as a single rail ATX supply. Additionally, the 12V1 and 12V2 rails may be combined in parallel to increase available current. One thing to keep in mind is that you will not be able to draw full combined current for joined rails -- the specification placards on the better supplies will provide the maximum combined wattage from both rails. For example, the 12V1 rail may be rated at 130 watts and the 12V2 rail at 92, but maximum combined output may be 195 watts -- the combined output is dependent on the power distribution architecture of that particular model.

ANTEC and SPARKLE also have reputations for being good supplies. We have found Newegg to be very competitive and shipping is both quick and reasonable.

andrew


_____________________________

the "other" andrew
I'm not older than dirt, but I can remember when it was patent pending

(in reply to mrasmm)
       Post #: 79

RE: How to convert an ATX power supply to rc use - 4/26/2008 10:35:32 PM   
Calin666


 

Posts: 386
Joined: 4/12/2007
From: SLC, UT, USA
Status: offline 		HWS, I just got done doing the conversion, and it worked perfect! Excellent tutorial, and thanks for posting this!

(in reply to Andrew)
       Post #: 80

RE: How to convert an ATX power supply to rc use - 5/11/2008 1:58:05 AM   
hands without shadows



Posts: 5760
Joined: 11/23/2005
From: denfield, ON, CANADA
Status: online 		No problem, just pay it forward!

_____________________________

_________
O||||||||O

(in reply to Calin666)
       Post #: 81

RE: How to convert an ATX power supply to rc use - 6/11/2008 8:30:13 PM   
chadr


 

Posts: 20
Joined: 1/21/2008
From: tampa, FL, USA
Status: offline 		Check out this method of adjusting the voltage, no need for 4 x 1 ohm 10w resistors in series. He is using a 5k pot tied in somewhere on the control circuit of the power supply.

http://www.mp3car.com/vbulletin/power-supplies/31652-car-power-supply-battery-charger-old-pc-supply.html

(in reply to hands without shadows)
       Post #: 82

Page:   <<   < prev  1 2 3 [4]
All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> RE: How to convert an ATX power supply to rc use
Page: <<   < prev  1 2 3 [4]





Jump to:


Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Member Video Posts | RCU Video Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

© 2001 - 2007 24-7 RC, LLC, all rights reserved.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America

Kaango.com Classifieds

0.563RCU1