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Date:         Fri, 5 Dec 2003 22:53:59 -0700
Reply-To:     Gnarlodious <gnarlodious@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Gnarlodious <gnarlodious@EARTHLINK.NET>
Subject:      Re: Making a 12v battery charger from a peecee power supply
Comments: To: EMZ <vw4x4@FYI.NET>
In-Reply-To:  <Pine.GSO.4.21.0312060014290.27899-100000@oola>
Content-type: text/plain; charset="US-ASCII"

What Felder failed to mention is that this is no ordinary battery charger. This is a "Switched Mode" Power Supply. It doesn't have the huge heavy transformer but uses a small light transformer running at about 40kHz to transform the current. The frequency is controlled by a PWM chip that regulated the input and output by using Pulse Width Modulation. This means input voltage can be anywhere between 80 volts and 240 volts. No transformer overheating buzzing.

A switching charger normally costs about $270, Felder is saying you can do it for about $25 if you're willing to play.

-- Gnarlie http://www.Gnarlodious.com/Vanagon/Electrical/Pages/Bay.html

Entity EMZ spoke thus:

> Man do you guy love to over complaicate things. Power supplies for > batteries are very easy to build. All you need is a transformer > bridge rectifier and a capacitor. Yuo don't even need to regulate it. > > Eric 86-VW4x4 > vw4x4@fyi.net 86-SS Syncro > Pittsburgh, PA USA 1936-Chrysler > 92-Jetta GWC > www.fyi.net/~vw4x4/vw4x4.htm > > On Fri, 5 Dec 2003, Felder wrote: > >> I've been talking with another listmemember about making a 12v batter >> charger from a pc supply according to some directions my dad found. >> Thought I'd go ahead and distribute to the group. The idea is to >> install this in my camper so when I'm plugged into 120v at a campsite, >> I'm charging my batteries automatically. My dad pointed me to a >> magazine article that detailed the process. Look for a 10 or 15 amp >> power supply to begin with. I know virtually nothing about electricity, >> but it worked till I fried the board with a microtorch. Will be more >> patient next time. >> >> Here's how they did it. It's in September 2003 Model Aviation, and if >> my description doesn't work, email me and I'll send you a copy of the >> article. >> >> 1. Make sure it works, if you can. My first one did not and I didn't >> know it until I had done all this (only takes 15 minutes or so, not >> counting the trip to radio shack if necessary). >> >> 2. Cut ALL the wire off at 6 inches. >> >> 3. Remove the "motherboard" >> >> 4. Locate the black ground wires and clip all but two close to the >> board. >> >> 5. Locate the +12 wires, and clip all but two close to the board. >> >> 6. Locate the -5 stuff, +5 stuff, -12 stuff and anything else and cut >> it off as close to the board as you can. >> >> 7. Take a soldering iron and open a hole in one of the cropped +5 wires >> and another at a ground hole. >> >> 8. Now, you should be ready with two black grounds, two reds (or >> orange) +12v, a hole at one ground and a hole at one +5v. >> >> Everything else should be gone. >> >> 9. Now you are going to run a load between +5v and ground using the two >> open holes. The load is what the PS expects to see in a device such as >> a hard drive. >> >> 10. The article suggests that you use either a 1 ohm, 25w resistor or >> an automotive light bulb type 1156 or similar to provide this load. It >> says that the light bulb is nice because you can read by it and it >> serves as a pilot light, but he actually ended up using a Radio shack >> 50-ohm, 10W resistor (RS item # 271-133). That didn' t work for me, I >> went with a resistor somewhere close to the 1 ohm 25w which worked >> fine. He was worried about the inefficiency of the latter, I was not. >> The author warns that you may need to experiement as all the PSs are >> identical in many ways but subtly different in others. >> >> 11. Take the two reds and the two blacks and double them for the >> increased current to the battery. >> >> 12. Cut a strip of plastic that will span the two holes in the metal >> case of the PS (assuming you removed the plastic grommets that secure >> all the wires through these holes, and you bridged the wires properly >> to obviate the switch). Drill the plastic in the two holes for Radio >> Shack Multipurpose posts 274-661. Mount the posts in the hole in the >> plastic you mounted behind the metal holes in the case, and run the >> respective wires to each. Now you can have screw on and banana-jack >> connections for 12v at 10 a or greater, depending on the power supply >> you acquire. >> >> Everything worked great when I had it clipped together, the resistor I >> chose was showing 13.4 v on my DMM. Then I went to solder the >> connections and melted something down between the board layers which >> hosed the whole deal so it would barely turn the fan (used a small >> torch, should have used an iron). Now I'm out of peecee power supplies, >> but I know what to do and I saw it work. I will get a few more when >> convenient. >> >> If this isn't clear, I will either scan and email or mail you a copy of >> the article. >> >> Nice fan, too. >> >> BTW I took the 4" fan out of the bad unit and epoxied a radio shack >> slide switch to it to make an exhaust fan for the kitchen. I will mount >> it in the upper left corner of the driver's side window screen frame, >> marking and drilling the frame with three small holes at the mounting >> holes of the fan, and leaving the lower right hole cantilevered over >> the screen. I'll wire it into the light directly above it, behind the >> curtain rod so the curtain can slide. Just right for a sightly warm >> night, a day away from the car in the sun, or to exhaust the kitchen >> steam etc. >> >> I don't have one yet, but for a cool light see Harbor Freight item >> 4274-0VGA. >> >> Jim >> >> On Thursday, December 4, 2003, at 08:09 AM, Gnarlodious wrote: >> >>> Entity Felder spoke thus: >>> >>>> My dad found a copy of a recent model airplane magazine that had >>>> explicit instructions for turning a peecee power supply into a 12V >>>> charger. >>> Can you send me a copy of that article, or turn me on to a webpage >>> describing the process? >>> >>> --Gnarlie >>> >>> >>


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