Date: Fri, 5 Dec 2003 17:51:46 -0800
Reply-To: Felder <felder@KNOLOGY.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Felder <felder@KNOLOGY.NET>
Subject: Making a 12v battery charger from a peecee power supply
In-Reply-To: <BBF4AA2F.2EC58%gnarlodious@earthlink.net>
Content-Type: text/plain; charset=US-ASCII; format=flowed
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
>
>