Off Grid Living / Camping > Tents / RV

Desk Top PS Charge Deep cycle ?

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seajinn:
I was wonder if any one here knows off the top of the head if it is possible to use 1 or 2 stranded computer power supply maintain a pair of 109ah battery, I want to change out my trailer lighting to low volt led's and do some of the charging with portal wind and solar. Have on hand a few 18 and 24 amp desk top power supply's on hand and want to get the inefficient monster out from under the trailers sink !
Thank for any ideas or thoughts

tomw:
seajinn;

Once again, I cannot track what you are getting at?

What is a "1 or 2 stranded computer power supply "?

I know what a computer power supply is but not a 1 or 2 stranded...

Bit of a terminology barrier I think?

Can you be a bit more specific what you mean?

I think a computer power supply may have limitations for keeping a battery at the proper voltage but fairly sure it can do it with some kind of outside regulation or control? A "12 volt" battery is not really kept charged by 12 volts it may need anything up from  about 14 15 volts to do it properly depending on the battery in use.

Probably doable but not just hook it up and go.

Tom

oztules:
Yes you can try this for start.

http://www.thebackshed.org/forum/forum_posts.asp?TID=1693&PN=2&TPN=3

Dinges has also posted complete material on doing the tl494 conversions on that site somewhere.

oztules

seajinn:
Sorry Tomw  I meant a more basic power supply for the average home or office desk top. A unit around 12 to 20 amp output on the 12 volt side. The one im experimenting seams to hold at 13.4v and climb to 14.5 under load and I know i need 14.8 or better. My math is a real challenge to me these days . My best calculations seam to show if I was to use desk top PS I would need 2 if I am to try top off 2 109 ah marine battery's, Worse is I tossed several larger server power supply's away that one would of been more then enough. I wanted to list them for postage but I had a brief absence on the board and though me trying to long in at the other board got be booted because I was logging in from around the world. Then i got to south central China were there internet gave me shear he__ ware i thought i was found some threat. Just a few months ago realized the board split in two. Aggravating how these days the littlest a thing can be a major over  sight on my behalf, But a few fellow here got me back on track.
 So basically I will be on different locations that all ready are equipped for travail trailers on Horse training centers or farms. My biggest load to the battery's will be in transit keeping the 120volt refrigerator running , Then when set up for the days I run my demo's the load is just a few lights and the water pump. The truck keeps the charge of coarse while in transit. I think I will find 90 percent my stops will allow me grid access, But this is not certain. Starting this venture I can not afford a newer trailer power pack to start , and I hope along the many roads I find a repair shop to get my Marine Excide 2000EX back in service since it handles my required system needs. Or afford a newer up dated power pack for this travail trailer in time.
  I am working on a small wind charger building small and light so it can be portable. I have the advantage i will be set up in wide open air typical of a race tracks so I am building for easy up and quick down and packing. Small prop and self feathered blades I came to admire all over China ! NO KIDDING! Home builds every ware! Its a hobby bigger then kite's ?
 At that point I i might become even more independent on the grid power and the power pack just strictly back up.
  I hate i be a nuisance and come off to frugal but life as disabled has been a life i create even my income . Or is it my Dutch Blood.
  So I am trying to do the best I can and draw from the vast amount of experience collected here.
  I also expect, the moderators might see the membership numbers rise once i begin flying my mill across the country. I don't need a wind vain but it is free advertising and promotion and most people not knowing better will be expecting to see one. See I am selling wind for speed to there horses !  Gotta fly a wind mill ! !
  Hay Oztules. Were near enough neighbors now. Home is Cebu and I will soon be treading your turf and stone tracks to, doing the same nonsense in your back yard ! One tough country to get a  Business Visa in , Ay ? @ least I got a good connection in the race Commission.  One of your heads Runs the State of Pennsylvania racing here to.
  The link is quite handy ,
Thanks folks

MadScientist267:
 In short, yes, a PC power supply can be converted into a battery charger, but be prepared to make a whole bunch of modifications to do it properly. A PC supply has a series of protection devices built in that need to be bypassed and/or dealt with to prevent crowbar, and current limiting needs to be addressed.

A PC power supply does not generally monitor the +12V rail for voltage regulation purposes, as the 12V is primarily for driving the various motors found in the PC, which are more tolerant of voltage variances, although too high or too low may trigger the crowbar and shut the supply down.

The primary voltage  regulation takes place on the 5V rail, as this is the most critical. The +12 essentially just "follows" the 5V regulator (eg, an increase in load on the 5V rail that causes the voltage there to dip will result in the regulator pushing harder on the 5V, and the 12V rail typically will rise slightly as a result).

To get past all of this, you have to eliminate (or heavily modify) the crowbar circuitry, and change the regulation feedback source from the 5V rail to the 12V rail, then make it variable so you can adjust it to the proper voltage for charging the battery.

Then, because you've essentially eliminated the protection system (crowbar), you need to devise a current limiter so that you don't exceed the supply's capabilities during the heavy load times (eg, bulk charging).

And, then as if that weren't enough, there really should be a temperature compensation mechanism that adjusts the voltage regulation based on the core battery temperature. This involves relatively precision voltage correction and can get tricky in a situation like that.

The other thing is, to do it right, you should have a mode switch mechanism in place to switch to a lower voltage (for float) at the end of the absorption stage.

So, can it be done? Sure.

Is it simple? No.

Are there much better ways? Absolutely.

But if you're looking for a serious challenge and have plenty of time, spare parts and/or money to throw at it, as well as the patience and skill to play with it until it works, by all means, go for it.

Personally, I've been playing with electronics for approaching 30 years now, and wouldn't mess with it myself, but that's just me. YMMV. ;)

Steve

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