12VDC Input Variable Output Power Supply

[spencer]

I am going to convert a computer power supply into a a bench top power supply so I can use it to power the RC charger that I will be purchasing soon. Is there a device that can take 12VDC in and allow me to output constant voltage and constant current. Basically a lab power supply that takes 12VDC in. Something similar to this but with constant current and the ability to supply more amps. I would like something closer to this in features.

Does such a unit exist at a reasonable price or am I better getting something that takes 120/240VAC? If I am better off getting an AC unit then what do you guys suggest at a reasonable price?

I would say I want a unit that can supply 0-12V (or more) and 0-10A. It also must have a CC option because I would like to use it to test LED's with.

Thanks,
Spencer

 

[65535]

I'd say go with a mains powered lab supply. I'm not even sure exactly how current limiting is done, but with DC input you are forced to use purely solid state equipment with AC you can transform the voltage to very close to output then deal with it from there.

 

[VidPro]

you should just know that most computer power supplies never really have to DELIVER the rated capacity listed on them, except for very short times in Init of the computer.
so a 350W type of power supply is really good for a computer using about 100W .
the general specs listing on them is (often) the max surge capability, so you see some person with a 35AMP 5v rail on the power supply and they are usually only useing it at 5-7amps for real.

so if you have a computer power supply that can pump out 12amps to the 12V rail, it might not be adequite at all for driving it AT 10amps for hours. depending of course on how its REALLY rated, like an underrated high quality one.

Add up the total watts out of these power supplies CLAIM, then use a wattmeter to determine the actual consumption of the computer , and its way lower usually while running,most people even high end SLI gamers are using NUMBERS that are at least 2 times over thier actual consumption ever. except at init.

 

[LuxLuthor]

As VidPro says, computer 12V PS's are over rated in general, with some of the high end such as "PC Power & Cooling" brand being more of an exception. Depends on how much of a sustained load your battery charger is going to be needing.

For my Larry 14K spotlight with 24 x Elite SubC 4500mAh NiMH cells, I had to get a beefier 13.8V/22A AC adapter PS with a thicker heavy duty passive cooling radiator. Lesser models not only got dangerously hot (with that "lovely" burning wire/electronics smell), and/or tripped their fuses. As it cranks up, the Hyperion 1210i charger starts delivering 3-4 Amps while voltage is going up towards peak of 36V. That's some serious sustained Wattage!

 

[spencer]

I can see the old computer PSU idea is not too hot here and the reasoning behind it makes sense. Lets try the question another way.

Could I run my charger off of a lab power supply? If so what do you guys recommend. I would like it to have both CC and CV and be able to supply at least 15A at 18VDC (around 250 watts). I wouldn't be too happy if my charger can't charge at a higher rate because its input was too low.

What do you guys use? Hit me with it. Price and all. I'll try to be ready:eeksign:.

 

[BVH]

I use a Mastech PS for my Schulze, 10 + 5 Amp and my TritonII 7 Amp charger. I have the 30 Volt, 50 Amp model because I run other high current applications. They make many different Voltage/Amperage models. Search Mastech on Ebay, that's where you'll find two larger sellers listing many models. Mine is about $425 but the lower Voltage/Amperage units are in the $100 and $200 range. They are capable of both CC and CV.

 

[LuxLuthor]

The PC power supplies are just fine for lower wattage sustained charging.

If you are going to be charging 15A rates for any duration, then you need the beefier 20A supply. You don't need the more expensive Variable PS like BVH just mentioned.

The fixed output are not that expensive. Let me get a link of the one I bought.....sec

Here is one (PS-106) link from KitUSA for $70 + shipping.

They have the PS-105 15A for $10 cheaper, but it's not worth trying to save $10, IMHO.

Here was another Bookmark I had, but I think I bought that one from KitUSA.

 

[BVH]

I'm by no means an expert, but isn't a variable supply needed to obtain constant current? My little pyrimids are 13.8V and 12 amp but there's no way to limit the current. The load will determine and draw what it needs.

 

[LuxLuthor]

I'm by no means an expert, but isn't a variable supply needed to obtain constant current? My little pyrimids are 13.8V and 12 amp but there's no way to limit the current. The load will determine and draw what it needs.

BVH, I'm no expert either, but no to your first question.

The charger has PCB with components that sense and do the adjusting of current and voltage...and governed by a software/hardware programmed algorhythm. The charger just needs a reliable power supply to deliver the juice that it controls. The more juice (watts) needed to be delivered, the more is demanded from your power supply. Computer PS's as was said earlier, do not anticipate the high sustained demands & heat output you can get with charging.

The main purpose of the variable PS is so you can manually change the input current and/or voltage as you see fit. It is governed by the cellular protoplasm between your ears. It could be set at a high enough voltage and current so it could be used as a power source for Schultze, or you could use a variable power supply to deliver a set low current & voltage to do a 16 hour 0.1C conditioning charge...but you are paying the money for the "Hobby Charger" to do all that adjusting and sensing. No need to add more expense of a variable (aka: adjustable) power supply for normal charging.

Most Hobby Chargers are used by, and designed for RC users, and the idea behind the 12V power supply requirement is that they can run a charger off their car battery, or drag one out into the air flying field. A good example of why a variable power supply would be needed was the destructive bulb testing I did (link in my sig for spencer), where I needed to crank up the voltage and/or amps to test various bulbs.

 

[VidPro]

I can see the old computer PSU idea is not too hot here and the reasoning behind it makes sense.

its a good supply fan and all, all i tried to indicate was get a good overrating on it.
like something with 28amp 12v rails to run the 10amps. lots of those about, and most you can find out like at neweggs reviews, if they are solid or not.

and dont use the old 250 power supply you decomissioned in the corner over there gathering dust that is all i am saying, the price is reasonable with a nice 120mm thermal controlled fan it would be quiet, and on a surge it will handle a bit more, mabey toss in a external fuse so you dont have to take it apart to get to the ones inside if you pop them.
plus you have a 5v output and 2 smaller 5 and 12v outputs.

then there is the slight thing where if you dont USE one set of rails for power, the other set can vary slightly in voltage, but its very minimal, and wouldnt be a issue for driving a 12v car battery type of device.

if you gotta have voltage regulation, or current regulation, then you usually need more volts, to start with, but for a 12v hobby / cb / car adapter type of power its good.

 

[BVH]

Lux i understand everything you said and agree with all of it. I was basing his need of a variable supply to accomplish his testing of his leds mentioned in the last sentence of his OP. I thought he wanted to use power directly from the PS to power the led's with a constant current and voltage of his choice. I'm not sure that the hobby chargers allow those settings.