I saw the reviews and I didn't pay much attention to them because I know that BG would not suggest I buy a piece of crap. Harold how could you insinuate such a thing about Brian! Shame on you. :lol: Now go build yourself a proper power supply. :tongue:

Now watch and the switch you get breaks proving Harold right. I would have to hang my head in shame. :lol:

If that happens, at least it's not difficult to replace it. :smile: RadioShack carries a number of DPDT switches. It comes down to how much room you have for the switch. Some are quite large, but if you have room for it, using a larger version won't hurt.

And yes, eBay also has a large selection (and probably cheaper too), but even though I don't especially like RS (their stuff is quite pricey), sometimes it's nice to be able to get something right away locally.

I was just parroting the reviews, I know BG knows his stuff.:yes:

I got a server power supply on the way!

Thanks to everyone in this thread I decided to start working on a power supply for myself only I'm going about it a bit differently. I have access to old used up copiers and thought since they are setup to run 24v I would give it a go to see how things worked out.

Here is a picture of the power supply that I am using. The question I have to all of you is there any way to figure out how many amps or what the wattage of this power supply actually is? If it isn't sufficient I'll most likely go the server PS route. Right now I have a nice stable 24.5 volts on this supply and will be mounting it in a custom aluminum box if I can find a way to figure out what amp's or wattage I am getting out of it.

https://lh3.googleusercontent.com/-O...5092012201.jpg

Any ideas??

Google the PS model number from a sticker or something? The printer itself should have the power requirements printed on it, and then you can make a rough calculation based on that.

The power requirements are all AC specs, this particular has a requirement of 15amps at 120v. We are a dealer of the copiers it came out of and I have the schematics and part numbers to the power supply but there are no specifications published about it.

I guess what I was hoping is that there might be a way to identify it by the components or if there was a tool that I could use to get those ratings I could go that route.

I assume all the red wires are 24v and the blues are ground? If so, then loosely judging by the number (8?) and gauge of the wires, I'd say each wire is good for ~2A, which is around 16A, maybe a bit more.

What you could do is monitor the output with a voltmeter while steadily loading down the supply with resistors or something until it shuts down from over-current. Then a little math to figure out the shut-down current, and then subtract ~10% as the "working" current.

There are 11 red 24v wires ranging from 18-22gauge wire. I thought I saw a video that had a charger showing the operating amperage? Maybe that was the amperage that the user set the charger to draw.

Thanks for the idea on the resistors I'm just afraid of "frying" the supply doing that. Is that a possibility?

Yeah, some chargers show input voltage/current, but they don't care if the supply is struggling as long as the voltage and current is there. And yes, increasingly loading down a supply until it shuts down can conceivably cause harm, but any decently engineered supply should shut down well before that happens.

Looking at your loosely judged "estimate" with 11 24v wires I should be able to safely assume 24v at 20amps I'd believe. That should be more then enough power to run this charger: Icharger 306B

Correct?

so if i buy this powersupply, it takes a standard desktop power cord is that correct?

And a spare servo connector will jumper the pins, no soldering for that? then i just solder up the servo connector wires correctly or add a switch and solder on my positive and negative and my power supply is ready?

Its not that i don't have the skills, but converting the atx supplies seemed like way too much of a hassle, but this seems really easy to do even with my 3 year old wrapped around my leg while I'm doing it :)

Yes, it takes a standard cord you'd find on any PC.

Not sure on the servo connector though. The pins would fit, but a servo connector has three wires in a row and the pin on the power supply that need to be shorted are not all together. In short, you can use the servo connector, just remove each connector from the plastic housing, wrap each in heatshrink, and then slide each one over the pins.

It is an easy conversion if you want to just get it to work. I personally like to solder connections for reliability and have all the circuitry (wires and such) inside the supply to reduce clutter.

Just bought one of these powersupplies. I was thinking of the 575w one originally posted, but the charger I want is 2x 400w chargers. While I don't own any 6S batteries alone my Jammin truggy uses 2x 3S 5000mah lipos and 2x 2S 5000mah lipos. I also have some adapters that let me charge two 3S lipos as a single 6S, same for 2S as 4S.

So I was figuring at a 3C charge rate that would be about 630w not counting losses so that would be maxing out the 575 and getting into bad territory.

The 1300w is only on 240v but on 120 its rated at 910w I think it was (12v x 75a). Which should still be plenty for the twin 400w model.

Realistically as i won't be using both 2S and 3S sets at the same time I'll be charging the twin 3S separately which is about 500w or so.

Glad I found this thread, was struggling to find a DC PS before I'd put money down on a good DC charger.

^ thanks for that. Now the thread title should be how to build a $17 74A power supply. haha.

Well. I can't take any credit. And I haven't even received it yet. But the conversion looks ridiculously easy. Might try to do some cooling stuff though to quiet it down, maybe a small LCD temp display.

Could also use the 12v rail to feed a fan and use a Rheostat to control temps Every PC fan I've ever seen was designed to run on 12v so you could find one that fits the cooling needs without sounding like a 747 and just power it off the 12v while sending the yellow wire to the RPM sensor in the PSU.

I have received the 1300w power supply.

Will check it tonight. It looks like there is room for two 60mm fans up front. Could probably install them there reduce the noise a bit by using a slower speed.

Might want to note for those looking at the 1300w PSU to convert, it requires a IEC-320-C19 type power cord. Seeing as I work in IT, I have a bazillion of these things laying around for servers so its no big deal. But if you don't, and are thinking of using this PSU you'll need to visit a store and get a C19 power cord. Standard ATX power cords will not work.
http://www.taiwantrade.com.tw/resour...2bfd0_TC19.jpg

Works just fine!

Now, if I only had a good charger to really place a load on it. But I'm going to bet it'll work fine. :yipi:

http://farm9.staticflickr.com/8190/8...d853792152.jpg
HP_DL580 G5 - 1300w PSU by thirdgen89gta, on Flickr

I thought it was loud when I started it up, but when I tripped the 3 wires together it got REALLY loud.

Must look into building a "case" for it and using larger, lower speed but higher volume fans.

Its a noisy little beastie.

[YOUTUBE]Xcb84X5lCeg[/YOUTUBE]

good info on the power plug, figured it was standard computer style. Thanks for that.

That vid is crazy, it is SO loud. Normally I don't mind fan noise, but that's more like a leaf blower.
Let us know if you get any pots in there to slow them down or something.

Another area of concern, many of the high wattage chargers require 24V for full output. So while this PSU will put out all the current they could handle, the charger is limited on 12V. Just something to consider if someone is looking to utilize all the power of a powerful charger.

I measured it with my SPL Meter (yes, I have one for setting up the home theater, I'm that anal).

65db with the PSU in the off position, and 73db in the On position. Its a mix of frequencies but the loudest with it off is 1khz, and on it shows 2 spikes in the 3-5khz range.

its pretty darn loud, gonna have to do something about that. I'm thinking of replacing the two fans with a quiet high flow model 60mm fan in the 3000-4000 range. Or simply modifying the top of the case to mount a 120mm fan and running that off the boards connector. Though I'm not sure what RPM the fans are required to run at.

The fans inside are 60x38mm 8800rpm fans. If I looked up the right model fan they flow 50cfm each.


Thinking of buying 4 of these fans: http://www.newegg.com/Product/Produc...82E16835426033

Two will replace the internal fans. They are much quieter than the original fans. I also plan to install two of the fans in the front as a "pusher" fan that I can manually turn on. which should bring the total airflow back near what it was with the twin 60x38s. If they are quiet enough I might just leave them on completely.

Looking for a relatively thin LCD temp display I can put in there and either feed it off 12v or 3.3v, the PSU only puts out those two voltages. Would be nice to keep an eye on the temps as I am messing with its original fans.


Edit: Scratch that! It think I might buy two of these fans plus 2 very quiet stealth fans. These things have a built in internal PWM thermal switch! If thats the case then I might not even have to worry about fan speed as they'll just be quiet when its cool and ramp up as needed on their own.

Though the PSU is capable of controlling the fan speeds, so I don't know how that would interact with the fans on control method. Hmmm, need more information.

That PSU is cool. Nice to have a different option.
But I rather use 24V @ 47A for my chargers. Keeps the power wires cooler and charger happy.

does the PSU need that much cooling? You probably aren't taxing it very much at all. Maybe if you want to future proof it for expansion.
Also, depending on how smart the PSU is, it might monitor fan speed and no operate if it senses a failed fan.
http://dx.com/p/mini-1-5-lcd-digital...-x-lr44-126092
That's a little temp display I got from there one time. Only displays in C.
Mines been going for 3 years on the same batteries. Not super thin or high tech, but it's cheap.

I don't have a charger that supports the 24v input, and I'm honestly not going to be going to >6S for a while, so this works fine. I also didn't want to go through the fun of running two PSUs in series with the the possible risks as I'll be carting this power supply to the track and such. There are kids there would would probably find a way to shock themselves pretty good.

Most of the time I'll either be charging two 3S packs at once, or two 2S packs, both 5000mah. So I won't really be using everything the charger can do.

Thats why I'm thinking about replacing the stock twin fans with 4 of these: http://www.newegg.com/Product/Produc...82E16835426033.

The original fans are something like a this Sunon 60x38mm 8000rpm fan. Its rated at 56dB while the other fans I posted are 23db and are significantly quieter.

It was nice to charge both the 4S and 6S batteries at once and have them charged in about 30 minutes. I say "about" 30 minutes because apparently my 3S LiPos are getting rather old. I ran them down yesterday with the truggy so they'd be near dead, but they recovered to 3.8v which tells me the batteries are just about junk now. They have to be balance charged every time.

Oh well, I've known its been time to purchase new batteries for a while now. The 4S battery is in perfect harmony with each cell, I don't think any of them were more than .01v off from the others.

the 6S battery on the other hand had most of the cells at 4.15v, but one was at 4.02, and the other was at 4.2. So its pretty much junk and only good for the 10TT now due to the 10TT's much less demanding powertrain.

Well, the fans arrived today. And without a pulse generator of some sort to feed the twin yellow fan speed inputs a signal the PSU likes, it automatically shuts down after 10 seconds. I tried feeding it the signal wires from two of the 3200rpm fans, but they obviously aren't fast enough to keep the PSU happy. I knew it was a possibility.

:(

Thats almost $30 wasted. Now I need to figure out how to make a pulse generator that runs off 12v and outputs a signal the PSU likes.

An astable oscillator using a 555 timer IC and a few resistors and caps. A little experimentation may be needed to find the right frequency to satisfy the supply.

or, use just one fan and route the rpm signal so that it also goes to the other fan slot.

The fans I bought had tach outputs, its just too slow for the PSU to be happy. If the fan work like I think the tach output works then its 2 signals per revolution. If thats the case then the PSU is probably looking for a 16khz signal or something close to that. (fans are 8800rpm)

But since I don't have oscilloscope I have no way of measuring the fans output. They look like normal 3 wire 12v DC fans for PCs though. I will have to look at a 555 circuit.

At this point I may just modify an old tape carrying case. I did a quick test, its so quiet when the lids closed. But I need to drill holes and use fans for circulation. Might work for this weekend, but I don't want to make the box a permanent solution. Will have to look at building a 555 circuit.

If you have a multimeter that has a frequency display, you could use that to get an idea of the frequency; sometimes frequency measurement is a mode of AC voltage measurement. This won't tell you the duty cycle though, for that it will just take some experimentation. It would be much faster to borrow a oscope if at all possible.

I'd start by trying to nail down the frequency by starting with fan rpm - 66Hz for a 4000rpm fan. 4000 rpm (rev/min) is 66.67 rev/sec (Hz=rpm/60), and then double it if that doesn't work, and so on. Once you get the frequency, start with a low duty cycle (very narrow pulse) and work your way up to 50% duty cycle.

The 555 timer will allow adjustments in both frequency and DC% (duty cycle). However, there are a few things to consider. IIRC, a 555 timer will have limits on DC%, if it won't get as narrow (or wide) as you need, you may need to use a transistor configured as an emitter-follower which will basically "invert" the output. Also, adjusting the resistances tends to adjust both freq and DC% at the same time, so sometimes it is easier to use two 555's in series, the first one as the astable oscillator to generate the right frequency, the second as a monostable oscillator to adjust the DC%. More complex but much easier to control freq and DC% independently. The 556 timer is just two 555 timers in one IC case, so that might be a better way.

I know you want to replace both fans, but how loud is just one fan by itself? Because like I said, you could tap into the tach signal of one fan and feed it to the other input and then use whatever fan you want as the second one if you need it.

If you still want to go with building your own oscillator, here are a couple datasheets for the 555 and 556 timers. Each has an applications section at the end with circuit examples: 555 Timer, 556 Timer.

I will have to look at that, possibly also using a thermister to control fan speeds. Read up a bit on that last night. Never really got into building circuit boards, but I can follow a diagram and do the math. So I'll eventually do that. Kinda tapped out for money currently.

In the mean time? I present a PSU.....in a box. This box was meant for the safe transport of LTO3 tapes in a very sensitive fashion. Which means the plastic is quite thick, and the open cell foam padding makes an adequate sound insulator.

I drilled a few holes in one side for the cables. Though I will visit radio shack tomorrow an pickup some insulated terminals for banana plugs and mount those to the box so I don't have to feed the charger leads through the air hole I made. I used a 92mmn 44cfm 41db PC fan for exhaust. I may add another 92mm fan to the front of the case of the same type if this proves insufficient. Using the left over padding I created and air dam to force air through the PSU.

So far its been running for about 1hr now and the air coming out of the fan vent is luke warm.

Before the box the PSU was about 74db, with the PSU in the box and lid closed its averaging 48db. Not a bad change for free.

http://farm9.staticflickr.com/8190/8...ea7fa002_c.jpg
psubox by thirdgen89gta, on Flickr

Looks like im going to be converting one of these guys soon. Got a 200w charger coming from HK and im going to need it to charge my new 6s packs aswell. I got an old PSU in my spare computer parts that im going to tear into and configure.

I've been running my PSU's like mad and they just keep on going. What a bargain heh!

WOOT! I'm not sure if this has been posted yet. A way to quiet the fan & adjust voltage!

I was working on my HP 575w 12v supplies and came across this page - https://sites.google.com/site/tjingu...projects/HP47A

I just connected 4 to 8 (using 6-8-10 to power up)(so I connect 4, 6, 8, and 10 all together) and lone behold the fan didn't ramp up yet I still got power! :yipi: I haven't loaded it up yet to see if the fan turns on when needed. I'll report back if I can

And just extra reading- this guy's page on putting them in series - https://sites.google.com/site/tjingu...ts/diy-24v-47a

I've got a stupid question. I'm finally getting around to building one of the 47a power supplies like on the first post on the first page.

Do I need to wait until I plug in the power supply to 120vac before I connect the 3 wires, or can I just hard wire the 3 wires to the pins and just plug and unplug the power supply from the wall?

Just hard wire them..

Thanks man.

Thank's for posting that. It is much more pleasent charging my batteries without my power supply sounding like its about to take off.