Don't forget; once you get the outputs paralleled, monitor heatsink temps after a few minutes of heavy operation. Shouldn't be a problem since it's really a single rail, but any regulation differences between the two coils/regulation circuit may cause an issue. It should be quite obvious after only a couple minutes, but I think you should be fine.

Will do.

I should only be using roughly 8-10A current for charging anyway so there should be some headroom available from the power supply. Hopefully the regulation between outputs should be similar seeing as they based off a common rail.

We'll see.....

Alrighty....

Got the power supply up and running and seems to be outputting power as per it's specs.

Hooked up the 720i and setup to charger my 5s 4200 Hyperions. Trying to charge at 2c so 8.4A @ 12v. Problem I'm seeing is some pretty significant voltage sag. Charger is reporting ~10.6v input and I'm reading 11.1v with my Fluke loaded. Unloaded it's running about ~12.2'ish

Not so hot. Matter of fact, seems as if the charger stops charging for ~4-5sec every so often. No error report and doesn't terminate the charging cycle but assuming a low input voltage issue....

Ok, charger just dropped out due to a low voltage issue. Bummer

Reset and dropped to 1c charge rate and charger is now pulling 11.197v. Still way on the low side.

Not sure what my options are as of now??? Any suggestions?

Issue 1: Did you attempt to load the 3.3v and/or 5v line(s)? Sometimes that makes the 12v line more stable under load. The PS mod thread explains this, and what values to use.

Issue 2: If the charger's input voltage is correct, there could be voltage drop on the input power leads. My old EOS7i came with really long (like 6') cables. Shortening them helps a LOT.

I haven't tried to load the 3.3/5v lines as of yet. Could be on the list of things to try as I'm a little surprised at the voltage drop. According to the reviews, the PS handled high load (max) during overload protection testing with very minimal main line drop. This even at nearly 500w.

Good info on the input cable length on the charger. I did find it interesting that I'm losing ~.6/.7v on the input side just between the PS cable 12v output and what the charger is reporting for line voltage. Seems significant.

Cable trimming to commence shortly and we'll see where we are.

Some supplies have totally independent 3.3v, 5v, and 12v regulation, so no loading is needed (and doesn't help at all). This is how the Antec TruePower units work. But, for most other supplies, one rail is monitored and regulated and affects the other two rails. After all, these units are meant for computers, so all the rails are used.

Yeah, if the wires are long, they can introduce a voltage drop. I created a thread about this a while back. I was losing a total of almost 0.5v just on the wiring, and that was at 9A (from the PS). This equates to a resistance of 0.056 ohms, so at a 15A draw from the PS, you can lose over 0.8v, which can make a difference.

Update:


So I shortened the length of the input leads on the 720i and it certainly helped. Originally I was losing roughly .6-.7v when measuring the bullets off the PS and then reading what the charger is/was seeing for input voltage. With the shortened leads on both PS and charger and addition of 6.5mm castle bullets, I'm seeing roughly .1-.2v loss now. Better for sure.

Still haven't tried loading the 3.3 or 5v lines. Next on the list. Yesterday I got to run the setup and get some batts charged at 1c and I was seeing about 11.4v on the input side(this at only 4.2A charge rate) No load on the ps/charger is about 12.1v.

I know there is more available from this PS so need to keep digging. At a minimum per ATX specs, I should be able to pull ~15A from one of those single pads. I've tied the 2x together via 12AWG so was hoping to have the full 30A available but clearly something isn't totally right here.

I just can't believe I'd see nearly a ~1V main line loss off the rail only pulling 4.2A @ 11.3v. We're only talking ~48watts here. Most processors alone draw more than that and any modern GPU draws a hell of a lot more than that......

PS doesn't seem to be heating up at all really. Nice and cool and quiet.

Still missing something...

"The +12 V output is produced by two SBR30A50CT (30 A, 15 A per internal diode at 110º C, maximum voltage drop of 0.55 V) connected in parallel. This gives us a maximum theoretical current of 43 A or 514 W for the +12 V output."

Chances are that loading one of the 5v or 3.3v lines will help. Unfortunately, since all supplies are different, it could be the 3.3v line OR the 5v line, no way to tell until you experiment unless you want to reverse-engineer the circuit to determine the current sampling coil. So, it's just easier to temporarily hook up your resistor to each rail, and load whichever rail produces the most benefit the 12v line. Usually, drawing around 1A from either of these rails is enough to stabilize the 12v line, which means 5 ohms for the 5v line and ~3 ohms for the 3.3v line.

BTW: Even at 1A, the resistor should be mounted on a heatsink somewhere.

Also make sure the resistor power rating is sufficient. So, let's say you find that you need to draw 1.5A from the 5v line for sufficient 12v stability; that's 3.33 ohms and 7.5w. You want a resistor that has at least double the power rating of what you calculated.

Brian,

Talking with my buddy here, he's wondering if the charger is drawing way more current than the required for charging? DC's lossy but I can't imagine it's that lossy, no?


Based on what I've seen, makes me wonder if the jumpered 12v could be the issue here? Seems during testing, they were pulling 15A on a single line 100% duty cycle and the 12v line stabilty was still within the 5% spec (actually 3%). Based on my numbers, I'm no where near that. That "would" equate to roughly 11.64v based on 15A load with 12v feed....

The switching supply inside the charger is roughly 80% efficient from the chargers I've measured. If they were more "lossy", the extra inefficiency would be evident by heat somewhere (probably on the heatsink). So, if you are charging a 4s battery pack at 5A, the highest output power would be 84w (4.2v X 4 cells X 5A). At 80% efficiency, the input power would be 105w. At 12v input voltage, the current required would be 8.75A.

The jumpered output could very well be the issue. You could remove the jumper and run off one of the 12v outputs as a test. Generally, paralleling outputs isn't recommended because most multi-output 12v supplies have seperate FETs, but in this case where there is one ultimate 12v source, I thought it might be ok. Just to be sure, where did you put the jumper? If anything, it should be after the coils (where the original wires were).

Ya, I've got the jumper from those 2 pads on the output of the coils. Should be anyway....

Easy enough to pull the jumper and check it. I'm going to swing by my local Shack and see if I can find the 10ohm/10w resistors and wire that up regardless and see what happens to the regulation...

I searched and found your antec for like $30 so could go that route too.

I've also got a PC Power and Cooling 750w Quad here too. ;) 60A single rail. lol Doesn't power up for some reason so planning on sending it in for RMA.

If the jumper is the problem, would a couple high-current diodes from the pads leading into one wire help? Since the diodes would block the voltage from one pad to the other they would retain their individual regulation but feed into one output. I am assuming the low output is from interference within the current sensing circuit on each pad.

Isolation like that could be done, but the diodes would:

- Be VERY beefy. A diode capable of handling 15+ amps each would be large indeed.

- Have a low forward voltage drop. Most diodes have a drop of 0.7v. Schottkey diodes can get as low as ~0.3v.

- Must be mounted on a heatsink. Even a 0.3v drop diode will dissipate 4.5w @ 15A.

- Expensive.