50V, 2950W server power supply conversion

[Smoggie]

With chargers getting ever more power hungry finding a suitable AC to DC power supply to feed then can be a big challenge, and works out very expensive if you opt for the proprietary solutions on offer.

A while back i picked up an iCharger 4010 duo which has a maximum charge power of 2000W. I was powering this off by home made dual HP DPS-600PB 24v / 48Amp converted computer server power supply. For most charging duties this unit is a great option and is the same as being sold by the likes of 'Feathermerchant' and others. But all things have their limit and at about 1100W the dual DPS-600PB unit cant supply anywhere near enough power to max out the monster iCharger.

This lack of power hadn't been an issue for me until recently when I started flying large helis, and have to charge the big batteries that go with them. I found myself being limited on charge rate not by my charger but due to PSU output limitations. What I also discovered is that a 24v PSU isn't ideal for charging 6s batteries because during the charge cycle the charger fluctuates between buck (voltage step down) and boost (voltage step-up). This can cause instability when charging at very high rates and can trip the charger.

What's really needed to get the most out of the big icharger is a PSU that will deliver at least 2200W at 36v to 50v. I could use four DPS-600PB coupled in series, but that would get messy and would require a fair bit of wiring spaghetti to couple them up, plus althoug the DPS-600PB can be had quite cheap for four of them the cost starts stocking up. Luckily I found a computer server PSU that seemed to offer the solution in a single unit. This monster PSU is the HP ESP-120, the specs are as follows:

Voltage : 51.4V
Current: 57Amps
Power: 2950W

I managed to find one on eBay that was dirt cheap (about equivalent of $25). The only real problem seemed to be the voltage which was too high for the 50V limit of the iCharger. After searching on line I found some instructions on how to trim down the voltage, so it seemed i was good to go. Here is a quick overview of what needs doing to accomplish the conversion:

(Usual 'health warnings' apply. High voltage electricity is potentially dangerous, you do this at your own risk, if you burn your house down or electrocute yourself don't come crying to me etc etc)

So here is the beast, ESP120 at the top and my old dual DPS-600PB unit below, mobile phone is for scale:


This PSU is intended to fit a rack mount type server so it has special quick connections at the AC input and DC output. Here is what you see looking on the end (image is marked up to show what the various connections do):


DC output is on left, AC input on right. The three small pins highlighted by the red box need to be shorted together to turn the unit on.

Here is how I soldered it all up. 3.5mm bullet connectors fit perfectly inbetween the DC output spade connectors. Great care needs to be taken with the AC input, the terminals need to be insulated to prevent shorting/electricution and the input cable needs to be anchored. The solution on the AC side isn't as pretty as it might be, but it works ok. A standard servo plug fits perfectly on the three small pins, just connect the servo wires together to short the pins.


The trickiest part is the modification to trim down the voltage. The PSU is fitted with a 700Ohm trimmer but this is not enough to get the output below 50v. Screwing the trimmer all the way gives 50.6V output which is still too high and causes an over-voltage error message on the icharger. To reduce voltage further you need a resistor with higher value. Either a trimmer or a fixed 2k2 or 2k7 resistor will get the voltage down around 48v. The original trimmer is surface mounted, you need to heat the base with a soldering iron and lift it off with tweezers or long nose pliers. It comes off quite easily once you get some heat in. Here is the trimmer:


It comes off leaving three solder pads. you need to put the new resistor between the two pads near the outer edge of the card, like this (borrowed photo):


After soldering on carefully check with a multimeter to make sure that the resistor is properly attached and that the two pads havent become bridged with solder. This is very important as the PSU could be damaged if the resistor isn't properly connected.

Pop the cover back on and that's all there is to it

Once you check that the PSU is running correctly and that the output is around 48v (48.7V in my case) then you can hook up your charger. Here's my charging set up:


And a shot of the icharger screen showing input voltage:


The complete conversion only too a couple of hours and I've got a PSU that's probably better in performance terms than even the mega bucks proprietary items that you can buy.


Steve

[Smoggie]

Here's a screen shot of the charger running off the new PSU during a dual channel 40A per channel charge, pulling just under 2000W out of the PSU. It remained dead stable throughout the charge and the PSU hardly got warm.

Previous attempts using my old 24V PSU to do a 40A charge on 6s packs , even using only a single channel would cause the charger to error due to the boost/buck issue.

[Rick_H]

One thing to note is this power supply requires 220 volts AC to run. Not everyone has that available.

[Smoggie]

Originally Posted by Rick_H

One thing to note is this power supply requires 220 volts AC to run. Not everyone has that available.

Yes, this is true. It's not an issue for me as here in the UK we are on 220-240V AC but in the US it would be a problem. I only realised the input voltage issue after it was pointed out elsewhere.

I guess for those on 110V AC there is still the option of triple or quad DPS600PB units, providing your wall sockets will take the amps.


Tell me.. in the US how do you manage to run stuff with high power demand like electric ovens, or hobs, or dryers and the like. Even a normal kettle can pull 2500W which would probably exceed the limit of a 110v wall socket

[helibus]

Originally Posted by Grumpy_Old_Man

Tell me.. in the US how do you manage to run stuff with high power demand like electric ovens, or hobs, or dryers and the like. Even a normal kettle can pull 2500W which would probably exceed the limit of a 110v wall socket

Homes are fed with two phases of 120V. The circuits that are 120V just use one of the phases. Branch circuits can pick up both phases and provide 240V to the high power stuff.

[Smoggie]

Just a quick update.. The ESP120 continues to run like a dream. I's never missed a beat no matter how hard I try to push it. Even the 4010Duo at full power really isn't driving the big PSU close to it's max.

If you have a 220-240v AC supply and your charger can cope with 48v input this is the way to go IMHO.

[lastdown]

Hi,
I have a question. How do you ensure you always plug in the mains plug the right way, or does this PS not care where L or N is offered?
On most PS you find a standard plug to connect to the mains, so on these it does not matter, but this PS is usually placed in a special case so here one can assume (should be at least) that the cage is providing neutral and live on the correct positions.
Best regards,
Bas

[TeroS]

Originally Posted by lastdown

Hi,
I have a question. How do you ensure you always plug in the mains plug the right way, or does this PS not care where L or N is offered?
On most PS you find a standard plug to connect to the mains, so on these it does not matter, but this PS is usually placed in a special case so here one can assume (should be at least) that the cage is providing neutral and live on the correct positions.
Best regards,
Bas

It does not matter, it's AC. You can put the plug in two ways to wall socket also.

[lastdown]

Ok, thanks for the feedback. This must be made then to ensure that each PSU is connected the same way when they are placed in the cage they are supposed to operate in.

[earhythmic]

I just purchased a 4010 Duo on sale for Labor Day and also ordered this monster power supply. This tutorial is done in the UK, but here in the states I'm going to have to get clever. I've been researching and read many threads over in RCG, but it seems like the more research I do about US 240 power the more unnerving this project gets.

I am planning on using my dryer outlet in the garage to power this supply, it is the 3 prong NEMA 10-30 receptacle. I understand that in the US there is HOT, HOT and Neutral. What guys recommend over on RCG is to connect the Hot 1 to L, Hot 2 to N, and "ground" to ground (it's all been discussed, but never a post saying "it works!") In theory it seems that this may work, my worry is that the 3-prong US 240v receptacle does not have a true ground, it is a neutral. So by RCG logic I would be connecting Hot 1 to L, Hot 2 to N, and NEUTRAL to ground. Will this work as intended or am I in store for an explosion/electrocution when touching the chassis?

Photos for reference:

[Smoggie]

I wish I could help. What i can say is that UK supply is single phase 240V, so in the UK the 'Neutral' connection is at the same voltage as the ground connection. This is very different to your 2 phase supply.

[earhythmic]

Thanks for the reply Grumpy. After some more digging I did find some success stories. Mainly on this thread: http://www.rcgroups.com/forums/showthread.php?t=1823759

So for future reference for anyone looking at this thread, here's my "it works!" post:

Here's the wiring diagram for US users:


I carefully wired everything up with a Nema 10-30 plug, typically sold for use as a three-prong clothes dryer replacement cable.

Double, triple, quadruple check proper continuity and wiring with a multimeter.

Shorted the 3 pins with an extra servo cable in order for the unit to turn on (per the first post)

Installed bullets on the DC output pins. Female EC5s wedge in between the PS blades/pins perfectly. Just cover the outside of the EC5 and the inner side of the PS pins with flux, stick in the EC5, and hold the tip of the soldering iron against the part where the bullet and pin meet, and melt solder all around. (I should have used this method for the AC pins too instead of trying to tin everything separately. Learn from my mistake.)

Turned off the dryer breaker, plugged in the power supply, flipped breaker on. Fans spooled up without an explosion! Fantastic!

Used the multimeter on AC setting to ensure I wouldn't get shocked by the metal case (since there's no real ground, only a neutral). Just touch one prong on the chassis of the PS and the other prong to a known ground. I used the center screw of a nearby AC outlet (confirmed ground by first testing with the 110v outlet). Safe to touch! Great!

Confirmed the DC power output was working, albeit a little high for the iCharger.

Then proceeded to follow the rest of steps from the original post by installing the resistor (tricky to find because it's covered with gray rubbery goo). I went with a 2k2 ohm resistor. I actually found this step pretty easy. Soldering PCBs just requires a quick touch of the soldering iron and since there was already solder on the board left over from the removal of the voltage adjustment potentiometer, it makes for quick work.

Retested everything with the multimeter, confirmed my DC output is under 50v (mine is at 48.5) and connected my charger.

I'm now charging my first set of batteries on my brand new iCharger 4010 Duo!

[ticedoff8]

I totally appreciate what you guys are doing with this power supply.
But, I totally don't understand why I would do this in the US.

In the US, 99% of the homes are wired with a 15A circuit breaker that feeds a string of 3-prong wall outlets 110v outlets.

From one circuit breaker, I can get 1600W before I trip the breaker.

If I am building a portable (or simiportable) charging station, then I can assume the field where I fly will also have 15A circuits

And, if I buy a Honda EU2000 generator, it is rated at 2000W surge and 1600 continuous.

I do have an 8kW generator that has 220v output, but it weighs 150lbs and I wouldn't take it to the field.

So, personally, I use multiple Dell server power supplies and run them off of 110v.
I have two 850W PS and that drives my 308 Duo up to it's limit.

This gives me the flexibility to charge anywhere in the world (110V to 220V input) by changing the AC power cord.

And, I don't have to have a dedicated outlet in the garage.

[earhythmic]

I weighed a few options but ultimately decided on this PS for several reasons. I should preface by saying I do use all of the power available to me with the iCharger 4010 duo. I parallel charge a bunch of 6s packs on both sides at 40a (about 2c charge rate). I can charge all of my batteries in about 30 minutes which is nice for my weekend schedule.

To get max power out of my charger I would have to run 4 power supplies in series. I have several 110v 15a outlets around the garage but they're all wired to the same 15a breaker, so i would have to run an extension chord into the house to split the load on two circuits. What a mess.

On that note, if running all 4 PS off two circuits, what happens if one of the circuits trip? From what I gather it's really bad news when half your supplies are still on trying to feed others that are off. I know there's ground mods to get around this sort of thing, but more hassle.

Speaking of hassle, for this large PS I only have to do the conversion one time instead of 2 or 4 times, and likely for a lot less $$ than 4 discrete power supplies.

[Smoggie]

Originally Posted by ticedoff8

I totally appreciate what you guys are doing with this power supply.
But, I totally don't understand why I would do this in the US.

As already explained in the post before yours, in the US you can (apparently) use your 2 phase supply to power this unit and get full power from it without tripping any breaker.

Why would you do it... Simple - it's about the only way to get the full rated power from the 4010 Duo.

The 308 Duo is rated at 'only' 1300W so doesn't have quite the same power demand as the 2000W 4010 Duo, so less of an issue. As for a solution that 'works anywhere in the world'....It's a moot point because you can't transport LiPos by air anyway. Few if anyone will be ever considering this as a portable solution.

[earhythmic]

Glorious 60 amp charging. Not even breaking a sweat.

[anything can fly]

Hi grumpy old man
I am looking at doing this conversation to the esp120 and have found this very useful, can you advise how you do the ac connection? How do you connect it to the mains.

Cheers Miles

[pkm_heliman]

The ground and neutral are connected together in the MAIN panel per code. SO therefore, the neutral and ground are the same. In a sub panel (a smaller panel feeding off the main panel) they are separate...NOT tired together...

[Number]

Now fit it into a charging case

[Smoggie]

Originally Posted by anything can fly

Hi grumpy old man
I am looking at doing this conversation to the esp120 and have found this very useful, can you advise how you do the ac connection? How do you connect it to the mains.

Cheers Miles

Hi Miles,

I'm away from home this week but I can take a pic when I get back. Drop me a PM to remind me if you still need the info.

Steve