HP Server Power Supply, SERIES Connection HELP...

[saiyan]

Hey guys,
I know there have been a few topics regarding what i am trying to do but after hours of searching i still have a few questions im still unsure of before i go ahead with my project.
basically i would like to run 2 hp power supplys in series to double the voltage for my rc charger. ill post up links on exactly what i want if it helps.

http://www.ebay.com.au/itm/171386176239?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT this is what i am going to buy.

https://www.youtube.com/watch?v=aVbk7cpOJuE this is what i would like to do.

ok so my question are,
1 - in the video with the guy removing the ground to 1 of the case, would it be better for me to do it to both of the supplys? the reason i ask is sometime in the future i will be connection 4 power supply to make about 48v for bigger rc charger.
at the moment i will only be running 2 but i have no problem spending abit of time making sure it is more safer for me to use.

2 - in the video i notice the guy had both power supplys plugged in to the power outlet. is it possible to simply cut and wire up the power chord in parallel to make just 1 power chord? do you need to modify anything if you do that?

3 - is it possible to slighty change the voltage in the power supplys as my current rc charger shows on the back it takes voltage between 13v-18v.

any other information regarding my project would much be appreciated guys.

bruce

 

[motomech]

It's been awhile since I was looking at this, but for various isolated 2 server set-ups, what you need to do in enter the server model # @ google with a tag like, "wiring" or "isolated".
This will lead you to the RC forums where there is a huge amount of info for this.
But, if you focus on model specific info, it should take you to lists of model specific mods.

 

[skWarDog]

1) Yes, you would want to isolate the ground on one PS to prevent ground loops since the neutral white wire of both PS's are already linked to a common buss at the panel. ground loops can occur when the signal voltage developed by current from one of the circuits on the return path will disrupt the operation of the other circuit causing a loss of voltage.

1a) Possible, but no, you would only want to isolate the ground of 1 PS if 2 were linked in series (24v) or 3PS's if 4 were linked in series (48v). Idea being you still want one common ground. If you disconnected all the grounds or "float the buss", voltage regulators would be more susceptible to voltage level shifts from the unregulated grid power source (high demand, lightening strikes, etc). One common ground is preferred.

2) OK, looking at that power supply, 575watts at 100-110 volts draws roughly 5.5 amps x 2= 11amps...... Sure, you can connect 2 AC power cords by wiring together or just plug into a power strip type extension cord and be good to go on most common household circuits rated at 15 amp, as long as not much else is on same circuit. If you were trying to make a 48 volt DC supply though, you would prolly have to draw from 2 separate circuits so you don't trip the breaker. Common household currents in North 'Merica are 15 amp (14ga wire) or 20 amp (12ga wire).

3) They prolly have a pot for small adjustment, but I don't think you could get down to 18 volts. You might want to consider a variable or multiple voltage supply for this. Maybe someone else here with more knowledge will answer this question better than I.......

Edit: When you isolate the ground in the power supply, please be aware that there are multiple ground locations. You should verify that ALL grounds are isolated (disconnected) with a multimeter set to AC volts between input+ and metal framework of unit!
Also, back-biased diodes should be connected between the + and - DC outputs of each PS rated at the same capacity (575w) to protect the internals from reverse voltage in the event of a short or powering on of one unit only!
SDog

 

[Brake]

I did this same type of thing not too long ago. As the other guys said, the rc guys have done this type of thing a lot.
I used four HP dps-600pb power supplies. The way I went about it was to float the dc section grounds on three of them. The first one in the series I left grounded. Can't remember if I also removed the AC grounds on the three. Here is the thread that helped me out, although I think there were others too.
http://www.rcgroups.com/forums/showthread.php?t=1581061

Here is one on eBay over here.

http://m.ebay.com/itm/HP-DPS-600PB-server-power-supply-575W-321632-501-367238-501-406393-001-/111440987185

After floating the grounds I checked with a meter. I don't let the cases touch each other, just to stay on the safe side.

Anyway, it's a pretty cheap way to go about it and they can charge the batteries up fast through the Adaptto controller. Oh, and I did connect two power supplies up to one power cord, like you said, by paralleling the female plug ends together. Like a y splitter.
Then I use two separate 120v circuits.

 

[Brake]

I just watched that video you posted and it is basically the exact same thing that I had to do to three of my power supplies. [SMILING FACE WITH OPEN MOUTH]

 

[saiyan]

Thanks for all the quick replies guys, much appreciated. I think i kinda get it now.
i might just leave the project until im ready to build my 4 ps in series to make 48v.
So to be 100% sure, if i was to make 4 ps in series i need to float 3 of the 4?
Which means i need to do what the guy did in the video for 3 of the power supplies And break the ground connection for 3 ps and leave the last 1 as is.
then ill run the 1 ps that is grounded 1st in the series connection.

Cheers

Bruce

 

[saiyan]

Lol i just read your last post again brake. It just answered my last question....duuuhhhhh.
thanks brake.

Bruce