Wiring server PSUs in parallel

Hi guys and gals,

I've been really enjoying my motion sim and it's holding up well considering how low-tech the job was

I thought it was time to upgrade from a car battery to a server PSU, and I found a bunch of Dell Poweredge 2950 units really cheap.

They are 750W. My rig is going to be pulling 1440W, and I use a Sabretooth 2x60, with 1 12V input, so I need to wire these suckers in parallel.

I see these 2950s have a current share pin, but I can't find much info about doing this parallel wiring properly. Can anyone offer any advice before I give it a go and blow myself up

Here is a picture showing my thoughts....as it says - DO NOT COPY THIS! It's most probably wrong!

The questions I have are

1) The current share pin A2, do they just simpy connect togther between PSUs?
2) Can I just use 2 standard plugs, or do I need to modify them to remove/share a GND?
3) The 'logic return' pins are GND, I use B1. Do I need 1 common GND pin between PSUs, or can I just the individual ones? ie, in the setup below I connect PSU1 A1 to B1 and PSU2 A1 to B1 - but should I connect PSU1 A1 and PSU2 A1 to PSU B1?



Thanks everyone.
Ben

NEVER remove the A/C ground.

For parallel, you should be fine as you illustrated.

For serial (24V), you want to lift the DC ground on one of the supplies, not the A/C ground (doing so can result in a very bad day).

Also worth noting, while the server PSUs are awesome, the huge benefit over batteries is size (batteries are huge) and maintenance (batteries outgas hydrogen and need to be regularly checked for fluid levels, while server PSUs are pretty much plug-it-in-and-forget-about-it-except-the-frik-n-noise).

If you really are bumping up against the current that a single PSU can provide, it's hard to ignore batteries as a way to augment over a second PSU, as that second PSU adds even more noise.

I have two, but that's for 24V. I am seriously considering batteries, if for no other reason that the intermittent spikes against my household wiring. Batteries trickle charge, so at most a couple hundred watts of A/C power doesn't potentially trip my breaker and shut down my computer...

Hi @Kirk , great reply - thank you.

Yes the frik'n' noise is surprising! These Dell PSUs let you adjust the fan speed, so I'll play around with that and find a balance.

My 12volt car battery has been great, can't fault it really, I just wanted my sim to feel more 'complete' and be a bit more transportable / fool proof.

I would personally check on Rcgroups before plugging ANY thing in, They are BY far the guru's of the Server modding community and will most likely know if your going to blow the shit up or not.

Cheers @Nick Moxley , I will certainly dig around and post over there, thanks.

So, a mixed response over at RC Groups, but mostly a Yes for my above theory. http://www.rcgroups.com/forums/showthread.php?t=2334892

Now I just need to wait for the delivery and I'll give it a shot. Perhaps with big rubber gloves and a fire extinguisher nearby! Hahaha.

Good news. I wired this all up last night and nothing went bang

I ran my rig for a couple of hours using Dirt 3, No Limits and Burnout, and keeping a close eye on those PSUs and wiring in case of any smoke or melting...

Everything is running fine, and amazingly well. Almost too well. The rig now has about 2x more torque than the 12v car battery So I'll have to redo all my profiles - or just keep it like this but it's a bit like 'insane mode' especially on hard crashes in Burnout!!

Highly recommended upgrade. £15 per PSU, plug and play, no more battery charging, more torque = winner

I fully second to never remove the AC ground. Unfortunately there are a number of posts on the web who show this as an option when connecting to supplies in series. Floating the DC ground on one of the supplies can be easily done with nylon washers / insulators for mounting power transistors to insulate the whole PCB from the casing.

I spent ~20 years in IT support & many hours/days/weeks/months in windowless server rooms, may as well have been sitting in a dungeon...

anyhoo, I can vouch for the noise, especially no the Dell & IBM PSU's, on most all (but the oldest architecture) servers they are normally hot swappable, allowing you to remove a dead PSU (as long as you had redundant PSU's) & replace it.

We used to perform failover testing on our sandpit environment (also in a large server room) prior to commissioning boxes, & it is amazing that in amongst all that ambient noise of hundreds of other servers PSU's screaming away, when you pull 1x PSU out of a server, the second ones fan kicks in with a vengeance, normally requiring a courious glance to ensure the server rack wasn't taking off...

Question : has anyone wired 2x 12V server PSU's in series to get a 24V unit?
(or is this query worthy of another thread?)

I'm looking at doing that to support 3x 24vdc wheelchair motors for my (bergison) integrated motion g-seat project


I followed the links here & discovered some people doing it for RC activities
http://www.tjinguytech.com/my-projects/diy-24v-47a
http://www.tjinguytech.com/my-projects/server-ps

obviously very concious of mod being potentially lethal...

so I intend to have it enclosed in its only plastic enclosure, as well as wiring up e-stop to a relay switch as illustrated.



Im hoping i can string together a temporary solution until i can afford a meanwell UHP-1000-24....
cheers

working on a acrylic shroud to keep fingers out & sparks in...