48 volt DC power supplies

[macrules34]

I was looking at a lot of servers but they come with DC power supplies. Does anyone know how to power these servers with DC power?

o have searched the internet for such solutions but have come up empty. I know that I have to convert from AC to DC but that’s about all I know.

These power supplies are 48V DC 660 watts.

 

[JSchuricht]

That sounds like telco equipment being 48v and likely positive ground. The easiest thing would be to swap the power supplies out for traditional AC units.

If you want to use the DC power supplies, look up their specs to verify they are positive ground and their min/max DC input operating voltage. From there, build a 48v battery bank to power the servers and use an appropriate sized 48v battery charger to keep the batteries topped up. You could try forklift batteries or banks of 8 6v golf cart batteries in series. For some batteries you will need to keep them in a ventilated space and water them.

 

[macrules34]

That sounds like telco equipment being 48v and likely positive ground. The easiest thing would be to swap the power supplies out for traditional AC units.

If you want to use the DC power supplies, look up their specs to verify they are positive ground and their min/max DC input operating voltage. From there, build a 48v battery bank to power the servers and use an appropriate sized 48v battery charger to keep the batteries topped up. You could try forklift batteries or banks of 8 6v golf cart batteries in series. For some batteries you will need to keep them in a ventilated space and water them.

They are sun netra T5440’s being sold in bulk of 10. I just don’t know what would be the most cost effective solution (DC or AC).

Also would I need to create 48 volt banks for each power supply? These systems have 4 power supplies.

 

[Blinky 42]

How many of the servers are you thinking of?

Yes the -48v DC supplies are normally for telco rack integration or a server room with a DC plant in it. If you determine the max power draw of your setup (4x power supplies @ xx VA each * N servers = total VA) then you can scale the solution accordingly.

For one or 2 servers probably cheaper to swap the power supplies to normal AC input versions.

Example of what you might see in a colo with a small room-level DC plant for a rack or 2 of equipment

Flatpack2 48V/24kW

www.eltek.com

At larger scale the DC plant is usually tied into the UPS / Battery room infrastructure as you can avoid the % of loss doing extra AC -> DC -> AC conversions. The cost of this is not trivial unless you stumble upon an old facility where you can scavenge the massive copper DC distribution network yourself.

 

[macrules34]

How many of the servers are you thinking of?

Yes the -48v DC supplies are normally for telco rack integration or a server room with a DC plant in it. If you determine the max power draw of your setup (4x power supplies @ xx VA each * N servers = total VA) then you can scale the solution accordingly.

For one or 2 servers probably cheaper to swap the power supplies to normal AC input versions.

Example of what you might see in a colo with a small room-level DC plant for a rack or 2 of equipment

Flatpack2 48V/24kW

www.eltek.com

At larger scale the DC plant is usually tied into the UPS / Battery room infrastructure as you can avoid the % of loss doing extra AC -> DC -> AC conversions. The cost of this is not trivial unless you stumble upon an old facility where you can scavenge the massive copper DC distribution network yourself.

10 servers with 4x 48v 19A 660watt power supplies in each server.

So would that be 9120 VA, did I calculate that correctly?

 

[luckylinux]

10 servers with 4x 48v 19A 660watt power supplies in each server.

So would that be 9120 VA, did I calculate that correctly?

Not sure how you got these Figures.

First of all:
48 V * 19A = 912 W (not 660W)

So not sure what is going on there with 660W <-> 912W.

Probably 19A is a Maximum not a "Nominal" / "Rated" or 660W is only including the 12V and NOT the 5V/3.3V Rail.

Secondly:
10 Servers * 4 PSUs / Server * 660W / PSU = 26'400 W = 26.4 kW

Thirdly: that's the Server-Side DC (Output) Power. The Input Power needs to account for the Efficiency, so let's divide that by 0.93 (96% for the PSU but then a bit of extra losses in Cables / Fuse-Breakers / etc) or so for a ballpark Efficiency, so we get 26.4 kW / 0.93 = 28.4 kW

Something like this (a Emerson/Vertiv 3kW 48V) could do the Trick, but be sure to choose the correct Voltage, as these can go up to 58V !

https://www.aliexpress.com/item/1005003755306962.html

Efficiency is typically higher than 96%, at least at 220 VAC Input !



There might also be higher Power ones available.

That is quite the Power ! That's a bit more (if it was AC) than a 3-Phase 32A CEE Socket (22 kW) !

Not sure how much Oversizing and Redundancy you did ... What is the ACTUAL Load Power Consumption in the Worst Case ?

 

[nexox]

48 V * 19A = 912 W (not 660W)

I imagine it's two things: 48V is the nominal voltage of the battery bank, the voltage will be somewhat lower when the bank is at a low state of charge during and after a power loss, plus there's the PSU efficiency between the input current and voltage and the output power. I would just find AC PSUs to swap but if I was going to build a big DC power system I would just look at the 19A rating and design for that.

 

[luckylinux]

I imagine it's two things: 48V is the nominal voltage of the battery bank, the voltage will be somewhat lower when the bank is at a low state of charge during and after a power loss, plus there's the PSU efficiency between the input current and voltage and the output power. I would just find AC PSUs to swap but if I was going to build a big DC power system I would just look at the 19A rating and design for that.

He didn't mention Battery in his OP but alright, then you can go all the Way to 56 VDC or so, which would yield 56 VDC * 19 ADC ~ 1064 W .

If the 19A were intended at lowest SoC, then for LiFePO4 Batteries (2.5 VDC) that would yield 40 VDC at 16s, so 40 VDC * 19 ADC ~ 760 W.

Highest Voltage would be 58.4 VDC (16s x 3.65 VDC/Cell) but that is an extreme Case ...

As for Efficiency you are right, he didn't mention on which Side of the PSU the 660W apply. Although if you take the worst case, then 660W / 760W ~ 86 % Efficiency which is VERY BAD for a DC/DC Converter of this Scale (worse than an AC/DC).

 

[nexox]

then for LiFePO4 Batteries

If it's a telco standard then it's 100+ years old and would be based on lead acid batteries of some flavor, and there's always some voltage drop in the supply lines so the PSUs are probably rated for full power at under 40V, but likely the 19A rating has some headroom. Still sounds like a huge project to avoid.

 

[luckylinux]

If it's a telco standard then it's 100+ years old and would be based on lead acid batteries of some flavor, and there's always some voltage drop in the supply lines so the PSUs are probably rated for full power at under 40V, but likely the 19A rating has some headroom. Still sounds like a huge project to avoid.

I have LiFePO4 Batteries and I agree, IMHO it's NOT worth to replace the PSU.

Sure you *might* gain something going to a DC/DC PSU in Terms of Efficiency, but it's a "niche" (outside of Datacenters where they roll out their own custom Solutions anyways), so even if I have a Battery System, I still go through a standard 230V PSU which are widely available and cheap to power my Systems.

Looking for a "special" PSU will surely raise Cost not to mention that it's unlikely to fit in the same Form Factor etc.

 

[macrules34]

This is the title to the auction: 10 LOT Sun Netra T5440 2x Ultra SPARC T4 128GB w/ 4x 660W PSU 12x 2.5" HDD Caddy.

there it mentions the 660 watt power supply.

 

[luckylinux]

Are you sure it's worth to buy ? Or did you buy it already ?

I just did a quick Google Search but it seems to be a CPU from 2011 (SPARC T4). I think latest SPARC CPUs released were from 2017 or so.

 

[macrules34]

No I haven’t bought them.
Just looking into the power set-up cost for them.
I’m interested in buying them though, seems like a good deal.

 

[luckylinux]

No I haven’t bought them.
Just looking into the power set-up cost for them.
I’m interested in buying them though, seems like a good deal.

I hope you did your Research well .

To me it looks like a super Proprietary System with a weak CPU but I might be 100% wrong on that .

 

[macrules34]

SPARC been a cpu used by Sun/Oracle for a long time, this system runs Solaris and can use ldoms or known as containers on Linux.

 

[luckylinux]

SPARC been a cpu used by Sun/Oracle for a long time, this system runs Solaris and can use ldoms or known as containers on Linux.

I know that SPARC was used by Sun/Oracle for a long Time. Also Fujitsu apparently .

And you are sure that the CPU Performance is "reasonable" to justify its cost and Power Consumption ?

I'm not trying to change your Mind, at the end of the Day it's your Choice . To me it just looks like something that can be easily be beaten by a 1U EPYC / Xeon Scalable / Xeon E5 v4 for a Fraction of the Cost and the Power Consumption.

 

[macrules34]

I’ll get a pic of the ratings label on the power supply so we can more accurately come up with a solution.

 

[luckylinux]

I’ll get a pic of the ratings label on the power supply so we can more accurately come up with a solutio.

Well you are looking at > 24 kW of Power. I would have bigger Issues to worry about if you plan on running it 24/7 .

I think it's greatly oversized, like many Server Systems.

I have several Supermicro SC825 / SC826 and by default they come with 2 x 920W PSU. With a Xeon v4 System, heck even Dual Socket with say 8 HDDs, I don't think it goes above 300W-400W Total Power Consumption (at full Load) ...

EDIT 1: The Emerson/Vertiv PSU that I mentioned before (R48- 3000e) could be a viable Option. There are also higher Power Versions available (e.g. R48-4000e / R48-5800e but the 3000 (what I use for my Solar System as Charger) is difficult to beat at that Price Point (~ 70 EUR / Piece).

 

[nexox]

I have to imagine there are 120/230V AC PSUs available for those systems and buying a pile of them would be much easier and cheaper than setting up a complete DC power system from scratch.

 

[luckylinux]

I have to imagine there are 120/230V AC PSUs available for those systems and buying a pile of them would be much easier and cheaper than setting up a complete DC power system from scratch.

Probably yes, and probably it's a proprietary System so Price and Availability are going to be challenging either Way.

You'd avoid a Double Conversion (2 PSUs in Series) and related Losses if you can find an AC Unit though.