Possible to get more 5V amps with 12V to 5V step-down converter?

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Sawtaytoes

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Oct 17, 2023
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tl;dr

I want to find a way to take the 12V power from a 4-pin Molex plug, bypass the PSU's 5V rail, and step down that 12V into 5V.

I don't wanna use the PSU's 5V rail because it only has 250W available, but my 12V rail has 1000W available. I figure I can use the 12V rail somehow myself, but I need a converter that can maintain a stable voltage under load. Let's say load is 250W.

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I have a Storinator XL60 chassis which has this pair of redundant PSUs:
https://www.zippy.com/pwproductshowdetail.aspx?pp_rfnbr=1867&pp_code=MTW2-5AD0B2V

Each PSU has 50A available on the +5V rail (250W) and 100A on the +12V rail (1200W).

The PSUs share the load when both are plugged in, but their redundant nature means I'm supposed to be able to take one out and be fine. Still, I'm theoretically able to get up to 500W of 5V power.

Right now, I have 100 SSDs in there, and I'm missing two adapters to make it 132 SSDs.

My 4TB Crucial MX500 SSDs say 5V 1.7A (8.5W) on the sticker. But they only seem to be using between 2.2W (440mA) and 4W (800mA) based on some rough calculations after plugging in 32 more drives.

I'm not sure how much power they use under load, but with 132 drives, at 4W each, I'll be using over 100A of +5V which is more than the max these PSUs allow.

But... The PSUs have plenty of power available on the +12V rail. And I figure, if I could step down the +12V rail using molex plugs to +5V, I could safely use my existing case and PSUs with all 132 drives.

Is there a solution that lets me bypass the PSU's +5V rail, so I can use the +12V rail to step down with relatively high amperage?
 

bayleyw

Active Member
Jan 8, 2014
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If the drives are on a backplane, you could probably bypass the 5V power line and feed it with your own solution, but if I'm not mistaken that's $32K of drives plugged into a $16K NAS - why not find a proper backplane that runs the drives from the 12V rail instead?
 

Sawtaytoes

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Oct 17, 2023
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Unless I'm not understanding something, the drives are on a backplane, but SSDs still power via 5V rather than 12V.

I've not seen a backplane that does step-down conversion. Every one I've seen takes Molex plugs directly.

Here's an example of a Supermicro backplane:
1700569196486.png

Just like my Storinator's direct-connect backplane, this one takes 4-pin Molex plugs. I don't see any sort of power regulator on this board.
 

Dave Corder

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Dec 21, 2015
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Sawtaytoes

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Oct 17, 2023
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I was stumbling around the Interwebs last night, and I came across this 3D printed thing: 10" Server rack 1U panel - HP HSTNS-PL11 PSU to 5vdc 12vdc by ayanev

It's relevant because there are a couple of reviews the maker did of a 200W and a 300W step down converters:

Review of SZBK07 300W 20A Buck converter 1.2V to 36V with constant Current
Review of XL4016 8A 200W Adjustable DC-DC Step Down Converter Module 4.5-30V to 0.8-30V

Thought those might be helpful.
Thanks! I checked the video, but that converter, like many others, only does 6A. To get a total of 50A, I'd need a bunch of these. That's simply not isn't feasible.
 

Dave Corder

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Dec 21, 2015
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Thanks! I checked the video, but that converter, like many others, only does 6A. To get a total of 50A, I'd need a bunch of these. That's simply not isn't feasible.
You're right, I didn't really look at the detailed specs - those are relatively low on the max amperage, and can only hit those 200W and 300W numbers at higher voltages than 5v. Drat.
 

UhClem

just another Bozo on the bus
Jun 26, 2012
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There do exist (but I won't/can't vouch for them) 12v/24v-to-5v30A buck converters. Here's the first 2 links I got from Google for:
12v to 5v 30a buck converter
https://www.amazon.com/Cllena-Converter-Regulator-Waterproof-Transformer/dp/B07VGN79X5?th=1

12V/24V to 5V 30A 150W DC DC Step Down Converter Voltage Regulator

Even IF you were to use 2-3 of these to get your needed 5v power, you COULD have a problem with Molex connectors on your backplane. That 1.7A on the Crucial sticker is not some marketing-exaggerrated number; it is likely the current draw for the 4TB model during sustained (write?) activity. That is 2x the current draw for a 12TB HDD (active-write) ... AND you are putting 2 SSDs in each of your HDD slots. Any connector has a maximum per-pin current rating. Ergo ...
 

Sawtaytoes

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Oct 17, 2023
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There do exist (but I won't/can't vouch for them) 12v/24v-to-5v30A buck converters. Here's the first 2 links I got from Google for:
12v to 5v 30a buck converter
https://www.amazon.com/Cllena-Converter-Regulator-Waterproof-Transformer/dp/B07VGN79X5?th=1

12V/24V to 5V 30A 150W DC DC Step Down Converter Voltage Regulator

Even IF you were to use 2-3 of these to get your needed 5v power, you COULD have a problem with Molex connectors on your backplane. That 1.7A on the Crucial sticker is not some marketing-exaggerrated number; it is likely the current draw for the 4TB model during sustained (write?) activity. That is 2x the current draw for a 12TB HDD (active-write) ... AND you are putting 2 SSDs in each of your HDD slots. Any connector has a maximum per-pin current rating. Ergo ...
I need at least 50A for all these drives. Ideally, 60A or more. It's headroom more than anything.

I saw 4 models on Amazon when I was searching, and I was searching for 4 days before posting here:
  1. https://www.amazon.com/Cllena-Converter-Regulator-Waterproof-Transformer/dp/B07VGN79X5/ref=pd_ci_mcx_mh_mcx_views_0?pd_rd_w=LXt7V&content-id=amzn1.sym.225b4624-972d-4629-9040-f1bf9923dd95:amzn1.symc.40e6a10e-cbc4-4fa5-81e3-4435ff64d03b&pf_rd_p=225b4624-972d-4629-9040-f1bf9923dd95&pf_rd_r=SNRG9FFGK717BWM08VDB&pd_rd_wg=fALqQ&pd_rd_r=6175c475-8189-4c4c-bb88-e115709d0747&pd_rd_i=B07VGN79X5&th=1
  2. https://www.amazon.com/Voltage-Regulator-Converter-Reducer-Transformer/dp/B095J1LPXG/ref=pd_ci_mcx_mh_mcx_views_4?pd_rd_w=LXt7V&content-id=amzn1.sym.225b4624-972d-4629-9040-f1bf9923dd95:amzn1.symc.40e6a10e-cbc4-4fa5-81e3-4435ff64d03b&pf_rd_p=225b4624-972d-4629-9040-f1bf9923dd95&pf_rd_r=SNRG9FFGK717BWM08VDB&pd_rd_wg=fALqQ&pd_rd_r=6175c475-8189-4c4c-bb88-e115709d0747&pd_rd_i=B095J1LPXG&th=1
  3. https://www.amazon.com/EPBOWPT-Converter-Regulator-Voltage-Transformer/dp/B07V7YY5X6/ref=pd_ci_mcx_mh_mcx_views_2?pd_rd_w=LXt7V&content-id=amzn1.sym.225b4624-972d-4629-9040-f1bf9923dd95:amzn1.symc.40e6a10e-cbc4-4fa5-81e3-4435ff64d03b&pf_rd_p=225b4624-972d-4629-9040-f1bf9923dd95&pf_rd_r=SNRG9FFGK717BWM08VDB&pd_rd_wg=fALqQ&pd_rd_r=6175c475-8189-4c4c-bb88-e115709d0747&pd_rd_i=B07V7YY5X6&th=1
  4. https://www.amazon.com/DROK-Converter-Adjustable-Regulator-Voltmeter/dp/B017SLMVXM/ref=pd_ci_mcx_mh_mcx_views_1?pd_rd_w=LXt7V&content-id=amzn1.sym.225b4624-972d-4629-9040-f1bf9923dd95:amzn1.symc.40e6a10e-cbc4-4fa5-81e3-4435ff64d03b&pf_rd_p=225b4624-972d-4629-9040-f1bf9923dd95&pf_rd_r=SNRG9FFGK717BWM08VDB&pd_rd_wg=fALqQ&pd_rd_r=6175c475-8189-4c4c-bb88-e115709d0747&pd_rd_i=B017SLMVXM
All of these have awful reviews. "Product is nice, but cannot sustain 5V under load" or that "product does 4.8V" or "product does 5.2V with no way to change it" or "this isn't 20A, it's actually more like 10A".

What I don't want is to buy some jank Chinese step-down converter that destroys $8K of SSDs. I don't mind paying a couple hundred bucks for a good one that's not gonna break and will work reliably for years like a PC PSU.

Also, the one you linked, I think, is a linear regulator rather than a switching mode one. Because of that, it's always drawing power and creates a lot of heat. These switching ones use a chip and quickly turn the power on and off (guessing) to sustain 5V no matter the load or fluctuations in the input power.

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If 1.7A was true, then when I had 72 SSDs in here, it would've caused a power failure as that's 122A if all drives are active. That's far more than the max amperage with both PSUs combined.

I never ran into an issue; in fact, with the 100 SSDs I have in there right now, my total power draw (including the Epyc processor and server motherboard) never goes over 540W peak. Average is 400W.

The last hour's stats:
1700728570533.png

The last day's stats:
1700728550160.png

The last week's stats got messed up with some weird impossible 20K watts peak 2 days ago, but the highest I saw was 582W peak with a 442W average:
1700728664504.png

From my calculations of the before and after adding a bunch of SSDs to this NAS, my server, these drives are pulling anywhere from 2.4-4.0W each. The only reason I haven't run into any power issues today with 100 SSDs comes from the fact that the redundant PSUs are loadbalancing.
 
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Sawtaytoes

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Oct 17, 2023
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I think I found it!

Anyone familiar with this product? Looks EXACTLY like what I'm looking for _and_ it has the PCIe connectors to boot!

1700733051069.png

First, I think this product is vaporware, but let's say it does exist and someone will sell it to me, then here's what's odd:

1700733204955.png

None of these PCIe connectors have 5V. So even if I plug them in, I'm not sure how I'd get 5V out of this unit. That and there are no other pictures available :(. I'm pretty sure this is a low-amp unit, but you're plugging in 375W of power into it. That or you're plugging in 150W and outputting 225W through the 3 x 6-pin ports?

EDIT: After going through that whole thread, it's possible the product does exist, but it must've been made in very limited quantities, or it has a different name now.

Second, those aren't PCIe power ports. The 8-pin input is PCIe, but the 6-pin outputs are Corsair PSU outputs for Corsair Type 3 and 4 cables which output 12V, 5V, and 3.3V. I have a bunch of those!

If I could grab 4 of these devices, I should be set. The fact that it takes a 150W cable means it might have 20-30A output! With 4 of these, I should be safe. The real question is: do these even exist?
 
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Sawtaytoes

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Oct 17, 2023
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It's for real! And yeah, 20A like I said: https://www.corsair.com/us/en/p/acc...CzTT-EyvbsjE8ZcRha8UcL0hh3ZVpNhTqS-yKCXY6ICdY

That means I can do 1 set of 16 drives for each of these and have enough headroom!

Because of some wiring magic I have to go through with these redundant rackmount PSUs, I bought 8 of these Corsair units. That should give me extras in case something goes wrong.

Also, these are not PCIe 8-pin, they're EPS12V (the 8-pin ports on your motherboard for the CPU). Same power output though. 160W or 5V 30A based on the spec sheet:
1700736543271.png
1700736517407.png

So I'm gonna specifically wanna find 1 x 4-pin Molex (11A 12V -> 132A) to 1 x EPS12V adapters to power this thing. Or 2 x 4-pin Molex to 1 x EPS12V. Not sure what I should use since it's 100W max, and I'm not drawing more than 12.5-15A (75W).
 
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