Good day

Can anyone tell me (from experience, or deep knowledge of hard drives) - Would I be able to run my USB-connected hard-drive array off 13.7V? How about 14.4V?

I have a mixture of 3TB and 4TB WD and Seagate drives, Black, Green, Purple, Red...

The reason being - our power supply is extremely unreliable. I am trying to build an enclosure with with a 10A 13.7V power supply connected directly to the battery - and I would like to skip installing a DC Buck converter if possible, because they are hard to find around here.

This way I can access my 20TB array - that consumes up to 8A, via USB from my laptop - and the array (and my long copy processes) won't drop when the power dips.

HDDs have a TVS diode on the 12V and 5V inputs. The battery voltage would be close to, or exceed, the diode's breakdown voltage. So not a viable proposition, IMHO.

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You would have to be able to drop the voltage and stabilize it. HDDs are on the sensitive side. I assume your HDDs are 2.5" since you're powering by USB, so you'd have to go from 14.4 down to 5.

Sounds like a more viable option would be building an uninterruptible power supply for your laptop. You're playing with fire a bit there, too, since the power centers are part of the MB and if you fry it, it's over for the laptop.

I imagine that the disks are powered by a controller that will have a voltage regulator to 12v and another to 5v, which I see these voltages quite appropriate.
Anyway, I would not play it either, since it would be necessary to control possible voltage drops of the batteries.

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Seagate's and WD's external drives are powered directly from the 12V regulated output of the AC adapter. The bridge PCB steps down the +12V supply to +5V via an onboard switchmode regulator.

The SMBJ12A is a typical choice for the 12V TVS diode:
https://www.littelfuse.com/~/media/electronics/datasheets/tvs_diodes/littelfuse_tvs_diode_smbj_datasheet.pdf.pdf

Reverse stand-off voltage = 12.0V
Breakdown voltage = 13.30V min, 14.70V max

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A backup a day keeps DR away.

Thanks for the info.
What I do not understand is how to regulate the Voltage +5 and do not regulate the + 12v, unless the TVS uses it to stabilize the + 12v?

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The +12V supply is regulated within the AC adapter, while the +5V supply is generated and regulated on the bridge PCB. The drive does not regulate either of these inputs.

Typical WD Bridge PCB Block Diagram:
http://www.hddoracle.com/viewtopic.php?f=112&t=1032&p=4805#p4805

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A backup a day keeps DR away.

Thanks for the link I already understand the design quite well.

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Are you not just trying to reinvent the UPS?

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Luke
Recovery Force Data Recovery

I know it sounds like I'm trying to make a ghetto UPS - but it feels wrong throwing away 40% of your battery power converting it to 110V/220V and then back down to 12V...

It's an array of 3.5" USB3 hard drive enclosures that come with 12V 1.5A power supplies, going into a USB3 hub, which also runs off 12V. I'm getting super throughput, and the enclosures and USB3 hub are reputable brands, and super cheap.

Obviously having 7 x 12V power supplies is a bit silly. Even more that your raid gets knocked out if one of them has a bad connection.

I guess my drives, and data, deserves a good power supply - which a battery is. You can't argue that it would've been a lot simpler to just string everything up to the battery without having to put an extra chip or big expensive regulator in between though.

Let's turn this around, what if I under-volted it? It would conceivably be cheaper to bypass one of the cells in the battery to get 11.4V... Is there any risk of damage running the drives at, say, 10V? Or 9V?

I am pretty sure that the USB enclosure does not regulate the voltage either save for its own needs or the 5V... I guess I will have to check the specs on both the enclosure boards as well as the harddrives. Well, this is my holiday project, so I will do this, and report back

If those power adapters are what is regulating the 12v, and you replace it with 13.7, and it goes to the hard drives, say goodbye to the hard drives.

Why not build your own regulator? Shouldn't be that difficult, just look up how to do it and order a few components, although you will need to do some soldering. Shouldn't cost much either.

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You could use a 24V battery with a high current 24V-to-12V switchmode voltage reducer. Be careful that the reducer's output is actually 12.0V rather 13.8V, as is the typical rating for automotive applications.

That said, a UPS would be better, if not cheaper. The other advantage is that the UPS would keep the battery charged, and it would allow the computer system to shutdown in an orderly fashion, plus it would not allow the battery voltage to run down below a preset level.

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A backup a day keeps DR away.

Have you measured the output voltage of one of the 12v power adapters to see if it is regulated? If it is very close to exactly 12v dc then yes, it is regulated and you would need to regulate the voltage from any other source. But there is the possibility that the power adapter is not regulated (it would produce a voltage of 13-15 or so unloaded), in which case the enclosure is doing the 12v regulating. It is something to check anyway. If it turns out the enclosure is doing the regulating, then maybe the direct battery connection would work without (much) issue.

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Since you are talking about an enclosure that is for 3.5" drives that almost certainly require the 12v, undervoltage would most likely make the drive not work, possibly even click like it was bad. If the hard drive needs 12v, it needs a proper regulated 12v.

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