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So i want to power a 3TB WD Green 3.5 inch hard drive (WD30EZRX)

Power Management 12VDC ±10% (A, peak) 1.73A

Average power requirements (W) Read/Write 4.1W Idle 3.0W Standby/Sleep 0.4W

The before in the laptop was 500GB WD Scorpio Black (WD5000BPKT)

Power Management 5VDC ±10% (A, peak) 1.15A

Average power requirements (W) Read/Write 1.75W Idle 0.8W Standby/Sleep 0.2W

on sata power port of a laptop motherboard asus pro50rl (spec Pentium T2370, 2GB OCZ DDR2 800 RAM, Radeon Xpress 128 MB)

Spec of the laptop power supply

Model SADP-65KB B

INPUT 100-240V ~ 1.5A (50-60Hz)

OUTPUT 19V - 3.42A

Efficiency level: IV

Spec of the hard drive enclosure power supply (wd my book 3tb enclosure)

Model KSAS0241200150HE

INPUT 100-240V ~ 0.6 A (50-60Hz)

OUTPUT 12V - 1.5A

this power supply was powering the hard drive and the sata to usb3 controller board 4061-705094-001

here is a pic of the way i was running this before. it worked fine for years but now i want to power it even more efficiently just by using the laptop power supply. before i was running the hard drive in the external enclosure and 3 power supplies one for the cooling fan, one for hard drive and one for the laptop so my question now is can i power the fan and the hard drive without frying my laptop power supply/board or i am being too optimistic?

The laptop power supply was taking 15W power draw on my watt meter before on normal usage so not even close to 60W of the spec of it but the real problem is Amps so what do you guys think will this work or i am just dumb?

Does the laptop motherboard sata power port even supply 12V?

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  • Your question is hard to follow. Very hard.
    – cde
    Commented Oct 9, 2015 at 23:17
  • That was not my intention. I wanted to provide as much information i see to you guys so you can give me a more correct answer. I will try to format my questions in a different way next time i post.
    – user507753
    Commented Oct 10, 2015 at 8:17

2 Answers 2

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Watts = Amps * Volts. So if you measure fewer watts, it necessarily pulls fewer amps (since the voltage is the same).

Beware however that you need measure peak [power] usage to be covered in all circumstances. On modern computers, the idle to peak difference/ratio can be quite significant. You need make it use as much CPU and disk simultaneously; run benchmark programs for both in parallel for example. There are some utilities that do this for you automatically; google "system stress test program" and see what's out there.

Does the laptop motherboard sata power port even supply 12V?

Yes, it usually does. It's part of the SATA standard for most connectors. But if you're blessed with a SATA 2.6 slimline connector then it doesn't. Your WD5000BPKT seems rather old so it seems unlikely it used that.

If present, the 12V line is derived from the power supply voltage via a DC/DC converter located somewhere on the motherboard.

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  • Thanks for the info. I will test everything when i get the sata extender as at this point i cannot connect the drive to the port as it is too tall.
    – audison
    Commented Oct 9, 2015 at 22:47
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Assuming your laptop board doesn't have a battery to charge, and no lcd/inverter to power, then lets round the power up to 20W to account for peak draw. Power = Voltage * Current, so the opposite is Current = Power / Voltage. At 19V, 20W of power is 1.052 Amps. That means only 1/3rd of the 3.42 Amps available from the power supply are unused. You have 45 Watts of power free. The Drive supply is 12V * 1.5A = 18 Watts. Even with a step down regulator efficiency of 80%, you have plenty of power available.

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  • The T2370 is a 2008-era CPU with a TDP of 35W. I had a laptop of that era that blew 50W (measured at the wall) with the CPU+GPU in action.
    – got trolled too much this week
    Commented Oct 10, 2015 at 0:28
  • @RespawnedFluff OP has it stripped down. Remove the internal drive, the onboard fan, and the lcd/inverter and the power reqs would drop. Of course, I'm going with OPs stated 15W.
    – cde
    Commented Oct 10, 2015 at 1:05
  • Yes the laptop is running on the external monitor and anything that can be stripped down it's taken off. I am thinking of running this without even using GPU so just core linux system without gui managed via lan. I have to check if i can turn off the graphics in bios but i think that is not possible. Will see when i get everything up and running. Thanks again for all your help guys i am now more confident plugging in the hard drive and expecting everything to work out of the box except some complication with detecting 3TB hard drive on laptop sata port but will see...
    – user507753
    Commented Oct 10, 2015 at 8:23

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