Immediately spin down a HDD on Windows

I have 2 non-system SATA HDDs which are not mapped to a dir and normally kept 'offline' on my Windows 7 OS. Even this way they spin up from time to time, including but not limited to windows update times.

It's easy on Linux but, what is the best way to spin down a HDD on demand using as small 3rd party software as possible on Windows? Or even, is there a 3rd party software allowing this?

Since you are familiar with Linux, stick to the smartctl command-line utility of smartmontools. You can spin down disks with the -s switch. From the man page:

-s NAME[,VALUE], --set=NAME[,VALUE]
standby,now - [ATA only] Places the drive in the STANDBY mode. This usually spins down the drive. The setting of the standby timer is not affected.

It requires an elevated prompt and the Linux /dev/sdX-style of referring to disks when they are unmapped, otherwise:

> smartctl.exe -s standby,now d:
smartctl 6.5 2016-05-07 r4318 [x86_64-w64-mingw32-win10] (sf-6.5-1)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

Device placed in STANDBY mode

Unfortunately, there is not much to prevent Windows from spinning the disks back up again whenever it so pleases.

For many years I've been using utility RevoSleep for exactly that purpose - it has simple taskbar popup menu that allows to manually spin-down (sleep) or spin-up (wake) any hard drive of your computer.

While this tool is made almost 8 years ago (for Windows XP originally), it still works even these days in Windows 10.

On Windows 7, "HDDScan" version v3.3 worked for me. Startup HDDScan, select your disk from the drop-down box, click the icon of the magnifying glass overtop the hard disk, click Features -> IDE Features, click Spindown.

Looks like there is also an option to set an inactivity timer.

I downloaded the program from here: http://majorgeeks.com/HDDScan_for_Windows_d6321.html

I was originally going to download Devcon but this was much quicker and I'm on a limited data plan.