Can my power cord w/ transformer or the 3.5 inch enclosure harm my 2,5 inch hard disk drive (HDD)?

Question

I got two enclosures suitable for both 3.5 inch and 2.5 inch HDDs. It says on the outside they need 12 Volts and 2 ampere (2000 mA) which, imho, is the same thing. Their power cords+transformator delivers exactly that to the enclosures.

I put a 2.5 inch HDD in it which needs only 5 volts and .75 ampere.

It has been working for a couple of hours now, but what I'd like to know is this:

Will it not damage the HHD in it in the long run? Because 12 volts is too high? Is there a mechanism somewhere which brings the current down from 12 volts to 5?

Answer 1

Your first sentence basically answers this:

I got two enclosures suitable for both 3.5 inch and 2.5 inch HDDs.

If it's designed for them, it will work with them.

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Technical explanation:

SATA power connector used by 3.5" drives actually provides 3 voltages: 3.3V, 5V and 12V. Your enclosures may be powered with 12V adapters, but they must have some built-in circuitry that generates 3.3V and 5V. All of these are provided to the HDDs. Whether they are used or not is a matter of HDD's design. In case of 2.5" drives, they are not. Unused 12V connectors aren't connected to anything.

2000 mA is the maximum current an enclosure may draw from power supply. Maximum is the key: electricity doesn't just get pumped into devices, it's rather drawn by them. Your HDDs will draw as much current as they need. This is true for all electrical devices. It doesn't matter if the power supply can provide more. (This is not the case with voltage.)