USB ports provide power to connected devices, making it possible to power some external hard drives directly via USB without needing a separate power cable. The amount of power supplied over USB has increased with newer USB standards, enabling more devices to be powered solely by USB.
However, not all external hard drives can be powered over USB, since hard drives – especially larger 3.5″ desktop models – may require more power than a USB port can provide. This often depends on the drive’s specifications and interface. For example, a 2.5″ laptop hard drive typically requires less power than a high-capacity 3.5″ desktop drive.
This article will examine the power capabilities of USB ports versus the power requirements of different types of hard drives. It will look at whether USB alone can power various drive types and capacities and discuss methods of supplying additional power when needed.
USB Power Specifications
USB ports provide power to connected devices like hard drives, smartphones, and more. The amount of power a USB port can provide depends on the USB version.
The original USB 1.0 and 1.1 standards provided up to 500mA or 0.5A of current at 5V. This equals 2.5W of power (P=IV). USB 2.0 also has a 500mA current limit.1
USB 3.0 increased the power output up to 900mA or 0.9A. That equates to 4.5W of power. The USB 3.1 standard can provide up to 1.5A and 7.5W. Lastly, USB 3.2 can deliver up to 3A and 15W of power to connected devices.2
So in summary, USB ports can provide between 2.5W to 15W of power depending on the USB version. This power is used to run and charge connected devices.
Power Requirements for Hard Drives
The power draw for a hard drive depends on several factors like the drive type, rotational speed, and capacity. Generally speaking:
- 2.5-inch hard drives used in laptops draw between 2-5 watts, with most using around 2-3 watts while active. Some high performance 2.5-inch drives can use up to 6 watts.
- 3.5-inch desktop hard drives draw more power, typically between 5-12 watts depending on factors like rpm speed. 7200 rpm drives tend to use more power, around 8-12 watts when active.
- Newer 4TB or higher 3.5-inch drives may use up to around 20 watts or more when active due to denser platters requiring more power for the motor.
- Solid state drives use much less power, generally under 5 watts for most drives, even high capacity models. Some SSDs use as little as 2-3 watts.
In summary, high capacity and high performance hard drives require the most power, especially larger form factor 7200rpm+ 3.5-inch drives. SSDs are the lowest power consumers. Smaller 2.5-inch laptop drives use modest power typically under 5 watts.
Sources:
[1] https://superuser.com/questions/565653/how-much-power-does-a-hard-drive-use
2.5-inch Hard Drives
2.5-inch hard drives are commonly used in laptops and portable external hard drives. These smaller drives have lower power requirements compared to 3.5-inch desktop drives. According to Super User, a typical 2.5-inch external hard drive draws around 1.5 watts while reading or writing data. This low power draw allows many 2.5-inch drives to be powered directly via USB, without requiring a separate power cable.
More specifically, popular 2.5-inch hard drive models tend to have power usage in the 1-3 watt range. For example, the Seagate BarraCuda 2.5-inch HDD draws around 1.8 watts while the Western Digital Blue Mobile 2.5-inch HDD uses only 1.4 watts. Overall, the small form factor and low power needs make 2.5-inch drives well-suited for external enclosures powered over USB.
3.5-inch Hard Drives
3.5-inch hard disk drives (HDDs) are commonly used in desktop computers and require more power than smaller drives. According to SuperUser, a typical 3.5-inch 7200 rpm HDD requires around 8-10W on average during operation.
Some examples of power draw for common 3.5-inch HDDs:
– Western Digital Caviar Blue 7200 rpm uses 6W idle, 8W operating (Raspberry Pi Forums).
– Seagate Barracuda 7200 rpm uses 6W idle, 12W operating (SuperUser).
– WD Red Pro NAS drive uses 6.1W idle, 9.6W operating (WD specifications).
Since most 3.5-inch drives require around 8-12W during normal operation, the 5V/0.9A (4.5W) power from a typical USB 2.0 port is not enough. An additional power source is required to operate 3.5-inch HDDs via USB.
Solid State Drives (SSD)
Solid state drives (SSDs) use flash memory, which consumes significantly less power than traditional hard disk drives (HDDs). SSDs consume between 5 to 20 watts of power, according to tests by Scality (Which uses more power, an HDD or an SSD?). The power consumption depends on the SSD type and usage:
- SATA SSDs typically consume under 4 watts at maximum load (SSD Power Consumption and How It’s Managed).
- Lower-end NVMe SSDs consume around 3.5 watts.
- Higher-end NVMe SSDs can consume over 8.5 watts under load.
In general, SSDs are optimized to be energy efficient for mobile devices, with very low power usage when idle. Power consumption ramps up during intense read/write usage. Overall, SSDs consume far less power than traditional HDDs.
Powering Drives via USB
Whether a hard drive can be powered solely through a USB port depends on the power requirements of the specific drive. Smaller 2.5-inch hard drives often use less power and can usually operate with just the 5V power supplied over USB, without any additional power source. Larger 3.5-inch desktop hard drives have higher power requirements that typically exceed what USB alone can provide.
According to Quora, an external drive often needs a Y-cable to draw power from two USB 2.0 ports, as the 500mA from a single port is not enough (Source). SuperUser discussions also note that the power from a single USB 3.0 port is generally insufficient for a 3.5″ drive. While the USB 3.0 specification allows up to 900mA, most ports only supply up to 600mA (Source).
So in summary, 2.5″ notebook hard drives have the best chance of being powered solely via USB, while most 3.5″ desktop drives will require a secondary power source. Check your drive’s specifications to determine its exact power needs.
Using Y-Cables
One way to provide extra power to a hard drive or SSD through USB is by using a Y-cable, also known as a USB splitter cable. Y-cables have one USB connector on one end that plugs into the computer, and two USB connectors on the other end – one for data and one for additional power.
The data connector provides the standard power from the USB port, which is limited to 0.5A or 0.9A in USB 2.0 and USB 3.0, respectively. This may not be enough to power a high capacity hard drive. The extra power connector allows you to draw more current from a second USB port to provide sufficient power to the drive. This allows a total of up to 1A from two USB 2.0 ports or 1.8A from two USB 3.0 ports.
Essentially, Y-cables split the data and power lines from a single USB port so that the data is still communicated over one USB connection, but additional power can be drawn from a second USB port. This provides a simple way to meet the peak power requirements of power-hungry external hard drives and SSDs without needing a separate AC adapter.
For example, this Cable Matters USB 3.0 Y-Cable can provide extra power from a second USB port to power an external drive.
Additional Power Options
In addition to USB power, there are other ways to provide power to external hard drives that have higher power requirements. Some options include:
AC adapter: Many external hard drives come with a dedicated AC power adapter that plugs into a wall outlet. The adapter connects to the drive via a DC power connector and can provide consistent power. For example, most 3.5″ external drives come with an AC adapter since USB cannot provide enough power.
External power supply: Hard drives with higher power needs can use an external power brick or supply. These convert the AC wall power to DC power for the drive. The GFORCE 3 Replacement Power Supply is one example of an external power supply designed for hard drives.
Y-cable: A Y-shaped USB cable has two USB connectors that can plug into two USB ports. This allows the drive to draw power from two USB ports instead of just one, potentially doubling the power available. Y-cables work best for 2.5″ drives.
Extra USB ports: Devices like a powered USB hub can provide extra power over USB. Connecting the drive to a powered hub instead of directly to the computer may provide enough extra power in some cases.
Laptop USB power adapter: Adapters like USB car chargers can be used to power USB devices, providing an alternative source of power when AC power is not available.
The key is to look at the power requirements of the specific hard drive and match it with a suitable power source. Drives that need more power have options like dedicated AC adapters or external power supplies to provide sufficient and stable power.
Conclusion
In summary, most 2.5-inch hard disk drives and solid state drives can be powered directly via USB, while most 3.5-inch hard disk drives require additional power sources. Specifically:
- 2.5-inch HDDs below 2TB can be powered by USB 2.0 ports, while drives above 2TB may require USB 3.0 for sufficient power delivery.
- 3.5-inch HDDs generally cannot be powered solely by USB due to higher power requirements. Additional power sources like a DC power adapter, Molex connector from the power supply, or a Y-cable are needed.
- Most 2.5-inch and M.2 SSDs can be powered directly via USB without issue, due to lower power demands.
So in summary, USB ports can power most standard 2.5-inch hard drives and solid state drives without issue, but most 3.5-inch drives will require an additional power source to operate.