Each end of the Thunderbolt cable consumes 1.5w worst case, then there is the overhead of the Thunderbolt controller and related circuitry which is another 3-4w.
As activity in an SSD increases, power consumption increases.
I have several SSDs here that consume more power than specified, worst case. Note well, that most SSD suppliers do not specifiy worst-case power consumption.
Just a word of warning as you venture more into DIY.
Review the previous posts from other users when attempting to use SSD devices larger than 256GB.
The good news? Newer SSDs seem to be getting more efficient, power wise. We're not too far from seeing suitable 500GB and larger capacities that may work well within the power envelope.
Your first clue should be that no manufacturer, except for the Promise J2, is offering a bus powered Thunderbolt drive larger than 512GB. And with the Promise, there is power and performance throttling. Inside the casing is power management which reduces the performance of the SSDs inside when bus-powered. Only when an external power supply is used does performance achieve what you would expect from a few SSDs.
To summarize, the 10W of power available from Thunderbolt is to power the cable, the controller and power management circuitry, and the device. No manufacturer specifies the power available to the SATA device inside accounting for the entire power allocation.
Be careful! Your data corruption may come at the most inopportune time. Review the previous efforts experimenting with larger SSD devices.
