External HDD powering question.

[Arseen]

I have bunch of loose 2.5" Sata HDDs and external USB 2.0 cases for them.
The cases use those triple ended USB cables where mini USB end goes to the case and 2 USB type A cables go to computer.
As both USB As are required to be connected for the HDDs to work each case takes up 2 USB ports.
The main USB A is the data and side USB A is power.

Howerer as my computer doesn't have too many USB ports I was wondering few things:

1: I could instead connect the power connection to USB power brick (you know those that one uses to charge phones)?
2: If I buy power brick that has multiple USB slots could I use one to power several?
3: How many could I power from 1 power brick?
4: If I want to connect several (2-4) how strong (as amperes) one should I buy.

[Tech13]

ok I am an IT guy so this may get technical

The USB 1.x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices.

A unit load is defined as 100 mA in USB 2.0, and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0; 6 (900 mA) in USB 3.0.

I would suggest this for your setup:
https://www.monoprice.com/product?p_id=13914

[Arseen]

Thank you that one seems perfect.

So as the cases are 2.0 and have 2 plugs they each draw 1 Amps max right?

My hubs are powered as well so that helps too.
Altough power supplies are maybe bit small:
- 7-port USB 2.0 has 0.85A
- 4-port USB 3.0 has 0.5A
Should I upgrade those, or do you think using the device you listed is enought to control (in case of the 7-port USB 2.0 hub) 4 external HDDs and printer/scanner?

[Tech13]

I don't see the need  to upgrade.