Independent power supply/s for Raspberry Pi 3 with peripherals

Hi Guys.
I am building a small stereo video camera for mapping purposes (SLAM). I need to power a RaspPi3 which has a Stereo Vision USB 3.0 camera attached and the data sent to a 1TB mini harddrive (which also needs power…
So a power bank of 5V with an output of say 4A will be required with a working time of 1 - 1.5 hours. What is available that is compact?
Or, I use two power supplies, one for the Pi 5V 2.5A and one for the Harddrive 5V 1.5A but I will need a data cable between the Pi and the Harddrive… Are there “splitter” cables like the use to have with the older USBs. We are now using USB 3.0
Any help will be appreciated… Cheers. JDZ

Hi John,
If you are going ahead with the 2 power supply option, you should be able to connect your Camera to your Pi using a USB cable that will transfer the data to your Pi.

Does your camera only have a USB port for both power and data?

the canera does not require any outside power source, and is connected to the Pi via USB 3.0. I am using this (advance) prototype…

That’s great news, what HDD were you planning on using with the setup?

Any 2.5" external HDD USB3.0 eg WD Passport etc 1TB

Okay, we don’t have any USB-USB Splitter cables available, perhaps try out something like this -