Best power option out there?


Hi everyone!

I'm just one week away to finally buy my OpenRov!
And I've decided to ask around this:

Which is the best option (batteries, cells, etc...) to power up the OpenRov?
Let's say I'm looking to invest some extra money on batteries to make long dives, and the option is not sized limited on the actual batteries compartment, I wouldnt mind to add an extra battery compartment.

Which are the power requirements of the unit?
(Like criteria to have in mind while looking for options)

Thanks everyone in advance!