I power it off two of these.
The batteries are located in the home made bow box at the front of the Sib.
I have a little shelf in the box with the batteries strapped in.
I run a power cord from the box to the tablet and fish finder.
I have a couple of cigarette lighter sockets wired up in there as well for charging my phone and VHF radio. One battery has thus far always lasted me the whole day sibbing/fishing.
I like having a spare as piece of mind tho.
The batteries sit at the front of the bow box I like a bit of ballast up front.
Gonna need a bigger boat soon as running out of space for mods.