Far as I know Humminbird are the only ones making the castable version which I think is really a bit of a gimmick but will readily apologise if anybody is a fan. I do a lot of kayak fishing so am used to tinkering and modifying stuff myself. Have you ever priced a gel battery? They are really exy mate. If you do get the smart cast from humminbird you could just run a little sealed lead acid 7A/H they are only about $40 and run my top of the line 3005 Deep Humminbird for several days of 4 to 8 hour fishing missions before I need to recharge it.