Ff battery pack

I just stumbled upon this site for battery pack just thought I would put it on here for a easy setup http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=121376741315&category=48618&pm=1&ds=0&t=1493426579460

Its seems like overkill.  If  you have sealed lead batterys (SLA) then you don't mind them getting  a little wet.  Hobie sells a mount that doesn't even have a cover.

 https://www.amazon.com/Hobie-12V-Battery-Holder/dp/B00CP240QQ

Others sell use a pouch and hang it.  The only thing is that you don't let it stay submersed.  So save the money and have something that has less weight.  Also, you really dont  need 2 batteries for a fishfinder.

Wilderness Systems' new battery is in that price range and is a better deal imo.