This is likely going to be overkill for most people but I like nice stuff, more importantly equipment that allows for quick hassle free setup and teardown. This battery box was constructed for use in a 2013 Hobie Mirage Oasis tandem kayak. A Yuasa 12V, 7Ah SLA battery will be powering a Lowrance Elite-4 Gold fishfinder/ chartplotter which draws ~250mA @13.5V. This should easily power the Elite-4 unit for an entire day of fishing. The Pelican case is secured under the front seat with 1/4” diameter shock cord looped around the seat scuppers. This mounting arrangement prevents unnecessary holes, allows for quick setup/ removal and keeps the weight forward for solo use.
Hope this information helps in the design and construction of your own kayak battery box.
Bill of materials:
Pelican 1120 case with foam
Littelfuse MINI inline fuse holder - (PN: 01530002H) - Digi-Key
Bulgin 400 Series Buccaneer plug - (PN: PX0410/02P/5560) - Digi-Key
Bulgin 400 Series Buccaneer female contacts - (PN: SA3350/1) - Digi-Key
Bulgin 400 Series Buccaneer plug cap - (PN: PX0481) - Digi-Key
Bulgin 400 Series Buccaneer inline socket - (PN: PX0411/02S/5560) - Digi-Key
Bulgin 400 Series Buccaneer male contacts - (PN: SA3349/1) - Digi-Key
Bulgin 400 Series Buccaneer inline socket cap - (PN: PX0480/1) - Digi-Key
Bud Industries PG-7 cable gland - (PN: NG-9511) - Digi-Key
18ga, 2 conductor, red/black zip cord - Powerwerx
3A MINI blade fuse
12V 7Ah SLA battery - (PN: Yuasa NP7-12) - JMAC
Battery Tender 800 12V charger
1/4” diameter shock cord - Austin Kayak
Bungee buttons - Austin Kayak
Miscellaneous hardware