I've had the same lead acid 12v 7amp battery in my kayaks for about 5 years now. I am convinced its no longer holding a decent charge because on my last trip [even though the battery was charged overnight] all I got from my fishfinder was 15 minute spurts of sufficient voltage and then the unit would blink out again. Also the charger cable for the battery did not indicate that the battery was charged (binary indicator: charging vs charged).
I think I would like to step it up to a 10 amp battery, but I don't want anything super heavy. All I plan to run from the battery is my Lowrance Hook-4 and a BerleyPro LED light. So lets hear some reviews and suggestions with prices folks!
Hobie Kayak angler for life!