Ice Fishing
Lithium Iron Phosphate batteries for Ice Fishing
The sonar i mentioned in the OP is a vexilar FL8, and it pulls 0.21A. 6Ah battery would give this sonar 6/0.21= 28 hours operation nominal, room temperature. Check your manual or google to find your sonars draw, likely similar unless you have a large lcd display.
I would subtract 20% if the usage is well below 20F, like outdoors on the ice.
So as others said, i would go with the larger battery if you really want 2 full 12+ hour days.
The original post was made over 6 years ago so the use of lithium batteries and availability of them was not nearly as widespread as it is now.
The first two power boxes I built used SLA and lithium batteries. No issues with either type of battery. More often than not “battery failure” is attributable to user error, specifically, not taking care of them.
I shifted away from the standard style of batteries and last year rigged up a couple of units utilizing buck converters and power tool batteries to run my stuff. I’m bringing a drill along anyway so why not use the same battery platform for everything? It offers a lot more flexibility in what I can use those batteries for than a dedicated lithium or SLA ”flasher” battery can.
Neat project, but why not just get an Amped Outdoors 6AH Lithium battery for $50? That battery does weigh 20oz more, but still substantially lighter than the 5# battery it replaced.
I keep the the parts around to run a graph or camera of my M18 batteries if necessary too. Never have had to do it with my 12AH Amped Outdoors Lithium's but have had to borrow it to friends running old $19 sealed lead acid.
Those of you who are using lithium 12V batteries now instead of the lead acid batteries how do you like them? My 18 year old Vexilar battery is finally getting retired this year and I upgraded to Vexilar's Lithium Ion battery. I hope it lasts as long as the one that came with the unit did.