What size battery for a 55 lb vs 80 lb trolling motor?

Rule of thumb: a 55 lb 12V trolling motor draws up to ~50A at full thrust, so a 100Ah LiFePO4 gives roughly 2 hours wide open or a full day at trolling speeds (10–20A draw). An 80 lb motor is 24V and draws ~56A – pair it with a 24V 100Ah battery (2.56kWh) for similar endurance. Because lithium holds voltage flat, thrust stays constant all day, unlike lead-acid which fades.

For most kayak and small-boat anglers a single 12V 100Ah is the sweet spot; go 24V 100Ah when you run 70–100 lb thrust or fish long days against current.