It’s that morning sun, the stillness of water around you and you’re sitting there in your boat with a school of bass just ahead. You ease up and creep toward them. The battery gauge falls quicker then you thought it would…because you got it going at wide open throttle to reach the fish. That’s when importance of run time becomes more clear than simply purchasing largest battery you can find. Capacity isn’t everything. You also need to plan and be efficient.
The chart above shows how thrust rating relate to amp hours and how much time that give you on water. Most of us think that if we have a hundred amp hour battery with that rating on label we’ll get ten hours. This is not true. It is not just because lead acid cannot be fully discharged without damage, but also because nothing is truly safe when it comes to physics. To calculate usable energy you need to multiply their rating by roughly point six which alters everything in the book including these calculations. A theoretical eight hour trip become a realistic five hour one when run at half throttle which could strand you right next to shore unless you know this formula.
How to Make Your Battery Last Longer
The largest variable within your control is speed. You can see from the infographic just how dramatic of an effect speed have on runtime. With a stock setup, running at 20 percent may give you a dozen hours. Turn it up to max throttle and that same pack will only last you an hour and a half. That’s a severe trade-off. Most anglers aren’t running their motors wide open while they’re fishing anyway; most times we’re simply positioning. Running at low settings save energy but doesn’t sacrifice coverage, which lets you cover more water before recharging.
Thrust matters; Matching the right thrust to your boat’s weight prevents unnecessary drain. A kayak with a 30 pound motor are ideal. The same little rig on a large aluminum boat has to work hard all the time. That pulls way more amps because it is pushing around so much extra weight. Nothing kills a battery down like overworking it, besides speed, wind, and cold. Thrust needs to match the load. A good starting point is two pounds of thrust per one hundred pounds of boat. This will keep you in most efficient range of your motor.
These estimates take into account battery chemistry as well. For example, lithium batteries has almost all of their rated capacity available (nearly ninety five percent) versus flooded lead acids that have only about half of their capacity available. Lithium costs much more initially, lasts longer on the charge and weighs less. If you fish casually on weekends, a great compromise between performance and price is an AGM battery. There’s no maintenance whatsoever and they stand up better to vibration then older models. Just plug it in and go.
Sometimes even the best plans are foiled by outside forces. Amp draw can triple when wind fight with your bow. Battery capacity can drop by as much as forty percent in freezing temperatures because chemical reactions inside their cells slow down. A full battery in July might feel empty in January. Always check the weather before hitting the water. Shorten your trip or have a back-up power source if it’s cold or windy. These variables do not care about your math.
Longer days on the water can come from simple habits. Keep batteries charged to full before launch. Partial charging damage lead acid plates over time. Parallel wiring of like batteries will double amp hour capacity while leaving voltage unchanged. It’s also safer and cheaper than purchasing one big honking unit. Get a cheap meter mounted close to the switch so you can monitor voltage. If you want to have the battery last three or more years, never let it drop below half way discharge.
Experience is the great gap filler, but a chart is the great leveler to put you on a solid base to start with. So that’s where we go. We stop guessing because we know how weather, weight, and speed will impact our power source. We begin to manage our energy as a resource. Charge it up all the way. Be respectful of the cold. And keep throttle down. Because once you do those things, then the fish gets to decide how long you’ll be out there.