Trolling Motor Batteries: The Complete Guide to Choosing, Using, and Maintaining Your Power Source
Whether you’re chasing bass at dawn or drifting for crappie all afternoon, one thing stands between you and a great day on the water: your battery. This guide covers everything you need to know about trolling motor batteries, from picking the right type to calculating your runtime to keeping it alive for seasons to come.
What Kind of Battery Does a Trolling Motor Need?
Not just any battery will do. Trolling motors require deep-cycle batteries, a specific category designed to deliver steady, sustained power over long periods and withstand repeated drain-and-recharge cycles. This is the opposite of a standard car battery, which delivers a short burst of energy to start an engine and then gets continuously topped off by the alternator.
There are three main types of deep-cycle batteries used in trolling motor setups today:
1. Flooded Lead-Acid (Wet Cell)
The classic, budget-friendly option. Flooded batteries are widely available, typically costing under $100, and can handle the frequent discharging that comes with trolling motor use. The tradeoff: they require occasional maintenance (topping off distilled water), are sensitive to vibration, and can spill if tipped. Expect a lifespan of 2–3 years with regular use.
2. AGM (Absorbent Glass Mat)
AGM batteries are sealed, maintenance-free, and significantly more resistant to vibration than flooded lead-acid batteries. The electrolyte is absorbed into fiberglass mat separators, which means no risk of spillage even if the battery is installed at an angle. They hold their charge well during storage. AGMs typically last 5 and more years and cost more upfront than flooded batteries, but the safety and stability often make the difference worth it for serious anglers.
If you’re shopping for a quality AGM option, Uplus Battery offers a well-rounded marine lineup worth considering. Uplus produces maintenance-free AGM batteries engineered specifically for marine environments.
Uplus flagship 12V 100Ah Deep Cycle AGM Battery (Group 27) is purpose-built for trolling motors, fish finders, and onboard electronics, and is rated for 2,000+ cycles at moderate depths of discharge, with a lifespan of up to 8 years under optimal conditions.
For boaters who want a single battery that handles both engine starting and deep-cycle duties, Uplus also offers dual-purpose AGM models in Group 24M, Group 27, and Group 31M configurations, with cold cranking amps ranging from 550 to 825 CCA. All models are sealed, spill-proof, and vibration-resistant, well suited to the bumps and splashes that come with a full day on the water!
3. Lithium (LiFePO4)
Lithium iron phosphate batteries have become increasingly popular in recent years, and for good reason. They’re roughly 70% lighter than equivalent lead-acid batteries. A quality lithium battery holds consistent voltage from the first cast to the last. The catch is cost. Lithium batteries are significantly more expensive upfront.
Voltage: Matching Your Battery to Your Motor
Your battery voltage must match your trolling motor system. This is non-negotiable. Mismatched voltage either won’t run the motor or risks damaging your equipment.
- 12V motors — common on smaller boats, kayaks, and jon boats, require a single 12V battery
- 24V motors — typically used on mid-size boats, traditionally require two 12V batteries wired in series, or a single 24V lithium battery.
- 36V motors — reserved for larger, heavier vessels in demanding conditions, traditionally require three 12V batteries in series, or a single 36V lithium pack.
If you like DIY, you can buy Uplus 12V trolling battery and DIY for 24v, 36v, and even 48v…
Amp Hours and Group Size: What the Numbers Actually Mean
Amp Hour (Ah) Rating
The amp hour rating is your fuel tank. A 100Ah battery can theoretically supply 10 amps for 10 hours, or 20 amps for 5 hours. The larger the Ah number, the longer your motor will run before needing a recharge.
For most trolling motor applications, a minimum of 100Ah is recommended for lead-acid or AGM batteries. Like: Uplus 12V 100Ah Group 27 deep cycle battery, and if you need a battery that can both start the engine and handle deep cycling, you might want to try Uplus dual-purpose marine batteries. There are three main models: Group 24M dual purpose marine battery, Group 27 dual purpose marine battery, and Group 31M dual purpose marine battery.
Battery Group Size
Group size refers to the physical dimensions of a battery, standardized across manufacturers:
- Group 24 — smaller, typically 79Ah; good for kayaks and compact installs.
- Group 27 — the most common marine size, typically 92Ah, like Uplus battery.
- Group 31 — the largest standard size, offering 105Ah; preferred for high-demand setups.
Always verify that your battery tray can accommodate the group size you’re buying, especially on smaller craft where space is tight.
How Long Will Your Battery Last? A Simple Runtime Formula
One of the most common questions from anglers is: “How long will this battery run my motor?” The basic formula is:
Runtime (hours) = Battery Capacity (Ah) ÷ Motor Amp Draw
For example, if your motor draws 20 amps at medium speed and you have a 100Ah battery, you’ll get roughly 5 hours of runtime at that speed.
But there are a few important caveats:
1. You rarely run at full speed. Most anglers average around 30% throttle while fishing. At 50% speed, amp draw drops dramatically, and since the relationship between speed and power follows a cubic curve, cutting speed in half can more than quadruple your runtime in practice.
2. Other electronics share the battery. Fish finders, running lights, and livewells all draw current. Add up your total amp draw from all devices when calculating runtime.
3. Conditions matter. Wind, current, and heavy boat loads force the motor to work harder. A battery that lasts all day on a calm lake might only last half as long fighting a river current.
4. Battery age and condition. Older batteries hold less charge. If your battery used to last all day and now dies by noon, it may be time for a replacement. Therefore, it is best to replace the battery with a brand-new one before it reaches the end of its service life.
Choosing the Right Charger (This Step Matters More Than You Think)
Using the wrong charger is one of the fastest ways to shorten a battery’s life — or damage it entirely. The rule is simple: match your charger to your battery chemistry.
- Flooded lead-acid: Use a charger with a float/maintenance mode; periodic equalization charges help balance cells and extend life.
- AGM: Requires a smart charger with a dedicated AGM setting to prevent overcharging, which can permanently damage the sealed cells.
- Lithium (LiFePO4): Requires a lithium-compatible charger. Do not use a standard lead-acid charger unless it has a specific lithium mode. Using the wrong charger voids most lithium warranties and can pose safety risks.
Multi-stage smart chargers, which automatically cycle through bulk, absorption, and float stages, are the gold standard for all battery types. They charge faster, charge more completely, and stop before overcharging. If you have multiple battery banks, an onboard multi-bank charger lets you top them all off with a single plug-in after each trip.
Battery Maintenance: How to Make Your Investment Last
Charge after every use. Batteries left in a partially discharged state, especially below 12.4V for lead-acid, are vulnerable to sulfation, a buildup of lead sulfate crystals on the internal plates that permanently reduces capacity. Get in the habit of plugging in as soon as you return to the dock.
Keep terminals clean. Corrosion at the terminals increases resistance and reduces charging efficiency. Clean them periodically with a baking soda and water solution and a wire brush.
Store properly in the off-season. Remove the battery from the boat and store it somewhere cool and dry, not a freezing garage or a hot shed. For lead-acid and AGM, store fully charged and check voltage every 1–3 months, recharging if it drops below 12.4V. For lithium, store at 50–60% charge; lithium has very low self-discharge and typically only needs attention every 6 months.
Don’t let lead-acid batteries sit discharged. Sulfation begins quickly in discharged lead-acid and AGM batteries. A battery left discharged through an entire winter may never recover full capacity.
Avoid deep discharges with AGM and lead-acid. Repeatedly draining these batteries below 50% is hard on the plates and significantly reduces cycle life. If you find yourself regularly running out of battery before the day ends, it’s a sign to upgrade capacity, not to keep pushing your existing battery past its limits.
Final Thoughts
The right trolling motor battery isn’t the most expensive one, it’s the one that fits your boat, your motor, and your fishing style. For most recreational anglers who get out a handful of times per season, a quality AGM in Group 24M, Group 27 or Group 31M is a reliable, affordable choice that will handle years of use with minimal fuss.
