We get the same two emails almost every week. The first one is short: “Switched to lithium last month. Fished till dark, still had juice left. Best money I ever spent.” The second one is longer, usually contains the phrase “died halfway across the lake,” and ends with a question we’ve answered a hundred times: what size battery do I actually need?
If you’re putting a lithium battery on a trolling motor this season, here’s the stuff that matters. Runtime math, voltage choices, and four mistakes we see people make over and over.
Start with runtime, not voltage
Most buyers start by asking “12, 24 or 36 volts?” That’s the wrong first question. The right one is: how many hours do you need on the water?
A 100Ah battery at 12.8V has 1,280Wh of rated energy. Usable energy depends on the selected model’s depth-of-discharge limit, BMS settings, current, temperature, wiring losses and reserve requirement.
Measure or obtain the motor’s average current at the intended operating setting. Divide usable amp-hours by average current for an initial estimate, then include wind, current, hull load, electronics and a return reserve.
Want a full day plus reserve? Go bigger or go 24V. That’s it. Everything else is detail.
12V vs 24V vs 36V: pick by boat, not by habit
12V is for smaller boats and lighter use. A 12–16 ft aluminum hull running a 45–55 lb motor, half-day trips. One 100Ah battery, simple wiring, done. For the full model range and sizing tables, see our marine battery guide.
24V is the sweet spot most anglers end up at. Two 12V batteries in series (or a single 24V unit, which is what we usually recommend. Fewer connections, fewer failure points). You get double the voltage, which means half the current for the same thrust: less heat, less voltage sag, and noticeably more efficient over a long day.
36V is tournament territory. Big boats, 80+ lb thrust, running all day against wind. It’s also the setup where cheap lead-acid setups fall apart fastest, because you’re burning through three batteries a season.
One sizing note people miss: doubling voltage does not double your runtime. It doubles your power. Runtime comes from total watt-hours, which means total amp-hours across all batteries. Two 100Ah batteries wired for 24V still give you 100Ah “at 24V”. That’s 2,560Wh. Think in Wh, not Ah, and you’ll never size wrong.
Trolling Motor Battery Size by Thrust
| Motor thrust | System voltage | Cruise current | Battery for 4–6 hours |
|---|---|---|---|
| 30–45 lb | 12V | 15–25A | 12V 100Ah |
| 50–55 lb | 12V | 25–35A | 12V 100–150Ah |
| 60–80 lb | 24V | 20–30A | 24V 100Ah |
| 80–112 lb | 24V or 36V | 30–45A | 24V 150Ah or 36V 100Ah |
Why everyone is switching to lithium (it’s not just the weight)
OK, it’s partly the weight. A 100Ah lead-acid deep cycle tips the scales at around 30 kg. Our 100Ah lithium trolling model weighs about 12 kg. On a small boat, dropping 18 kg off the stern changes how the hull sits, how it planes, and how tired you are after loading it into the truck.
Usable capacity depends on the chemistry, stated depth of discharge, BMS limits, current, temperature and system efficiency. Compare batteries under the same operating assumptions rather than using the Ah label alone.
A 6,000-cycle specification is meaningful only with its stated test conditions. The dedicated trolling model publishes at least 6,000 cycles; actual service life depends on depth of discharge, current, temperature, charging and storage.
Four mistakes we see all the time
1. Keeping an incompatible charger. Do not assume the existing charger is suitable. Compare its output voltage, current and charge stages with the selected battery specification, and replace or reconfigure it when the values do not match.
2. Ignoring the BMS discharge rating. Check the motor’s maximum current and transient demand against the battery’s published limits. The dedicated LINEX trolling model publishes a 100A BMS and 100A maximum discharge.
3. Mismatched batteries in series. Running two 12V units as 24V works fine, but only if they’re the same capacity, same age, and same state of charge. Mix a new one with a two-year-old one and the older battery drags the whole string down. If that sounds like a hassle, a single 24V battery sidesteps it entirely.
4. Cooking the battery in a sealed compartment. Lithium doesn’t vent like lead-acid, so people assume it can live anywhere. It can’t. Sustained heat above 45°C makes the BMS pull power to protect itself. Keep the compartment vented, and don’t stack it right against a hot livewell pump.
Quick answers
Can I keep my old charger? Only if its output voltage, current and charge stages match the selected battery specification. Check the charger manual and battery limits before use.
12V or 24V? Use the voltage specified by the motor manufacturer. Capacity is a separate decision based on average current and required operating time.
How long will a 100Ah lithium battery last? Divide usable amp-hours by measured average current for an initial estimate, then include wind, current, hull weight, electronics and a return reserve. There is no universal runtime for every boat.
If you’re not sure what fits your setup, send us your motor’s model or a photo of the spec plate. We’ll tell you what to run, even if it’s not our battery. Our 100Ah trolling model covers most 12V setups at 12 kg with a 100A BMS, and the full lithium range goes up from there, or jump straight to the 12V or 24V collections.
Frequently Asked Questions
For a 60–80lb motor drawing 20–30A at cruise, a 24V 100Ah battery gives about four to five hours. Running at full throttle roughly halves that.
No. It maintains voltage under load better than lead-acid, so the motor holds its rated speed longer as the battery discharges, but peak thrust is set by the motor.
No. A 24V motor needs 24V, either one native 24V battery or two 12V units in series with matched capacity and age.
